Publications using TDT

The mediodorsal thalamic nucleus (MD) forms neural circuits with various brain regions, including the prefrontal cortex (PFC), the reticular thalamic nucleus (TRN), and the midbrain reticular nucleus (MRN). However, the specific roles and underlying mechanisms in auditory information processing remain unclear. Here, we perform multi-channel electrophysiological recordings in awake mice to investigate the response patterns of the MD to auditory stimuli, as well as the regulatory effects of PFC, MRN, and TRN inputs. We identify two distinct types of sound-evoked responses. The Phasic-response features a transient burst firing to the stimulus with short latency, rapidly adapting to baseline and corresponding to the onset fluctuation of the local field potential. The Sustained-response is marked by prolonged firing with longer latency and is accompanied by persistent enhancement of oscillatory power following stimulus offset. The response patterns of MD neurons remain consistent across different types of auditory stimuli. Optogenetic inactivation of the MRN suppresses both response types in the MD. The Sustained-response is attenuated by PFC inactivation but enhanced by TRN inactivation, while the Phasic-response remains unaffected by inactivation of either the PFC or TRN. Our findings expand the understanding of the MD's role in sound information integration and auditory cognitive regulation.

Stereocilia are rod-like mechanosensory projections consisting of unidirectionally oriented actin filaments that extend into the inner ear hair cell cytoskeleton, forming dense rootlets. Taperin (TPRN) localizes to the narrowed-down base of stereocilia, where they pivot in response to sound and gravity. We show that TPRN-deficient mice have progressive deafness characterized by gradual asynchronous retraction and fusion of outer and inner hair cell stereocilia, followed by synaptic abnormalities. Stereocilia that lack TPRN develop warped rootlets with gradual loss of TRIOBP-5 and ANKRD24 from mechanosensory rows starting postnatally. In contrast, TPRN overexpression causes excessive F-actin bundling, extra rows, and over-elongation of stereocilia during development. Purified full-length mouse TPRN cross-links F-actin into bendable bundles reflecting in vivo data. This F-actin–bundling ability is attributed to the TPRN N-terminal region. TPRN interacts with the membrane receptor PTPRQ, connecting the F-actin core to the plasma membrane, stabilizing stereocilia. Thus, TPRN is a specialized F-actin bundler strategically located to augment stereocilia rootlet formation and their pivot point flexibility for sustained sound-induced deflections.

Ventral tegmental area (VTA) glutamatergic neurons participate in reward, aversion, drug-seeking, and stress. Subsets of these neurons cotransmit glutamate and GABA (VGluT2 + VGaT + neurons), transmit glutamate without GABA (VGluT2 + VGaT − neurons), or cotransmit glutamate and dopamine (VGluT2 + TH + neurons), but whether these molecularly distinct subpopulations show behavior-related differences is not wholly understood. We identified in male and female mice that VGluT2 + subpopulations are sensitive to the reward value in unique ways. VGluT2 + VGaT + neurons increased maximum activity with increased sucrose concentration, whereas VGluT2 + VGaT − neurons increased maximum and sustained activity with increased sucrose concentration, and VGluT2 + TH + neurons increased sustained but not maximum activity with increased sucrose concentration. VGluT2 + subpopulations also uniquely signaled consumption of sweet/noncaloric (saccharine) and nonsweet/high-calorie rewards (fat). VGluT2 + VGaT + neurons uniquely signaled lower-calorie sucrose over fat, whereas both VGluT2 + VGaT − neurons and VGluT2 + TH + neurons showed a signaling preference for higher-calorie fat over sucrose but in temporally distinct ways. Further experiments suggested that VGluT2 + VGaT + consummatory reward-related activity was related to sweetness, partially modulated by prefeeding, and not dependent on caloric content. Additionally, aversive stimuli increased activity for each VGluT2 + subpopulation, but VGluT2 + VGaT + neurons uniquely scaled their magnitude and sustained activity with footshock intensity. Optogenetic activation of VGluT2 + VGaT + neurons during low-intensity footshock enhanced fear-related behavior without inducing place preference or aversion. About half of VGluT2 + VGaT + sucrose-sensitive neurons were transcriptionally activated by footshock. We interpret these data such that VTA glutamatergic subpopulations signal different elements of rewarding and aversive experiences and highlight the unique role of VTA VGluT2 + VGaT + neurons in salience signaling.

