A network analysis of mechanisms of change during exposures over the course of intensive OCD treatment

Exposure and response prevention (ERP) is an evidence-based treatment for obsessive-compulsive disorder (OCD). Theories for how it works vary in their emphasis on active mechanisms of change. The current study aimed to clarify mechanisms of change in ERP for OCD using network analysis, comparing ERP networks at the start and end of intensive treatment (partial hospital and residential). In our sample of 182 patients, the most central node in both networks was engagement with exposure, which was consistently related to greater understanding of ERP rationale, higher willingness, and less ritualization, accounting for all other variables in the network. There were no significant differences in networks between the start and end of treatment. These results suggest that nonspecific parameters like facilitating engagement in exposures without ritualizing and providing a clear rationale to clients may be key to effective treatment. As such, it may be useful for clinicians to spend adequate time underscoring the need to eliminate rituals to fully engage in exposure tasks and explaining the rationale for ERP prior to doing exposures, regardless of theoretical orientation. Nonetheless, findings represent group-level statistics and more fine-grained idiographic analyses may reveal individual-level differences with respect to central mechanisms of change. Other limitations include demographic homogeneity of our sample.

Habituation of Brain Activity with Repetition in Color and Picture-Word Stroop Tests

As a widely used mental task for functional near-infrared spectroscopy (fNIRS), the original color-word Stroop task has the advantage of being difficult to habituate, but also the disadvantage of being difficult to understand, especially for children. While the introduction of derived Stroop tasks offers highly promising countermeasures, changes in brain activity during these tests have not been well tested. We investigated the degree of habituation between the original and a derived Stroop task by measuring brain activity to obtain a better fNIRS task design. Fourteen healthy adults participated in the study, and a 10-channel fNIRS device was used. A picture-word Stroop task with lower linguistic conflict than the original was conducted. The original and derived Stroop tests were repeated four times in a 1-week interval. We found that the original Stroop test did not show any significant changes in brain activity with repeated measures; however, brain activity decreased during the derived test. The differences in habituation between the original and derived tests may be due to the differences in the strength of the linguistic conflict. Our findings also highlight the need to consider the effects of habituation when using derived Stroop tasks in repeated measures.

Brain Signatures of Early and Late Neural Measures of Auditory Habituation and Discrimination in Autism and Their Relationship to Autistic Traits and Sensory Overresponsivity

Sensory differences are included in the DSM-5 criteria of autism for the first time, yet it is unclear how they relate to neural indicators of perception. We studied early brain signatures of perception and examined their relationship to sensory behaviors and autistic traits. Thirteen autistic children and 13 Typically Developing (TD) children matched on age and nonverbal IQ participated in a passive oddball task, during which P1 habituation and P1 and MMN discrimination were evoked by pure tones. Autistic children had less neural habituation than the TD comparison group, and the MMN, but not P1, mapped on to sensory overresponsivity. Findings highlight the significance of temporal and contextual factors in neural information processing as it relates to autistic traits and sensory behaviors.

Effects of 700 and 3500 MHz 5G radiofrequency exposure on developing zebrafish embryos

Telecommunications industries are rapidly deploying the fifth generation (5G) spectrum and there is public concern about the safety and health impacts of this type of Radio Frequency Radiation (RFR), in part because of the lack of comparable scientific evidence. In this study we have used a validated commercially available setting producing a uniform field to expose zebrafish embryos (ZFe) to unmodulated 700 and 3500 MHz frequencies. We have combined a battery of toxicity, developmental and behavioral assays to further explore potential RFR effects. Our neurobehavioral profiles include a tail coiling assay, a light/dark activity assay, two thigmotaxis anxiety assays (auditory and visual stimuli), and a startle response - habituation assay in response to auditory stimuli. ZFe were exposed for 1 and 4 h during the blastula period of development and endpoints evaluated up to 120 hours post fertilization (hpf). Our results show no effects on mortality, hatching or body length. However, we have demonstrated specific organ morphological effects, and behavioral effects in activity, anxiety-like behavior, and habituation that lasted in larvae exposed during the early embryonic period. A decrease in acetylcholinesterase activity was also observed and could explain some of the observed behavioral alterations. Interestingly, effects were more pronounced in ZFe exposed to the 700 MHz frequency, and especially for the 4 h exposure period. In addition, we have demonstrated that our exposure setup is robust, flexible with regard to frequency and power testing, and highly comparable. Future work will include exposure of ZFe to 5G modulated signals for different time periods to better understand the potential health effects of novel 5G RFR.

Cellular forgetting, desensitisation, stress and ageing in signalling networks. When do cells refuse to learn more?

Recent findings show that single, non-neuronal cells are also able to learn signalling responses developing cellular memory. In cellular learning nodes of signalling networks strengthen their interactions e.g. by the conformational memory of intrinsically disordered proteins, protein translocation, miRNAs, lncRNAs, chromatin memory and signalling cascades. This can be described by a generalized, unicellular Hebbian learning process, where those signalling connections, which participate in learning, become stronger. Here we review those scenarios, where cellular signalling is not only repeated in a few times (when learning occurs), but becomes too frequent, too large, or too complex and overloads the cell. This leads to desensitisation of signalling networks by decoupling signalling components, receptor internalization, and consequent downregulation. These molecular processes are examples of anti-Hebbian learning and 'forgetting' of signalling networks. Stress can be perceived as signalling overload inducing the desensitisation of signalling pathways. Ageing occurs by the summative effects of cumulative stress downregulating signalling. We propose that cellular learning desensitisation, stress and ageing may be placed along the same axis of more and more intensive (prolonged or repeated) signalling. We discuss how cells might discriminate between repeated and unexpected signals, and highlight the Hebbian and anti-Hebbian mechanisms behind the fold-change detection in the NF-κB signalling pathway. We list drug design methods using Hebbian learning (such as chemically-induced proximity) and clinical treatment modalities inducing (cancer, drug allergies) desensitisation or avoiding drug-induced desensitisation. A better discrimination between cellular learning, desensitisation and stress may open novel directions in drug design, e.g. helping to overcome drug resistance.

Face masks in action: Birds show reduced fear responses to people wearing face masks during the COVID-19 pandemic in three Asian countries

The 2019 zoonotic pandemic (COVID-19), has led to a massive global lockdown that provides a good opportunity to study how wildlife responds to changes in human activity. Wearing a mask after the COVID-19 outbreak was widely used to prevent the spread of the causative pathogen. It has been shown that tree sparrows (Passer montanus) at two sites in south China exhibit reduced fear responses to people with face masks after a period of heavy exposure to them, whereas European studies showed the opposite, with no changes in the behaviour of the birds towards mask wearers in either rural or urban areas. To further study this, from October 2021 to January 2022, we conducted a flight initiation distance (FID) survey in Pakistan, Bangladesh, and Xi'an, China for a variety of field bird species by comparing the FID for researchers wearing masks to that for researchers not wearing masks to assess whether wearing masks in public places caused birds to adjust their flight response. Results from the three Asian countries showed that after a period of sustained contact with people wearing masks, in both rural and urban areas, birds were significantly more adapted to them and had a shorter FID to people wearing masks. We suggest that the rapid habituation of birds to people wearing masks with a reduced fear response could have some fitness advantage, allowing them to adapt rapidly to the new environmental conditions induced by COVID-19.

High intensity interval training as a novel treatment for impaired awareness of hypoglycaemia in people with type 1 diabetes (HIT4HYPOS): a randomised parallel-group study

AIMS/HYPOTHESIS

Impaired awareness of hypoglycaemia (IAH) in type 1 diabetes may develop through a process referred to as habituation. Consistent with this, a single bout of high intensity interval exercise as a novel stress stimulus improves counterregulatory responses (CRR) to next-day hypoglycaemia, referred to as dishabituation. This longitudinal pilot study investigated whether 4 weeks of high intensity interval training (HIIT) has sustained effects on counterregulatory and symptom responses to hypoglycaemia in adults with type 1 diabetes and IAH.

METHODS

HIT4HYPOS was a single-centre, randomised, parallel-group study. Participants were identified using the Scottish Diabetes Research Network (SDRN) and from diabetes outpatient clinics in NHS Tayside, UK. The study took place at the Clinical Research Centre, Ninewells Hospital and Medical School, Dundee, UK. Participants were aged 18-55 years with type 1 diabetes of at least 5 years' duration and HbA1c levels <75 mmol/mol (<9%). They had IAH confirmed by a Gold score ≥4, modified Clarke score ≥4 or Dose Adjustment For Normal Eating [DAFNE] hypoglycaemia awareness rating of 2 or 3, and/or evidence of recurrent hypoglycaemia on flash glucose monitoring. Participants were randomly allocated using a web-based system to either 4 weeks of real-time continuous glucose monitoring (RT-CGM) or RT-CGM+HIIT. Participants and investigators were not masked to group assignment. The HIIT programme was performed for 20 min on a stationary exercise bike three times a week. Hyperinsulinaemic-hypoglycaemic (2.5 mmol/l) clamp studies with assessment of symptoms, hormones and cognitive function were performed at baseline and after 4 weeks of the study intervention. The predefined primary outcome was the difference in hypoglycaemia-induced adrenaline (epinephrine) responses from baseline following RT-CGM or RT-CGM+HIIT.

