Aversive Research Articles

Inhibition of the Basolateral Amygdala to Prelimbic Cortex Pathway Enhances Risk-taking during Risky Decision-making Shock Task in Rats.

Many animal studies have explored decision-making under risk and punishment, particularly regarding potential rewards, but less focus has been placed on contexts involving net losses. Understanding decision-making under net loss conditions can shed light on the neural mechanisms involved. The basolateral amygdala to prelimbic cortex (BLA→PL) pathway is crucial for risky decision-making. In this study, we investigated how rats make decisions under no-reward but shock conditions, specifically examining the role of the BLA→PL pathway. In the risky decision-making shock task (RDST), rats chose between a "small/certain" lever, which consistently delivered one pellet, and a "large/risky" lever, offering variable rewards with a 50% probability of reward and a 50% probability of 1-s foot-shock. The results showed that the shock condition decreased the preference for the large/risky lever, despite increasing rewards. Importantly, inhibiting the BLA→PL pathway significantly increased the selection of the "large/risky" lever compared to the control. Although rats in the clozapine N-oxide (CNO) group did not exhibit significant differences in response latency between levers, they exhibited heightened sensitivity to rewards and losses, suggesting that the BLA→PL pathway affects the encoding of the relationship between aversive stimuli and reward-seeking. Overall, these results provide valuable insights into the neural mechanisms of risk-taking, particularly regarding how inhibition in the BLA→PL pathway can influence reward processing and decision-making under no-reward but shock conditions, with implications for understanding risk-related psychiatric disorders.

Physiological Responses to Aversive and Non-aversive Audiovisual, Audio, and Visual Stimuli.

We examined differences in physiological responses to aversive and non-aversive naturalistic audiovisual stimuli and their auditory and visual components within the same experiment. We recorded five physiological measures that have been shown to be sensitive to affect: electrocardiogram, electromyography (EMG) for zygomaticus major and corrugator supercilii muscles, electrodermal activity (EDA), and skin temperature. Valence and arousal ratings confirmed that aversive stimuli were more negative in valence and higher in arousal than non-aversive stimuli. Valence also showed an emotional enhancement effect for cross-modal integration. Both heart rate deceleration and facial EMG potentiation for corrugator supercilii were larger for aversive compared to non-aversive conditions for audiovisual stimuli and their auditory components, even after controlling for arousal. Facial EMG potentiation for zygomaticus major was greater for aversive compared to non-aversive conditions for audiovisual stimuli and EDA was greater for aversive compared to non-aversive conditions for visual stimuli. Neither of these effects remained significant after controlling for arousal. These findings provide a benchmark for examining atypical sensory processing of mundane aversive stimuli for clinical populations.

Repetitive grooming behavior following aversive stimulus coincides with a decrease in anterior hypothalamic area activity.

The anterior hypothalamic area (AHA) is a key brain region for orchestrating defensive behaviors. Using in vivo calcium imaging in mice, we observed that AHA neuronal activity increases during foot shock delivery and foot-shock associated auditory cues. We found that following shock-induced increases in AHA activity, a decrease in activity coincides with the onset of grooming behavior. Next, we optogenetically activated the projections from the ventromedial hypothalamus (VMH) to the AHA and observed that photoactivation of the VMH→AHA pathway drives avoidance. Interestingly, repetitive grooming behavior occurs following cessation of stimulation. To identify changes in brain-wide activity patterns that occur due to optogenetic VMH→AHA stimulation, we combined optogenetic stimulation with positron emission tomography (PET) based metabolic mapping. This approach revealed the amygdala as a downstream area activated by the stimulation of this pathway. Our findings show that the rise and fall of AHA neuronal activity triggers repetitive grooming behavior following learned fear and optogenetic stimulation. In addition, activation of the VMH→AHA pathway triggers changes in the activity patterns of downstream brain regions that are reported to be associated with displacement grooming.Significance statement This work identifies an association between grooming behavior and anterior hypothalamic area (AHA) activity patterns. Regardless of whether the activation of the AHA is initiated by shock-associated conditioned fear or optogenetic stimulation of excitatory inputs from the ventromedial hypothalamus, repetitive self-grooming behavior emerges during the post-activation decrease in activity. Further, this work identifies that even in anesthetized mice, AHA activation serves as a trigger for downstream network changes in the amygdala and striatum, which are associated with repetitive behavior. Together, this work positions the anterior hypothalamic area as a potential etiological factor to be considered at the intersection of fear experience and subsequent repetitive behaviors.