Electroanalytical methods are used to understand, modify, and control bionic devices. Bionic devices can record or stimulate cells to understand and/or control normal or abnormal biological processes. These devices contain electrodes that transduce electrical current within the electrical circuit into ionic current within a tissue. Despite the similarity between electroanalysis and electrophysiology, there remains a poor understanding of the relationship between the two techniques, including their methodology and theory. This paper investigates the electrochemical and acute electrophysiological recording performance of neural electrodes. A range of behaviors is achieved by modifying electrodes with the conducting polymer poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with chondroitin sulfate, dextran sulfate, or para ‐toluene sulfonate. The results support previous studies showing that increased electrode area reduced total impedance below the Maxwell–Wagner relaxation frequency and thermal noise while increasing the signal‐to‐noise ratio and neural spike count. The results allowed novel investigation of relative contributions of biological and electrode properties to electrophysiological performance, with increased electrode area having a larger impact on neural population within recording range rather than reducing thermal noise. The utility of measuring electrode impedance for predicting electrophysiological performance is mainly for an indirect measure of electrode area. The results provide insight into noise sources from electrophysiological recordings and limitations in cable theory in neuroscience.

Animals make decisions based on the value of potential outcomes. This perceived value is not fixed; it changes depending on internal needs, such as hunger or thirst, and past experiences. The basolateral amygdala (BLA) is known to be crucial for updating predicted reward values. However, it has been unclear how the BLA represents the specific value of different rewards. Two-photon calcium imaging in male mice showed that population response magnitude scaled with subjective value, and different rewards recruited distinct neuronal subpopulations. Value representations quickly re-scaled when a novel, higher-value reward appeared, and internal state shaped them: thirst selectively boosted responses to water, whereas aversive experience dampened sucrose responses. Thus, BLA circuits carry flexible, stimulus-specific value signals that integrate relative value and current affective or homeostatic conditions, providing a neural basis for adaptive decision making and learning. Our findings reveal that the BLA maintains adaptable, reward-specific value signals, essential for guiding choices according to current needs and changing circumstances.

Central glucagon-like peptide-1 (GLP-1), secreted by a distinct population of nucleus tractus solitarius neurons, suppresses feeding but the exact mechanisms of action in the brain remain unclear. Here, we investigate a descending circuit formed by GLP-1 receptor (GLP-1R) neurons in the paraventricular hypothalamic nucleus (PVNGLP-1R) projecting to the dorsal vagal complex (DVC) of the brain stem in mice. PVNGLP-1R→DVC synapses release glutamate and are augmented by GLP-1. Chemogenetic activation of PVNGLP-1R→DVC suppresses feeding. Under an energy deficit (that is, hunger) state, synaptic strength is weaker but is more profoundly augmented by GLP-1R activation than under energy-replete state. In an obese condition, the dynamic synaptic changes in this circuit are disrupted. Optogenetic activation of PVNGLP-1R→DVC projections suppresses food intake energy state dependently, and blocking its synaptic release or ablating GLP-1Rs in the presynaptic neurons impairs metabolic health. These findings indicate that the state-dependent synaptic regulation by GLP-1 in PVNGLP-1R→DVC descending circuit is important for energy homeostasis.