RESULTS

Eighteen participants (nine men and nine women) with type 1 diabetes (median [IQR] duration 27 [18.75-32] years) and IAH were included, with nine participants randomised to each group. Data from all study participants were included in the analysis. During the 4 week intervention there were no significant mean (SEM) differences between RT-CGM and RT-CGM+HIIT in exposure to level 1 (28 [7] vs 22 [4] episodes, p=0.45) or level 2 (9 [3] vs 4 [1] episodes, p=0.29) hypoglycaemia. The CGM-derived mean glucose level, SD of glucose and glucose management indicator (GMI) did not differ between groups. During the hyperinsulinaemic-hypoglycaemic clamp studies, mean (SEM) change from baseline was greater for the noradrenergic responses (RT-CGM vs RT-CGM+HIIT: -988 [447] vs 514 [732] pmol/l, p=0.02) but not the adrenergic responses (-298 [687] vs 1130 [747] pmol/l, p=0.11) in those participants who had undergone RT-CGM+HIIT. There was a benefit of RT-CGM+HIIT for mean (SEM) change from baseline in the glucagon CRR to hypoglycaemia (RT-CGM vs RT-CGM+HIIT: 1 [4] vs 16 [6] ng/l, p=0.01). Consistent with the hormone response, the mean (SEM) symptomatic response to hypoglycaemia (adjusted for baseline) was greater following RT-CGM+HIIT (RT-CGM vs RT-CGM+HIIT: -4 [2] vs 0 [2], p<0.05).

CONCLUSIONS/INTERPRETATION

In this pilot clinical trial in people with type 1 diabetes and IAH, we found continuing benefits of HIIT for overall hormonal and symptomatic CRR to subsequent hypoglycaemia. Our findings also suggest that HIIT may improve the glucagon response to insulin-induced hypoglycaemia.

TRIAL REGISTRATION

ISRCTN15373978.

FUNDING

Sir George Alberti Fellowship from Diabetes UK (CMF) and the Juvenile Diabetes Research Foundation.

Seasickness susceptibility and the vestibular time constant: a prospective study

Human passive motion during boat, car or airplane travel may trigger motion sickness. Seasickness is the most provoking manifestation of motion sickness. It imposes major constraints on quality of life and human performance. Based on seasickness susceptibility the population is usually categorized into susceptible (S) and non-susceptible (NS). During repeated exposure some susceptible individuals undergo habituation and obtain symptoms relief, reflecting a third group of habituating (H) individuals. Recently, accumulative evidence suggests that the vestibular time constant (Tc) is associated with motion sickness susceptibility and attenuation of symptoms. These studies demonstrated that repeated passive motion stimuli lead to temporary short-term (days) changes in Tc, whereas sea sickness habituation process lasts 3 to 6 months. Therefore, the goal of the present study was to examine the behavior of Tc during the entire span of the seasickness habituation process between the H, S and NS groups to find an objective test for seasickness severity prediction. Tc of 30 subjects was prospectively evaluated pre, 3 and 6 months post exposure to sea environment using a computerized rotatory chair system protocol. Seasickness severity was evaluated by Wiker questionnaire. Significantly shorter Tc was found in the S group compared with the NS and H groups. Further analysis revealed lower maximal Slow Phase Velocity (mSPV) and nystagmus frequency (total number of beats/second) in the S group. Our results suggest that Tc, mSPV and nystagmus frequency might serve as a prediction for seasickness severity. This study was retrospectively registered on December 7th 2022 and assigned the identifier number NCT05640258.

Reliability of repeated exposure to the human elevated plus-maze in virtual reality: Behavioral, emotional, and autonomic responses

Approach-avoidance conflicts are a hallmark of anxiety-related behaviors. A gold standard for assessing anxiety-related behaviors in rodents is the elevated plus-maze (EPM), which was recently translated to humans using immersive virtual reality. Repeated behavioral testing is particularly interesting for clinical and pharmacological research in humans but could be limited by habituation effects. Here, we tested whether comparable strategies that are used in rodents (different environments and inter-trial interval of 28 days) are sufficient to avoid habituation or sensitization effects on the EPM, making it possible to perform repeated measurement of anxiety-related behavior in humans. Moreover, we developed two novel virtual environments for repeated testing to explore whether a scenario resembling the real world is superior to a video game-like EPM in terms of lifelike physiological, emotional, and behavioral responses. On a behavioral level, no significant differences but a high correlation between first and repeated exposure to the human EPM independent of EPM version were found. On a psychophysiological level, salivary alpha-amylase, skin-conductance, and respiratory frequency increased at first and second exposure independent of EPM version. However, at repeated exposure, skin-conductance and heart rate showed indicators for anticipatory anxiety and a small sensitization effect, while no effect of real-world resemblance on these physiological measures was found. This was also reflected in slightly higher subjective anxiety levels at second exposure, although subjective anxiety still correlated strongly between first and second exposure. In conclusion, the human EPM can be used for longitudinal assessments of human anxiety-related behavior when strategies to avoid habituation and sensitization are considered.

[Sensitivity of the sympathetic skin response and scintigraphy in the diagnosis of complex regional pain syndrome]

OBJECTIVE

To evaluate the sensitivity of sympathetic skin response (SSR) and compare it with scintigraphy in patients with complex regional pain syndrome diagnosed according to the Budapest criteria.

MATERIAL AND METHODS

Twenty-two patients with complex regional pain syndrome who attended the Rehabilitation and Physical Medicine Department between January-2018 and May-2022 have been prospectively evaluated. The scintigraphy was considered positive if in the 1st-2nd phase slight asymmetric and diffuse uptake was observed, or when in the 3rd phase marked periarticular radioisotope uptake was observed. SSR was abnormal if: a) no response after 20 stimuli; b) lack of habituation with permanence of the stimuli greater than 67.2%.

RESULTS

Age 55.4±8.57 years. Complex regional pain syndrome was more frequent in women (90.9%), more common in upper limbs (68.2%) than lower limbs (31.8%). In SSR, we have observed normal response (<67.2%) in 2 patients (11.1%), lack of SSR in 2 patients (11.1%) and lack of habituation (>67.2%) in 14 patients (77.8%). In total, 16 patients presented abnormal or absent responses (88.8%). The diagnostic sensitivity of scintigraphy is similar to that of SSR (89.5% vs 88.8%), with no statistical difference (P=.6721).

CONCLUSION

Scintigraphy has shown similar sensitivity to SSR, although the simplicity, security, low cost, non-ionizing and non-invasiveness of the latter technique suggest that it could be more cost-effective. The lack of habituation and the absence of response could identify response patterns and localize the involvement in the afferent, central, efferent or post-ganglionic pathways.

A preliminary evaluation of habituation and dishabituation of operant responding in mice

Previous research has suggested that operant response decrements within experimental sessions are due in part to habituation to the repeated presentation of reinforcers. One way to assess the role of habituation in within-session response decrements is to conduct a test for dishabituation, a phenomenon in which a habituated response to a given stimulus recovers following the presentation of some strong or novel stimulus other than the habituated stimulus. Dishabituation of operant responding has been demonstrated on several occasions in the literature, but studies with non-human subjects have thus far been limited to those using rats and pigeons. Two experiments attempting to replicate these findings with mice were conducted. Two groups of mice nose-poked for a sweetened condensed milk/water reinforcer on either a fixed-ratio 4 or variable-interval 15 s schedule of reinforcement. During testing, baseline sessions were then alternated with two test conditions and a control condition. Test conditions included a 5 s auditory stimulus or flashing of the house light presented mid-session. Control conditions were identical to baseline. Dishabituation was not observed for either group in Experiment 1. In Experiment 2, dishabituation was not observed for the fixed-ratio 4 group but was observed for the variable interval 15 s group. Considerations for further study of operant dishabituation in mice are discussed.

Habituation to visual onsets is affected by local and global distractors rate

Recent findings demonstrate that habituation of capture is stronger where onset distractors are frequent and weaker where they are rare, thus showing that habituation to onsets has a spatial selective nature. However, a debated question is whether habituation at a specific location is exclusively determined by the distractors' local rate, or whether instead local habituation is also affected by the global rate of the distractors, which may occur also at other locations. Here, we report the results from a between-participants experiment involving three groups of participants exposed to visual onsets during a visual search task. In two groups, onsets appeared at a single location with a high 60% rate or a low 15% rate, respectively, whereas in a third group, distractors could appear in four distinct locations with the same 15% local rate, leading to a 60% global rate. Our results confirmed that locally, habituation of capture was stronger the higher the distractors rate. However, the key finding was that we found a clear and robust modulation of the global distractors rate on the local habituation level. Taken together, our results unambiguously show that habituation has both a spatially selective and a spatially nonselective nature.