Absolute measurement of fast and slow neuronal signals with fluorescence lifetime photometry at high temporal resolution.

The concentrations of extracellular and intracellular signaling molecules, such as dopamine and cAMP, change over both fast and slow timescales and impact downstream pathways in a cell-type specific manner. Fluorescence sensors currently used to monitor such signals in vivo are typically optimized to detect fast, relative changes in concentration of the target molecule. They are less well suited to detect slowly-changing signals and rarely provide absolute measurements of either fast and slow signaling components. Here, we developed a system for fluorescence lifetime photometry at high temporal resolution (FLIPR) that utilizes frequency-domain analog processing to measure the absolute fluorescence lifetime of genetically-encoded sensors at high speed but with long-term stability and picosecond precision in freely moving mice. We applied FLIPR to investigate dopamine signaling in two functionally distinct regions in the striatum, the nucleus accumbens core (NAC) and the tail of striatum (TOS). We observed higher tonic dopamine levels at baseline in the TOS compared to the NAC and detected differential and dynamic responses in phasic and tonic dopamine to appetitive and aversive stimuli. Thus, FLIPR enables simple monitoring of fast and slow time-scale neuronal signaling in absolute units, revealing previously unappreciated spatial and temporal variation even in well-studied signaling systems.

Parabrachial CGRP neurons modulate active defensive behavior under a naturalistic threat.

Recent studies suggest that calcitonin gene-related peptide (CGRP) neurons in the parabrachial nucleus (PBN) represent aversive information and signal a general alarm to the forebrain. If CGRP neurons serve as a true general alarm, their activation would modulate both passive nad active defensive behaviors depending on the magnitude and context of the threat. However, most prior research has focused on the role of CGRP neurons in passive freezing responses, with limited exploration of their involvement in active defensive behaviors. To address this, we examined the role of CGRP neurons in active defensive behavior using a predator-like robot programmed to chase mice. Our electrophysiological results revealed that CGRP neurons encode the intensity of aversive stimuli through variations in firing durations and amplitudes. Optogenetic activation of CGRP neuron during robot chasing elevated flight responses in both conditioning and retention tests, presumably by amyplifying the perception of the threat as more imminent and dangerous. In contrast, animals with inactivated CGRP neurons exhibited reduced flight responses, even when the robot was programmed to appear highly threatening during conditioning. These findings expand the understanding of CGRP neurons in the PBN as a critical alarm system, capable of dynamically regulating active defensive behaviors by amplifying threat perception, ensuring adaptive responses to varying levels of danger.

Assessing the role of BNST GABA neurons in backward conditioned suppression.

Conditioned suppression is a useful paradigm for measuring learned avoidance. In most conditioned suppression studies, forward conditioning is used where a cue predicts an aversive stimulus. However, backward conditioning, in which an aversive stimulus predicts a cue, provides unique insights into learned avoidance due to its influence on both conditioned excitation and inhibition. We trained mice to consume sucrose in context A, associated an aversive stimulus in context B to few or many forward or backwards paired cues (CS+), and then tested for conditioned suppression in context A in response to the CS+. We found that few or many forward CS+ and few backward CS+ produced conditioned suppression, but many backwards cues did not. Administration of diazepam, a positive allosteric modulator of the GABA-A receptor, prevented conditioned suppression to the backward CS+ but not to the forward CS+. Furthermore, freezing behavior was observed in response to the forward CS+ but not the backward CS+, and diazepam had no effect on freezing or locomotion. We next examined BNST GABA neurons for potential sensitivity to backwards cues and conditioned suppression. VGaT BNST signaling increased in response to sucrose licks during the backward CS+ but not to licks outside the CS+ and not to the backward CS+ onset or offset. Using designer receptors, we found that BNST VGaT neuron activation, but not its inhibition, prevented backward conditioned suppression expression. We conclude that backward conditioned suppression is dependent on both positive allosteric modulation of GABA on GABA-A receptors by diazepam and BNST GABA neurons.