Frequency analysis by the cochlea forms a key foundation for all subsequent auditory processing. Stimulus-frequency otoacoustic emissions (SFOAEs) are a potentially powerful alternative to traditional behavioral experiments for estimating cochlear tuning without invasive testing, as is necessary in humans. Which methods accurately predict cochlear tuning remains controversial due to only a single animal study comparing SFOAE-based, behavioral, and cochlear frequency tuning in the same species. The budgerigar ( Melopsittacus undulatus ) is a parakeet species with human-like behavioral sensitivity to many sounds and the capacity to mimic speech. Intriguingly, previous studies of critical bands, psychophysical tuning curves, and critical ratios in budgerigars show that behavioral tuning sharpness increases dramatically with increasing frequency from 1 to 3.5 kHz, doubling once per octave with peak tuning sharpness from 3.5 to 4 kHz. The pattern contrasts with slower monotonic growth of behavioral tuning sharpness with increasing frequency in other animals, including most avian species, suggesting a possible auditory specialization in budgerigars. We measured SFOAE-based and cochlear-afferent tuning in budgerigars, for comparison to previously reported behavioral results. SFOAE-based and cochlear-afferent tuning sharpness both increased monotonically and relatively slowly for higher frequencies, in contrast to the behavioral pattern. SFOAE-based tuning in budgerigars accurately predicted cochlear frequency tuning, and both measures aligned with typical patterns of cochlear tuning in other species. Divergent behavioral tuning in budgerigars is unlikely attributable to the periphery and could reflect specializations for central processing of masked signals. Our findings highlight the value of SFOAEs for estimating cochlear tuning and caution against direct inference of peripheral tuning from behavioral critical bands, psychophysical tuning curves, and critical ratios.

A crucial aspect of auditory perception is the ability to use sound cues to predict future events and to time actions accordingly. For example, the sound of an approaching vehicle signals when it is safe to cross the street; distinct smartphone notification sounds reflect a call that needs to be answered within a few seconds, or a text that can be read later. Other animals similarly use sounds to plan, time and execute behaviors such as hunting, evading predation and tending to offspring. However, the neural mechanisms that underlie sound-guided prediction of upcoming salient event timing are not well understood. To address this gap, we employed an appetitive sound-triggered reward time prediction behavior in head-fixed mice. We find that mice trained on this task reliably estimate the time from a sound cue to upcoming reward on the scale of a few seconds, as demonstrated by learning-dependent well-timed increases in predictive licking for reward. Moreover, mice showed a dramatic impairment in their ability to use sound to predict delayed reward when the auditory cortex was inactivated, demonstrating its causal involvement. To identify the neurophysiological signatures of auditory cortical reward-timing prediction, we recorded local field potentials during learning and performance of this behavior and found that the magnitude of auditory cortical responses to the sound prospectively encoded the duration of the anticipated sound-reward time interval. Next, we explored how and where these sound-triggered time interval prediction signals propagate from the auditory cortex to time and initiate consequent action. We targeted the monosynaptic projections from the auditory cortex to the posterior striatum and found that chemogenetic inactivation of these projections impaired animals’ ability to predict sound-triggered delayed reward. Simultaneous neural recordings in the auditory cortex and posterior striatum during task performance revealed coordination of neural activity across these regions during the sound cue predicting the time interval to reward. Collectively, our findings identify an auditory cortical-striatal circuit supporting sound-triggered timing-prediction behaviors.

The preservation of synaptic integrity and physiological activity is pivotal for post-traumatic auditory rehabilitation following acoustic overexposure. Neuritin, a neurotrophic factor that facilitates synapse formation, maturation, and enhanced synaptic transmission, is essential for synapse development. In this study, we established a noise-induced cochlear synaptopathy model in CBA/CaJ mice, revealing a temporal association between endogenous Neuritin expression and synaptic density. Furthermore, administration of recombinant Human Neuritin (rhNeuritin) effectively preserves synaptic density in the cochlear basal turn at 7 days and 14 days following noise exposure. Importantly, it preserves the density of functional synapses (represented by overlapping CtBP2 and GluA2 puncta) and synapse function (indicated by ABR I wave amplitudes), thus diminishing the impairment of auditory function. In addition, rhNeuritin reverses the decrease in phosphorylated extracellular signal-regulated protein kinase 1/2 (p-ERK1/2) levels resulting from noise exposure. By primarily preserving both the number and functionality of synapses in the basal turn, potentially via the induction of ERK1/2 phosphorylation, rhNeuritin mitigated hearing loss. These findings underscore the protective efficacy of rhNeuritin against noise-induced synaptic injury.

