Cell-Type Specific and Frequency-Dependent Centrifugal Modulation in Olfactory Bulb Output Neurons in Vivo

Mitral/tufted cells (M/TCs) form complex local circuits with interneurons in olfactory bulb and are powerfully inhibited by these interneurons. The horizontal limb of the diagonal band of Broca (HDB), the only GABAergic/inhibitory source of centrifugal circuit with olfactory bulb is known to target olfactory bulb interneurons and we have shown targeting also to olfactory bulb glutamatergic neurons in vitro. However, the net efficacy of these circuits under different patterns of activation in vivo and the relative balance between the various targeted intact local and centrifugal circuits was the focus of this study. Here ChR2 was expressed in HDB GABAergic neurons to investigate the short-term plasticity of HDB-activated disinhibitory rebound excitation of M/TCs. Optical activation of HDB interneurons increased spontaneous M/TC firing without odor presentation and increased odor-evoked M/TC firing. HDB activation induced-disinhibitory rebound excitation (burst or cluster of spiking) in all classes of M/TCs. This excitation was frequency dependent, with short term facilitation only at higher HDB stimulation frequency (5 Hz and above). However, frequency-dependent HDB regulation was more potent in the deeper layer M/TCs compared to more superficial layer M/TCs. In all neural circuits the balance between inhibition and excitation in local and centrifugal circuits plays a critical functional role and this patterned input-dependent regulation of inhibitory centrifugal inputs to the olfactory bulb may help maintain the precise balance across the populations of output neurons in the different environmental odors, putatively to sharpen the enhancement of tuning specificity of individual or classes of M/TCs to odors.

Specialized connectivity of molecular layer interneuron subtypes leads to disinhibition and synchronous inhibition of cerebellar Purkinje cells

Molecular layer interneurons (MLIs) account for approximately 80% of the inhibitory interneurons in the cerebellar cortex and are vital to cerebellar processing. MLIs are thought to primarily inhibit Purkinje cells (PCs) and suppress the plasticity of synapses onto PCs. MLIs also inhibit, and are electrically coupled to, other MLIs, but the functional significance of these connections is not known. Here, we find that two recently recognized MLI subtypes, MLI1 and MLI2, have a highly specialized connectivity that allows them to serve distinct functional roles. MLI1s primarily inhibit PCs, are electrically coupled to each other, fire synchronously with other MLI1s on the millisecond timescale in vivo, and synchronously pause PC firing. MLI2s are not electrically coupled, primarily inhibit MLI1s and disinhibit PCs, and are well suited to gating cerebellar-dependent behavior and learning. The synchronous firing of electrically coupled MLI1s and disinhibition provided by MLI2s require a major re-evaluation of cerebellar processing.

Functional specialization of hippocampal somatostatin-expressing interneurons

Hippocampal somatostatin-expressing (Sst) GABAergic interneurons (INs) exhibit considerable anatomical and functional heterogeneity. Recent single-cell transcriptome analyses have provided a comprehensive Sst-IN subpopulations census, a plausible molecular ground truth of neuronal identity whose links to specific functionality remain incomplete. Here, we designed an approach to identify and access subpopulations of Sst-INs based on transcriptomic features. Four mouse models based on single or combinatorial Cre- and Flp- expression differentiated functionally distinct subpopulations of CA1 hippocampal Sst-INs that largely tiled the morpho-functional parameter space of the Sst-INs superfamily. Notably, the Sst;;Tac1 intersection revealed a population of bistratified INs that preferentially synapsed onto fast-spiking interneurons (FS-INs) and were sufficient to interrupt their firing. In contrast, the Ndnf;;Nkx2-1 intersection identified a population of oriens lacunosum-moleculare INs that predominantly targeted CA1 pyramidal neurons, avoiding FS-INs. Overall, our results provide a framework to translate neuronal transcriptomic identity into discrete functional subtypes that capture the diverse specializations of hippocampal Sst-INs.

Neuropsychiatric Symptoms and White Matter Hyperintensities in Older Adults without Dementia

OBJECTIVE

We aimed to examine associations between neuropsychiatric symptoms (NPS) and white matter hyperintensities (WMH) status in older adults without dementia under the hypothesis that WMH increased the odds of having NPS.

DESIGN

Longitudinal analysis of data acquired from the National Alzheimer's Coordinating Center Uniform Data Set.

SETTINGS

Data were derived from 46 National Institute on Aging - funded Alzheimer's Disease Research Centers.

PARTICIPANTS

NACC participants aged ≥50 years with available data on WMH severity with a diagnosis of mild cognitive impairment (MCI) or who were cognitively unimpaired (CU) were studied. Among 4617 CU participants, 376 had moderate and 54 extensive WMH. Among 3170 participants with MCI, 471 had moderate and 88 had extensive WMH.Measurements: Using Cardiovascular Health Study (CHS) scores, WMH were coded as no to mild (CHS score: 0-4), moderate (score: 5-6) or extensive (score: 7-8). NPS were quantified on the Neuropsychiatric Inventory Questionnaire. Binary logistic regression models estimated the odds of reporting each of 12 NPS by WMH status separately for individuals with MCI or who were CU.

RESULTS

Compared to CU individuals with no to mild WMH, the odds of having elation [9.87,(2.63-37.10)], disinhibition [4.42,(1.28-15.32)], agitation [3.51,(1.29-9.54)] or anxiety [2.74,(1.28-5.88)] were higher for the extensive WMH group, whereas the odds of having disinhibition were higher for the moderate WMH group [1.94,(1.05-3.61)]. In the MCI group, he odds of NPS did not vary by WMH status.

CONCLUSIONS

Extensive WMH were associated with higher odds of NPS in CU older adults but not in those with MCI.

Disinhibition in dementia related to reduced morphometric similarity of cognitive control network

Disinhibition is one of the most distressing and difficult to treat neuropsychiatric symptoms of dementia. It involves socially inappropriate behaviours, such as hypersexual comments, inappropriate approaching of strangers and excessive jocularity. Disinhibition occurs in multiple dementia syndromes, including behavioural variant frontotemporal dementia, and dementia of the Alzheimer's type. Morphometric similarity networks are a relatively new method for examining brain structure and can be used to calculate measures of network integrity on large scale brain networks and subnetworks such as the salience network and cognitive control network. In a cross-sectional study, we calculated morphometric similarity networks to determine whether disinhibition in behavioural variant frontotemporal dementia (n = 75) and dementia of the Alzheimer's type (n = 111) was associated with reduced integrity of these networks independent of diagnosis. We found that presence of disinhibition, measured by the Neuropsychiatric Inventory Questionnaire, was associated with reduced global efficiency of the cognitive control network in both dementia of the Alzheimer's type and behavioural variant frontotemporal dementia. Future research should replicate this transdiagnostic finding in other dementia diagnoses and imaging modalities, and investigate the potential for intervention at the level of the cognitive control network to target disinhibition.

Mismatch novelty exploration training shifts VPAC1 receptor-mediated modulation of hippocampal synaptic plasticity by endogenous VIP in male rats

Novelty influences hippocampal-dependent memory through metaplasticity. Mismatch novelty detection activates the human hippocampal CA1 area and enhances rat hippocampal-dependent learning and exploration. Remarkably, mismatch novelty training (NT) also enhances rodent hippocampal synaptic plasticity while inhibition of VIP interneurons promotes rodent exploration. Since VIP, acting on VPAC1 receptors (Rs), restrains hippocampal LTP and depotentiation by modulating disinhibition, we now investigated the impact of NT on VPAC1 modulation of hippocampal synaptic plasticity in male Wistar rats. NT enhanced both CA1 hippocampal LTP and depotentiation unlike exploring an empty holeboard (HT) or a fixed configuration of objects (FT). Blocking VIP VPAC1Rs with PG 97269 (100 nM) enhanced both LTP and depotentiation in naïve animals, but this effect was less effective in NT rats. Altered endogenous VIP modulation of LTP was absent in animals exposed to the empty environment (HT). HT and FT animals showed mildly enhanced synaptic VPAC1R levels, but neither VIP nor VPAC1R levels were altered in NT animals. Conversely, NT enhanced the GluA1/GluA2 AMPAR ratio and gephyrin synaptic content but not PSD-95 excitatory synaptic marker. In conclusion, NT influences hippocampal synaptic plasticity by reshaping brain circuits modulating disinhibition and its control by VIP-expressing hippocampal interneurons while upregulation of VIP VPAC1Rs is associated with the maintenance of VIP control of LTP in FT and HT animals. This suggests VIP receptor ligands may be relevant to co-adjuvate cognitive recovery therapies in aging or epilepsy, where LTP/LTD imbalance occurs.

Exploring neuropsychological underpinnings of poor communication after traumatic brain injury: The role of apathy, disinhibition and social cognition

BACKGROUND

Dysarthria, aphasia and executive processes have been examined for their role in producing impaired communicative competence post traumatic brain injury (TBI). Less understood is the role of emotional dysregulation, that is, apathy and disinhibition, and social cognition, that is, reading and interpreting social cues.