Dynamic representation of appetitive and aversive stimuli in nucleus accumbens shell D1- and D2-medium spiny neurons

The nucleus accumbens (NAc) is a key brain region for motivated behaviors, yet how distinct neuronal populations encode appetitive or aversive stimuli remains undetermined. Using microendoscopic calcium imaging in mice, we tracked NAc shell D1- or D2-medium spiny neurons’ (MSNs) activity during exposure to stimuli of opposing valence and associative learning. Despite drift in individual neurons’ coding, both D1- and D2-population activity was sufficient to discriminate opposing valence unconditioned stimuli, but not predictive cues. Notably, D1- and D2-MSNs were similarly co-recruited during appetitive and aversive conditioning, supporting a concurrent role in associative learning. Conversely, when contingencies changed, there was an asymmetric response in the NAc, with more pronounced changes in the activity of D2-MSNs. Optogenetic manipulation of D2-MSNs provided causal evidence of the necessity of this population in the extinction of aversive associations. Our results reveal how NAc shell neurons encode valence, Pavlovian associations and their extinction, and unveil mechanisms underlying motivated behaviors.

Neurophysiological Markers of Regulation Success in Everyday Life in Depression.

Self-regulation often is disrupted in depression and is characterized by negative affect and inflexible parasympathetic responses. Yet, our understanding of brain mechanisms of self-regulatory processes largely has been limited to laboratory contexts. Measuring individual differences in self-regulatory processes in everyday life - and their neural correlates - could inform our understanding of depression phenotypes and reveal novel intervention targets that impact everyday functioning. In individuals with remitted major depressive disorder (rMDD) and healthy comparison participants (N=74), we measured two dimensions of regulation success in everyday life - perceived success with regulating affect, and physiological success (parasympathetic augmentation following regulation attempts) - and their neural correlates using an fMRI emotion regulation task. Perceptions of success were weakly associated with physiological success and had partially distinct neural correlates. Perceived success and physiological success in everyday life predicted reduced activity in brain regions involved in emotional salience while reacting to aversive stimuli in the scanner. During reappraisal in the scanner, greater perceived success in everyday life was dimensionally associated with more reappraisal-related activity in regions involved in cognitive control (including dorsolateral and dorsomedial prefrontal cortex); in contrast, physiological success predicted enhanced downregulation of salience network activity (amygdala, insula). Results suggest linking psychophysiology with behavior in everyday life can provide a window into dissociable dimensions of self-regulatory functioning. Integrating ambulatory and brain-based metrics may elucidate self-regulatory phenotypes with distinct neurophysiological mechanisms and targets for intervention to impact functioning in daily life.

Computational modeling of fear and stress responses: validation using consolidated fear and stress protocols.

Dysfunction in fear and stress responses is intrinsically linked to various neurological diseases, including anxiety disorders, depression, and Post-Traumatic Stress Disorder. Previous studies using in vivo models with Immediate-Extinction Deficit (IED) and Stress Enhanced Fear Learning (SEFL) protocols have provided valuable insights into these mechanisms and aided the development of new therapeutic approaches. However, assessing these dysfunctions in animal subjects using IED and SEFL protocols can cause significant pain and suffering. To advance the understanding of fear and stress, this study presents a biologically and behaviorally plausible computational architecture that integrates several subregions of key brain structures, such as the amygdala, hippocampus, and medial prefrontal cortex. Additionally, the model incorporates stress hormone curves and employs spiking neural networks with conductance-based integrate-and-fire neurons. The proposed approach was validated using the well-established Contextual Fear Conditioning paradigm and subsequently tested with IED and SEFL protocols. The results confirmed that higher intensity aversive stimuli result in more robust and persistent fear memories, making extinction more challenging. They also underscore the importance of the timing of extinction and the significant influence of stress. To our knowledge, this is the first instance of computational modeling being applied to IED and SEFL protocols. This study validates our computational model's complexity and biological realism in analyzing responses to fear and stress through fear conditioning, IED, and SEFL protocols. Rather than providing new biological insights, the primary contribution of this work lies in its methodological innovation, demonstrating that complex, biologically plausible neural architectures can effectively replicate established findings in fear and stress research. By simulating protocols typically conducted in vivo-often involving significant pain and suffering-in an insilico environment, our model offers a promising tool for studying fear-related mechanisms. These findings support the potential of computational models to reduce the reliance on animal testing while setting the stage for new therapeutic approaches.

Ketamine Reduces Avoidance Responses During Re-Exposition to Aversive Stimulus: Comparison Between (S)-Isomer and Racemic Mixture.

