Stress and laterality – The comparative perspective

A longitudinal study on the impact of high-altitude hypoxia on perceptual processes

This study aimed to explore the neural mechanisms underlying high-altitude (HA) adaptation and deadaptation in perceptual processes in lowlanders. Eighteen healthy lowlanders were administered a facial S1-S2 matching task that included incomplete face (S1) and complete face (S2) photographs combined with ERP technology. Participants were tested at four time points: shortly before they departed the HA (Test 1), twenty-five days after entering the HA (Test 2), and one week (Test 3) and one month (Test 4) after returning to the lowlands. Compared with those at sea level (SL), shorter reaction times (RTs), shorter latencies of P1 and N170, and larger amplitudes of complete face N170 were found in HAs. After returning to SL, compared with that of HA, the amplitude of the incomplete face P1 was smaller after one week, and the complete face was smaller after one month. The right hemisphere N170 amplitude was greater after entering HA and one week after returning to SL than at baseline, but it returned to baseline after one month. Taken together, the current findings suggest that HA adaptation increases visual cortex excitation to accelerate perceptual processing. More mental resources are recruited during the configural encoding stage of complete faces after HA exposure. The perceptual processes affected by HA exposure are reversible after returning to SL, but the low-level processing stage differs between incomplete and complete faces due to neural compensation mechanisms. The configural encoding stage in the right hemisphere is affected by HA exposure and requires more than one week but less than one month to recover to baseline.

Associations between somatomotor-putamen resting state connectivity and obsessive-compulsive symptoms vary as a function of stress during early adolescence: Data from the ABCD study

Obsessive-compulsive symptoms (OCS) are relatively common during adolescence although most individuals do not meet diagnostic criteria for obsessive-compulsive disorder (OCD). Nonetheless, OCS during adolescence are associated with comorbid psychopathologies and behavioral problems. Heightened levels of environmental stress and greater functional connectivity between the somatomotor network and putamen have been previously associated with elevated OCS in OCD patients relative to healthy controls. However, the interaction of these factors within the same sample of individuals has been understudied. This study examined somatomotor-putamen resting state connectivity, stress, and their interaction on OCS in adolescents from 9-12 years of age. Participants (n = 6386) were drawn from the ABCD Study 4.0 release. Multilevel modeling was used to account for nesting in the data and to assess changes in OCS in this age range. Stress moderated the association between somatomotor-putamen connectivity and OCS (β = 0.35, S.E. = 0.13, p = 0.006). Participants who reported more stress than their average and had greater somatomotor-left putamen connectivity reported more OCS, whereas participants who reported less stress than their average and had greater somatomotor-left putamen connectivity reported less OCS. These data suggest that stress differentially affects the direction of association between somatomotor-putamen connectivity and OCS. Individual differences in the experience or perception of stress may contribute to more OCS in adolescents with greater somatomotor-putamen connectivity.

Reduced neural responses to pleasant odor stimuli after acute psychological stress is associated with cortisol reactivity

Acute stress alters olfactory perception. However, little is known about the neural processing of olfactory stimuli after acute stress exposure and the role of cortisol in such an effect. Here, we used an event-related olfactory fMRI paradigm to investigate brain responses to odors of different valence (unpleasant, pleasant, or neutral) in healthy young adults following an acute stress (Trier Social Stress Test, TSST) induction (N = 22) or a non-stressful resting condition (N = 22). We obtained the odor pleasantness, intensity, and familiarity ratings after the acute stress induction or resting condition. We also measured the participants' perceived stress and salivary cortisol at four time points during the procedure. We found a stress-related decrease in brain activation in response to the pleasant, but not to the neutral or unpleasant odor stimuli in the right piriform cortex extending to the right amygdala, the right orbitofrontal cortex, and the right insula. In addition, activation of clusters within the regions of interest were negatively associated with individual baseline-to-peak increase in salivary cortisol levels after stress. We also found increased functional connectivity between the right piriform cortex and the right insula after stress when the pleasant odor was presented. The strength of the connectivity was positively correlated with increased perceived stress levels immediately after stress exposure. These results provide novel evidence for the effects of acute stress in attenuating the neural processing of a pleasant olfactory stimulus. Together with previous findings, the effect of acute stress on human olfactory perception appears to depend on both the valence and the concentration (e.g., peri-threshold or suprathreshold levels) of odor stimuli.

Neural responses to acute stress predict chronic stress perception in daily life over 13 months

The importance of amygdala, hippocampus, and medial prefrontal cortex (mPFC) for the integration of neural, endocrine, and affective stress processing was shown in healthy participants and patients with stress-related disorders. The present manuscript which reports on one study-arm of the LawSTRESS project, aimed at investigating the predictive value of acute stress responses in these regions for biopsychological consequences of chronic stress in daily life. The LawSTRESS project examined law students either in preparation for their first state examination (stress group [SG]) or in the mid-phase of their study program (control group [CG]) over 13 months. Ambulatory assessments comprising perceived stress measurements and the cortisol awakening response (CAR) were administered on six sampling points (t1 = - 1 year, t2 = - 3 months, t3 = - 1 week, t4 = exam, t5 =  + 1 week, t6 =  + 1 month). In a subsample of 124 participants (SG: 61; CG: 63), ScanSTRESS was applied at baseline. In the SG but not in the CG, amygdala, hippocampus, and (post-hoc analyzed) right mPFC activation changes during ScanSTRESS were significantly associated with the trajectory of perceived stress but not with the CAR. Consistent with our finding in the total LawSTRESS sample, a significant increase in perceived stress and a blunted CAR over time could be detected in the SG only. Our findings suggest that more pronounced activation decreases of amygdala, hippocampus, and mPFC in response to acute psychosocial stress at baseline were related to a more pronounced increase of stress in daily life over the following year.

Hemispheric asymmetries in mental disorders: evidence from rodent studies

The brain is built with hemispheric asymmetries in structure and function to enable fast neuronal processing. In neuroimaging studies, several mental disorders have been associated with altered or attenuated hemispheric asymmetries. However, the exact mechanism linking asymmetries and disorders is not known. Here, studies in animal models of mental disorders render important insights into the etiology and neuronal alterations associated with both disorders and atypical asymmetry. In this review, the current literature of animal studies in rats and mice focusing on anxiety and fear, anhedonia and despair, addiction or substance misuse, neurodegenerative disorders as well as stress exposure, and atypical hemispheric asymmetries is summarized. Results indicate overall increased right-hemispheric neuronal activity and a left-sided behavioral bias associated with symptoms of anxiety, fear, anhedonia, behavioral despair as well as stress exposure. Addiction behavior is associated with right-sided bias and transgenic models of Alzheimer's disease indicate an asymmetrical accumulation of fibrillar plaques. Most studies focused on changes in the bilateral amygdala and frontal cortex. Across studies, two crucial factors influencing atypical asymmetries arose independently of the disorder modeled: sex and developmental age. In conclusion, animal models of mental disorders demonstrate atypical hemispheric asymmetries similar to findings in patients. Particularly, increased left-sided behavior and greater right-hemispheric activity were found across models applying stress-based paradigms. However, sex- and age-dependent effects on atypical hemispheric asymmetries are present that require further investigation. Animal models enable the analysis of hemispheric changes on the molecular level which may be most effective to detect early alterations.