METHODS & PROCEDURES

In this study, we examined 49 adults with moderate to severe TBI and 18 neurologically healthy adults. We hypothesised that apathy and disinhibition would predict communication outcomes as would social cognition. We also predicted that apathy and disinhibition would influence social cognition. Communication outcomes were measured by the La Trobe Communication Questionnaire (LCQ) and the Social Skills Questionnaire-TBI (SSQ-TBI). Apathy and disinhibition were measured by the Frontal Systems Behavior Scale (FrSBe). We measured four aspects of social cognition: emotion perception and theory of mind using The Awareness of Social Inference Test (TASIT) and the Complex Audio-Visual Evaluation of Affect Test (CAVEAT), empathy using the Questionnaire of Cognitive and Affective Empathy (QCAE) and the Balanced Emotional Empathy Scale (BEES), and alexithymia using the Toronto Alexithymia Scale (TAS-20) and the Bermond-Vorst Alexithymia Questionnaire.

OUTCOMES & RESULTS

Consistent with predictions, the LCQ and SSQ-TBI were associated with disinhibition and the LCQ was also associated with apathy. The LCQ was associated with the full range of social cognition constructs although the SSQ-TBI was not. Finally, apathy and disinhibition predicted a number of social cognition measures.

CONCLUSIONS AND IMPLICATIONS

These results are discussed in relation to understanding the nature of communication disorders following TBI and how they are measured, as well as the interrelation between emotion dysregulation and social cognition.

WHAT THIS STUDY ADDS

What is already known on this subject The role of emotional dysregulation and social cognition in producing impaired communicative competence post traumatic brain injury (TBI) is not well understood. Although most adults with severe TBI have minimal or possibly no language impairment, they often struggle with functional communication in everyday situations. Many have been reported to be overtalkative, insensitive, childish and self-centred, displaying an inappropriate level of self-disclosure and making tangential and irrelevant comments. Conversely, some speakers with TBI have been noted to have impoverished communication, producing little language either spontaneously or in response to the speaker's questions and prompts. What this paper adds to existing knowledge We found that both apathy and disinhibition were strongly associated with the Latrobe Communication Questionnaire both empirically and conceptually, despite the LCQ being developed from a different, pragmatic orientation. Disinhibition was also associated with the Social Skills Questionnaire for TBI. We also found that poor social cognition scores predicted communication difficulties. Finally, we found that behavioural dysregulation itself, i.e., both apathy and disinhibition, predicted poor social cognition. What are the potential or actual clinical implications of this work? Our findings highlight the central role that apathy and disinhibition play in both communication and social cognition. These insights point to the importance of remediation to target behavioural and autonomic dysregulation as a means to improve everyday social function.

Atrophy network mapping of clinical subtypes and main symptoms in frontotemporal dementia

Frontotemporal Dementia (FTD) is a disease of high heterogeneity, apathy and disinhibition present in all subtypes of FTD and imposes a significant burden on families/society. Traditional neuroimaging analysis has limitations in elucidating the network localization due to individual clinical and neuroanatomical variability. The study aims to identify the atrophy network map associated with different FTD clinical subtypes and determine the specific localization of the network for apathy and disinhibition. Eighty FTD patients [45 behavioral variant FTD (bvFTD) and 35 semantic variant progressive primary aphasia (svPPA)] and 58 healthy controls (HCs) at Xuanwu Hospital were enrolled as Dataset 1; 112 FTD patients including 50 bvFTD, 32 svPPA, and 30 non-fluent variant PPA (nfvPPA) cases, and 110 HCs from Frontotemporal Lobar Degeneration Neuroimaging Initiative (FTLDNI) dataset were included as Dataset 2. Initially, single-subject atrophy maps were defined by comparing cortical thickness in each FTD patient versus HCs. Next, the network of brain regions functionally connected to each FTD patient's location of atrophy was determined using seed-based functional connectivity in a large (n = 1000) normative connectome. Finally, we used atrophy network mapping to define clinical subtype-specific network (45 bvFTD, 35 svPPA and 58 HCs in Dataset 1; 50 bvFTD, 32 svPPA, 30 nfvPPA and 110 HCs in Dataset 2) and symptom-specific networks [combined dataset 1 and 2, apathy without depression Vs non-apathy without depression (80:26), disinhibition Vs non-disinhibition (88:68)]. We compare the result with matched symptom networks derived from patients with focal brain lesions or conjunction analysis. Through the analysis of two datasets, we identified heterogeneity in atrophy patterns among FTD patients. However, these atrophy patterns are connected to a common brain network. The primary regions affected by atrophy in FTD included the frontal and temporal lobes, particularly the anterior temporal lobe. bvFTD connects to frontal and temporal cortical areas, svPPA mainly impacts the anterior temporal region, and nfvPPA targets the inferior frontal gyrus and precentral cortex regions. The apathy-specific network was localized in the orbital frontal cortex and ventral striatum, while the disinhibition-specific network was localized in the bilateral orbital frontal gyrus and right temporal lobe. Apathy and disinhibition atrophy networks resemble known motivational and criminal lesion networks respectively. A significant correlation was found between the apathy/disinhibition scores and functional connectivity between atrophy maps and the peak of the networks. This study localizes the common network of clinical subtypes and main symptoms in FTD, guiding future FTD neuromodulation interventions.

Extracellular glutamate and GABA transients at the transition from interictal spiking to seizures

Focal epilepsy is associated with intermittent brief population discharges (interictal spikes), which resemble sentinel spikes that often occur at the onset of seizures. Why interictal spikes self-terminate whilst seizures persist and propagate is incompletely understood. We used fluorescent glutamate and GABA sensors in an awake rodent model of neocortical seizures to resolve the spatiotemporal evolution of both neurotransmitters in the extracellular space. Interictal spikes were accompanied by brief glutamate transients which were maximal at the initiation site and rapidly propagated centrifugally. GABA transients lasted longer than glutamate transients and were maximal ∼1.5 mm from the focus where they propagated centripetally. Prior to seizure initiation GABA transients were attenuated, whilst glutamate transients increased, consistent with a progressive failure of local inhibitory restraint. As seizures increased in frequency, there was a gradual increase in the spatial extent of spike-associated glutamate transients associated with interictal spikes. Neurotransmitter imaging thus reveals a progressive collapse of an annulus of feed-forward GABA release, allowing seizures to escape from local inhibitory restraint.

Disinhibition Is an Essential Network Motif Coordinated by GABA Levels and GABA B Receptors

Network dynamics are crucial for action and sensation. Changes in synaptic physiology lead to the reorganization of local microcircuits. Consequently, the functional state of the network impacts the output signal depending on the firing patterns of its units. Networks exhibit steady states in which neurons show various activities, producing many networks with diverse properties. Transitions between network states determine the output signal generated and its functional results. The temporal dynamics of excitation/inhibition allow a shift between states in an operational network. Therefore, a process capable of modulating the dynamics of excitation/inhibition may be functionally important. This process is known as disinhibition. In this review, we describe the effect of GABA levels and GABAB receptors on tonic inhibition, which causes changes (due to disinhibition) in network dynamics, leading to synchronous functional oscillations.

Implications of variable synaptic weights for rate and temporal coding of cerebellar outputs

Purkinje cell (PC) synapses onto cerebellar nuclei (CbN) neurons allow signals from the cerebellar cortex to influence the rest of the brain. PCs are inhibitory neurons that spontaneously fire at high rates, and many PC inputs are thought to converge onto each CbN neuron to suppress its firing. It has been proposed that PCs convey information using a rate code, a synchrony and timing code, or both. The influence of PCs on CbN neuron firing was primarily examined for the combined effects of many PC inputs with comparable strengths, and the influence of individual PC inputs has not been extensively studied. Here, we find that single PC to CbN synapses are highly variable in size, and using dynamic clamp and modeling we reveal that this has important implications for PC-CbN transmission. Individual PC inputs regulate both the rate and timing of CbN firing. Large PC inputs strongly influence CbN firing rates and transiently eliminate CbN firing for several milliseconds. Remarkably, the refractory period of PCs leads to a brief elevation of CbN firing prior to suppression. Thus, individual PC-CbN synapses are suited to concurrently convey rate codes and generate precisely timed responses in CbN neurons. Either synchronous firing or synchronous pauses of PCs promote CbN neuron firing on rapid time scales for nonuniform inputs, but less effectively than for uniform inputs. This is a secondary consequence of variable input sizes elevating the baseline firing rates of CbN neurons by increasing the variability of the inhibitory conductance. These findings may generalize to other brain regions with highly variable inhibitory synapse sizes.