Drosophila genotypes can be predicted from their exploration locomotive trajectories using supervised machine learning

This study employs supervised machine learning algorithms to test whether locomotive features during exploratory activity in open field arenas can serve as predictors for the genotype of fruit flies. Because of the nonlinearity in locomotive trajectories, traditional statistical methods that are used to compare exploratory activity between genotypes of fruit flies may not reveal all insights. 10-minute-long trajectories of four different genotypes of fruit flies in an open-field arena environment were captured. Turn angles and step size features extracted from the trajectories were used for training supervised learning models to predict the genotype of the fruit flies. Using the first five minute locomotive trajectories, an accuracy of 83% was achieved in differentiating wild-type flies from three other mutant genotypes. Using the final 5 min and the entire ten minute duration decreased the performance indicating that the most variations between the genotypes in their exploratory activity are exhibited in the first few minutes. Feature importance analysis revealed that turn angle is a better predictor than step size in predicting fruit fly genotype. Overall, this study demonstrates that features of trajectories can be used to predict the genotype of fruit flies through supervised machine learning methods.

Assessing learning in mosquito larvae using video-tracking

Mosquito larvae display a stereotyped escape response when they rest attached to the water surface. It consists in detaching from the surface and diving, to return to the surface after a brief time. It has been shown that this response can be evoked several times, by repeatedly presenting a moving shadow. Diving triggered by a potential danger revealed as a simple bioassay for investigating behavioural responses in mosquito larvae, in particular their ability to learn. In the present work, we describe an automated system, based on video-tracking individuals, and extracting quantitative data of their movements. We validated our system, by reinvestigating the habituation response of larvae of Aedes aegypti reared in the laboratory, and providing original data on field-collected larvae of genera Culex and Anopheles. Habituation could be demonstrated to occur in all the species, even though it was not possible to induce dishabituation in Culex and Anopheles mosquitoes. In addition to non-associative learning, we characterised motor activity in the studied species, thanks to the possibility offered by the tracking system to extract multiple variables. The here-described system and algorithms can be easily adapted to multiple experimental situations and variables of interest.

Olfactive short-term habituation in children and young people with profound intellectual and multiple disabilities

BACKGROUND

Despite its importance for learning, the existence of the habituation process and its characteristics in people with profound intellectual and multiple disabilities (PIMD) remains understudied. Habituation is, however, considered the simplest form of learning, and a significant neuroadaptive mechanism. Even though habituation occurs in all sensory modalities, the olfactory system is where it manifests itself very visibly.

AIM

This study explores the olfactory short-term habituation abilities of children and young people with PIMD.

METHOD

Twenty children and young people with PIMD (7-18 years) were presented six times successively with a 30-second habituating olfactory stimulus. The interstimulus interval was 15 s. A new odour was presented on the seventh trial. The scenario was carried out two times with two pairs of stimuli. The participants' head alignment duration on the odour was measured.

RESULTS

Seventeen participants out of 20 manifested a decline in response, which reached about 50 % between the first and sixth presentation of the habituation odour. All habituators also showed a distinctive response when exposed to a novel odour. The participants who did not habituate showed a strong, non-fluctuating response to the stimulus throughout the presentations. Three participants only habituated to one of the two habituation stimuli.

CONCLUSION AND IMPLICATIONS

The results raise theoretical, scientific, and practical issues. They question the factors explaining olfactory habituation mechanisms, namely the stimulus properties and the severity of impairment, reveal the need for points of comparison for interpreting this population's responses, and point to the consequences of stimuli repetition and or variety in therapeutic or educational settings for these individuals' learning and cognitive functioning.

Exploring sensory sensitivity, cortical excitability, and habituation in episodic migraine, as a function of age and disease severity, using the pattern-reversal task

BACKGROUND

Migraine is a cyclic, neurosensory disorder characterized by recurrent headaches and altered sensory processing. The latter is manifested in hypersensitivity to visual stimuli, measured with questionnaires and sensory thresholds, as well as in abnormal cortical excitability and a lack of habituation, assessed with visual evoked potentials elicited by pattern-reversal stimulation. Here, the goal was to determine whether factors such as age and/or disease severity may exert a modulatory influence on sensory sensitivity, cortical excitability, and habituation.

METHODS

Two similar experiments were carried out, the first comparing 24 young, episodic migraine patients and 28 healthy age- and gender-matched controls and the second 36 middle-aged, episodic migraine patients and 30 healthy age- and gender-matched controls. A neurologist confirmed the diagnoses. Migraine phases were obtained using eDiaries. Sensory sensitivity was assessed with the Sensory Perception Quotient and group comparisons were carried out. We obtained pattern-reversal visual evoked potentials and calculated the N1-P1 Peak-to-Peak amplitude. Two linear mixed-effects models were fitted to these data. The first model had Block (first block, last block) and Group (patients, controls) as fixed factors, whereas the second model had Trial (all trials) and Group as fixed factors. Participant was included as a random factor in both. N1-P1 first block amplitude was used to assess cortical excitability and habituation was defined as a decrease of N1-P1 amplitude across Blocks/Trials. Both experiments were performed interictally.

RESULTS

The final samples consisted of 18 patients with episodic migraine and 27 headache-free controls (first experiment) and 19 patients and 29 controls (second experiment). In both experiments, patients reported increased visual hypersensitivity on the Sensory Perception Quotient as compared to controls. Regarding N1-P1 peak-to-peak data, there was no main effect of Group, indicating no differences in cortical excitability between groups. Finally, significant main effects of both Block and Trial were found indicating habituation in both groups, regardless of age and headache frequency.

CONCLUSIONS

The results of this study yielded evidence for significant hypersensitivity in patients but no significant differences in either habituation or cortical excitability, as compared to headache-free controls. Although the alterations in patients may be less pronounced than originally anticipated they demonstrate the need for the definition and standardization of optimal methodological parameters.

Resilience as a predictor of habituation

Habituation refers to the physiological adaptation to recurrent stressors, which can be measured by cortisol levels, and is considered a central mechanism in reducing allostatic load. Resilience, a potential factor influencing stress reduction, is the focus of this study. Specifically, the study aims to investigate the impact of resilience, as assessed by the Brief Resilience Scale (BRS), on habituation. The Trier Social Stress Test (TSST) was used as the recurrent stressor, and it was administered to each of the 56 subjects at 4 consecutive measurements. To assess habituation, various physiological parameters including the area under the curve with respect to the ground (AUCg) and with respect to the increase (AUCi), cortisol peak, slope from baseline to peak, and recovery were calculated. Mixed linear models were employed to examine the differences in the influence of resilience on habituation across the different time points. The findings indicate that the influence of resilience significantly varies from the first to the fourth measurement time point for AUCg (p = .048), while no significant differences were observed for the other cortisol parameters. The effects plot suggests that individuals with higher levels of resilience exhibit lower AUCg values throughout the measurements. These findings provide initial evidence supporting resilience as a predictor of cortisol habituation. However, future studies should also consider dynamic resilience models, utilizing longitudinally assessed resilience as a predictor for habituation, to explore whether resilience acts as a determinant of habituation or if habituation itself constitutes a resilience mechanism.

The 5XFAD mouse model of Alzheimer's disease displays age-dependent deficits in habituation to a novel environment

Habituation is a form of learning characterized by a decrement in responsiveness to a stimulus that is repeated or prolonged. In rodents, habituation to a novel environment is characterized by a decrease in locomotion over time spent in a novel environment. Habituation to a novel environment is dependent on hippocampal function, suggesting that habituation behavior may be a relevant readout for hippocampal-dependent memory deficits that are characteristic of Alzheimer's disease (AD). Current assays that measure hippocampal-dependent memory in preclinical animal models of AD have not accurately predicted the cognitive protection of novel interventions in human trials. Here, we tested whether a behavioral habituation paradigm could detect age-associated changes in a common preclinical mouse model of AD-like amyloid pathology, the 5XFAD mouse. We exposed 5XFAD mice and age-matched wild-type (WT) littermates at 3, 6, and 9 months of age to a novel environment over two sessions separated by 24 h and measured their locomotion. WT mice habituated to the novel environment over time, while 5XFAD mice displayed age-dependent deficits in behavioral habituation. We replicated our results using publicly available open field data from 5XFAD and late-onset AD mouse models with TREM2*R47H and APOE4 mutations. Overall, we present behavioral habituation as a potentially sensitive task to assess age-associated behavioral deficits in 5XFAD mice and other mouse models of AD that could be used to test the preclinical efficacy of novel AD therapeutics.