A 108-h total sleep deprivation did not impair fur seal performance in delayed matching to sample task

While the majority of studies have concluded that sleep deprivation causes detrimental effects on various cognitive processes, some studies reported conflicting results. We examined the effects of a 108-h total sleep deprivation (TSD) on working memory in the northern fur seal, an animal with unusual sleep phenomenology and long-range annual migrations. The performance of fur seals was evaluated in a two-choice visual delayed matching to sample (DMTS) task, which is commonly used to evaluate working memory. In baseline conditions, the performance of fur seals in a DMTS task based on the percentage of errors was somewhat comparable with that in nonhuman primates at similar delays. We have determined that a 108-h TSD did not affect fur seals' performance in a visual DMTS task as measured by overall percentage of errors and response latencies. On the contrary, all fur seals improved task performance over the study, including the baseline, TSD and recovery conditions. In addition, TSD did not change the direction and strength of the pattern of behavioral lateralization in fur seals. We conclude that a 108-h TSD did not interfere with working memory in a DMTS test in northern fur seals.

Knowledge of lateralized brain function can contribute to animal welfare

The specialized functions of each hemisphere of the vertebrate brain are summarized together with the current evidence of lateralized behavior in farm and companion animals, as shown by the eye or ear used to attend and respond to stimuli. Forelimb preference is another manifestation of hemispheric lateralization, as shown by differences in behavior between left- and right-handed primates, left- and right-pawed dogs and cats, and left- and right-limb-preferring horses. Left-limb preference reflects right hemisphere use and is associated with negative cognitive bias. Positive cognitive bias is associated with right-limb and left-hemisphere preferences. The strength of lateralization is also associated with behavior. Animals with weak lateralization of the brain are unable to attend to more than one task at a time, and they are more easily stressed than animals with strong lateralization. This difference is also found in domesticated species with strong vs. weak limb preferences. Individuals with left-limb or ambilateral preference have a bias to express functions of the right hemisphere, heightened fear and aggression, and greater susceptibility to stress. Recognition of lateralized behavior can lead to improved welfare by detecting those animals most likely to suffer fear and distress and by indicating housing conditions and handling procedures that cause stress.

Assessment of Frontal Hemispherical Lateralization in Plaque Psoriasis and Atopic Dermatitis

BACKGROUND

Each brain hemisphere plays a specialized role in cognitive and behavioral processes, known as hemispheric lateralization. In chronic skin diseases, such as plaque psoriasis (Pso) and atopic dermatitis (AD), the degree of lateralization between the frontal hemispheres may provide insight into specific connections between skin diseases and the psyche. This study aims to analyze the hemispherical lateralization, neurovegetative responses, and psychometric characteristics of patients with Pso and AD.

METHODS

The study included 46 patients with Pso, 56 patients with AD, and 29 healthy control (Ctrl) subjects. The participants underwent frontal electroencephalogram (EEG) measurement, heart rate variability (HRV) assessment, and psychological tests. Statistical analyses were performed using ANOVA, with Bonferroni correction applied for multiple comparisons.

RESULTS

This study shows a significant right-lateralized prefrontal activity in both AD patients (p < 0.001) and Pso patients (p = 0.045) compared with Ctrl, with no significant difference between the AD and Pso groups (p = 0.633). AD patients with right-hemispheric dominant prefrontal activation exhibited increased inhibition and avoidance markers, while Pso patients showed elevated sympathetic nervous system activity.

CONCLUSION

Psychophysiological and psychometric data suggest a shared prevalence of right-hemispheric dominance in both AD and Pso patient groups. However, the findings indicate distinct psychodermatological mechanisms in AD and Pso.

Serotonin transporter (5-HTT) gene network moderates the impact of prenatal maternal adversity on orbitofrontal cortical thickness in middle childhood

In utero, the developing brain is highly susceptible to the environment. For example, adverse maternal experiences during the prenatal period are associated with outcomes such as altered neurodevelopment and emotion dysregulation. Yet, the underlying biological mechanisms remain unclear. Here, we investigate whether the function of a network of genes co-expressed with the serotonin transporter in the amygdala moderates the impact of prenatal maternal adversity on the structure of the orbitofrontal cortex (OFC) in middle childhood and/or the degree of temperamental inhibition exhibited in toddlerhood. T1-weighted structural MRI scans were acquired from children aged 6-12 years. A cumulative maternal adversity score was used to conceptualize prenatal adversity and a co-expression based polygenic risk score (ePRS) was generated. Behavioural inhibition at 18 months was assessed using the Early Childhood Behaviour Questionnaire (ECBQ). Our results indicate that in the presence of a low functioning serotonin transporter gene network in the amygdala, higher levels of prenatal adversity are associated with greater right OFC thickness at 6-12 years old. The interaction also predicts temperamental inhibition at 18 months. Ultimately, we identified important biological processes and structural modifications that may underlie the link between early adversity and future deviations in cognitive, behavioural, and emotional development.

Serum cortisol is negatively related to hippocampal volume, brain structure, and memory performance in healthy aging and Alzheimer's disease

Objective

Elevated cortisol levels have been frequently reported in Alzheimer's disease (AD) and linked to brain atrophy, especially of the hippocampus. Besides, high cortisol levels have been shown to impair memory performance and increase the risk of developing AD in healthy individuals. We investigated the associations between serum cortisol levels, hippocampal volume, gray matter volume and memory performance in healthy aging and AD.

Methods

In our cross-sectional study, we analyzed the relationships between morning serum cortisol levels, verbal memory performance, hippocampal volume, and whole-brain voxel-wise gray matter volume in an independent sample of 29 healthy seniors (HS) and 29 patients along the spectrum of biomarker-based AD.

Results

Cortisol levels were significantly elevated in patients with AD as compared to HS, and higher cortisol levels were correlated with worse memory performance in AD. Furthermore, higher cortisol levels were significantly associated with smaller left hippocampal volumes in HS and indirectly negatively correlated to memory function through hippocampal volume. Higher cortisol levels were further related to lower gray matter volume in the hippocampus and temporal and parietal areas in the left hemisphere in both groups. The strength of this association was similar in HS and AD.

Conclusion

In AD, cortisol levels are elevated and associated with worse memory performance. Furthermore, in healthy seniors, higher cortisol levels show a detrimental relationship with brain regions typically affected by AD. Thus, increased cortisol levels seem to be indirectly linked to worse memory function even in otherwise healthy individuals. Cortisol may therefore not only serve as a biomarker of increased risk for AD, but maybe even more importantly, as an early target for preventive and therapeutic interventions.

Acute and chronic stress alter behavioral laterality in dogs

Dogs are one of the key animal species in investigating the biological mechanisms of behavioral laterality. Cerebral asymmetries are assumed to be influenced by stress, but this subject has not yet been studied in dogs. This study aims to investigate the effect of stress on laterality in dogs by using two different motor laterality tests: the Kong™ Test and a Food-Reaching Test (FRT). Motor laterality of chronically stressed (n = 28) and emotionally/physically healthy dogs (n = 32) were determined in two different environments, i.e., a home environment and a stressful open field test (OFT) environment. Physiological parameters including salivary cortisol, respiratory rate, and heart rate were measured for each dog, under both conditions. Cortisol results showed that acute stress induction by OFT was successful. A shift towards ambilaterality was detected in dogs after acute stress. Results also showed a significantly lower absolute laterality index in the chronically stressed dogs. Moreover, the direction of the first paw used in FRT was a good predictor of the general paw preference of an animal. Overall, these results provide evidence that both acute and chronic stress exposure can change behavioral asymmetries in dogs.