Examining the Association between Psychopathic Traits and Fearlessness among Maximum-Security Incarcerated Male Adolescents

Studies have reported positive associations between youth psychopathy scores and measures of 'fearlessness'. However, prior studies modified fearlessness items to be age appropriate, shifting from assessing hypothetical, extreme forms of physical risk-taking (e.g., flying an airplane) to normative risk-taking (e.g., riding bicycles downhill). We hypothesize that associations between youth psychopathy scores and alternative forms of sensation seeking (i.e., Disinhibition) have been conflated under a false fearlessness label. We tested this hypothesis among incarcerated male adolescents, investigating whether youth psychopathy scores were significantly associated with two different forms of sensation seeking: Disinhibition and Thrill and Adventure Seeking (TAS). Youth psychopathic traits were assessed using the Psychopathy Checklist: Youth Version (PCL:YV), Antisocial Process Screening Device (APSD), Child Psychopathy Scale (CPS), Inventory of Callous and Unemotional Traits (ICU), and Youth Psychopathic Traits Inventory (YPI). Disinhibition and fearlessness (i.e., TAS) were assessed using an unmodified version of the Zuckerman Sensation Seeking Scales (SSS). Consistent with hypotheses, youth psychopathy scores were associated with higher Disinhibition and lower TAS scores. Our results contribute to a growing body of literature suggesting that psychopathic traits, including among adolescents, are not concomitant with physical risk-taking and descriptions of psychopathy including fearlessness distort a precise understanding of psychopathy's core features.

Intranasal Delivery of Ketamine Induces Cortical Disinhibition

Our previous studies find that subcutaneously administered (s.c.) subanesthetic ketamine promotes sustained cortical disinhibition and plasticity in adult mouse binocular visual cortex (bV1). We hypothesized that intranasal delivery (i.n.) of subanesthetic ketamine may have similar actions. To test this, we delivered ketamine (10 mg/kg, i.n.) to adult mice and then recorded excitatory pyramidal neurons or PV+ interneurons in L2/3 of bV1 slices. In pyramidal neurons the baseline IPSC amplitudes from mice treated with ketamine are significantly weaker than those in control mice. Acute bath application of neuregulin-1 (NRG1) to cortical slices increases these IPSC amplitudes in mice treated with ketamine but not in controls. In PV+ interneurons, the baseline EPSC amplitudes from mice treated with ketamine are significantly weaker than those in control mice. Acute bath application of NRG1 to cortical slices increases these EPSC amplitudes in mice treated with ketamine but not in controls. We also found that mice treated with ketamine exhibit increased pCREB staining in L2/3 of bV1. Together, our results show that a single intranasal delivery of ketamine reduces PV+ interneuron excitation and reduces pyramidal neuron inhibition and that these effects are acutely reversed by NRG1. These results are significant as they show that intranasal delivery of ketamine induces cortical disinhibition, which has implications for the treatment of psychiatric, neurologic, and ophthalmic disorders.

What interventions can treat arthrogenic muscle inhibition in patients with chronic ankle instability? A systematic review with meta-analysis

PURPOSE

To identify, critically appraise, and synthesize the existing evidence regarding the effects of therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle instability (CAI).

MATERIALS AND METHODS

Two reviewers independently performed exhaustive database searches in Web of Science, PubMed, Medline, CINAHL, and SPORTDiscus.

RESULTS

Nine studies were finally included. Five types of disinhibitory interventions were identified: focal ankle joint cooling (FAJC), manual therapy, fibular reposition taping (FRT), whole-body vibration (WBV), and transcranial direct current stimulation (tDCS). There were moderate effects of FAJC on spinal excitability in ankle muscles (g = 0.55, 95% CI = 0.03-1.08, p = 0.040 for the soleus and g = 0.54, 95% CI = 0.01-1.07, p = 0.046 for the fibularis longus). In contrast, manual therapy, FRT, WBV were not effective. Finally, 4 weeks of tDCS combined with eccentric exercise showed large effects on corticospinal excitability in 2 weeks after the intervention (g = 0.99, 95% CI = 0.14-1.85 for the fibularis longus and g = 1.02, 95% CI = 0.16-1.87 for the tibialis anterior).

CONCLUSIONS

FAJC and tDCS may be effective in counteracting AMI. However, the current evidence of mainly short-term studies to support the use of disinhibitory interventions is too limited to draw definitive conclusions.

Associations Between Hyperactive Neuropsychiatric Symptoms and Brain Morphology in Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND

Hyperactive neuropsychiatric symptoms (NPS) (i.e., agitation, disinhibition, and irritability) are among the most challenging symptoms to manage in Alzheimer's disease (AD). However, their underlying brain correlates have been poorly studied.

OBJECTIVE

We aimed to investigate the associations between the total score of hyperactive NPS and brain structures in participants with AD, mild cognitive impairment (MCI), and cognitively normal older adults (CN).

METHODS

Neuropsychiatric and 3T MRI data from 216 AD, 564 MCI, and 660 CN participants were extracted from the Alzheimer's Disease Neuroimaging Initiative database. To define NPS and brain structures' associations, we fitted a general linear model (GLM) in two ways: 1) an overall GLM including all three groups (AD, MCI, CN) and 2) three pair-wise GLMs (AD versus MCI, MCI versus CN, AD versus CN). The cortical changes as a function of NPS total score were investigated using multiple regression analyses.

RESULTS

Results from the overall GLM include associations between 1) agitation and the right parietal supramarginal surface area in the MCI-CN contrast, 2) disinhibition and the cortical thickness of the right frontal pars opercularis and temporal inferior in the AD-MCI contrast, and 3) irritability and the right frontal pars opercularis, frontal superior, and temporal superior volumes in the MCI-CN contrast.

CONCLUSIONS

Our study shows that each hyperactive NPS is associated with distinct brain regions in AD, MCI, and CN (groups with different levels of cognitive performance). This suggests that each NPS is associated with a unique signature of brain morphology, including variations in volume, thickness, or area.

Mediation and moderation of genetic risk of obesity through eating behaviours in two UK cohorts

BACKGROUND

The mechanisms underlying genetic predisposition to higher body mass index (BMI) remain unclear.

METHODS

We hypothesized that the relationship between BMI-genetic risk score (BMI-GRS) and BMI was mediated via disinhibition, emotional eating and hunger, and moderated by flexible (but not rigid) restraint within two UK cohorts: the Genetics of Appetite Study (GATE) (n = 2101, 2010-16) and the Avon Longitudinal Study of Parents and Children (ALSPAC) (n = 1679, 2014-18). Eating behaviour was measured by the Adult Eating Behaviour Questionnaire and Three-Factor Eating Questionaire-51.

RESULTS

The association between BMI-GRS and BMI were partially mediated by habitual, emotional and situational disinhibition in the GATE/ALSPAC meta-mediation [standardized betaindirect 0.04, 95% confidence interval (CI) 0.02-0.06; 0.03, 0.01-0.04; 0.03, 0.01-0.04, respectively] external hunger and internal hunger in the GATE study (0.02, 0.01-0.03; 0.01, 0.001-0.02, respectively). There was evidence of mediation by emotional over/undereating and hunger in the ALSPAC study (0.02, 0.01-0.03; 0.01, 0.001-0.02; 0.01, 0.002-0.01, respectively). Rigid or flexible restraint did not moderate the direct association between BMI-GRS and BMI, but high flexible restraint moderated the effect of disinhibition subscales on BMI (reduction of the indirect mediation by -5% to -11% in GATE/ALSPAC) and external hunger (-5%) in GATE. High rigid restraint reduced the mediation via disinhibition subscales in GATE/ALSPAC (-4% to -11%) and external hunger (-3%) in GATE.

CONCLUSIONS

Genetic predisposition to a higher BMI was partly explained by disinhibition and hunger in two large cohorts. Flexible/rigid restraint may play an important role in moderating the impact of predisposition to higher BMI.

Short- and Long-Term High-Fat Diet Exposure Differentially Alters Phasic and Tonic GABAergic Signaling onto Lateral Orbitofrontal Pyramidal Neurons

The chronic consumption of caloric dense high-fat foods is a major contributor to increased body weight, obesity, and other chronic health conditions. The orbitofrontal cortex (OFC) is critical in guiding decisions about food intake and is altered with diet-induced obesity. Obese rodents have altered morphologic and synaptic electrophysiological properties in the lateral orbitofrontal cortex (lOFC). Yet the time course by which exposure to a high-fat diet (HFD) induces these changes is poorly understood. Here, male mice are exposed to either short-term (7 d) or long-term (90 d) HFD. Long-term HFD exposure increases body weight, and glucose signaling compared with short-term HFD or a standard control diet (SCD). Both short and long-term HFD exposure increased the excitability of lOFC pyramidal neurons. However, phasic and tonic GABAergic signaling was differentially altered depending on HFD exposure length, such that tonic GABAergic signaling was decreased with early exposure to the HFD and phasic signaling was changed with long-term diet exposure. Furthermore, alterations in the short-term diet exposure were transient, as removal of the diet restored electrophysiological characteristics similar to mice fed SCD, whereas long-term HFD electrophysiological changes were persistent and remained after HFD removal. Finally, we demonstrate that changes in reward devaluation occur early with diet exposure. Together, these results suggest that the duration of HFD exposure differentially alters lOFC function and provides mechanistic insights into the susceptibility of the OFC to impairments in outcome devaluation.SIGNIFICANCE STATEMENT This study provides mechanistic insight on the impact of short-term and long-term high-fat diet (HFD) exposure on GABAergic function in the lateral orbitofrontal cortex (lOFC), a region known to guide decision-making. We find short-term HFD exposure induces transient changes in firing and tonic GABA action on lOFC pyramidal neurons, whereas long-term HFD induces obesity and has lasting changes on firing, tonic GABA and inhibitory synaptic transmission onto lOFC neurons. Given that GABAergic signaling in the lOFC can influence decision-making around food, these results have important implications in present society as palatable energy dense foods are abundantly available.