Recent studies have investigated the effects of ketamine on fear memory in animals. However, it is unclear if ketamine might affect avoidance memory and emotional behaviors concomitantly. In this study, we compared the effects of (R,S)- and (S)-ketamine in modulating avoidance responses, depression- and anxiety-related behaviors in stressed mice. Mice were previously exposed to inescapable footshock stress, and 24 h later, they were trained in the active avoidance task. (R,S)-ketamine or (S)-isomer was administered 1 h prior to re-exposition to the active avoidance task. Three hours after drug administration, mice were tested in the tail suspension, followed by the open field test. Neither form of ketamine affected avoidance memory retrieval, while (S)-ketamine, and tangentially, (R,S) reduced avoidance responses during re-exposition to aversive stimulus. In the tail suspension test, (R,S)- and (S)-ketamine equally evoked antidepressant effects. In the open field test, the racemic mixture, but not (S)-ketamine, induced anxiolytic actions. These findings reinforce the therapeutic potential of ketamine for the treatment of stress-related disorders, with (R,S)-ketamine being more effective in simultaneously inducing antidepressant and anxiolytic responses and reducing avoidance responses in stressed mice.

Identifying the Brain Circuits that Regulate Pain-Induced Sleep Disturbances.

Pain therapies that alleviate both pain and sleep disturbances may be the most effective for pain relief, as both chronic pain and sleep loss render the opioidergic system, targeted by opioids, less sensitive and effective for analgesia. Therefore, we first studied the link between sleep disturbances and the activation of nociceptors in two acute pain models. Activation of nociceptors in both acute inflammatory (AIP) and opto-pain models led to sleep loss, decreased sleep spindle density, and increased sleep fragmentation that lasted 3 to 6 hours. This relationship is facilitated by the transmission of nociceptive signals through the spino-parabrachial pathways, converging at the wake-active PBelCGRP (parabrachial nucleus expressing Calcitonin Gene-Related Peptide) neurons, known to gate aversive stimuli. However, it has never been tested whether the targeted blocking of this wake pathway can alleviate pain-induced sleep disturbances without increasing sleepiness. Therefore, we next used selective ablations or optogenetic silencing and identified the key role played by the glutamatergic PBelCGRP in pain-induced sleep disturbances. Inactivating the PBelCGRP neurons by genetic deletion or optogenetic silencing prevented these sleep disturbances in both pain models. Furthermore, to understand the wake pathways underlying the pain-induced sleep disturbances, we silenced the PBelCGRP terminals at four key sites in the substantia innominata of the basal forebrain (SI-BF), the central nucleus of Amygdala (CeA), the bed nucleus of stria terminalis (BNST), or the lateral hypothalamus (LH). Silencing of the SI-BF and CeA also significantly reversed pain-induced sleep loss, specifically through the action on the CGRP and NMDA receptors. This was also confirmed by site-specific blockade of these receptors pharmacologically. Our results highlight the significant potential for selectively targeting the wake pathway to effectively treat pain and sleep disturbances, which will minimize risks associated with traditional analgesics.

Role of Anterior Cingulate Cortex in the exacerbated facial response to mechanical stimuli as a sign of early orofacial neuropathic pain.

The study of orofacial neuropathic pain necessitates the use of innovative assessment techniques, such as the facial expression of pain, which mirrors the internal state of the animals and could be utilized to identify the neural correlations involved. The Anterior Cingulate Cortex (ACC) is a crucial center in the processing of sensory and affective components of acute and neuropathic pain. However, its role in the facial response to pain remains a mystery. In this project, we set out to determine the changes in the facial response of early trigeminal neuropathic pain and the contribution of ACC in this process. We evaluated the facial response to mechanical stimulation using a machine-vision analysis in a head-fixed system before and after mental nerve compression in C57BL/6 mice. The role of ACC in the facial response was characterized via acute electrophysiological recording, and both glutamatergic ACC neural-ablation and optogenetic inhibition in a cre-dependent manner. Our results indicate that trigeminal nerve injury leads to an exacerbation of the intensity of the pain-like facial response to aversive stimuli in an early period. ACC neuronal activity is modulated by mechanical stimulation and during the dynamics of the facial response in different proportions before and after the lesion onset. The neuropathic pain-induced changes in the intensity of the facial response are nullified by the ablation or optogenetic inhibition of ACC glutamatergic neurons. Our study underscores the significant role of ACC in the development of signs of orofacial neuropathic pain, such as exacerbated facial response to mechanical stimuli. PERSPECTIVE: This article presents evidence on the sensory coding of mechanical stimulation in a neuropathic pain model in the Anterior Cingulate Cortex, using facial expression as a manifestation of the internal painful state. This evaluation provides a novel approach to evaluating the well-being of animals with neuropathic pain.