Performance on inhibitory tasks does not relate to handedness in several small groups of Callitrichids

Brain lateralization, a trait ubiquitous in vertebrates and invertebrates, refers to structural differences between the left and right sides of the brain or to the left and right sides controlling different functions or processing information in different ways. Many studies have looked into the advantages of lateralized brains and discovered that cerebral lateralization confers a fitness advantage. Enhancing cognitive ability has been proposed as one of the potential benefits of the lateralized brain, however, this has not been widely validated. In this study, we investigated the handedness of 34 subjects from four groups of Callitrichids, as well as their performance in two inhibitory control tasks (the revised A-not-B task and the cylinder task). The subjects had strong individual hand preferences, and only a few zoo-born individuals were ambidextrous. Sex and generation influence the strength of hand preference. In the cylinder task, the subjects showed differences between groups, and the performance of the second-generation was better than that of the first-generation. We found that neither the strength of hand preferences (ABS-HI) or direction of hand preferences (HI) was linked with success on the two inhibitory tasks. That is, we were unable to support the enhanced cognitive function hypothesis. We believe that individual ontogeny and the type of cognitive task have an impact on the support of this hypothesis. The advantages of lateralized brain may be reflected in tests that require multiple cognitive abilities.

Laterality in the Damaraland Mole-Rat: Insights from a Eusocial Mammal

Lateralization is the functional control of certain behaviors in the brain being processed by either the left or right hemisphere. Behavioral asymmetries can occur at an individual and population level, although population-level lateralization is less common amongst solitary species, whereas social species can benefit more from aligning and coordinating their activities. We assessed laterality (individual and population) through turning biases in the eusocial Damaraland mole rat, Fukomys damarensis. We considered factors such as breeding status (queen or subordinate), environment (wild-caught or captive), sex (male or female), colony and body mass. All individuals together demonstrated significant left-turning biases, which was also significant at the population level. Wild-caught animals were more strongly lateralized, had a wider spread over a laterality index and lacked the population-level left-turning bias as compared to captive mole rats. Subordinate animals were more lateralized than queens, demonstrating social status differences in turning biases for social mole rats. This emphasizes the importance of animal handling and context when measuring and interpreting behavioral asymmetries.

Behavioral lateralization of mice varying in serotonin transporter genotype

In humans, non-right-handedness is associated with a higher incidence of psychiatric disorders. Since serotonin seems to be involved in both, the development of psychiatric disorders and lateralization, the present study focuses on the effect of the serotonin transporter (5-HTT) gene on behavioral lateralization. For this, we used the 5-HTT knockout mouse model, a well-established animal model for the study of human depression and anxiety disorders. For female mice from all three 5-HTT genotypes (wild type, heterozygous, and homozygous knockout), we repeatedly observed the direction and strength of lateralization of the following four behaviors: grid climbing (GC), food-reaching in an artificial test situation (FRT), self-grooming (SG), and barrier crossing (BC), with the FRT being the standard test for assessing behavioral lateralization in mice. We found no association between behavioral lateralization and 5-HTT genotype. However, in accordance with previous findings, the strength and temporal consistency of lateralization differed between the four behaviors observed. In conclusion, since the 5-HTT genotype did not affect behavioral lateralization in mice, more research on other factors connected with behavioral lateralization and the development of symptoms of psychiatric disorders, such as environmental influences, is needed.

A single dose of hydrocortisone does not alter interhemispheric transfer of information or transcallosal integration

Stress has been suggested as a factor that may explain the link between altered functional lateralization and psychopathology. Modulation of the function of the corpus callosum via stress hormones may be crucial in this regard. Interestingly, there is evidence that interhemispheric integration and hemispheric asymmetries are modifiable by endocrinological influences. In previous studies, our group could show an enhancing effect of acute stress on interhemispheric integration. To investigate if this effect can be attributed to an increase in the stress hormone cortisol, 50 male participants received 20 mg hydrocortisone or a placebo in a double-blind crossover design. In each test session, we collected EEG data while participants completed a lexical decision task and a Poffenberger paradigm. In the lexical decision task, we found shorter latencies of the N1 ERP component for contralateral compared to ipsilateral presentation of lexical stimuli. Similarly, we replicated the classical Poffenberger effect with shorter ERP latencies for stimuli presented in the contralateral visual field compared to the ipsilateral visual field. However, no effect of cortisol on latency differences between hemispheres could be detected. These results suggest that a temporary increase in cortisol alone might not be enough to affect the interhemispheric transfer of information via the corpus callosum. Together with previous results from our group, this suggests that chronically elevated stress hormone levels play a more central role in the relationship between altered hemispheric asymmetries and a variety of mental disorders.

Harnessing the Power of Advanced Fetal Neuroimaging to Understand In Utero Footprints for Later Neuropsychiatric Disorders

Adverse intrauterine events may profoundly impact fetal risk for future adult diseases. The mechanisms underlying this increased vulnerability are complex and remain poorly understood. Contemporary advances in fetal magnetic resonance imaging (MRI) have provided clinicians and scientists with unprecedented access to in vivo human fetal brain development to begin to identify emerging endophenotypes of neuropsychiatric disorders such as autism spectrum disorder, attention-deficit/hyperactivity disorder, and schizophrenia. In this review, we discuss salient findings of normal fetal neurodevelopment from studies using advanced, multimodal MRI that have provided unparalleled characterization of in utero prenatal brain morphology, metabolism, microstructure, and functional connectivity. We appraise the clinical utility of these normative data in identifying high-risk fetuses before birth. We highlight available studies that have investigated the predictive validity of advanced prenatal brain MRI findings and long-term neurodevelopmental outcomes. We then discuss how ex utero quantitative MRI findings can inform in utero investigations toward the pursuit of early biomarkers of risk. Lastly, we explore future opportunities to advance our understanding of the prenatal origins of neuropsychiatric disorders using precision fetal imaging.

Nx4 attenuated stress-induced activity of the anterior cingulate cortex-A post-hoc analysis of a randomized placebo-controlled crossover trial

OBJECTIVE

Stress-related symptoms are associated with significant health and economic burden. Several studies suggest Nx4 for the pharmacological management of the stress response and investigated the underlying neural processes. Here we hypothesized that Nx4 can directly affect the stress response in a predefined stress network, including the anterior cingulate cortex (ACC), which is linked to various stress-related symptoms in patients.

METHODS

In a randomized, placebo-controlled, double-blind, crossover trial, 39 healthy males took a single dose of placebo or Nx4. Psychosocial stress was induced by the ScanSTRESS paradigm inside an MRI scanner, and stress network activation was analyzed in brain regions defined a priori.

RESULTS

Using the placebo data only, we could validate the activation of a distinct neural stress pattern by the ScanSTRESS paradigm. For Nx4, we provide evidence of an attenuating effect on this stress response. A statistically significant reduction in differential stress-induced activation in the right supracallosal ACC was observed for the rotation stress task of the ScanSTRESS paradigm. The results add to previously published results of Nx4 effects on emotion regulation.

CONCLUSIONS

Our results strengthen the hypothesis that Nx4 modulates the stress response by reducing the activation in parts of the neural stress network, particularly in the ACC.

TRIAL REGISTRATION

NCT02602275; ClinicalTrials.gov.

Extra food provisioning does not affect behavioural lateralization in nestling lesser kestrels

Costs and benefits of brain lateralization may depend on environmental conditions. Growing evidence indicates that the development of brain functional asymmetries is adaptively shaped by the environmental conditions experienced during early life. Food availability early in life could act as a proxy of the environmental conditions encountered during adulthood, but its potential modulatory effect on lateralization has received little attention. We increased food supply from egg laying to early nestling rearing in a wild population of lesser kestrels Falco naumanni, a sexually dimorphic raptor, and quantified the lateralization of preening behaviour (head turning direction). As more lateralized individuals may perform better in highly competitive contexts, we expected that extra food provisioning, by reducing the level of intra-brood competition for food, would reduce the strength of lateralization. We found that extra food provisioning improved nestling growth, but it did not significantly affect the strength or direction of nestling lateralization. In addition, maternal body condition did not explain variation in nestling lateralization. Independently of extra food provisioning, the direction of lateralization differed between the sexes, with female nestlings turning more often towards their right. Our findings indicate that early food availability does not modulate behavioural lateralization in a motor task, suggesting limited phenotypic plasticity in this trait.