Hippocampal GABAergic interneurons and memory

One of the most captivating questions in neuroscience revolves around the brain's ability to efficiently and durably capture and store information. It must process continuous input from sensory organs while also encoding memories that can persist throughout a lifetime. What are the cellular-, subcellular-, and network-level mechanisms that underlie this remarkable capacity for long-term information storage? Furthermore, what contributions do distinct types of GABAergic interneurons make to this process? As the hippocampus plays a pivotal role in memory, our review focuses on three aspects: (1) delineation of hippocampal interneuron types and their connectivity, (2) interneuron plasticity, and (3) activity patterns of interneurons during memory-related rhythms, including the role of long-range interneurons and disinhibition. We explore how these three elements, together showcasing the remarkable diversity of inhibitory circuits, shape the processing of memories in the hippocampus.

Local and long-range GABAergic circuits in hippocampal area CA1 and their link to Alzheimer's disease

GABAergic inhibitory neurons are the principal source of inhibition in the brain. Traditionally, their role in maintaining the balance of excitation-inhibition has been emphasized. Beyond homeostatic functions, recent circuit mapping and functional manipulation studies have revealed a wide range of specific roles that GABAergic circuits play in dynamically tilting excitation-inhibition coupling across spatio-temporal scales. These span from gating of compartment- and input-specific signaling, gain modulation, shaping input-output functions and synaptic plasticity, to generating signal-to-noise contrast, defining temporal windows for integration and rate codes, as well as organizing neural assemblies, and coordinating inter-regional synchrony. GABAergic circuits are thus instrumental in controlling single-neuron computations and behaviorally-linked network activity. The activity dependent modulation of sensory and mnemonic information processing by GABAergic circuits is pivotal for the formation and maintenance of episodic memories in the hippocampus. Here, we present an overview of the local and long-range GABAergic circuits that modulate the dynamics of excitation-inhibition and disinhibition in the main output area of the hippocampus CA1, which is crucial for episodic memory. Specifically, we link recent findings pertaining to GABAergic neuron molecular markers, electrophysiological properties, and synaptic wiring with their function at the circuit level. Lastly, given that area CA1 is particularly impaired during early stages of Alzheimer's disease, we emphasize how these GABAergic circuits may contribute to and be involved in the pathophysiology.

A miniaturized nigrostriatal-like circuit regulating locomotor performance in a protochordate

To gain insight into the evolution of motor control systems at the origin of vertebrates, we have investigated higher-order motor circuitry in the protochordate Oikopleura dioica. We have identified a highly miniaturized circuit in Oikopleura with a projection from a single pair of dopaminergic neurons to a small set of synaptically coupled GABAergic neurons, which in turn exert a disinhibitory descending projection onto the locomotor central pattern generator. The circuit is reminiscent of the nigrostriatopallidal system in the vertebrate basal ganglia, in which disinhibitory circuits release specific movements under the modulatory control of dopamine. We demonstrate further that dopamine is required to optimize locomotor performance in Oikopleura, mirroring its role in vertebrates. A dopamine-regulated disinhibitory locomotor control circuit reminiscent of the vertebrate nigrostriatopallidal system was thus already present at the origin of ancestral chordates and has been maintained in the face of extreme nervous system miniaturization in the urochordate lineage.

The Pathogenesis of Disinhibition in Patients with Traumatic Brain Injury: A Two Patient Case Report

Higher brain dysfunction commonly occurs following traumatic brain injury (TBI), and may manifest in a social behavioral impairment which can significantly impede active social participation. We report two cases, one of voyeurism and the second of alcohol abuse, which might have been caused by TBI resulting in disinhibition, a type of social behavioral impairment. We discuss the underlying pathophysiological mechanisms to raise awareness of such cases and aid the development of effective interventions. Patient 1 suffered a TBI at 18 years of age, 2 years after which he presented repeated episodes of sexually deviant behavior (voyeurism). At 28, he committed suicide, since he was unable to control his aberrant behavior. Patient 2 suffered a TBI at the age of 13. He first displayed problematic behavior 7 years later, which included drinking excessive amounts of alcohol and stealing while inebriated. Despite both patients having sound moral judgment, they had irrational and uncontrollable impulses of desire. Imaging findings could explain the possible causes of impulse control impairments. Damage to the basal ganglia and limbic system, which are involved in social behavior, presumably led to desire-dominated behavior, leading to the patients conducting unlawful acts despite intact moral judgment. It is crucial to educate society about the prevalence of these disorders, explain how these disinhibitions start, and develop effective interventions.

Stroke-Induced Central Pain: Overview of the Mechanisms, Management, and Emerging Targets of Central Post-Stroke Pain

The incidence of stroke plays the foremost role in the genesis of central neuropathic pain. Central post-stroke pain (CPSP) is a central pain arising from a vascular lesion in the central nervous system that elicits somatosensory deficits, often contralateral to stroke lesions. It is expressed as continuous or intermittent pain accompanied by sensory abnormalities like dysesthesia and allodynia. CPSP remains de-emphasized due to the variation in onset and diversity in symptoms, besides the difficulty of distinguishing it from other post-stroke pains, often referred to as a diagnosis of exclusion. Spinothalamic dysfunction, disinhibition of the medial thalamus, and neuronal hyperexcitability combined with deafferentation in thalamocortical regions are the mechanisms underlying central pain, which play a significant role in the pathogenesis of CPSP. The treatment regimen for CPSP seems to be perplexed in nature; however, based on available studies, amitriptyline and lamotrigine are denoted as first-line medications and non-pharmacological choices may be accounted for cases intractable to pharmacotherapy. This review attempts to provide an overview of the mechanisms, existing management approaches, and emerging targets of CPSP. A profound understanding of CPSP aids in optimizing the quality of life among stroke sufferers and facilitates further research to develop newer therapeutic agents for managing CPSP.

Heightened sensitivity to the disinhibiting effect of alcohol in women during the late follicular phase of the menstrual cycle

Compared with men, women are disproportionately affected by alcohol, including greater risks of physiological damage, behavioral impairment, and relapse. One likely mechanism underlying the sexual disparity in this vulnerability is the fluctuation of ovarian hormones, particularly estradiol (E2), across phases of the menstrual cycle. Several preclinical and clinical studies have shown that higher E2 levels positively correlate with drinking, suggesting E2 may play a significant role in modulating drinking. Inhibitory control also modulates drinking; when it is reduced or compromised by alcohol, the drinker's ability to stop the self-administration of alcohol could be impaired, leading to a binge episode. The present study aimed to examine the degree to which menstrual cycle phase can influence the disinhibiting effect of alcohol. Twenty-four healthy young adult women participated in a within-subjects placebo-controlled study of the acute disinhibiting effect of 0.60 g/kg alcohol over the course of two test sessions. A cued go/no-go task measured the disinhibiting effects of alcohol and placebo beverages during the early follicular phase of the cycle when E2 levels were low and the late follicular phase (i.e., ovulation) when E2 was elevated. Results showed that the disinhibiting effect of alcohol increased nearly twofold during the late follicular phase when E2 was elevated. These findings highlight the role of alcohol-induced disinhibition as a potential behavioral mechanism by which fluctuations in ovarian hormones as a function of the menstrual cycle contribute to increased risk for excessive alcohol use in women. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The ferroptosis inducer RSL3 triggers interictal epileptiform activity in mice cortical neurons

Epilepsy is a neurological disorder characterized by recurrent seizures, which result from excessive, synchronous discharges of neurons in different brain areas. In about 30% of cases, epileptic discharges, which vary in their etiology and symptomatology, are difficult to treat with conventional drugs. Ferroptosis is a newly defined iron-dependent programmed cell death, characterized by excessive accumulation of lipid peroxides and reactive oxygen species. Evidence has been provided that ferroptosis is involved in epilepsy, and in particular in those forms resistant to drugs. Here, whole cell patch clamp recordings, in current and voltage clamp configurations, were performed from layer IV principal neurons in cortical slices obtained from adult mouse brain. Application of the ferroptosis inducer RAS-selective lethal 3 (RSL3) induced interictal epileptiform discharges which started at RSL3 concentrations of 2 μM and reached a plateau at 10 μM. This effect was not due to changes in active or passive membrane properties of the cells, but relied on alterations in synaptic transmission. In particular, interictal discharges were dependent on the excessive excitatory drive to layer IV principal cells, as suggested by the increase in frequency and amplitude of spontaneously occurring excitatory glutamatergic currents, possibly dependent on the reduction of inhibitory GABAergic ones. This led to an excitatory/inhibitory unbalance in cortical circuits. Interictal bursts could be prevented or reduced in frequency by the lipophilic antioxidant Vitamin E (30 μM). This study allows identifying new targets of ferroptosis-mediated epileptic discharges opening new avenues for the treatment of drug-resistant forms of epilepsy.