Demarcation of anxiety and fear: Evidence from behavioral genetics.

Anxiety and fear are emotions often intertwined in response to aversive stimuli, complicating efforts to differentiate them and understand their distinct consequences. This study explores the common genetic and environmental factors contributing to the co-occurrence of anxiety disorders and dimensions of the revised Reinforcement Sensitivity Theory (rRST). A sample of 356 monozygotic (22.5% males; M=25.73, SD=8.3) and 386 dizygotic (33.9% males; M=24.21, SD=8.33) twins from the Serbian Twin Advanced Registry was analyzed. The Psychiatric Diagnostic Screening Questionnaire (PDSQ) provided scales for panic disorder, agoraphobia, social phobia, and generalized anxiety disorder (GAD), while the Reinforcement Sensitivity Questionnaire (RSQ) measured the Behavioral Inhibition System (BIS), Behavioral Activation System (BAS), and Fight/Flight/Freeze System (FFFS). Common additive genetic effects accounted for most of the variance in BIS, Fight, and panic, agoraphobia, and social phobia, while specific additive genetic effects were highest for Flight. Shared environmental effects were most pronounced for Fight across all models, with additional shared influences on BAS and BIS for panic, and BAS and Freeze for agoraphobia and social phobia. Nonshared environmental effects were the highest specific contributors across variables. Genetic overlap between anxiety disorders and rRST dimensions suggests pleiotropy, with unique environmental factors playing an important role in disorder development. While anxiety and fear may stem from distinct etiologies, their shared symptomatology complicates differentiation, highlighting the importance of considering both genetic and environmental influences in anxiety disorders.

Opening the Pandora box: Neural processing of self-relevant negative social information.

Curiosity is a powerful motivator of information-seeking behavior. People seek not only positive, but also aversive social information about others. However, whether people also seek unfavorable social information about themselves, as well as the neural mechanisms that may drive such seemingly counterintuitive behavior remain unclear. To address this gap, we developed a novel electroencephalography-compatible Social Incentive Delay (SID) task, which was implemented in 30 healthy young adults as they responded as fast as possible to a target to receive positive or avoid negative comments about their own or about others' Instagram photos. Reaction times were slower for negative vs positive comments' conditions, but only for participants' own photos, revealing less motivation to avoid negative rather than seek positive self-relevant social feedback. Coherently, receiving negative feedback, as opposed to avoiding it, evoked larger amplitudes in the Reward Positivity (RewP) and FB-P3 time-range, especially for participants' own photos, indicating that receiving a negative comment was more rewarding and more salient than not receiving any comment at all. Our findings challenge prior evidence suggesting that humans instinctively avoid aversive stimuli, and they shed light on the neurophysiological mechanisms that may underlie this counterintuitive behavior.

Supporting rotational grazing systems with virtual fencing: paddock transitions, beef heifer performance, and stress response.

Animal welfare is integral to sustainable livestock production, and pasture access for cattle is known to enhance welfare. Despite positive welfare impacts, high labour requirements hinder the adoption of sustainable grazing practices such as rotational stocking management. Virtual fencing (VF) is an innovative technology for simplified, less laborious grazing management and remote animal monitoring, potentially facilitating the expansion of sustainable livestock production. VF uses Global Navigation Satellite System technology, wireless communication, and stimuli (auditory and electrical) to manage livestock movements and contain animals without physical barriers. Training animals to associate the auditory cue with the subsequent aversive stimulus enables effective livestock containment without physical barriers. While previous studies have largely dispelled concerns about adverse effects on cattle behaviour associated with the use of VF collars, there is limited knowledge regarding the impacts on animal physiology, particularly in rotational stocking systems. Addressing this knowledge gap, this study investigated differences in diet digestibility, livestock performance, and stress response of beef heifers on pastures using a VF compared to a physical electric fence. The study was conducted over 8weeks, subdivided into two grazing cycles, with 32 heifers in four groups. Each experimental pasture was subdivided into four paddocks. The study monitored the interaction with the VF by analysing the temporal development of the ratio of auditory and electrical cues (success ratio and confidence ratio) emitted by the collars. Additionally, the grassland herbage quality, BW gain, and concentrations of faecal cortisol metabolites (FCMs) were assessed, as well as the time required for animals to cross into a new paddock. VF success ratios increased in the second grazing cycle, reflecting enhanced adaptation over time. Similarly, the reduction in time taken to cross into new paddocks in the VF groups indicated that animals learned to interact with the VF and rely on the auditory cues for directing movements. The absence of a significant effect of the fencing system on FCMs suggested that stress was unrelated to the VF technology. Further, animal performance was not affected as indicated by similar BW gains under both fencing systems. This study also attempts to establish a benchmark threshold for successful responses to the auditory cues, allowing comparative evaluation of VF systems. Overall, under rotational grazing, VF did not adversely impact animal welfare or performance compared to physical fencing, opening avenues for further exploration of VF technology in diverse grazing conditions.