Long-term reliability of microelectrodes implanted in the cortex is hindered due to the foreign body response that occurs at the electrode-tissue interface. Following implantation, there is disruption of the blood-brain-barrier and vasculature, resulting in activation of immune cells and release of erythrocytes. As a result of hemolysis, erythrocytes degrade to heme and then to free iron. Excess free iron can participate in the Fenton Reaction, producing reactive oxygen species (ROS). Iron-mediated ROS production can contribute to oxidation of lipids, proteins, and DNA, facilitating a hostile environment of oxidative stress leading to oxidative cellular damage, cytotoxicity, and cell death. The objective of this study was to show the iron accumulation and the downstream effects of oxidative stress at the injury site. A 16-channel microelectrode array (MEA) was implanted in the rat somatosensory cortex. Our results indicated significant elevation of NOX complex subunits across timepoints, suggesting sustained oxidative stress. In a separate group of animals, we administered an iron chelator, deferoxamine mesylate (DFX), to evaluate the effects of chelation on iron accumulation, oxidative stress and damage, and neuronal survival. Results indicate that animals with iron chelation showed reduced ferric iron and markers of oxidative stress and damage corresponding with increased expression of neuronal cell bodies and electrophysiological functional performance. In summary, the study reveals the role of iron in mediating oxidative stress and the effects of modulating iron levels using iron chelation at the electrode-tissue interface. STATEMENT OF SIGNIFICANCE: Iron accumulation has been observed in central nervous system injuries and in neurodegenerative diseases such as Alzheimer's and Parkinson's disease. While the role of iron is studied in various neurodegenerative diseases and traumatic brain injury, iron accumulation and its effect on oxidative stress is not known for intracortical implants where there is a persistent injury due to the presence of a foreign device in the brain tissue. The study seeks to understand the effects of iron accumulation on oxidative stress and damage at the electrode-tissue interface in intracortical implants by using iron chelation as a method of modulating iron levels at the interface.

Rett syndrome (RTT) is a neurodevelopmental disorder primarily caused by loss-of-function mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Genetic restoration of MECP2 in mice can reverse phenotypes, providing hope for disease-modifying therapies in the disease. Studies in people with and mouse models of RTT have identified neurophysiological features, such as auditory event-related potentials (AEPs), that correlate with disease severity, suggesting potential as translatable biomarkers. We have identified reductions in the expression and function of the group III metabotropic glutamate receptor 7 (mGlu7), a G protein-coupled receptor regulating presynaptic neurotransmitter release, in both human and mouse RTT brains. Additionally, treatment of RTT mice with a positive allosteric modulator (PAM) of the group III mGlu receptors (VU0422288) improves behavioral phenotypes, most likely via mGlu7 potentiation. To evaluate whether VU0422288 treatment modulates neurophysiological biomarkers, we acutely treated RTT mice with VU0422288 at 3,10, and 30 mg/kg and assessed neurophysiological features. VU0422288 treatment caused increases in AEP peak amplitudes in RTT mice but not in wild-type controls, with no effect on basal electroencephalogram power. Treatment with a different compound, ADX88178, a PAM that activates the mGlu4, 6and 8 receptors, did not affect neurophysiological assessments, suggesting that the target of VU0422288 is likely mGlu7. These findings suggest that neurophysiological features, like AEP, have potential as sensitive and quantitative biomarkers that may be useful in evaluating mGlu7 PAMs and other pharmacological interventions as novel RTT treatment strategies. SIGNIFICANCE STATEMENT: Correlations between neurophysiological features and disease severity in Rett syndrome suggest their potential as translatable biomarkers sensitive to pharmacological modulation. This study demonstrates that potentiation of group III metabotropic glutamate receptors improves neurophysiological features in Rett syndrome mice.