Perceived neighborhood disorder as a moderator of the relationship between marijuana use and disinhibition in a sample of emerging adult African American females

Disinhibition is associated with myriad risk-taking behaviors and adverse outcomes. Both marijuana use and poor neighborhood conditions have been associated with disinhibition. However, the extent to which neighborhood disorder interacts with marijuana use to influence disinhibition has not been studied, extensively. A better understanding of these relationships has implications for designing more effective tailored place-based interventions that aim to reduce risk taking behaviors and related adverse social and health outcomes associated with marijuana use. Thus, the purpose of this study was to examine the interactive effects of perceived neighborhood disorder and marijuana use on disinhibition. The sample included 120 African American female residents of disadvantaged neighborhoods (Mage = 23.6 ± 3.46). We employed hierarchical linear regression analysis to examine the interactive effects of marijuana use and perceived neighborhood disorder on disinhibition, while controlling for age and education. The interaction term was marginally significant (b = 5.66; t(109) = 1.72, p = .08). Next, the conditional effects were explored. Results indicated the association of marijuana use with disinhibition was stronger for females in the higher neighborhood disorder group, compared to those in the lower neighborhood disorder group (10.40 and 4.51, respectively). Our findings support the need for more research on the potential of neighborhood disorder to amplify the effects of marijuana use on disinhibition and related neurobehavioral traits. The identification of contextual moderators and high-risk sub-groups will aid in the design of more tailored place-based interventions that aim to reduce risk-taking behavior among those most vulnerable.

Are Emotional Eating and Other Eating Behaviors the Missing Link in the Relationship between Inadequate Sleep and Obesity? A Systematic Review

Evidence is emerging to explain that the relationship between inadequate sleep and obesity could be influenced by emotional eating and other eating behaviors such as disinhibition. Therefore, our aim was to conduct a systematic review to analyze the potential role of emotional eating and other eating behaviors in the relationship between inadequate sleep and obesity. We conducted a comprehensive search on 2 databases (Medline and Scopus) looking for records from 1 January 2011 until 31 December 2022 without language restrictions. Cross-sectional, longitudinal, and interventional studies were included if they assessed the association between sleep and emotional eating, as well as the role of emotional eating on the relationship between inadequate sleep and obesity. Secondary outcomes included studies analyzing the link between sleep and other eating behaviors as well as their role in the sleep-obesity relationship. Our results showed that emotional eating and disinhibition play a significant role in the relationship between inadequate sleep and obesity, especially in women. Furthermore, we provide evidence of other eating behaviors (e.g., external eating, eating competence, and hunger), which are also associated with poor sleep outcomes. However, these behaviors do not seem to be determinants of the association between sleep and obesity. In conclusion, our results suggest that individuals with inadequate sleep who are prone to emotional eating and/or disinhibition may require tailored approaches for obesity prevention and treatment.

Optogenetics reveals paradoxical network stabilizations in hippocampal CA1 and CA3

Recurrent connectivity between excitatory neurons and the strength of feedback from inhibitory neurons are critical determinants of the dynamics and computational properties of neuronal circuits. Toward a better understanding of these circuit properties in regions CA1 and CA3 of the hippocampus, we performed optogenetic manipulations combined with large-scale unit recordings in rats under anesthesia and in quiet waking, using photoinhibition and photoexcitation with different light-sensitive opsins. In both regions, we saw striking paradoxical responses: subsets of cells increased firing during photoinhibition, while other cells decreased firing during photoexcitation. These paradoxical responses were more prominent in CA3 than in CA1, but, notably, CA1 interneurons showed increased firing in response to photoinhibition of CA3. These observations were recapitulated in simulations where we modeled both CA1 and CA3 as inhibition-stabilized networks in which strong recurrent excitation is balanced by feedback inhibition. To directly test the inhibition-stabilized model, we performed large-scale photoinhibition directed at (GAD-Cre) inhibitory cells and found that interneurons in both regions increased firing when photoinhibited, as predicted. Our results highlight the often-paradoxical circuit dynamics that are evidenced during optogenetic manipulations and indicate that, contrary to long-standing dogma, both CA1 and CA3 hippocampal regions display strongly recurrent excitation, which is stabilized through inhibition.

Network Analysis of Neuropsychiatric Symptoms in Alzheimer's Disease

Background: Neuropsychiatric symptoms due to Alzheimer's disease (AD) and mild cognitive impairment (MCI) can decrease quality of life for patients and increase caregiver burden. Better characterization of neuropsychiatric symptoms and methods of analysis are needed to identify effective treatment targets. The current investigation leveraged the National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) to examine the network structure of neuropsychiatric symptoms among symptomatic older adults with cognitive impairment. Methods: The network relationships of behavioral symptoms was estimated from Neuropsychiatric Inventory Questionnaire (NPI-Q) data acquired from 12,494 older adults with MCI and AD during their initial visit. Network analysis provides insight into the relationships among sets of symptoms and allows calculation of the strengths of the relationships. Nodes represented individual NPI-Q symptoms and edges represented the pairwise dependency between symptoms. Node centrality was calculated to determine the relative importance of each symptom in the network. Results: The analysis showed patterns of connectivity among the symptoms of the NPI-Q. The network ( M =.28) consisted of mostly positive edges. The strongest edges connected nodes within symptom domain. Disinhibition and agitation/aggression were the most central symptoms in the network. Depression/dysphoria was the most frequently endorsed symptom, but it was not central in the network. Conclusions: Neuropsychiatric symptoms in MCI and AD are highly comorbid and mutually reinforcing. The presence of disinhibition and agitation/aggression yielded a higher probability of additional neuropsychiatric symptoms. Interventions targeting these symptoms may lead to greater neuropsychiatric symptom improvement overall. Future work will compare neuropsychiatric symptom networks across dementia etiologies, informant relationships, and ethnic/racial groups, and will explore the utility of network analysis as a means of interrogating treatment effects.

Functional specialization of hippocampal somatostatin-expressing interneurons

Hippocampal somatostatin-expressing (Sst) GABAergic interneurons (INs) exhibit considerable anatomical and functional heterogeneity. Recent single cell transcriptome analyses have provided a comprehensive Sst-IN subtype census, a plausible molecular ground truth of neuronal identity whose links to specific functionality remain incomplete. Here, we designed an approach to identify and access subpopulations of Sst-INs based on transcriptomic features. Four mouse models based on single or combinatorial Cre- and Flp- expression differentiated functionally distinct subpopulations of CA1 hippocampal Sst-INs that largely tiled the morpho-functional parameter space of the Sst-INs superfamily. Notably, the Sst;;Tac1 intersection revealed a population of bistratified INs that preferentially synapsed onto fast-spiking interneurons (FS-INs) and were both necessary and sufficient to interrupt their firing. In contrast, the Ndnf;;Nkx2-1 intersection identified a population of oriens lacunosum-moleculare (OLM) INs that predominantly targeted CA1 pyramidal neurons, avoiding FS-INs. Overall, our results provide a framework to translate neuronal transcriptomic identity into discrete functional subtypes that capture the diverse specializations of hippocampal Sst-INs.

Associations between polygenic risk of substance use and use disorder and alcohol, cannabis, and nicotine use in adolescence and young adulthood in a longitudinal twin study

BACKGROUND

Recent well-powered genome-wide association studies have enhanced prediction of substance use outcomes via polygenic scores (PGSs). Here, we test (1) whether these scores contribute to prediction over-and-above family history, (2) the extent to which PGS prediction reflects inherited genetic variation v. demography (population stratification and assortative mating) and indirect genetic effects of parents (genetic nurture), and (3) whether PGS prediction is mediated by behavioral disinhibition prior to substance use onset.

METHODS

PGSs for alcohol, cannabis, and nicotine use/use disorder were calculated for Minnesota Twin Family Study participants (N = 2483, 1565 monozygotic/918 dizygotic). Twins' parents were assessed for histories of substance use disorder. Twins were assessed for behavioral disinhibition at age 11 and substance use from ages 14 to 24. PGS prediction of substance use was examined using linear mixed-effects, within-twin pair, and structural equation models.

RESULTS

Nearly all PGS measures were associated with multiple types of substance use independently of family history. However, most within-pair PGS prediction estimates were substantially smaller than the corresponding between-pair estimates, suggesting that prediction is driven in part by demography and indirect genetic effects of parents. Path analyses indicated the effects of both PGSs and family history on substance use were mediated via disinhibition in preadolescence.

CONCLUSIONS

PGSs capturing risk of substance use and use disorder can be combined with family history measures to augment prediction of substance use outcomes. Results highlight indirect sources of genetic associations and preadolescent elevations in behavioral disinhibition as two routes through which these scores may relate to substance use.