African jewel fish (Hemichromis bimaculatus) distinguish individual faces based on their unique iridophore patterns

Previous research has shown that African jewel fish (Hemichromis bimaculatus) recognize pair-bonded mates during their exchanges of egg-guarding duties. The current research examined the perceptual cues for face recognition by comparing two face models displaying anatomically realistic arrangements of blue iridophores derived from discriminant function analysis of distinct sibling groups. Four groups each consisting of 9 subadults were examined using a narrow compartment restraining lateral movement where face models were presented at eye level for eight trials. Because respiratory movement of the operculum can mechanically displace the eye thereby shifting the retinal image, jewel fish reduce their respiration rate during increased attention. When two experimental groups were presented with the same face models on four trials following initial model presentations, both groups exhibited stable respiration rates indicative of model habituation. When the habituated face models were switched to novel face models on the fifth trial, the rates of respiration decreased as measured by reliable increases in the elapsed times of opercular beats. Switching the models back to the habituated models on the sixth trial caused reliable decreases in the elapsed times of opercular beats, resembling the earlier trials for the habituated models. Switching the face models again to the formerly novel models on the seventh trial produced respiration rates that resembled those of the habituated models. The two control groups viewing the same models for all eight trials exhibited no substantial change in respiration rates. Together, these findings indicate that jewel fish can learn to recognize novel faces displaying unique arrangements of iridorphores after one trial of exposure.

Reduced corticolimbic habituation to negative stimuli characterizes bipolar depressed suicide attempters

Suicide attempts in Bipolar Disorder are characterized by high levels of lethality and impulsivity. Reduced rates of amygdala and cortico-limbic habituation can identify a fMRI phenotype of suicidality in the disorder related to internal over-arousing states. Hence, we investigated if reduced amygdala and whole-brain habituation may differentiate bipolar suicide attempters (SA, n = 17) from non-suicide attempters (nSA, n = 57), and healthy controls (HC, n = 32). Habituation was assessed during a fMRI task including facial expressions of anger and fear and a control condition. Associations with suicidality and current depressive symptomatology were assessed, including machine learning procedure to estimate the potentiality of habituation as biomarker for suicidality. SA showed lower habituation compared to HC and nSA in several cortico-limbic areas, including amygdalae, cingulate and parietal cortex, insula, hippocampus, para-hippocampus, cerebellar vermis, thalamus, and striatum, while nSA displayed intermediate rates between SA and HC. Lower habituation rates in the amygdalae were also associated with higher depressive and suicidal current symptomatology. Machine learning on whole-brain and amygdala habituation differentiated SA vs. nSA with 94% and 69% of accuracy, respectively. Reduced habituation in cortico-limbic system can identify a candidate biomarker for attempting suicide, helping in detecting at-risk bipolar patients, and in developing new therapeutic interventions.

[Tinnitus]

Tinnitus have different forms and it is possible to identify their origins in many cases. Even if tinnitus is not a kind experience, it is commonly not troublesome. But in some cases, it may become very annoying and lead to psychiatric disorders. Tinnitus is a frequent complaint at the medical office since 10% of the adult population is concerned. Their origin can be defined with different exams. Habituation is the key for therapy.

The sensory and affective components of pain differentially shape pupillary dilatation during cold pressor tests

Nociceptive and affective stimuli increase reflex sympathetic outflow to the pupils. To investigate effects of stimulus intensity, unpleasantness and distress on these pupillary reflexes, and to assess their stability, healthy participants immersed their hand in ice-water three times (for 20, 40 and 60 s; or 60, 40 and 20 s; or three times for 60 s) (N = 21 in each condition). Each ice-water immersion was preceded by a 90 s warm water immersion. To evaluate phasic sympathetic influences on pupil diameter, pupillary re-dilatation after 1 s of bright light was assessed during the last 10 s of each immersion. By-and-large, pain ratings and pupil diameter were greater during longer than shorter ice-water immersions, and ice-water immersions facilitated pupillary re-dilatation after the flash stimulus. However, mean pupil diameter during ice- and warm water immersions, minor ipsilateral amplification of the pupillary response, and ratings of pain unpleasantness and distress decreased across the experiment. Together, these findings suggest that nociceptive input increased sympathetic pupillary tone and amplified phasic increases in sympathetic activity after exposure to light. However, tonic sympathetic influences on pupil diameter and lateralization decreased across repeated immersions, possibly as novel or threatening aspects of the experience declined. Pupillary nociceptive and affective reflexes involve the locus coeruleus, an integral component of neural circuits that heighten cortical arousal and regulate pain. As these reflexes appear to reflect different aspects of sensory and affective processing, their combined assessment might increase the sensitivity and specificity of tests of locus coeruleus function in patients with suspected deficits.

Delineating Visual Habituation Profiles in Preschoolers with Neurofibromatosis Type 1 and Autism Spectrum Disorder: A Cross-Syndrome Study

Atypical habituation to repetitive information has been commonly reported in Autism Spectrum Disorder (ASD) but it is not yet clear whether similar abnormalities are present in Neurofibromatosis Type 1 (NF1). We employed a cross-syndrome design using a novel eye tracking paradigm to measure habituation in preschoolers with NF1, children with idiopathic ASD and typically developing (TD) children. Eye movements were recorded to examine fixation duration to simultaneously presented repeating and novel stimuli. Children with NF1 showed a bias for longer look durations to repeating stimuli at the expense of novel stimuli, and slower habituation in NF1 was associated with elevated ASD traits. These findings could indicate aberrant modulation of bottom-up attentional networks that interact with the emergence of ASD phenotypes.

Imagined eating - An investigation of priming and sensory-specific satiety

While obesity remains a pressing issue, the wider population continues to be exposed to more digital food content than ever before. Much research has demonstrated the priming effect of visual food content, i.e., exposure to food cues increasing appetite and food intake. In contrast, some recent research points out that repeated imagined consumption can facilitate satiate and decrease food intake. Such findings have been suggested as potential remedies to excessive food cue exposure. However, the practically limitless variety of digital food content available today may undermine satiation attempts. The present work aims to replicate and extend prior findings by introducing a within-subjects baseline comparison, disentangling general and (sensory-) specific eating desires, as well as considering the moderating influence of visual and flavour stimulus variety. Three online studies (n = 1149 total) manipulated food colour and flavour variety and reproducibly revealed a non-linear dose-response pattern of imagined eating: 3 repetitions primed, while 30 repetitions satiated. Priming appeared to be specific to the taste of the exposed stimulus, and satiation, contrary to prior literature, appeared to be more general. Neither colour nor flavour variety reliably moderated any of the responses. Therefore, the results suggest that a more pronounced variety may be required to alter imagery-induced satiation.

Perception of audio-visual synchrony in infants at elevated likelihood of developing autism spectrum disorder

The inability to perceive audio-visual speech as a unified event may contribute to social impairments and language deficits in children with autism spectrum disorder (ASD). In this study, we examined and compared two groups of infants on their sensitivity to audio-visual asynchrony for a social (speaking face) and non-social event (bouncing ball) and assessed the relations between multisensory integration and language production. Infants at elevated likelihood of developing ASD were less sensitive to audio-visual synchrony for the social event than infants without elevated likelihood. Among infants without elevated likelihood, greater sensitivity to audio-visual synchrony for the social event was associated with a larger productive vocabulary.

CONCLUSION

Findings suggest that early deficits in multisensory integration may impair language development among infants with elevated likelihood of developing ASD.

WHAT IS KNOWN

•Perceptual integration of auditory and visual cues within speech is important for language development. •Prior work suggests that children with ASD are less sensitive to the temporal synchrony within audio-visual speech.

WHAT IS NEW

•In this study, infants at elevated likelihood of developing ASD showed a larger temporal binding window for adynamic social event (Speaking Face) than TD infants, suggesting less efficient multisensory integration.

Habituation: It's not what you think it is

In this review, we take a critical look at the methods used to document habituation and the theoretical assumptions that have been made about it. We point out problems associated with measuring habituation merely as a change over the course of repeated presentations of a stimulus. We argue that a common test procedure is essential to assess the relative magnitudes of habituation learning especially when different training procedures are examined. We further suggest that this would be required in order to draw meaningful conclusions about the conditions for optimizing habituation. We also challenge the view that habituation is nonassociative and consider the implications of various associative learning perspectives not only for context-specific habituation but for encoding a representation of the stimulus. We conclude with our recommendations for future research on habituation and we highlight the need to integrate behavioral and neurobiological studies.