Lipid sensing in the hypothalamus contributes to the control of feeding and whole-body metabolism. However, the mechanism responsible for this nutrient-sensing process is ill-defined. Here, we show that Nogo-A, encoded by reticulon 4 (Rtn4) gene and associated with brain development and synaptic plasticity, regulates feeding and energy metabolism by controlling lipid metabolism in Agouti-related protein (AgRP) neurons. Nogo-A expression was upregulated in AgRP neurons of fasted mice and was associated with a significant downregulation of enzymes involved in sphingolipid de novo biosynthesis and the upregulation of key enzymes in intracellular lipid transport and fatty acid oxidation. Deletion of Rtn4 in AgRP neurons reduced body weight, ghrelin-induced AgRP activity and food intake, and fasting-induced AgRP activation, together with an increase in ceramide levels. Finally, high-fat-diet-induced obesity induced a significant downregulation of Rtn4 and increased ceramide levels in AgRP neurons, suggesting a role for Nogo in AgRP dysregulation in obesity. Taken together, our data reveal that Nogo-A drives AgRP neuronal activity and associated feeding behavior by controlling mitochondrial function and cellular lipid metabolism.

Aging is associated with deficits in auditory functioning. Characterization of auditory deficits that originate in middle-age is crucial for understanding the initial age-related functional impairments and the spatio-temporal progression of age-related auditory pathophysiology. Early age-related deficits in auditory processing are evident in difficult listening conditions, such as background noise, before becoming evident in quiet. To investigate the effect of noise on age-related auditory dysfunction, we collected suprathreshold auditory brainstem responses (ABRs) from young, middle-aged, and aged CBA/CaJ mice in quiet and broad-band background noise. We utilized multiple ABR metrics, including phase locking value (PLV), a measure of neural synchrony correlated to speech-in-noise understanding in humans. Despite no differences in auditory processing in quiet between young and middle-aged mice, middle-aged mice exhibited a distinct auditory phenotype from both young and aged mice in background noise conditions. We found that noise significantly decreased amplitude in middle-aged mice more than in young and aged mice. Noise significantly increased latencies for wave I and V in young mice, but only affected wave V in middle-aged mice and did not affect aged latencies. Noise significantly decreased PLV in middle-aged mice to a greater extent than in young mice, but to a lesser extent in aged mice. These results show that middle-aged mice have a distinct, auditory dysfunction phenotype evident in background noise. Our data show that suprathreshold auditory function in noise can identify early age-related hearing loss and can be used as a sensitive tool for detecting auditory dysfunction in normal hearing animal models.

Noise-induced hearing loss (NIHL) poses an emerging global health problem with only ear protection or sound avoidance as preventive strategies. The cochlea receives some protection from medial olivocochlear efferent neurons, providing a potential target for therapeutic enhancement. Cholinergic efferents release acetylcholine (ACh) to hyperpolarize and shunt the outer hair cells (OHCs), reducing sound-evoked activation. The (α9)2(α10)3 nicotinic ACh receptor (nAChR) on the OHCs mediates this effect. Transgenic knockin mice with a gain-of-function nAChR (α9L9'T) suffer less NIHL. α9 knockout mice are more vulnerable to NIHL but can be rescued by viral transduction of the α9L9'T subunit. In this study, an HA-tagged gain-of-function α9 isoform was expressed in wild-type mice to reduce NIHL. Synaptic integration of the virally expressed nAChR subunit was confirmed by HA immunopuncta localized to the postsynaptic membrane of OHCs. After noise exposure, AAV2.7m8-CAG-α9L9'T-HA (α9L9'T-HA)-injected mice had less hearing loss (auditory brainstem response [ABR] thresholds and threshold shifts) than did control mice. ABRs of α9L9'T-HA-injected mice also had larger wave-1 amplitudes and better recovery of wave-1 amplitudes post noise exposure. Thus, virally expressed α9L9'T combines effectively with native α9 and α10 subunits to mitigate NIHL in wild-type cochleas.