Localized chemogenetic silencing of inhibitory neurons: a novel mouse model of focal cortical epileptic activity

Focal cortical epilepsies are frequently refractory to available anticonvulsant drug therapies. One key factor contributing to this state is the limited availability of animal models that allow to reliably study focal cortical seizures and how they recruit surrounding brain areas in vivo. In this study, we selectively expressed the inhibitory chemogenetic receptor, hM4D, in GABAergic neurons in focal cortical areas using viral gene transfer. GABAergic silencing using Clozapine-N-Oxide (CNO) demonstrated reliable induction of local epileptiform events in the electroencephalogram signal of awake freely moving mice. Anesthetized mice experiments showed consistent induction of focal epileptiform-events in both the barrel cortex (BC) and the medial prefrontal cortex (mPFC), accompanied by high-frequency oscillations, a known characteristic of human seizures. Epileptiform-events showed propagation indication with favored propagation pathways: from the BC on 1 hemisphere to its counterpart and from the BC to the mPFC, but not vice-versa. Lastly, sensory whisker-pad stimulation evoked BC epileptiform events post-CNO, highlighting the potential use of this model in studying sensory-evoked seizures. Combined, our results show that targeted chemogenetic inhibition of GABAergic neurons using hM4D can serve as a novel, versatile, and reliable model of focal cortical epileptic activity suitable for systematically studying cortical ictogenesis in different cortical areas.

Working Online During the Contemporary COVID-19 Pandemic

Within the psychoanalytic school there has been substantial and ongoing debate about the efficacy of teleanalysis. However, as a result of the current COVID-19 pandemic and the online work with which the Jungian analytic community has now had to engage, this paper initially focuses on analysts' actual experiences of working by teleanalysis. These experiences highlight a range of issues like "Zoom fatigue", "online disinhibition", dissonance, confidentiality, the frame and working with new patients. Alongside these issues, there were ample experiences by analysts of both productive psychotherapy apace with analytic work involving transference and countertransference phenomena, all indicating that a genuine and good enough analytic process can occur with teleanalysis. An overview of the research and literature both prior to the pandemic and as a result of it, confirms the validity of these experiences so long as analysts are cognizant of the specifics of such an online modality. Conclusions to do with the question, "what have we learned?", alongside training, ethics and supervision issues are subsequently discussed.

Inhibitory top-down projections from zona incerta mediate neocortical memory

Top-down projections convey a family of signals encoding previous experiences and current aims to the sensory neocortex, where they converge with external bottom-up information to enable perception and memory. Whereas top-down control has been attributed to excitatory pathways, the existence, connectivity, and information content of inhibitory top-down projections remain elusive. Here, we combine synaptic two-photon calcium imaging, circuit mapping, cortex-dependent learning, and chemogenetics in mice to identify GABAergic afferents from the subthalamic zona incerta as a major source of top-down input to the neocortex. Incertocortical transmission undergoes robust plasticity during learning that improves information transfer and mediates behavioral memory. Unlike excitatory pathways, incertocortical afferents form a disinhibitory circuit that encodes learned top-down relevance in a bidirectional manner where the rapid appearance of negative responses serves as the main driver of changes in stimulus representation. Our results therefore reveal the distinctive contribution of long-range (dis)inhibitory afferents to the computational flexibility of neocortical circuits.

Effect of swearing on strength: Disinhibition as a potential mediator

Swearing fulfils positive functions, including benefitting pain relief and physical strength. Here we present two experiments assessing a possible psychological mechanism, increased state disinhibition, for the effect of swearing on physical strength. Two repeated measures experiments were carried out with sample sizes N = 56 and N = 118. Both included the measures of physical performance assessing, respectively, grip and arm strength, and both included the Balloon Analogue Risk Task (BART) to measure risky behaviour. Experiment 2, which was pre-registered, additionally assessed flow, emotion including humour, distraction including novelty, self-confidence, and anxiety. Experiments 1 and 2 found that repeating a swear word benefitted physical strength and increased risky behaviour, but risky behaviour did not mediate the strength effect. Experiment 2 found that repeating a swear word increased flow, positive emotion, humour, distraction, and self-confidence. Humour mediated the effect of swearing on physical strength. Consistent effects of swearing on physical strength indicate that this is a reliable effect. Swearing influenced several constructs related to state disinhibition, including increased self-confidence. Humour appeared to mediate the effect of swearing on physical strength, consistent with a hot cognitions explanation of swearing-induced state disinhibition. However, as this mediation effect was part of an exploratory analysis, further pre-registered experimental research, including validated measures of humour, is required.

Time-dependent and selective microglia-mediated removal of spinal synapses in neuropathic pain

Neuropathic pain is a debilitating condition resulting from damage to the nervous system. Imbalance of spinal excitation and inhibition has been proposed to contribute to neuropathic pain. However, the structural basis of this imbalance remains unknown. Using a preclinical model of neuropathic pain, we show that microglia selectively engulf spinal synapses that are formed by central neurons and spare those of peripheral sensory neurons. Furthermore, we reveal that removal of inhibitory and excitatory synapses exhibits distinct temporal patterns, in which microglia-mediated inhibitory synapse removal precedes excitatory synapse removal. We also find selective and gradual increase in complement depositions on dorsal horn synapses that corresponds to the temporal pattern of microglial synapse pruning activity and type-specific synapse loss. Together, these results define a specific role for microglia in the progression of neuropathic pain pathogenesis and implicate these immune cells in structural remodeling of dorsal horn circuitry.

Voltage-gated calcium channel subunit α2δ-1 in spinal dorsal horn neurons contributes to aberrant excitatory synaptic transmission and mechanical hypersensitivity after peripheral nerve injury

Neuropathic pain, an intractable pain symptom that occurs after nerve damage, is caused by the aberrant excitability of spinal dorsal horn (SDH) neurons. Gabapentinoids, the most commonly used drugs for neuropathic pain, inhibit spinal calcium-mediated neurotransmitter release by binding to α₂δ-1, a subunit of voltage-gated calcium channels, and alleviate neuropathic pain. However, the exact contribution of α₂δ-1 expressed in SDH neurons to the altered synaptic transmission and mechanical hypersensitivity following nerve injury is not fully understood. In this study, we investigated which types of SDH neurons express α₂δ-1 and how α₂δ-1 in SDH neurons contributes to the mechanical hypersensitivity and altered spinal synaptic transmission after nerve injury. Using in situ hybridization technique, we found that Cacna2d1, mRNA coding α₂δ-1, was mainly colocalized with Slc17a6, an excitatory neuronal marker, but not with Slc32a1, an inhibitory neuronal marker in the SDH. To investigate the role of α₂δ-1 in SDH neurons, we used clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system and showed that SDH neuron-specific ablation of Cacna2d1 alleviated mechanical hypersensitivity following nerve injury. We further found that excitatory post-synaptic responses evoked by electrical stimulation applied to the SDH were significantly enhanced after nerve injury, and that these enhanced responses were significantly decreased by application of mirogabalin, a potent α₂δ-1 inhibitor, and by SDH neuron-specific ablation of Cacna2d1. These results suggest that α₂δ-1 expressed in SDH excitatory neurons facilitates spinal nociceptive synaptic transmission and contributes to the development of mechanical hypersensitivity after nerve injury.

Inhibitory circuits in fear memory and fear-related disorders

Fear learning and memory rely on dynamic interactions between the excitatory and inhibitory neuronal populations that make up the prefrontal cortical, amygdala, and hippocampal circuits. Whereas inhibition of excitatory principal cells (PCs) by GABAergic neurons restrains their excitation, inhibition of GABAergic neurons promotes the excitation of PCs through a process called disinhibition. Specifically, GABAergic interneurons that express parvalbumin (PV+) and somatostatin (SOM+) provide inhibition to different subcellular domains of PCs, whereas those that express the vasoactive intestinal polypeptide (VIP+) facilitate disinhibition of PCs by inhibiting PV+ and SOM+ interneurons. Importantly, although the main connectivity motifs and the underlying network functions of PV+, SOM+, and VIP+ interneurons are replicated across cortical and limbic areas, these inhibitory populations play region-specific roles in fear learning and memory. Here, we provide an overview of the fear processing in the amygdala, hippocampus, and prefrontal cortex based on the evidence obtained in human and animal studies. Moreover, focusing on recent findings obtained using genetically defined imaging and intervention strategies, we discuss the population-specific functions of PV+, SOM+, and VIP+ interneurons in fear circuits. Last, we review current insights that integrate the region-specific inhibitory and disinhibitory network patterns into fear memory acquisition and fear-related disorders.

Regulation of circuit organization and function through inhibitory synaptic plasticity

Diverse inhibitory neurons in the mammalian brain shape circuit connectivity and dynamics through mechanisms of synaptic plasticity. Inhibitory plasticity can establish excitation/inhibition (E/I) balance, control neuronal firing, and affect local calcium concentration, hence regulating neuronal activity at the network, single neuron, and dendritic level. Computational models can synthesize multiple experimental results and provide insight into how inhibitory plasticity controls circuit dynamics and sculpts connectivity by identifying phenomenological learning rules amenable to mathematical analysis. We highlight recent studies on the role of inhibitory plasticity in modulating excitatory plasticity, forming structured networks underlying memory formation and recall, and implementing adaptive phenomena and novelty detection. We conclude with experimental and modeling progress on the role of interneuron-specific plasticity in circuit computation and context-dependent learning.