Emotional auditory stimuli influence step initiation in Parkinson’s disease with freezing of gait

Freezing of gait (FOG) in Parkinson’s disease (PD) can be triggered by sensomotor, cognitive or limbic factors. The limbic system’s impact on FOG is attributed to elevated limbic load, characterized by aversive stimuli, potentially depleting cognitive resources for movement control, resulting in FOG episodes. However, to date, PD patients with and without FOG have not shown alterations of anticipatory postural adjustments during gait initiation after exposure to emotional images, possibly because visual stimuli are less immediately disruptive than auditory stimuli, which can more directly affect attention and the limbic system. This study aims to determine if step initiation is influenced by ecological auditory stimuli with emotional content in patients with FOG compared to those without. Forty-five participants, divided into 3 groups (15 PD with FOG, 15 PD without FOG in ON state, and 15 healthy subjects), stood on a force platform and were asked to step forward in response to neutral, pleasant, or unpleasant ecological auditory stimuli. Anticipatory postural adjustments were investigated in imbalance and unloading phases, while spatio-temporal parameters, including center of pressure (CoP) displacements, were computed for step initiation. PD with FOG showed a reduction of CoP displacements after listening to unpleasant stimuli. Conversely, pleasant stimuli facilitated CoP displacements in these subjects. No influence of affective stimuli on CoP displacements was found in the other two groups. Multiple regression analysis revealed that the behavioral pattern in PD with FOG, modulated by stimuli with affective valence, was mainly associated with the limbic area (i.e., depression). The findings showed that the emotional network plays a crucial role in the pathophysiology of freezing, generating probably interference with attentional reserves that trigger FOG.

Anxiety modulators elicit different behavioral outcomes in adult zebrafish: Emphasis on homebase-related parameters and spatio-temporal exploration

Anxiety is an emotion that represents a crucial anticipatory reaction of aversive stimuli, with clinical relevance in cases of disproportional and severe occurrences. Although distinct animal models have contributed to elucidate anxiety-related mechanisms, the influence of anxiogenic and anxiolytic modulations on both locomotion and exploration-related parameters in the open field test (OFT) is not fully elucidated. Here, we aimed to assess the influence of anxiogenic and anxiolytic manipulations on the exploratory dynamics of adult zebrafish (Danio rerio) focusing on homebase-related behaviors. As anxiogenic manipulations, we used the morphine (1.5 mg/L) withdrawal protocol (MOR); 3.5 mL/L conspecific alarm substance (CAS) for 5 min; and 100 mg/L caffeine (CAF) for 15 min. To evoke anxiolytic-like responses, animals were acutely exposed to 0.5 % (v/v) ethanol (ETOH) for 1 h; 100 μg/L fluoxetine (FLU) for 15 min; and 0.006 mg/L clonazepam (CZP) for 10 min. Then, fish were individually exposed to the 30-min OFT trial, with posterior analysis of behavioral activity. While MOR induced hyperlocomotion and increased periphery occupancy, CAS and CAF groups showed higher immobility and increased latency to homebase formation, respectively. Conversely, ETOH and FLU reduced homebase occupancy, supporting anxiolytic-like behaviors, while CZP did not change zebrafish behavior in the OFT. Cluster analysis was used to reconfirm the remarkable similarities and discrepancies between treatments, thus contributing to characterize the distinct responses measured. Overall, our novel data show the relevance of homebase-related analysis as a sensitive tool to reflect affective-like states in zebrafish, providing innovative approaches to unravel the spatio-temporal dynamics of anxiety-like behaviors in vertebrates.