Glucocorticoid treatment for non-cerebral diseases in children and adolescents is associated with differences in uncinate fasciculus microstructure

BACKGROUND

Evidence suggests that fronto-limbic brain regions and connecting white matter fibre tracts in the left hemisphere are more sensitive to glucocorticoids than in the right hemisphere. It is unknown whether treatment with glucocorticoids in childhood is associated with microstructural differences of the uncinate fasciculus and cingulum bundle, which connect fronto-limbic brain regions. Here, we tested the hypothesis that prior glucocorticoid treatment would be associated with differences in fractional anisotropy (FA) of the left relative to right uncinate fasciculus and cingulum bundle.

METHODS

We performed diffusion-weighted imaging in 28 children and adolescents aged 7-16 years previously treated with glucocorticoids for nephrotic syndrome or rheumatic disease and 28 healthy controls.

RESULTS

Patients displayed significantly different asymmetry in the microstructure of uncinate fasciculus with higher left but similar right uncinate fasciculus FA and axial diffusivity compared to controls. No apparent differences were observed for the cingulum. Notably, higher cumulative glucocorticoid doses were significantly associated with higher uncinate fasciculus FA and axial diffusivity bilaterally.

CONCLUSIONS

Our findings indicate that previous glucocorticoid treatment for non-cerebral diseases in children and adolescents is associated with long-term changes in the microstructure of the uncinate fasciculi, and that higher cumulative glucocorticoid doses have a proportional impact on the microstructure.

IMPACT

It is unknown if treatment with glucocorticoids in childhood have long-term effects on fronto-limbic white matter microstructure. The study examined if children and adolescents previously treated with glucocorticoids for nephrotic syndrome or rheumatic disorder differed in fronto-limbic white matter microstructure compared to healthy controls. The nephrotic and rheumatic patients had higher left but similar right uncinate fasciculus FA and axial diffusivity. Higher bilateral uncinate fasciculus FA and axial diffusivity was associated with higher cumulative glucocorticoid doses. We revealed new evidence suggesting that previous glucocorticoid treatment for non-cerebral diseases in children and adolescents is associated with long-term changes in uncinate fasciculi microstructure.

The mouse brain after foot shock in four dimensions: Temporal dynamics at a single-cell resolution

Acute stress involves the majority of brain areas, which can be sequentially organized in functional brain networks as shown by our study with foot shock in mice. We used whole-brain microscopy to investigate different spatial resolutions over time. From mesoscale region–based analyses, we identified the order of activation of brain areas. With single-cell analyses, we analyzed shifts in activation over time within small nuclei—a result impossible to achieve with functional MRI’s resolution. These findings required the development of a four-dimensional (4D) analytical pipeline, which is made available as an R package. This “atlas” of foot shock can be visualized in 4D in our interactive web portal.

Acute stress leads to sequential activation of functional brain networks. A biologically relevant question is exactly which (single) cells belonging to brain networks are changed in activity over time after acute stress across the entire brain. We developed a preprocessing and analytical pipeline to chart whole-brain immediate early genes’ expression—as proxy for cellular activity—after a single stressful foot shock in four dimensions: that is, from functional networks up to three-dimensional (3D) single-cell resolution and over time. The pipeline is available as an R package. Most brain areas (96%) showed increased numbers of c-fos+ cells after foot shock, yet hypothalamic areas stood out as being most active and prompt in their activation, followed by amygdalar, prefrontal, hippocampal, and finally, thalamic areas. At the cellular level, c-fos+ density clearly shifted over time across subareas, as illustrated for the basolateral amygdala. Moreover, some brain areas showed increased numbers of c-fos+ cells, while others—like the dentate gyrus—dramatically increased c-fos intensity in just a subset of cells, reminiscent of engrams; importantly, this “strategy” changed after foot shock in half of the brain areas. One of the strengths of our approach is that single-cell data were simultaneously examined across all of the 90 brain areas and can be visualized in 3D in our interactive web portal.

Are Anxiety and Depression Taking Sides with Knee-Pain in Osteoarthritis?

Introduction: Total knee arthroplasty (TKA) bears a potential of rendering patients unsatisfied with the operation as a result of negative affectivity related to osteoarthritis and TKA. Not only is pain a lateralized experience, but negative affect and other psychosomatic correlates of pain might also be processed on grounds of lateralization. Lateralization in this context is likely linked to the amygdalae, which display differential left/right patterns of association with psychopathology. What is noteworthy is that osteoarthritis itself is linked not only to negative effects but also to childhood abuse. Method: The present study tests lateralization of psychosomatic correlates of knee-pain using the brief symptom inventory-18 (BSI-18), the dissociative experiences scale (FDS-20), the pain catastrophizing scale (PCS), the Tampa scale of kinesiophobia (TSK), the childhood trauma screener (CTS) and WOMAC. More precisely, we were interested in predicting the side of operations by means of the above-mentioned constructs using binary logistic regression, based on 150 participants (78 left knees) awaiting TKA for knee-osteoarthritis. Results: Somatization (p = 0.003), childhood abuse (p = 0.04) and pain-catastrophizing (p = 0.04) predicted operations on the right side. Anxiety (p = 0.001) and kinesiophobia (p = 0.002) predicted operations on the left side. Conclusions: Knee-pain may be differentially modulated by its psychosomatic correlates as a result of lateralization and corresponding patterns of psychosomatic reagibility.

Improved interhemispheric connectivity after stress during lexical decision making

Functional hemispheric asymmetries emerge as the left and the right hemisphere are dominant for different aspects of task processing. However, the hemispheres do not work independent of each other but share information through the corpus callosum. The integration of information across the corpus callosum is dependent on its structural integrity and functionality. Several hormones, like estradiol and progesterone, can influence this function. Since earlier work has demonstrated that long-term changes in stress hormone levels are accompanied by changes in hemispheric asymmetries in several mental disorders, the aim of the current study was to investigate whether acute stress and the associated changes in stress hormone levels also affect information transfer across the corpus callosum. For this purpose, we collected EEG data from 51 participants while completing a lexical decision task and a Poffenberger paradigm twice, once after stress induction with the Trier Social Stress Test and once after a control-condition. While there were no differences in interhemispheric transfer between the stress and the non-stress condition in the Poffenberger paradigm, we observed shorter latencies to stimuli in the left visual field in the left hemisphere at the CP3-CP4 electrode pair after stress. These results suggest that the transfer of lexical material from the right to the left hemisphere was quicker under stress. Stress may increase callosal excitability and lead to more efficient signal transfer across the corpus callosum between language related areas. Future studies using pharmacological intervention are needed to further examine cooperation of the hemispheres under stress in more detail.