The Good, the Bad, and the Ugly? A Triarchic Perspective on Psychopathy at Work

Does psychopathy have an upside in vocational contexts? Applying the triarchic model of psychopathy, we propose that the dimensions of boldness, disinhibition, and meanness have different relations to workplace outcomes. Focusing on boldness and in line with socioanalytic personality theory, we propose that political skill moderates the relation between boldness and job performance. Using a sample of 477 target-coworker pairings, we found interaction effects of boldness and political skill on contextual and task performance, and the buffering of counterproductive work behavior. Furthermore, political skill moderated the relation between boldness and adaptive performance. Disinhibition and meanness were positively correlated with counterproductive work behaviors, thereby reflecting the dark core of psychopathy. In sum, boldness is a trait linked to career success in the absence of the other traits that make up psychopathy as a whole. Furthermore, we encourage the use of the triarchic model as an overarching framework in vocational contexts.

Childhood trauma moderates morphometric associations between orbitofrontal cortex and amygdala: implications for pathological personality traits

BACKGROUND

Research has demonstrated that chronic stress exposure early in development can lead to detrimental alterations in the orbitofrontal cortex (OFC)-amygdala circuit. However, the majority of this research uses functional neuroimaging methods, and thus the extent to which childhood trauma corresponds to morphometric alterations in this limbic-cortical network has not yet been investigated. This study had two primary objectives: (i) to test whether anatomical associations between OFC-amygdala differed between adults as a function of exposure to chronic childhood assaultive trauma and (ii) to test how these environment-by-neurobiological effects relate to pathological personality traits.

METHODS

Participants were 137 ethnically diverse adults (48.1% female) recruited from the community who completed a clinical diagnostic interview, a self-report measure of pathological personality traits, and anatomical MRI scans.

RESULTS

Findings revealed that childhood trauma moderated bilateral OFC-amygdala volumetric associations. Specifically, adults with childhood trauma exposure showed a positive association between medial OFC volume and amygdalar volume, whereas adults with no childhood exposure showed the negative OFC-amygdala structural association observed in prior research with healthy samples. Examination of the translational relevance of trauma-related alterations in OFC-amygdala volumetric associations for disordered personality traits revealed that trauma exposure moderated the association of OFC volume with antagonistic and disinhibited phenotypes, traits characteristic of Cluster B personality disorders.

CONCLUSIONS

The OFC-amygdala circuit is a potential anatomical pathway through which early traumatic experiences perpetuate emotional dysregulation into adulthood and confer risk for personality pathology. Results provide novel evidence of divergent neuroanatomical pathways to similar personality phenotypes depending on early trauma exposure.

Assessing general versus specific liability for externalizing problems in adolescence: Concurrent and prospective prediction of symptoms of conduct disorder, ADHD, and substance use

This study explored the generality versus specificity of two trait-liability factors for externalizing problems-disinhibition and callousness-in the concurrent and prospective prediction of symptoms of conduct disorder, attention-deficit/hyperactivity disorder (ADHD), and substance use (i.e., alcohol use disorder and history of illicit substance use). Disinhibition involves an impulsive, unrestrained cognitive-behavioral style; callousness entails a dispositional lack of social-emotional sensitivity. Participants were European adolescents from the multisite IMAGEN project who completed questionnaires and clinical interviews at ages 14 (N = 1,504, Mage = 14.41, 51.13% female) and 16 (N = 1,407, Mage = 16.46, 51.88% female). Disinhibition was related concurrently and prospectively to greater symptoms of conduct disorder, ADHD, and alcohol use disorder; higher scores on a general externalizing factor; and greater likelihood of having tried an illicit substance. Callousness was selectively related to greater conduct disorder symptoms. These findings indicate disinhibition confers broad liability for externalizing spectrum disorders, perhaps due to its affiliated deficits in executive function. In contrast, callousness appears to represent more specific liability for antagonistic (aggressive/exploitative) forms of externalizing, as exemplified by antisocial behavior. Results support the utility of developmental-ontogenetic and hierarchical-dimensional models of psychopathology and have important implications for early assessment of risk for externalizing problems. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Negative affectivity and disinhibition as moderators of an interpersonal pathway to suicidal behavior in borderline personality disorder

This longitudinal study examined whether personality traits moderate the link between interpersonal dysfunction and suicidal behavior in a high-risk sample of 458 individuals diagnosed with borderline personality disorder (BPD). Participants were assessed annually for up to 30 years (mean number of follow-ups = 7.82). Using multilevel structural equation modeling, we examined i) longitudinal, within-person relationships among interpersonal dysfunction, suicidal ideation, and suicide attempts; and ii) moderation of these relationships by negative affectivity and disinhibition. Negative affectivity predicted a stronger within-person coupling between interpersonal dysfunction and suicidal ideation. Disinhibition predicted a stronger coupling between ideation and suicide attempts. Assessing negative affectivity and disinhibition in a treatment setting may guide clinician vigilance toward those at highest risk for interpersonally triggered suicidal behaviors.

The contribution of behavioral features to caregiver burden in FTLD spectrum disorders

INTRODUCTION

Caregivers of patients with frontotemporal lobar degeneration (FTLD) spectrum disorders experience tremendous burden, which has been associated with the neuropsychiatric and behavioral features of the disorders.

METHODS

In a sample of 558 participants with FTLD spectrum disorders, we performed multiple-variable regressions to identify the behavioral features that were most strongly associated with caregiver burden, as measured by the Zarit Burden Interview, at each stage of disease.

RESULTS

Apathy and disinhibition, as rated by both clinicians and caregivers, as well as clinician-rated psychosis, showed the strongest associations with caregiver burden, a pattern that was consistent when participants were separated cross-sectionally by disease stage. In addition, behavioral features appeared to contribute most to caregiver burden in patients with early dementia.

DISCUSSION

Caregivers should be provided with early education on the management of the behavioral features of FTLD spectrum disorders. Interventions targeting apathy, disinhibition, and psychosis may be most useful to reduce caregiver burden.

Recurring Cholinergic Inputs Induce Local Hippocampal Plasticity through Feedforward Disinhibition

The CA1 pyramidal neurons are embedded in an intricate local circuitry that contains a variety of interneurons. The roles these interneurons play in the regulation of the excitatory synaptic plasticity remains largely understudied. Recent experiments showed that recurring cholinergic activation of α7 nACh receptors expressed in oriens-lacunosum-moleculare (OLMα2) interneurons can directly induce LTP in Schaffer collateral (SC)-CA1 synapses. Here, we pair in vitro studies with biophysically based modeling to uncover the underlying mechanisms. According to our model, α7 nAChR activation increases OLM GABAergic activity. This results in the inhibition of the fast-spiking interneurons that provide feedforward inhibition onto CA1 pyramidal neurons. This disinhibition, paired with tightly timed SC stimulation, can induce potentiation at the excitatory synapses of CA1 pyramidal neurons. Our work details the role of cholinergic modulation in disinhibition-induced hippocampal plasticity. It relates the timing of cholinergic pairing found experimentally in previous studies with the timing between disinhibition and hippocampal stimulation necessary to induce potentiation and suggests the dynamics of the involved interneurons play a crucial role in determining this timing.Significance StatementWe use a combination of experiments and mechanistic modeling to uncover the key role for cholinergic neuromodulation of feedforward disinhibitory circuits in regulating hippocampal plasticity. We found that cholinergic activation of α7 nAChR on α7 nACh receptors expressed in oriens-lacunosum-moleculare interneurons, when tightly paired with stimulation of the Schaffer collaterals, can cancel feedforward inhibition onto CA1 pyramidal cells, enabling the potentiation of the SC-CA1 synapse. Our work details how cholinergic action on GABAergic interneurons can tightly regulate the excitability and plasticity of the hippocampal network, unraveling the intricate interplay of the hierarchal inhibitory circuitry and cholinergic neuromodulation as a mechanism for hippocampal plasticity.

Striatonigrostriatal circuit architecture for disinhibition of dopamine signaling

The basal ganglia operate largely in closed parallel loops, including an associative circuit for goal-directed behavior originating from the dorsomedial striatum (DMS) and a somatosensory circuit important for habit formation originating from the dorsolateral striatum (DLS). An exception to this parallel circuit organization has been proposed to explain how information might be transferred between striatal subregions, for example, from the DMS to the DLS during habit formation. The “ascending spiral hypothesis” proposes that the DMS disinhibits dopamine signaling in the DLS through a tri-synaptic, open-loop striatonigrostriatal circuit. Here, we use transsynaptic and intersectional genetic tools to investigate both closed- and open-loop striatonigrostriatal circuits. We find strong evidence for closed loops, which would allow striatal subregions to regulate their own dopamine release. We also find evidence for functional synapses in open loops. However, these synapses are unable to modulate tonic dopamine neuron firing, questioning the prominence of their role in mediating crosstalk between striatal subregions.