Decoding threat neurocircuitry representations during traumatic memory recall in PTSD.

The neurocircuitry mechanisms underlying recall of traumatic memories remain unclear. This study investigated whether traumatic memory recall engages neurocircuitry representations that mirror activity patterns engaged during generalized threat stimulus processing in Post Traumatic Stress Disorder (PTSD). Multivariate pattern analysis was used to train 3 decoders. A "trauma" decoder was trained on fMRI patterns during idiographic trauma versus neutral narratives in a sample of 73 adult women with PTSD. A separate cohort of 125 adult participants completed a reward and threat learning task, from which "shock" and "reward loss" decoders were trained on neural patterns during threat or reward outcome delivery, respectively. These decoders were then cross-tested on the alternative datasets, allowing analyses of the degree to which traumatic memory recall engaged neurocircuitry representations that overlap with more general aversive stimuli. Decoders were trained and tested in four networks related to salience processing as well bilateral amygdala and hippocampal masks. The shock decoder trained in a midcingulate / posterior insula network demonstrated elevated predictions for shock during traumatic versus neutral memory recall. Similarly, the trauma decoder made elevated predictions about trauma recall during shock versus no shock delivery across multiple networks related to salience processing. There was no overlap between reward loss decoder predictions and trauma memory recall or vice versa. PTSD participants with elevated re-experiencing symptoms demonstrated the highest engagement of shock activity patterns during trauma memory recall. These results suggest that trauma memory recall engages neurocircuitry representations that overlap with threat, specifically painful, stimulus delivery.

Pupillometry reveals hyper-arousal in response to auditory stimuli in autistic children.

Atypical sensory responsivity is widely reported in autistic individuals and is related to elevated functional difficulties. Dynamically, altered initial responses and/or habituation rates could underlie their atypical averaged responses to repeated sensory stimuli. In this study we aimed to measure the arousal level in response to different types of auditory stimuli and the dynamic change of atypical arousal level using pupillometry in autistic children. In Experiment 1, 43 autistic children and 49 neurotypical (NT) children were asked to passively listen to a mild sound and an aversive sound repeatedly. In Experiment 2, 39 autistic children and 44 NT children who went through Experiment 1 listened to a gradually emerging non-startling sound and a suddenly emerging startling sound in a random order. We found that the autistic group showed hyper-arousal in response to the aversive sound and the startling sound as reflected by their larger change in pupil area. In comparison, these autistic children demonstrated normal arousal in response to the mild sound and the non-startling sound. Dynamically, the autistic group had a larger peak pupil area change than the NT group in the first trial and a normal habituation rate to the aversive sound. In summary, our results suggest hyper-arousal to aversive and startling stimuli and the role of larger initial responses in hyper-arousal in autism. Minimizing aversive and startling sensory stimuli or gradually increasing the volume of aversive auditory stimuli to allow autistic children to adapt using the principle of habituation is recommended to reduce the arousal level and problematic behaviors of autistic children.

Uncovering multiscale structure in the variability of larval zebrafish navigation

Animals chain movements into long-lived motor strategies, exhibiting variability across scales that reflects the interplay between internal states and environmental cues. To reveal structure in such variability, we build Markov models of movement sequences that bridge across timescales and enable a quantitative comparison of behavioral phenotypes among individuals. Applied to larval zebrafish responding to diverse sensory cues, we uncover a hierarchy of long-lived motor strategies, dominated by changes in orientation distinguishing cruising versus wandering strategies. Environmental cues induce preferences along these modes at the population level: while fish cruise in the light, they wander in response to aversive stimuli, or in search for appetitive prey. As our method encodes the behavioral dynamics of each individual fish in the transitions among coarse-grained motor strategies, we use it to uncover a hierarchical structure in the phenotypic variability that reflects exploration-exploitation trade-offs. Across a wide range of sensory cues, a major source of variation among fish is driven by prior and/or immediate exposure to prey that induces exploitation phenotypes. A large degree of variability that is not explained by environmental cues unravels hidden states that override the sensory context to induce contrasting exploration-exploitation phenotypes. Altogether, by extracting the timescales of motor strategies deployed during navigation, our approach exposes structure among individuals and reveals internal states tuned by prior experience.