Subdividing Stress Groups into Eustress and Distress Groups Using Laterality Index Calculated from Brain Hemodynamic Response

A stress group should be subdivided into eustress (low-stress) and distress (high-stress) groups to better evaluate personal cognitive abilities and mental/physical health. However, it is challenging because of the inconsistent pattern in brain activation. We aimed to ascertain the necessity of subdividing the stress groups. The stress group was screened by salivary alpha-amylase (sAA) and then, the brain’s hemodynamic reactions were measured by functional near-infrared spectroscopy (fNIRS) based on the near-infrared biosensor. We compared the two stress subgroups categorized by sAA using a newly designed emotional stimulus-response paradigm with an international affective picture system (IAPS) to enhance hemodynamic signals induced by the target effect. We calculated the laterality index for stress (LIS) from the measured signals to identify the dominantly activated cortex in both the subgroups. Both the stress groups exhibited brain activity in the right frontal cortex. Specifically, the eustress group exhibited the largest brain activity, whereas the distress group exhibited recessive brain activity, regardless of positive or negative stimuli. LIS values were larger in the order of the eustress, control, and distress groups; this indicates that the stress group can be divided into eustress and distress groups. We built a foundation for subdividing stress groups into eustress and distress groups using fNIRS.

Neuropsychological correlates of evocative multimodal speech: The combined roles of fearful prosody, visuospatial attention, cortisol response, and anxiety

Past research reveals left-hemisphere dominance for linguistic processing and right-hemisphere dominance for emotional prosody processing during auditory language comprehension, a pattern also found in visuospatial attention studies where listeners are presented with a view of the talker's face. Is this lateralization pattern for visuospatial attention and language processing upheld when listeners are experiencing a stress response? To investigate this question, participants completed the Trier Social Stress Test (TSST) between administrations of a visuospatial attention and language comprehension dual-task paradigm. Subjective anxiety, cardiovascular, and saliva cortisol measures were taken before and after the TSST. Higher language comprehension scores in the post-TSST neutral prosody condition were associated with lower cortisol responses, differences in blood pressure, and less subjective anxiety. In this challenging task, visuospatial attention was most focused at the mouth region, both prior to and after stress induction. Greater visuospatial attention on the left side of the face image, compared to the right side, indicated greater right hemisphere activation. In the Fear, but not the Neutral, prosody condition, greater cortisol response was associated with greater visuospatial attention to the left side of the face image. Results are placed into theoretical context, and can be applied to situations where stressed listeners must interpret emotionally evocative language.

Asymmetry in the Central Nervous System: A Clinical Neuroscience Perspective

Recent large-scale neuroimaging studies suggest that most parts of the human brain show structural differences between the left and the right hemisphere. Such structural hemispheric asymmetries have been reported for both cortical and subcortical structures. Interestingly, many neurodevelopmental and psychiatric disorders have been associated with altered functional hemispheric asymmetries. However, findings concerning the relation between structural hemispheric asymmetries and disorders have largely been inconsistent, both within specific disorders as well as between disorders. In the present review, we compare structural asymmetries from a clinical neuroscience perspective across different disorders. We focus especially on recent large-scale neuroimaging studies, to concentrate on replicable effects. With the notable exception of major depressive disorder, all reviewed disorders were associated with distinct patterns of alterations in structural hemispheric asymmetries. While autism spectrum disorder was associated with altered structural hemispheric asymmetries in a broader range of brain areas, most other disorders were linked to more specific alterations in brain areas related to cognitive functions that have been associated with the symptomology of these disorders. The implications of these findings are highlighted in the context of transdiagnostic approaches to psychopathology.

Specialized neurons in the right habenula mediate response to aversive olfactory cues

Hemispheric specializations are well studied at the functional level but less is known about the underlying neural mechanisms. We identified a small cluster of cholinergic neurons in the dorsal habenula (dHb) of zebrafish, defined by their expression of the lecithin retinol acyltransferase domain containing 2 a (lratd2a) gene and their efferent connections with a subregion of the ventral interpeduncular nucleus (vIPN). The lratd2a-expressing neurons in the right dHb are innervated by a subset of mitral cells from both the left and right olfactory bulb and are activated upon exposure to the odorant cadaverine that is repellent to adult zebrafish. Using an intersectional strategy to drive expression of the botulinum neurotoxin specifically in these neurons, we find that adults no longer show aversion to cadaverine. Mutants with left-isomerized dHb that lack these neurons are also less repelled by cadaverine and their behavioral response to alarm substance, a potent aversive cue, is diminished. However, mutants in which both dHb have right identity appear more reactive to alarm substance. The results implicate an asymmetric dHb-vIPN neural circuit in the processing of repulsive olfactory cues and in modulating the resultant behavioral response.

Dichotic listening performance and interhemispheric integration after administration of hydrocortisone

Chronic stress has been shown to have long-term effects on functional hemispheric asymmetries in both humans and non-human species. The short-term effects of acute stress exposure on functional hemispheric asymmetries are less well investigated. It has been suggested that acute stress can affect functional hemispheric asymmetries by modulating inhibitory function of the corpus callosum, the white matter pathway that connects the two hemispheres. On the molecular level, this modulation may be caused by a stress-related increase in cortisol, a major stress hormone. Therefore, it was the aim of the present study to investigate the acute effects of cortisol on functional hemispheric asymmetries. Overall, 60 participants were tested after administration of 20 mg hydrocortisone or a placebo tablet in a cross-over design. Both times, a verbal and an emotional dichotic listening task to assess language and emotional lateralization, as well as a Banich-Belger task to assess interhemispheric integration were applied. Lateralization quotients were determined for both reaction times and correctly identified syllables in both dichotic listening tasks. In the Banich-Belger task, across-field advantages were determined to quantify interhemispheric integration. While we could replicate previously reported findings for these tasks in the placebo session, we could not detect any differences in asymmetry between hydrocortisone and placebo treatment. This partially corroborates the results of a previous study we performed using social stress to induce cortisol increases. This suggests that an increase in cortisol does not influence dichotic listening performance on a behavioral level. As other studies reported an effect of stress hormones on functional hemispheric asymmetries on a neuro-functional level, future research using neuronal imaging methods would be helpful in the characterization of the relation of hemispheric asymmetries and stress hormones.

The memory trace of a stressful episode

Stress influences episodic memory formation via noradrenaline and glucocorticoid effects on amygdala and hippocampus. A common finding is the improvement of memory for central aspects of a stressful episode. This is putatively related to changes in the neural representations of specific experiences, i.e., their memory traces. Here we show that the memory improvement for objects that were encountered in a stressful episode relates to differences in the neural representations of these objects in the amygdala. Using functional magnetic resonance imaging, we found that stress specifically altered the representations of central objects: compared to control objects, they became more similar to one another and more distinct from objects that were not part of this episode. Furthermore, higher similarity of central objects to the main stressor-the faces of the stress-inducing committee members-predicted better memory. This suggests that the central objects were closely integrated into a stressor-centered memory representation. Our findings provide mechanistic insights into how stress shapes the memory trace and have profound implications for neurocognitive models of stressful and emotional memory.

Hemispheric and Sex Differences in Mustached Bat Primary Auditory Cortex Revealed by Neural Responses to Slow Frequency Modulations

The mustached bat (Pteronotus parnellii) is a mammalian model of cortical hemispheric asymmetry. In this species, complex social vocalizations are processed preferentially in the left Doppler-shifted constant frequency (DSCF) subregion of primary auditory cortex. Like hemispheric specializations for speech and music, this bat brain asymmetry differs between sexes (i.e., males>females) and is linked to spectrotemporal processing based on selectivities to frequency modulations (FMs) with rapid rates (>0.5 kHz/ms). Analyzing responses to the long-duration (>10 ms), slow-rate (<0.5 kHz/ms) FMs to which most DSCF neurons respond may reveal additional neural substrates underlying this asymmetry. Here, we bilaterally recorded responses from 176 DSCF neurons in male and female bats that were elicited by upward and downward FMs fixed at 0.04 kHz/ms and presented at 0-90 dB SPL. In females, we found inter-hemispheric latency differences consistent with applying different temporal windows to precisely integrate spectrotemporal information. In males, we found a substrate for asymmetry less related to spectrotemporal processing than to acoustic energy (i.e., amplitude). These results suggest that in the DSCF area, (1) hemispheric differences in spectrotemporal processing manifest differently between sexes, and (2) cortical asymmetry for social communication is driven by spectrotemporal processing differences and neural selectivities for amplitude.