Repeatability of an attention bias test for sheep suggests variable influence of state and trait affect on behaviour

Understanding the effects of repeated testing on behaviour is essential for behavioural tests that are re-applied to the same individuals for research and welfare assessment purposes. Assessing the repeatability of behaviour can also help us understand the influence of persistent traits vs transient states on animal responses during testing. This study examined the repeatability of behavioural responses in an attention bias test developed for sheep as a measure of affective state. Sheep were assessed in the attention bias test three times (n = 81 sheep), with testing occurring at intervals of 1 year then 2 weeks. During testing, individual sheep were exposed to a dog located behind a window for 3 s in a 4 × 4 m arena, then the dog was obscured from view, removed and sheep behaviours were recorded for 180 s. We hypothesised that behaviours in the test would have moderate-high repeatability but that the mean behavioural responses would change over consecutive trials as sheep habituated to the test environment. To estimate repeatability, data were modelled using restricted maximum likelihood linear mixed-effects models, fitting animal ID as a random effect. Vigilance behaviour, defined as having the head at or above shoulder height, was moderately repeatable (r = 0.58). Latency to eat (r = 0.20) and duration spent looking towards the previous location of the dog (attention to the dog wall) (r = 0.08) had low repeatability. Mean latency to eat did not differ significantly between trials (P = 0.2) and mean vigilance behaviour tended to decrease over the trials (P = 0.07). Mean duration of attention to the dog wall significantly decreased across the trials (P < 0.001), while mean zones crossed increased (P < 0.001), as did behaviours directed towards the exit door such as duration in proximity and pawing at the door. Overall, vigilance behaviour was moderately repeatable, suggesting it may have been driven by temperament or personality traits, while attention and feeding behaviours may have been more influenced by transient affective states or other factors, however further research is needed to better tease apart these potential effects. Sheep demonstrated some habituation to the test over consecutive trials. Care should therefore be taken during future application of the test to ensure all animals undergoing attention bias testing have equivalent experience for a valid interpretation of their relative behavioural responses.

Dispositional mindfulness, alexithymia and sensory processing: Emerging insights from habituation of the acoustic startle reflex response

There is growing evidence of beneficial effects of mindfulness developed through engaging in mindfulness training/practices on sensory and cognitive processing, emotion regulation and mental health. Mindfulness has also been conceptualised as a dispositional 'trait', i.e. the naturally-occurring ability of meditation-naïve individuals to display, in varying degree, a non-judgmental non-reactive present-moment awareness in everyday life. In this study we examined possible associations between dispositional mindfulness, alexithymia and sensory processing. Eye-blink startle responses to acoustic stimuli of varying intensity [90-dB or 100-dB over 70-dB (A) background] were assessed in 26 meditation-naïve adults (50 % men) using electromyographic recordings of the orbicularis muscle. All participants completed the Five Facet Mindfulness Questionnaire and the 20-item Toronto Alexithymia Scale. A negative association was found between dispositional mindfulness and alexithymia (r = -0.513). There was stronger startle habituation to 100-dB, compared to 90-dB probes. Stronger startle habituation (larger negative habitation slope values) to 100-dB probes was significantly associated with higher dispositional mindfulness (r = -0.528) and with lower alexithymia at trend level (r = 0.333). As indicated by commonality analysis, 10.6 % of explained variance in habituation (100-dB probes) was common to both alexithymia and mindfulness, 17.3 % was unique to mindfulness, but alexithymia made negligible unique contribution (0.5 %). These findings indicate similar startle habituation pattern in people with a high level of dispositional mindfulness to that reported previously by Antonova et al. (2015) in people with moderate mindfulness meditation practice intensity. Future studies should investigate the mechanisms, such as interoceptive awareness, that might underly these relationships.

Adaptation to social-evaluative threat: Effects of repeated acceptance and status stressors on cardiovascular reactivity

Social-evaluative threat plays a key role in research on stress, health and related psychophysiological mechanisms such as cardiovascular reactivity (CVR). Social-evaluative threats can activate two broad social motives: striving for status, achievement and influence, and/or striving for acceptance, inclusion, and connection. Prior research emphasizes threats related to status (e.g., task performance) or combined threats to status and acceptance, obscuring their independent effects. Further, because prior research has mostly utilized single stressors, it is not clear if effects of social-evaluative threats involving status and acceptance on CVR persist or adapt quickly over repeated exposures. To address these issues, 139 undergraduates (93 females) were randomly assigned to undergo two repetitions of a stressful role-played interaction with a pre-recorded antagonistic partner under one of four conditions in a factorial design: low evaluative threat, high status threat only, high acceptance threat only, or a combined threat. In a single laboratory session, systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) were recorded during baseline and two stressor exposures. Task-induced CVR demonstrated significant adaptation across exposures. Both forms of social evaluative threat produced additional CVR, and these differences between high and low social-evaluative threat were generally maintained across exposures. Hence, threats to social status and acceptance have independent and sustained effects on CVR across multiple stressor exposures, even in the context of overall adaptation of cardiovascular responses.

Behavioral and Psychosocial Risk Factors that Lead Individuals to Initiate and/or Maintain Betel Quid Chewing in Developed and Developing Countries: A Systematic Review

BACKGROUND

Betel quid (BQ) is the fourth most commonly used psychoactive substance and its use is highly prevalent among southeast Asian countries due to the influence of psychosocial, behavioral, and environmental factors. As a result, even young children and women are becoming addicted and find it difficult to achieve long-term abstinence. Systematic research addressing the influence of behavioral and psychosocial factors on BQ chewing is scarce, hence pointing to the need for understanding the interplay of these factors to develop tailored intervention strategies for BQ cessation.

OBJECTIVE

The objective of this systematic review is to assess various behavioral and psychosocial risk factors from pre-existing literature that lead individuals to initiate and/or maintain BQ chewing in developed and developing countries.

MATERIALS AND METHODS

The electronic retrieval systems and databases PUBMED [MEDLINE], EMBASE, SCOPUS, WEB OF SCIENCE, GOOGLE SCHOLAR, and SCIENCE DIRECT were searched independently by two authors for relevant articles from January 2011 to July 2021 using combinations of keywords. Primary studies published in English focusing on the behavioral and psychosocial risk factors for BQ chewing were included.

RESULTS

Out of the initial 264 articles searched, 12 articles met the selection criteria. Included studies addressed the influence of behavioral and psychosocial factors toward the initiation and/or maintenance of BQ chewing. Included studies reported that dependent BQ was not able to quit BQ chewing due to habituation, addiction, and withdrawal symptoms. Few social BQ chewers in Southeast Asian countries were not willing to initiate quitting as they considered AN as an important social and cultural identifier and claimed that they could not resist chewing in a peer group, and it has become part of their social life.

CONCLUSION

In the future, studies should take into consideration behavioral and psychosocial risk factors, which are major barriers toward successful quitting. These factors should be integrated into areca nut cessation guidelines, and there is a need to develop more comprehensive culture-specific intervention approaches to achieve long-term abstinence.

The influence of sleep on fear extinction in trauma-related disorders

In Posttraumatic Stress Disorder (PTSD), fear and anxiety become dysregulated following psychologically traumatic events. Regulation of fear and anxiety involves both high-level cognitive processes such as cognitive reattribution and low-level, partially automatic memory processes such as fear extinction, safety learning and habituation. These latter processes are believed to be deficient in PTSD. While insomnia and nightmares are characteristic symptoms of existing PTSD, abundant recent evidence suggests that sleep disruption prior to and acute sleep disturbance following traumatic events both can predispose an individual to develop PTSD. Sleep promotes consolidation in multiple memory systems and is believed to also do so for low-level emotion-regulatory memory processes. Consequently sleep disruption may contribute to the etiology of PTSD by interfering with consolidation in low-level emotion-regulatory memory systems. During the first weeks following a traumatic event, when in the course of everyday life resilient individuals begin to acquire and consolidate these low-level emotion-regulatory memories, those who will develop PTSD symptoms may fail to do so. This deficit may, in part, result from alterations of sleep that interfere with their consolidation, such as REM fragmentation, that have also been found to presage later PTSD symptoms. Here, sleep disruption in PTSD as well as fear extinction, safety learning and habituation and their known alterations in PTSD are first briefly reviewed. Then neural processes that occur during the early post-trauma period that might impede low-level emotion regulatory processes through alterations of sleep quality and physiology will be considered. Lastly, recent neuroimaging evidence from a fear conditioning and extinction paradigm in patient groups and their controls will be considered along with one possible neural process that may contribute to a vulnerability to PTSD following trauma.

Hyperreactivity and Impaired Habituation of Startle Amplitude During Unpleasant Pictures in Borderline but Not Schizotypal Personality Disorder: Quantifying Emotion Dysregulation

BACKGROUND

Borderline personality disorder (BPD) is characterized by greater intensity of reactions to unpleasant emotional cues and a slower-than-normal return of these responses to baseline. Habituation is defined as decreased response to repeated stimulation. Affect-modulated startle (AMS), a translational psychophysiological approach, is mediated by the amygdala and used to study emotion processing in both humans and animals. This is the first study to examine the specificity of habituation anomalies in BPD during passive emotional and neutral picture processing.