Ambrosi and Lerner investigate a basal ganglia circuit—the ascending spiral—long hypothesized to underlie habit formation by allowing disinhibition of dopamine signaling in the dorsolateral striatum (DLS). They find that synaptic connectivity in the ascending spiral is present, but the circuit cannot support straightforward disinhibition of DLS dopamine signaling.

Selective Inhibitory Circuit Dysfunction after Chronic Frontal Lobe Contusion

Traumatic brain injury (TBI) is a leading cause of neurologic disability; the most common deficits affect prefrontal cortex-dependent functions such as attention, working memory, social behavior, and mental flexibility. Despite this prevalence, little is known about the pathophysiology that develops in frontal cortical microcircuits after TBI. We investigated whether alterations in subtype-specific inhibitory circuits are associated with cognitive inflexibility in a mouse model of frontal lobe contusion in both male and female mice that recapitulates aberrant mental flexibility as measured by deficits in rule reversal learning. Using patch-clamp recordings and optogenetic stimulation, we identified selective vulnerability in the non-fast-spiking and somatostatin-expressing (SOM+) subtypes of inhibitory neurons in layer V of the orbitofrontal cortex 2 months after injury. These subtypes exhibited reduced intrinsic excitability and a decrease in their synaptic output onto pyramidal neurons, respectively. By contrast, the fast-spiking and parvalbumin-expressing interneurons did not show changes in intrinsic excitability or synaptic output, respectively. Impairments in non-fast-spiking/SOM+ inhibitory circuit function were also associated with network hyperexcitability. These findings provide evidence for selective disruptions within specific inhibitory microcircuits that may guide the development of novel therapeutics for TBI.SIGNIFICANCE STATEMENT TBI frequently leads to chronic deficits in cognitive and behavioral functions that involve the prefrontal cortex, yet the maladaptive changes that occur in these cortical microcircuits are unknown. Our data indicate that alterations in subtype-specific inhibitory circuits, specifically vulnerability in the non-fast-spiking/somatostatin-expressing interneurons, occurs in the orbitofrontal cortex in the context of chronic deficits in reversal learning. These neurons exhibit reduced excitability and synaptic output, whereas the other prominent inhibitory population in layer V, the fast-spiking/parvalbumin-expressing interneurons as well as pyramidal neurons are not affected. Our work offers mechanistic insight into the subtype-specific function of neurons that may contribute to mental inflexibility after TBI.

New monoamine antidepressant, hypidone hydrochloride (YL-0919), enhances the excitability of medial prefrontal cortex in mice via a neural disinhibition mechanism

Hypidone hydrochloride (YL-0919) is a novel antidepressant in clinical phase II trial. Previous studies show that YL-0919 is a selective 5-HT (serotonin) reuptake inhibitor, 5-HT_1A receptor partial agonist, and 5-HT₆ receptor agonist, which exerts antidepressant effects in various animal models, but its effects on neural function remain unclear. Medial prefrontal cortex (mPFC), a highly evolved brain region, controls highest order cognitive functions and emotion regulation. In this study we investigated the effects of YL-0919 on the mPFC function, including the changes in neuronal activities using electrophysiological recordings. Extracellular recording (in vivo) showed that chronic administration of YL-0919 significantly increased the spontaneous discharges of mPFC neurons. In mouse mPFC slices, whole-cell recording revealed that perfusion of YL-0919 significantly increased the frequency of sEPSCs, but decreased the frequency of sIPSCs. Then we conducted whole-cell recording in mPFC slices of GAD67-GFP transgenic mice, and demonstrated that YL-0919 significantly inhibited the excitability of GABAergic neurons. In contrast, it did not alter the excitability of pyramidal neurons in mPFC slices of normal mice. Moreover, the inhibition of GABAergic neurons by YL-0919 was prevented by pre-treatment with 5-HT_1A receptor antagonist WAY 100635. Finally, chronic administration of YL-0919 significantly increased the phosphorylation levels of mTOR and GSK-3β in the mPFC as compared with vehicle. Taken together, our results demonstrate that YL-0919 enhances the excitability of mPFC via a disinhibition mechanism to fulfill its rapid antidepressant neural mechanism, which was accomplished by 5-HT_1A receptor-mediated inhibition of inhibitory GABAergic interneurons.

Nucleus accumbens atrophy in Parkinson's disease (Mavridis' atrophy): 10 years later

Parkinson's disease (PD) is a common neurodegenerative disorder associated with gray matter atrophy. The human nucleus accumbens (NA) is a major part of the ventral striatum and modulator of the reward network of the brain. It plays an important role in several cognitive and emotional functions. In patients with PD, dysfunction of this nucleus is correlated not only with movement disorders but also with various neuropsychological deficits and psychiatric symptoms. The human NA suffers atrophy in PD, which is called Mavridis' atrophy (MA), a well established characteristic of PD that was first described 10 years ago. The purpose of this article is to review the current knowledge regarding the clinical significance of MA. We currently know that it begins in early-stage PD patients, precedes clinical phenotype, and is part of the degeneration of the dopaminergic nigrostriatal system in these patients. MA has several clinical consequences. It is, more specifically, associated with the expression (and severity) of specific neuropsychiatric PD symptoms, namely cognitive impairment, apathy, disinhibition, and impulsive behavior, while its association with motor symptoms remains unclear. MA was recently suggested as a marker of global dysfunction in the mesocorticolimbic network. With new research data, new questions about MA emerge and further research is obviously necessary in order to effectively apply MA, as an imaging finding, to clinical practice.

Hypnosis reduces food impulsivity in patients with obesity and high levels of disinhibition: HYPNODIET randomized controlled clinical trial

BACKGROUND

The obesogenic environment of Western countries raises questions about its current management. Some clinical studies have explored hypnosis, although the current state of knowledge does not lead to definitive conclusions about its efficacy.

OBJECTIVES

We assessed the impact of Ericksonian hypnosis and self-hypnosis on disinhibition of eating in adults with obesity and high food impulsivity levels, compared with standard nutritional education.

METHODS

From September 2014 to July 2015, adults with BMI (in kg/m2) of 30-40 and a high disinhibition score [>8 on the Three Factor Eating Questionnaire (TFEQ-51)] were included in a randomized controlled trial. The control and hypnosis groups received the same standard nutrition education in 8 workshops. In the hypnosis group, subjects had 8 sessions of hypnosis combined with training in self-hypnosis. Disinhibition (primary outcome) and other scores from the TFEQ-51 as well as anthropometric, food intake, cardiometabolic, and physical activity variables were collected at inclusion and at 8 mo.

RESULTS

Of 82 randomly assigned adults, 70 participated in all sessions; 80 participated in ≥1 session and were included in the main analysis (hypnosis group, n = 41; control group, n = 39). After 8 mo of follow-up, disinhibition scores adjusted for baseline values were lower in the hypnosis group, with a mean between-group difference of 4.2 (95% CI: 2.8, 5.5; P < 0.001); 67.7% of adults in the hypnosis group had normalized their disinhibition (compared with 11.1% in control; P < 0.0001). Differences for weight (1.8 kg; 95% CI: -0.1, 3.7 kg; P = 0.052), BMI (0.8; 95% CI: 0.1, 1.4; P = 0.028), susceptibility to hunger score (2.2; 95% CI: 1.0, 3.3; P < 0.001), and its 2 subscales also favored the hypnosis group.

CONCLUSIONS

In the management of adults with obesity and a high disinhibition score, hypnosis and self-hypnosis can significantly improve the deep mechanisms of eating behaviors and seem to have a beneficial effect on weight loss.This trial was registered at clinicaltrials.gov as NCT02292108.

The Disinhibiting Effects of Anonymity Increase Online Trolling

Research assessing online trolling-a behavior designed to trigger or antagonize other users for entertainment-has largely focused on identifying individual differences that underlie the behavior. Less attention has been given to how situational factors influence trolling, such as the disinhibiting effects of anonymity. In this study, we evaluated the roles of both individual differences and levels of anonymity in online trolling. We assessed these through experimentation, a relatively novel approach in trolling research. Australian undergraduate students (n = 242, 167 women, 75 men, M_age = 21.18) were allocated to one of three conditions: an anonymous condition where they were not visible to one another, an identifiable condition where they were visible to one another, or an external condition where they completed the study outside of a controlled laboratory environment. Participants first read a short news article before interacting in an online group discussion where participants could chat freely. The first comment participants wrote was later coded for trolling. Participants also completed assessments of psychopathy, sadism, and a global assessment of trolling. As predicted, participants in the anonymous condition trolled more than those in the identifiable condition. No differences were seen between these two conditions and the external condition. Analyses also revealed that sadism and global trolling were positively associated with trolling in the chat room, but psychopathy showed no association. These results demonstrate the importance of both individual differences and the disinhibiting effects of anonymity when investigating the complex nature of trolling.