Horses show individual level lateralisation when inspecting an unfamiliar and unexpected stimulus

Animals must attend to a diverse array of stimuli in their environments. The emotional valence and salience of a stimulus can affect how this information is processed in the brain. Many species preferentially attend to negatively valent stimuli using the sensory organs on the left side of their body and hence the right hemisphere of their brain. Here, we investigated the lateralisation of visual attention to the rapid appearance of a stimulus (an inflated balloon) designed to induce an avoidance reaction and a negatively valent emotional state in 77 Italian saddle horses. Horses’ eyes are laterally positioned on the head, and each eye projects primarily to the contralateral hemisphere, allowing eye use to be a proxy for preferential processing in one hemisphere of the brain. We predicted that horses would inspect the novel and unexpected stimulus with their left eye and hence right hemisphere. We found that horses primarily inspected the balloon with one eye, and most horses had a preferred eye to do so, however, we did not find a population level tendency for this to be the left or the right eye. The strength of this preference tended to decrease over time, with the horses using their non-preferred eye to inspect the balloon increasingly as the trial progressed. Our results confirm a lateralised eye use tendency when viewing negatively emotionally valent stimuli in horses, in agreement with previous findings. However, there was not any alignment of lateralisation at the group level in our sample, suggesting that the expression of lateralisation in horses depends on the sample population and testing context.

Paw preferences in mice and rats: Meta-analysis

Mice and rats are among the most common animal model species in both basic and clinical neuroscience. Despite their ubiquity as model species, many clinically relevant brain-behaviour relationships in rodents are not well understood. In particular, data on hemispheric asymmetries, an important organizational principle in the vertebrate brain, are conflicting as existing studies are often statistically underpowered due to small sample sizes. Paw preference is one of the most frequently investigated forms of hemispheric asymmetries on the behavioural level. Here, we used meta-analysis to statistically integrate findings on paw preferences in rats and mice. For both species, results indicate significant hemispheric asymmetries on the individual level. In mice, 81 % of animals showed a preference for either the left or the right paw, while 84 % of rats showed this preference. However, contrary to what has been reported in humans, population level asymmetries were not observed. These results are particularly significant as they point out that paying attention to potential individual hemispheric differences is important in both basic and clinical neuroscience.

Association between Uncinate Fasciculus Integrity and Agoraphobia Symptoms in Female Patients with Panic Disorder

Objective

Although neural correlates of sub-clinical agoraphobia (AG) symptoms have been previously suggested, only a few studies evaluating structural changes of the brain have been conducted in agoraphobic patients with panic disorder (PD). We investigated and compared white matter (WM) micro-structural alterations between PD patients with AG (PD ＋ AG) and those without AG (PD − AG).

Methods

Our study included 56 female PD patients, of which 25 were diagnosed with AG and 31 were diagnosed without AG. Diffusion tensor imaging was performed to investigate micro-structural changes in the WM tracts related to fronto-temporo-occipital areas (uncinate fasciculus, cingulum bundle, inferior longitudinal/fronto-occipital fasciculus, fornix column and body, and fornix/stria terminalis). All participants were subjected to the Anxiety Sensitivity Inventory-Revised (ASI-R), Beck Depression Inventory-II (BDI-II), and Albany Panic and Phobia questionnaires.

Results

The fractional anisotropy values of the right uncinate fasciculus in PD ＋ AG were significantly lower than that of PD − AG and showed significant correlations with BDI-II and ASI-R total scores. Mean diffusivity and radial diffusivity values of the right uncinate fasciculus were significantly higher in PD ＋ AG as compared to PD − AG.

Conclusion

Our findings suggest that the uncinate fasciculus may be associated with AG symptoms in PD, possibly through demyelination. Our findings may contribute to the neurobiological evidence regarding the association between AG and WM structural changes in PD.

Further to the Left: Stress-Induced Increase of Spatial Pseudoneglect During the COVID-19 Lockdown

BACKGROUND

The measures taken to contain the coronavirus disease 2019 (COVID-19) pandemic, such as the lockdown in Italy, do impact psychological health; yet, less is known about their effect on cognitive functioning. The transactional theory of stress predicts reciprocal influences between perceived stress and cognitive performance. However, the effects of a period of stress due to social isolation on spatial cognition and exploration have been little examined. The aim of the present study was to investigate the possible effects and impact of the COVID-19 pandemic on spatial cognition tasks, particularly those concerning spatial exploration, and the physiological leftward bias known as pseudoneglect. A right-hemisphere asymmetry for spatial attention processes crucially contributes to pseudoneglect. Other evidence indicates a predominantly right-hemisphere activity in stressful situations. We also analyzed the effects of lockdown on coping strategies, which typically show an opposite pattern of hemispheric asymmetry, favoring the left hemisphere. If so, then pseudoneglect should increase during the lockdown and be negatively correlated with the efficacy of coping strategies.

METHODS

One week before the start of the lockdown due to COVID-19 in Italy (T1), we had collected data from a battery of behavioral tests including tasks of peri-personal spatial cognition. During the quarantine period, from late April to early May 2020 (T2), we repeated the testing sessions with a subgroup of the same participants (47 right-handed students, mean age = 20, SD = 1.33). At both testing sessions, participants performed digitized neuropsychological tests, including a Cancellation task, Radial Arm Maze task, and Raven's Advanced Progressive Matrices. Participants also completed a newly developed COVID-19 Student Stress Scale, based on transactional models of stress, and the Coping Orientation to Problems Experienced-New Italian Version (COPE-NIV) to assess coping orientation.

RESULTS

The tendency to start cancelation from a left-sided item, to explore first a left-sided arm of the maze, and to choose erroneous response items on the left side of the page on Raven's matrices increased from T1 to T2. The degree of pseudoneglect increment positively correlated with perceived stress and negatively correlated with Positive Attitude and Problem-Solving COPE-NIV subscales.

CONCLUSION

Lockdown-related stress may have contributed to increase leftward bias during quarantine through a greater activation of the right hemisphere. On the other hand, pseudoneglect was decreased for better coping participants, perhaps as a consequence of a more balanced hemispheric activity in these individuals.

Laterality in the Cape mole-rat, Georychus capensis

Behavioural lateralization, the differential use one side of the body, and/or the bilateral use of sensory organs or limbs, is common in many vertebrates. One way in which behavioural lateralization can be detected in animals is through turning biases, which is an inherent preference to either turn left or right. Mole-rats are a unique group of mammals that demonstrate a wide range of social organizations ranging from solitary to eusociality. Behavioural asymmetry has not previously been investigated in mole-rats. In this study, captive and wild solitary Cape-mole rats (Georychus capensis) were investigated for individual (relative laterality (L_R)) and population-level (absolute laterality (L_A)) laterality. Mole-rats in the captive group were in the laboratory for at least one year, whereas the wild group were captured and experimented on within 2 weeks of capture. Animals were placed in a Y-maze facing away from the centre of the maze, and the turn towards the centre of the maze was evaluated to determine individual turning biases. Lateralized individual turning biases were more apparent in wild (7/9), compared to captive (3/10) individuals. Both captive and wild populations demonstrated a left bias, which was higher in wild animals, but not significantly so. Cape mole-rats are extremely xenophobic and aggressive, and this aggressive behaviour may underlie the turning biases in these animals, as aggression is primarily a right hemisphere dominant process. The reduced lateralization observed in captive animals may be due to a reduced need for these behaviours as a result of different environments in captivity.