METHODS

A total of 90 participants were studied: patients with BPD (n = 35), patients with schizotypal personality disorder (n = 26; included as a psychopathological comparison group), and healthy control subjects (n = 29). Participants received rigorous clinical assessments, and patients were unmedicated. AMS was examined during a series of intermixed unpleasant, neutral, and pleasant pictures.

RESULTS

Compared with the other groups, patients with BPD showed greater overall AMS during unpleasant pictures and prolonged habituation of startle amplitude during unpleasant pictures from early to later trials. The groups did not differ in AMS during neutral or pleasant pictures or self-reported picture valence. Among the patients with BPD, prolonged habituation to unpleasant pictures was associated with greater symptom severity and suicidal/self-harming behavior.

CONCLUSIONS

These findings 1) indicate that abnormal processing of and habituation to unpleasant pictures is observed in BPD but not schizotypal personality disorder, suggesting that these deficits are not simply characteristics of personality disorders in general; 2) are consistent with studies showing deficient amygdala habituation to unpleasant pictures in BPD; and 3) have significant implications for clinical assessment and treatment of BPD, e.g., alternative therapies for BPD such as gradual exposure to unpleasant emotional stimuli or amygdala neurofeedback may aid habituation deficits.

Genetics, molecular control and clinical relevance of habituation learning

Habituation is the most fundamental form of learning. As a firewall that protects our brain from sensory overload, it is indispensable for cognitive processes. Studies in humans and animal models provide increasing evidence that habituation is affected in autism and related monogenic neurodevelopmental disorders (NDDs). An integrated application of habituation assessment in NDDs and their animal models has unexploited potential for neuroscience and medical care. With the aim to gain mechanistic insights, we systematically retrieved genes that have been demonstrated in the literature to underlie habituation. We identified 258 evolutionarily conserved genes across species, describe the biological processes they converge on, and highlight regulatory pathways and drugs that may alleviate habituation deficits. We also summarize current habituation paradigms and extract the most decisive arguments that support the crucial role of habituation for cognition in health and disease. We conclude that habituation is a conserved, quantitative, cognition- and disease-relevant process that can connect preclinical and clinical work, and hence is a powerful tool to advance research, diagnostics, and treatment of NDDs.

Cortisol metabolites vary with environmental conditions, predation risk, and human shields in a wild primate, Cercopithecus albogularis

Environmental challenges are often associated with physiological changes in wildlife that allow animals to maintain homeostasis. Among these, scarcity in resources, and risks from predators, competitors, and humans can all result in psychological and physiological stress. Yet, for habituated species, it is not clear whether this relationship with humans still holds to a lesser degree or is outweighed by the benefits of human presence - such as serving as a buffer from competitors or predators. We investigated how human presence and environmental challenges such as resource availability, weather, predation, and competition may be associated with variation in fecal cortisol metabolite levels (FCMs) in a group of samango monkeys (Cercopithecus albogularis) in the Soutpansberg Mountains, South Africa. FCMs can often broadly track environmental challenges and perturbations. Initially, we employed an exploratory analysis comparing candidate models representing biological hypotheses and found that those incorporating information on human presence had less weight than models for food availability, thermoregulation, and water scarcity. When we examined a subset of the data that included information on intergroup competition and predator alarm calls, we found that FCMs were higher on the day following potential predator encounters but not competitive interactions. As observer numbers increased, responses to predators flattened, indicating that the presence of several humans might deter predators and/or affect samangos' perception of danger - yet we could not distinguish between these possibilities. Together, these results suggest that ecological perturbations track with FCMs in this study population and challenge long-held assumptions that human presence has negligible effects on habituated study animals.

Longitudinal monitoring of prefrontal cortical ensemble dynamics reveals new insights into stress habituation

The prefrontal cortex is highly susceptible to the detrimental effects of stress and has been implicated in the pathogenesis of stress-related psychiatric disorders. It is not well understood, however, how stress is represented at the neuronal level in the prefrontal cortical neuronal ensembles. Even less understood is how the representation of stress changes over time with repeated exposure. Here we show that the prelimbic prefrontal neuronal ensemble representation of foot shock stress exhibits rapid spatial drift within and between sessions. Despite this rapid spatial drift of the ensemble, the representation of the stressor itself stabilizes over days. Our results suggest that stress is represented by rapidly drifting ensembles and despite this rapid drift, important features of the neuronal representation are stabilized, suggesting a neural correlate of stress habituation is present within prefrontal cortical neuron populations.

Unravelling delayed therapy escape after thalamic deep brain stimulation for essential tremor? - Additional clinical and neuroimaging evidence

BACKGROUND

Delayed therapy escape after thalamic deep brain stimulation (DBS) for essential tremor is a serious yet frequent condition. It is often difficult to detect this process at onset due to its gradual evolution.

OBJECTIVE

Here we aim to identify clinical and neuroimaging hallmarks of delayed therapy escape.

METHODS

We retrospectively studied operationalized and quantitative analyses of tremor and gait, as well as [¹⁸F]fluorodeoxyglucose (FDG) PET of 12 patients affected by therapy escape. All examinations were carried out with activated DBS (ON) and 72 h after deactivation (OFF_72h); gait and tremor were also analyzed directly after deactivation (OFF_0h). Changes of normalized glucose metabolism between stimulation conditions were assessed using within-subject analysis of variance and statistical parametric mapping. Additionally, a comparison to the [¹⁸F]FDG PET of an age-matched control group was performed. Exploratory correlation analyses were conducted with operationalized and parametric clinical data.

RESULTS

Of the immediately accessible parametric tremor data (i.e. ON or OFF_0h) only the rebound (i.e. OFF_0h) frequency of postural tremor showed possible correlations with signs of ataxia at ON. Regional glucose metabolism was significantly increased bilaterally in the thalamus and dentate nucleus in ON compared to OFF_72h. No differences in regional glucose metabolism were found in patients in ON and OFF_72h compared with the healthy controls.

CONCLUSIONS

Rebound frequency of postural tremor seems to be a good diagnostic marker for delayed therapy escape. Regional glucose metabolism suggests that this phenomenon may be associated with increased metabolic activity in the thalamus and dentate nucleus possibly due to antidromic stimulation effects. We see reasons to interpret the delayed therapy escape phenomenon as being related to long term and chronic DBS.

Avoid or seek light - a randomized crossover fMRI study investigating opposing treatment strategies for photophobia in migraine

Background

Photophobia, the aberrantly increased sensitivity to light, is a common symptom in migraine patients and light discomfort is frequently found as a trigger for migraine attacks. In behavioral studies, planned exposure to light was found to reduce headache in migraine patients with photophobia, potentially by increasing habituation to this migraine trigger. Here, we aimed to elucidate neurophysiological mechanisms of light exposure versus light deprivation in migraine patients using functional magnetic resonance imaging (fMRI).

Methods

Ten migraine patients (9 female, age = 28.70 ± 8.18 years) and 11 healthy controls (9 female, age = 23.73 ± 2.24 years) spent one hour on 7 consecutive days exposed to flashing light (Flash) or darkness (Dark) using a crossover design with a wash-out period of 3 months. Study participants kept a diary including items on interictal and ictal photophobia, presence and severity of headache 7 days before, during and 7 days after the interventions. One week before and one day after both interventions, fMRI using flickering light in a block design was applied. Functional activation was analyzed at whole-brain level and habituation of the visual cortex (V1) was modeled with the initial amplitude estimate and the corrected habituation slope.

Results

Mean interictal photophobia decreased after both interventions, but differences relative to the baseline did not survive correction for multiple comparisons. At baseline, flickering light induced activation in V1 was higher in the patients compared to the controls, but activation normalized after the Flash and the Dark interventions. V1 habituation indices correlated with headache frequency, headache severity and ictal photophobia. In the Flash condition, the individual change of headache frequency relative to the baseline corresponded almost perfectly to the change of the habituation slope compared to the baseline.

Conclusions

On average, light exposure did not lead to symptom relief, potentially due to the short duration of the intervention and the high variability of the patients’ responses to the intervention. However, the strong relationship between visual cortex habituation and headache symptoms and its modulation by light exposure might shed light on the neurophysiological basis of exposure treatment effects.

Trial registration

NCT05369910 (05/06/2022, retrospectively registered).