Dichotic listening performance and interhemispheric integration after stress exposure

Functional hemispheric asymmetries (FHAs) have been thought to be relatively stable over time. However, past research has shown that FHAs are more plastic than initially thought. Endocrinological processes have been demonstrated to alter FHAs. As the product of the stress-activated hypothalamus–pituitary–adrenal axis, cortisol influences information processing at every level from stimulus perception to decision making and action. To investigate the influence of acute stress on FHAs, 60 participants performed a Banich–Belger task, as well as a verbal and an emotional dichotic listening task in two sessions. One session included a stress induction via the Trier Social Stress Test, the other session included a control procedure. We calculated across-field advantages (AFAs) in the Banich–Belger task and lateralization quotients for reaction times and responses per side in both dichotic listening tasks. There were no significant differences between the stress and control session in the dichotic listening tasks. In contrast, there was evidence for an influence of cortisol and sympathetic activation indicated by salivary alpha amylase changes on AFAs in the Banich–Belger task. This indicates that acute stress and the related increase in cortisol do not influence dichotic listening performance. However, stress does seem to affect interhemispheric integration of information. Future research using EEG, fMRI and pharmacological interventions is needed to further characterize the relation of hemispheric asymmetries and acute stress.

A conceptual critique of brain lateralization models in emotional face perception: Toward a hemispheric functional-equivalence (HFE) model

The present review proposes a novel dynamic model of brain lateralization of emotional (happy, surprised, fearful, sad, angry, and disgusted) and neutral face perception. Evidence to date suggests that emotional face perception is lateralized in the brain. At least five prominent hypotheses of the lateralization of emotional face perception have been previously proposed; the right-hemisphere hypothesis; the valence-specific hypothesis; the modified valence-specific hypothesis; the motivational hypothesis; and behavioral activation/inhibition system hypothesis. However, a growing number of recent replication studies exploring those hypotheses frequently provide inconsistent or even contradictory results. The latest neuroimaging and behavioral studies strongly demonstrate the functional capacity of both hemispheres to process emotions relatively successfully. Moreover, the flexibility of emotional brain-networks in both hemispheres is functionally high even to the extent of a possible reversed asymmetry of the left and the right hemisphere performance under altered neurophysiological and psychological conditions. The present review aims to a) provide a critical conceptual analysis of prior and current hypotheses of brain lateralization of emotional and neutral face perception; b) propose an integrative introduction of a novel hemispheric functional-equivalence (HFE) model in emotional and neutral face perception based on the evaluation of theoretical considerations, behavioral and neuroimaging studies: the brain is initially right-biased in emotional and neutral face perception by default; however, altered psychophysiological conditions (e.g., acute stress, a demanding emotional task) activate a distributed brain-network of both hemispheres toward functional equivalence that results in relatively equalized behavioral performance in emotional and neutral face perception. The proposed novel model may provide a practical tool in further experimental investigation of brain lateralization of emotional face perception.

The Impact of a 20-Minute Animal-Assisted Activity Session on the Physiological and Emotional States in Patients With Fibromyalgia

OBJECTIVE

To study the direct physiological and emotional impact of an animal-assisted activity (AAA) session (a form of complementary and integrative medicine) in patients with fibromyalgia (FM).

PATIENTS AND METHODS

The study population consisted of 221 participants with FM who were attending Mayo Clinic's Fibromyalgia Treatment Program between August 5, 2017, and September 1, 2018. This was a randomized controlled trial. Participants were randomly assigned to either the treatment group (a 20-minute session with a certified therapy dog and handler) or the control group (a 20-minute session with a handler only). To gain a better understanding of the direct physiological and emotional effects of AAA in patients with FM, we used multiple noninvasive physiologic-emotional biomarkers, including salivary cortisol and oxytocin concentrations, tympanic membrane temperatures, and various cardiac parameters, in addition to standardized pain and mood-based questionnaires.

RESULTS

Results show a decrease in heart rate, an increase in heart rate variability, an increase in well-being survey scores, an increase in salivary oxytocin, and subsequent tympanic membrane temperature changes, suggesting that participants in the treatment group were in a more positive emotional-physiologic state as a result of the AAA session compared with the control group.

CONCLUSION

Our results suggest that a 20-minute therapy dog visit in an outpatient setting can significantly and positively impact the physical and mental health of patients with FM.

Paw preference is associated with behavioural despair and spatial reference memory in male rats

Paw preference, one of the well-studied behavioural markers of asymmetry, has been associated with affective states and pathologies such as behavioural despair, a rodent model of clinical depression. However, a consistent differential effect of paw preference has not been observed for cognitive functions. In order to investigate the affective properties of paw preference together with its potential cognitive effects, we grouped male Wistar rats as left- or right-pawed, and tested them in the forced swim test and Morris water maze for behavioural despair and spatial memory performance, respectively. We found that left-pawed rats were significantly more susceptible to behavioural despair, while spatial learning performance of the two groups were not different over a five-day Morris water maze task. Left-pawed rats, however, displayed a better reference memory than the right-pawed ones on the subsequent probe trial when the hidden platform of the maze was removed. These findings indicate paw preference as a vulnerability factor for behavioural despair and reveal a previously unknown association between left-paw preference and reference memory performance as assessed in the probe trial of the Morris water maze.

Functional brain asymmetry for emotions: psychological stress-induced reversed hemispheric asymmetry in emotional face perception

Empirical evidence has demonstrated functional (mostly right-biased) brain asymmetry for emotion perception, whereas recent studies indicate that acute stress may modulate left and/or right hemisphere activation. However, it is still unknown whether emotion perception can be influenced by stress-induced hemispheric activation since behavioral studies report inconsistent or even contradictory results. We sought to reevaluate this gap. Eighty-eight healthy Caucasian university students participated in the study. In half of the randomly selected participants, acute psychological stress was induced by displaying a brief stressful movie clip (the stress condition), whereas the other half were shown a neutral movie clip (the non-stress condition). Prior to (the baseline) and following the movie clip display an emotion perception task was applied by presenting an emotional (happy, surprised, fearful, sad, angry, or disgusted) or neutral face to the left or right visual field. We found a more accurate perception of emotional and neutral faces presented to the LVF (the right hemisphere) in the baseline. However, we revealed that after watching a neutral movie clip, behavioral performance in emotional and neutral face perception accuracy became relatively equalized for both visual fields, whereas after watching a stressful movie clip, the RVF (the left hemisphere) even became dominant in emotional face perception. We propose a novel hemispheric functional-equivalence model: the brain is initially right-biased in emotional and neutral face perception by default; however, psychophysiological activation of a distributed brain-network due to watching neutral movie clips redistributes hemispheric performance toward relative equivalence. Moreover, even reversed hemispheric asymmetry may occur.

Physiological State of Therapy Dogs during Animal-Assisted Activities in an Outpatient Setting

Therapy dogs are increasingly being incorporated into numerous clinical settings. However, there are only a handful of studies that have focused on the impact of animal-assisted activity or therapy sessions on the wellbeing of the therapy dogs. Furthermore, these studies show mixed results. The goal of this study was to provide an in-depth picture of the effects of these interactions on the dogs involved by considering multiple physiological measures known to be associated with emotional state (continuous heart rate, heart rate variability, pre- and post-session tympanic membrane temperatures, and salivary cortisol and oxytocin concentrations). Nineteen Mayo Clinic Caring Canine therapy dogs completed five 20-minute animal-assisted activity (AAA) visits each in an outpatient clinical setting (Mayo Clinic Fibromyalgia and Chronic Fatigue Clinic). From a physiological perspective, the dogs showed a neutral to positive response to the AAA sessions. Heart rate (HR) was significantly lower at the end of the session compared with the beginning of the session (F = 17.26, df1 = 1, df2 = 29.7, p = 0.0003). The right tympanic membrane temperature was lower post-session (F = 8.87, df1 = 1, df2 = 107, p = 0.003). All other emotional indicators remained stable between pre- and post-session. These results suggest that the dogs involved were not negatively affected by their participation in the AAA. Moreover, there was some evidence suggesting the dogs may have been in a more relaxed state at the end of the session (lower HR and lower right tympanic membrane temperature) compared to the beginning of the session.