Exposure to humans after weaning does not reduce the behavioural reactivity of extensively reared Merino lambs

Human-directed fear in extensively reared sheep is often high due to the aversive nature of common husbandry procedures and infrequent interactions with humans. This study investigated whether additional human exposure provided to weaned lambs reduced human-directed fear and behavioural reactivity. Ninety Merino lambs were either exposed to low or moderately stressful human exposure sessions, or had no additional human contact, and their fear responses and behavioural reactivity to humans, a startle stimulus and confinement were tested. Overall, the imposed interventions did not reduce behavioural reactivity during these tests, suggesting fear towards humans had not been altered.

Arc-Mediated Plasticity in the Paraventricular Thalamic Nucleus Promotes Habituation to Stress

BACKGROUND

Habituation is defined as a progressive decline in response to repeated exposure to a familiar and predictable stimulus and is highly conserved across species. Disrupted habituation is a signature of posttraumatic stress disorder. In rodents, habituation is observed in neural, neuroendocrine, and behavioral responses to repeated exposure to predictable and moderately intense stress or restraint. We previously demonstrated that lesioning the posterior paraventricular thalamic nucleus (pPVT) impairs habituation. However, the underlying molecular mechanisms and specific neural connections among the pPVT and other brain regions that underlie habituation are unknown.

METHODS

Behavioral and neuroendocrine habituation was assessed in adult male Sprague Dawley rats using the repeated restraint paradigm. Pan-neuronal and Cre-dependent DREADDs (designer receptors exclusively activated by designer drugs) were used to chemogenetically inhibit the pPVT and the subpopulation of pPVT neurons that project to the medial prefrontal cortex (mPFC), respectively. Activity-regulated cytoskeleton-associated protein (Arc) expression was knocked down in the pPVT using small interfering RNA. Structural plasticity of pPVT neurons was assessed using Golgi staining. Local field potential recordings were used to assess coherent neural activity between the pPVT and mPFC. The attentional set shifting task was used to assess mPFC-dependent behavior.

RESULTS

Here, we show that Arc promotes habituation by increasing stress-induced spinogenesis in the pPVT, increasing coherent neural activity with the mPFC, and improving mPFC-mediated cognitive flexibility.

CONCLUSIONS

Our results demonstrate that Arc induction in the pPVT regulates habituation and mPFC function. Therapies that improve synaptic plasticity during posttraumatic stress disorder therapy may enhance habituation and the efficacy of posttraumatic stress disorder treatment.

Prevention of self-grooming in rats: Evidence for a rebound effect

Rodent self-grooming is a stereotyped behavior that can rise due to stressors such as novelty. In the present study, the occurrence of a rebound effect was investigated by means of manipulation of contextual novelty and of the possibility of self-grooming (with an Elizabethan collar which blocked head-body contact). Fourty-six male rats were submitted to an experiment latter replicated with 43 females. Half of the animals were submitted to habituation sessions (30 min) to the test box in three days. The other half was similarly handled but habituated to small cages. On the fourth day, rats from both conditions were assigned to Elizabethan or sham collar groups. Each animal was observed for 15 min with its respective collar and for other 15 min with no collars. Increased locomotion was observed in the rats not habituated to the test box. Such habituation did not affect any grooming parameter. On the other hand, the animals wearing Elizabethan collars during the first half of the test, as compared to those which wore sham collars, showed increased self-grooming during the second half of the test (i.e., with no collars). Females showed pretty similar results. Present results, thus, evidence a rebound effect in self-grooming.

Cumulative additional information does not improve the neuromuscular control during postural responses to perturbations in postural instability/gait disorders subtype of Parkinson's disease

BACKGROUND

Postural response impairments in postural instability and gait disorders (PIGD) subtype patients may be attributed to Parkinson's disease (PD)-deterioration in central-set (programing/modulating of central outputs during motor responses). Although additional information improves some PD motor impairments, an unanswered question is whether additional information can benefit postural response in PIGD subtype.

OBJECTIVE

To analyze the effect of cumulative additional information on postural responses after perturbation in PIGD and neurologically healthy older adults (CG).

METHODS

Perturbations were applied in 16 PIGD and 19 CG by the support-base translation. Participants performed 3 blocks of 5 trials without additional information (B1-B3, Day 1) and 5 trials of each cumulative additional information (C1-C4, Day 2): information about perturbation (C1), visual (C2), verbal (C3), and somatosensory information (C4). Electromyography and center of pressure (CoP) parameters were analyzed by ANOVAs with Group (PIGD × CG) and Block (B1 × B2 × B3) and with Group (PIGD × CG) and Condition (B3 × C1 × C2 × C3 × C4).

RESULTS

PIGD decreased the range of CoP in B3 while CG decreased both range of CoP and the integral of antagonist's muscle activity (iEMG) in B2. Also, PIGD decreased the recovery time in C4 while CG increased the iEMG of agonist's muscle in C2 and antagonist's muscle in all conditions except C2.

CONCLUSION

Additional information provided before postural control assessment influences the postural response in PIGD and CG differently. PIGD demonstrated inflexibility of central-set in modulating the neuromuscular control regardless of additional information. CG presents a flexible system evidenced by the increase of agonist muscle iEMG when provided visual information.

Rapid assessment of the temporal function and phenotypic reversibility of neurodevelopmental disorder risk genes in Caenorhabditis elegans

Recent studies have indicated that some phenotypes caused by decreased function of select neurodevelopmental disorder (NDD) risk genes can be reversed by restoring gene function in adulthood. However, few of the hundreds of risk genes have been assessed for adult phenotypic reversibility. We developed a strategy to rapidly assess the temporal requirements and phenotypic reversibility of NDD risk gene orthologs using a conditional protein degradation system and machine-vision phenotypic profiling in Caenorhabditis elegans. We measured how degrading and re-expressing orthologs of EBF3, BRN3A and DYNC1H1 at multiple periods throughout development affect 30 morphological, locomotor, sensory and learning phenotypes. We found that phenotypic reversibility was possible for each gene studied. However, the temporal requirements of gene function and degree of rescue varied by gene and phenotype. This work highlights the critical need to assess multiple windows of degradation and re-expression and a large number of phenotypes to understand the many roles a gene can have across the lifespan. This work also demonstrates the benefits of using a high-throughput model system to prioritize NDD risk genes for re-expression studies in other organisms.

Summary: We identified diverse temporal functional windows and phenotypic reversibility profiles for three neurodevelopmental disorder risk genes: EBF3•unc-3, BRN3A•unc-86 and DYNC1H1•dhc-1. Re-expression of certain genes could rescue multiple phenotypes later in life, prioritizing them for study.

Sensory over-responsivity and obsessive-compulsive disorder: Measuring habituation and sensitivity through self-report, physiological and behavioral indices

Individuals with obsessive-compulsive disorder (OCD) may report Sensory Over Responsivity (SOR), but evidence for specific shared mechanism is limited. This study investigated a habituation-sensitivity mechanism in individuals with OCD (n = 30). Sensory habituation and sensitivity were compared with a neurotypical sample, divided to high (n = 30) and low (n = 30) obsessive-compulsive symptoms (HOCS and LOCS). Participants completed self-report sensory questionnaires and a physiological protocol measuring Electro Dermal Activity (EDA) while presenting aversive and neutral sounds in two conditions: Aversive stimuli followed by neutral stimuli (AVfirst), or neutral stimuli followed by aversive stimuli (NEfirst). In addition, participants could shorten the stimulus duration by pressing a key. LOCS differed from HOCS and OCD in most sensory self-report scores, with no significant difference between OCD and HOCS. HOCS had no significant differences in habituation patterns across conditions, while OCD had no differences in habituation patterns in AVfirst (p = .08) but significantly slower habituation patterns to the NEfirst neutral stimuli (p < .001). Condition order determined sensitivity for LOCS (AVfirst p = .017; NEfirst p = .045) but not for OCD and HOCS. HOCS and OCD shortened aversive stimuli by key pressing more than LOCS, with no significant difference between OCD and HOCS. The habituation process of individuals with OCD and HOCS was more influenced by stimulus type than by condition order, which might be due to a cognitive bias of prediction. Individuals with elevated OCS have difficulty relying upon sensory input to respond adaptively to the environment. This process can explain the avoidant behavior and complains of individuals with OCD not being able to ignore and to habituate to the sensory environment. These evidence warrants design of psychoeducation and intervention methods for relying on prior sensory information to improve functioning in individuals with OCD and SOR.

Role of CRF1 and CRF2 receptors in the lateral hypothalamus in cardiovascular and anxiogenic responses evoked by restraint stress in rats: Evaluation of acute and chronic exposure

We investigated the role of corticotropin-releasing factor (CRF) neurotransmission within the lateral hypothalamus (LH) in cardiovascular and anxiogenic-like responses evoked by acute and repeated restraint stress in rats. For this, animals were subjected to intra-LH microinjection of a selective CRF₁ (CP376395) or CRF₂ (antisauvagine-30) receptor antagonist before either an acute or the 10th session of restraint stress. Restraint-evoked arterial pressure and heart rate increases, tail skin temperature decrease and anxiogenic-like effect in the elevated plus maze (EPM) were evaluated. We also assessed the effect of 10 daily sessions of restraint on expression of CRF₁ and CRF₂ receptors within the LH. We identified that antagonism of either CRF₁ or CRF₂ receptor within the LH decreased the tachycardia during both the acute and 10th session of restraint, but the effect of the CRF₁ receptor antagonist was more pronounced during the 10th session. Acute restraint stress also caused anxiogenic-like effect, and this response was inhibited in animals treated with either CP376395 or antisauvagine-30. Anxiety-like behaviors were not changed following the 10th session of restraint, and pharmacological treatments did not affect the behavior in the EPM in chronically stressed animals. Repeated restraint also did not change the level of the CRF receptors within the LH. Taken together, the findings indicate that CRF₁ and CRF₂ receptors within the LH are involved in tachycardic and anxiogenic-like responses to aversive stimuli. Control of tachycardia by the CRF₁ receptor is sensitized by previous stressful experience, and this effect seems to be independent of changes in expression of the receptor.

Attenuation and recovery of an avoidance response to a chemical antipredator cue in an invasive fish: implications for use as a repellent in conservation

The detection of predation risk without direct engagement with a predator is an important driver of prey movement strategies. Consequently, the application of alarm cues may prove an effective tool in guiding the movements of fishes targeted for control or conservation. However, failure to contemplate the sensory, physiological and cognitive outcomes of repeated or persistent exposure to the cue will likely lead to poor performance of management practices. Using a series of behavioural tests and physiological recordings from the olfactory organ, we examined the timing of onset and recovery of the alarm response in sea lamprey (Petromyzon marinus L.) when exposed continuously or sporadically to its alarm cue. In the laboratory, sea lamprey exhibited short-term, reversible attenuation of the alarm response over 2-4 h with continuous exposure. The alarm response spontaneously recovered after 30-60 min of removal from the cue. In long-duration free-swimming tests, where the animals were allowed to move into and out of the odour plume volitionally, repeated but sporadic encounter with the alarm cue over 5 h did not alter the alarm response. Electro-olfactogram recordings from the main olfactory epithelium indicated that olfactory sensory neurons quickly adapt to alarm cue and recovered within 15 min. Our findings strongly implicate habituation as the mechanism that induces reduction in the alarm response and provide insight into the design of effective management practices that seek to use fish alarm cues as repellents.

Responsiveness of domesticated goats towards various stressors following long-term cognitive test exposure

Current evidence suggests that frequent exposure to situations in which captive animals can solve cognitive tasks may have positive effects on stress responsiveness and thus on welfare. However, confounding factors often hamper the interpretation of study results. In this study, we used human-presented object-choice tests (in form of visual discrimination and reversal learning tests and a cognitive test battery), to assess the effect of long-term cognitive stimulation (44 sessions over 4-5 months) on behavioural and cardiac responses of female domestic goats in subsequent stress tests. To disentangle whether cognitive stimulation per se or the reward associated with the human-animal interaction required for testing was affecting the stress responsiveness, we conditioned three treatment groups: goats that were isolated for participation in human-presented cognitive tests and rewarded with food ('Cognitive', COG treatment), goats that were isolated as for the test exposure and rewarded with food by the experimenter without being administered the object-choice tests ('Positive', POS treatment), and goats that were isolated in the same test room but neither received a reward nor were administered the tests ('Isolation', ISO treatment). All treatment groups were subsequently tested in four stress tests: a novel arena test, a novel object test, a novel human test, and a weighing test in which goats had to enter and exit a scale cage. All treatment groups weretested at the same two research sites, each using two selection lines, namely dwarf goats, not selected for production traits, and dairy goats, selected for high productivity. Analysing the data with principal component analysis and linear mixed-effects models, we did not find evidence that cognitive testing per se (COG-POS contrast) reduces stress responsiveness of goats in subsequent stress tests. However, for dwarf goats but not for dairy goats, we found support for an effect of reward-associated human-animal interactions (POS-ISO contrast) at least for some stress test measures. Our results highlight the need to consider ontogenetic and genetic variation when assessing stress responsiveness and when interacting with goats.

How does risk preference change under the stress of COVID-19? Evidence from Japan

In this study, we investigated whether the risk preference systematically changed during the spread of COVID-19 in Japan. Traditionally, risk preference is assumed to be stable over one's life, though it differs among individuals. While recent studies have reported that it changes with a large event like natural disasters and financial crisis, they have not reached a consensus on its direction, risk aversion, or tolerance. We collected panel data of Japanese individuals in five waves from March to June 2020, which covered the period of the first cycle when COVID-19 spread rapidly and then dwindled. We measured risk preference through questions on the willingness to pay for insurance. The main results are as follows: First, people became more risk tolerant throughout the period; and second, people were more averse to mega risk than moderate risk, with the former correlating more strongly with the individual's perception of COVID-19. The first result may be interpreted as "habituation" to repeated stress, as is understood in neuroscience.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11166-022-09374-z.

Effects of body ownership illusion during exposure to disgusting stimuli

BACKGROUND

The Rubber Hand Illusion (RHI) refers to the feeling of ownership of a rubber hand by synchronously stroking the rubber hand and the own hand of a person. Previous research has shown that RHI can be used to simulate skin contact with a disgust-eliciting stimulus. We used a primary disgust elicitor (a living maggot) to replicate this finding and to gather data on disgust habituation during RHI, and effects on in-vivo exposure.

METHODS

A total of 82 healthy participants (25 males, 57 females) were randomly assigned to one of two conditions; synchronous stroking or asynchronous stroking (control condition) of the rubber/own hand. Subsequently, a maggot was placed on the rubber hand for five minutes. Participants rated experienced disgust at the beginning and end of the exposure. They were also asked if the maggot could be placed on their own hand.

RESULTS

Synchronous stroking successfully elicited RHI, which was associated with higher disgust ratings for the maggot at the beginning of exposure compared to asynchronous stroking. The two conditions did not differ in disgust habituation and the willingness to expose the own hand to the maggot.

CONCLUSION

RHI successfully simulated skin contact with a disgust stimulus. Future studies should apply longer exposure intervals and test individuals with higher disgust propensity to detect possible RHI effects on disgust habituation.

Recording the ventilation activity of free-swimming zebrafish and its application to novel tank tests

Bioelectric signals related to ventilatory movements in fish can be detected via externally located electrodes. In this study, a technique to continuously monitor the electric ventilatory signals in free-swimming zebrafish was developed. This technique was applied to monitoring ventilation activity as a physiological measure in conjunction with various behavioral measures in a novel tank environment. It was found that in addition to ventilation rate, time domain analysis of changes in ventilation rate is useful for evaluating the emotional state of zebrafish. By integrating the physiological and behavioral measures in analyses, a 1 h novel tank test trial revealed that the habituation process involves two phases. The first phase, which lasted 10 min, involved rapid attenuation of the initial fear/anxiety response to encountering a novel environment. The second phase lasted 20 min and involved further attenuation of anxiety and an increase in exploration behavior. These data suggest that combining ventilation-related physiological measures with conventional behavioral measures enables multidimensional examination of the habituation process in a novel tank environment with more precision than is possible when relying on behavioral responses alone.

Mechanisms of exposure and response prevention in obsessive-compulsive disorder: effects of habituation and expectancy violation on short-term outcome in cognitive behavioral therapy

BACKGROUND

Exposure and response prevention is effective and recommended as the first choice for treating obsessive-compulsive disorders (OCD). Its mechanisms of action are rarely studied, but two major theories make distinct assumptions: while the emotional processing theory assumes that treatment effects are associated with habituation within and between exposure sessions, the inhibitory learning approach highlights the acquisition of additional associations, implying alternative mechanisms like expectancy violation. The present study aimed to investigate whether process variables derived from both theories predict short-term outcome.

METHOD

In a university outpatient unit, 110 patients (63 female) with OCD received manual-based cognitive-behavioral therapy with high standardization of the first two exposure sessions. Specifically, therapists repeated the first exposure session identically and assessed subjective units of distress as well as expectancy ratings in the course of exposure sessions. Based on these data, individual scores for habituation and distress-related expectancy violation were calculated and used for prediction of both percentage change on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and remission status after 20 therapy sessions.

RESULTS

In a multiple regression model for percentage change, within-session habituation during the first exposure was a significant predictor, while in a logistic regression predicting remission status, distress-related expectancy violation during the first exposure revealed significance. A path model further supported these findings.

CONCLUSIONS

The results represent first evidence for distress-related expectancy violation and confirm preliminary findings for habituation, suggesting that both processes contribute to treatment benefits of exposure in OCD, and both mechanisms appear to be independent.