Brain and Behavioral Asymmetry: A Lesson From Fish

It is widely acknowledged that the left and right hemispheres of human brains display both anatomical and functional asymmetries. For more than a century, brain and behavioral lateralization have been considered a uniquely human feature linked to language and handedness. However, over the past decades this idea has been challenged by an increasing number of studies describing structural asymmetries and lateralized behaviors in non-human species extending from primates to fish. Evidence suggesting that a similar pattern of brain lateralization occurs in all vertebrates, humans included, has allowed the emergence of different model systems to investigate the development of brain asymmetries and their impact on behavior. Among animal models, fish have contributed much to the research on lateralization as several fish species exhibit lateralized behaviors. For instance, behavioral studies have shown that the advantages of having an asymmetric brain, such as the ability of simultaneously processing different information and perform parallel tasks compensate the potential costs associated with poor integration of information between the two hemispheres thus helping to better understand the possible evolutionary significance of lateralization. However, these studies inferred how the two sides of the brains are differentially specialized by measuring the differences in the behavioral responses but did not allow to directly investigate the relation between anatomical and functional asymmetries. With respect to this issue, in recent years zebrafish has become a powerful model to address lateralization at different level of complexity, from genes to neural circuitry and behavior. The possibility of combining genetic manipulation of brain asymmetries with cutting-edge in vivo imaging technique and behavioral tests makes the zebrafish a valuable model to investigate the phylogeny and ontogeny of brain lateralization and its relevance for normal brain function and behavior.

The fluctuations of metabotropic glutamate receptor subtype 5 (mGluR5) in the amygdala in fear conditioning model of male Wistar rats following sleep deprivation, reverse circadian and napping

Sleep is involved in metabolic system, mental health and cognitive functions. Evidence shows that sleep deprivation (SD) negatively affects mental health and impairs cognitive functions, including learning and memory. Furthermore, the metabotropic glutamate receptor subtype 5 (mGluR5) is a metabolic biomarker, which is affected by various conditions, including stress, sleep deprivation, and cognitive and psychiatric disorders. In this research, we investigated the effect of SD and reverse circadian (RC), and two models of napping (continuous and non-continuous) combined with SD or RC on fear-conditioning memory, anxiety-like behavior and mGluR5 fluctuations in the amygdala. 64 male Wistar rats were used in this study. The water box apparatus was used to induce SD/RC for 48 h, and fear-conditioning memory apparatus was used to assess fear memory. The results showed, fear-conditioning memory was impaired following SD and RC, especially in contextual stage. However, anxiety-like behavior was increased. Furthermore, mGluR5 was increased in the left amygdala more than the right amygdala. Additionally, continuous napping significantly improved fear-conditioning memory, especially freezing behavior. In conclusion, following SD and RC, fear-conditioning memory in contextual stage is more vulnerable than in auditory stage. Furthermore, increase in anxiety-like behavior is related to increase in the activity of left amygdala and mGluR5 receptors.

Atypical lateralization in neurodevelopmental and psychiatric disorders: What is the role of stress?

Hemispheric asymmetries are a major organizational principle of the human brain. In different neurodevelopmental and psychiatric disorders, like schizophrenia, autism spectrum disorders, depression, dyslexia and posttraumatic stress disorder, functional and/or structural hemispheric asymmetries are altered compared to healthy controls. The question, why these disorders all share the common characteristic of altered hemispheric asymmetries despite vastly different etiologies and symptoms remains one of the unsolved mysteries of laterality research. This review is aimed at reviewing potential reasons for why atypical lateralization is so common in many neurodevelopmental and psychiatric disorders. To this end, we review the evidence for overlaps in the genetic and non-genetic factors involved in the ontogenesis of different disorders and hemispheric asymmetries. While there is evidence for genetic overlap between different disorders, only few asymmetry-related loci have also been linked to disorders and importantly, those effects are mostly specific to single disorders. However, there is evidence for shared non-genetic influences between disorders and hemispheric asymmetries. Most neurodevelopmental and psychiatric disorders show alterations in the hypothalamic-pituitary adrenocortical (HPA) axis and maternal as well as early life stress have been implicated in their etiology. Stress has also been suggested to affect hemispheric asymmetries. We propose a model in which early life stress as well as chronic stress not only increases the risk for psychiatric and neurodevelopmental disorders but also changes structural and functional hemispheric asymmetries leading to the aberrant lateralization patterns seen in these disorders. Thus, pathology-related changes in hemispheric asymmetries are not a factor causing disorders, but rather a different phenotype that is affected by partly overlapping ontogenetic factors, primarily stress.

Asymmetries in social touch-motor and emotional biases on lateral preferences in embracing, cradling and kissing

In human social interaction, affective touch plays an integral role to communicate intentions and emotions. Three of the most important forms of social touch are embracing, cradling and kissing. These behaviours have been demonstrated to be lateralized, but the underlying mechanisms are still not well understood. Both motor and emotive biases have been suggested to affect laterality of social touch. We aimed to systematically investigate how motor preferences and emotive biases influence the lateralization of embracing, cradling and kissing within the same sample. Participants performed all three forms of social touch in neutral, positive and negative emotional conditions. Like a previous study, we found a rightward bias for embracing that was modulated by both motor preferences and the emotional content of the situation. Kissing and cradling were not influenced by motor preferences. In general, a negative emotional connotation of the situation led to a reduction of lateral biases in social touch, independent of the individual direction.

Sheep Quickstep while the Floor Rock and Rolls: Visuomotor Lateralization during Simulated Sea Travel

Unpredictable floor motions during transport disturbs animals' balance, requiring stepping to move the centre of gravity in the direction of body movement. When repeated regularly, this may be stressful, requiring involvement of the right brain hemisphere, hence we investigated the existence of behavioral laterality in sheep during prolonged floor motions. Six sheep were restrained in pairs on a programmable rocking platform, in which they were unable to turn around. They were exposed to three continuous rocking motion treatments (roll, pitch or both) in a regular or irregular pattern for 1 h periods in a changeover design. Right forelimb and left hindlimb diagonal stepping was more frequent in response to the motion treatment of irregular roll and pitch, which previous research has suggested to be the most stressful from heart rate measurements. An overall strategy to maintain balance appeared to be the use of the right hindlimb as a stabilizer, which was repositioned least often of all limbs until towards the end of the hour of experimental treatment. Of each tested pair, sheep restrained on the left side of the rocking floor stepped significantly often than its partner restrained on the right side, and we postulate the existence of visuomotor lateralization as left restrained sheep were unable to view their partner within the field of view of their left eye. We also investigated which side sheep lie down on, which if left lateralized could explain our observed bipedal diagonal control of sheep balance under stress. From the observation of 412 web-based images of sheep, there was an overall left-sided laterality to their lying, as has been observed in cattle. We conclude that stepping activity in sheep in response to a motion stressor is lateralized, providing evidence that floor motion experienced in transport may induce stress responses.