Extracellular recordings in freely moving mice, especially those with movable electrodes (microdrives), are crucial for understanding brain function. However, existing microdrives are often heavy, expensive, fragile, and unsuited for long-term studies with multichannel recordings. The OptoDrive is a new, lightweight (3.2 g), low-cost system for chronic neural recordings and optogenetic manipulation in mice. It features a detachable, 16-channel tungsten-wire electrode assembly with a 3 mm stroke (15 μm step displacement) and an integrated optical fiber. This system enables repeated implantation and explantation without surgery, requiring only gas anesthesia. The OptoDrive has demonstrated stable recordings from the lateral hypothalamus of freely behaving mice for nearly 1 month and successful optogenetic silencing of neuronal activity. In conclusion, OptoDrive offers a cost-effective, compact solution for long-term electrophysiology and optogenetics in freely moving mice.

Objective. The development of electrodes for chronic peripheral nerve stimulation faces several challenges, including complex compositions, intricate manufacturing processes, and high costs associated with the availability and fabrication of suitable materials. These limitations hinder the accessibility and feasibility of producing effective devices for chronic preclinical studies. This study evaluated the feasibility of a simple-to-manufacture gold helical microwire structure electrode (Au-HMSE) for peripheral nerve stimulation, electromyography (EMG) recording, and preliminary tissue response on the rat sciatic nerve. Approach. Manufactured electrodes were used for up to 8 weeks in rats for nerve stimulation and EMG recordings, with electrode-tissue impedances and motor thresholds measured to assess in vivo stability and feasibility. Evoked motor responses were measured via gastrocnemius muscle activity and ankle torque. Terminal histology was performed at 12 weeks to assess chronic tissue response to the implanted electrodes. Main results. Implanted electrodes with impedances <10 kΩ effectively evoked motor responses in monopolar and bipolar configurations and successfully recorded EMG activity. Gastrocnemius activation overlapped with off-target motor responses, likely due to the electrode’s size relative to rat nerve anatomy and the absence of anchoring, which may have allowed migration. High impedance failure appeared related to interconnects between electrodes and tunneled leads and at solder joints in the stimulating and recording setup. Histology showed typical fibrotic encapsulation, with the helical design promoting tissue in-growth around the microwires, creating a high surface area electrode-tissue interface. Significance. This study evaluated the early feasibility of Au-HMSE for chronically implanted rodent nerve stimulation and EMG recordings. While gold electrodes are non-standard for chronic stimulation, the construction of these devices may be appropriate for the evaluation of chronic peripheral nerve stimulation in the preclinical setting due to their simple composition, manufacturing, and availability of gold microwire as a raw material. The findings provide valuable insights for developing future implantable leads used for peripheral nerve stimulation.

Socially effective vocal communication requires brain regions that encode expressive and receptive aspects of vocal communication in a social context-dependent manner. Here, we combined a novel behavioral assay with microendoscopic calcium imaging to interrogate neuronal activity (regions of interest [ROIs]) in the posterior insula (pIns) in socially interacting mice as they switched rapidly between states of vocal expression and reception. We found that largely distinct subsets of pIns ROIs were active during vocal expression and reception. Notably, pIns activity during vocal expression increased prior to vocal onset and was also detected in congenitally deaf mice, pointing to a motor signal. Furthermore, receptive pIns activity was modulated strongly by social context. Lastly, tracing experiments reveal that deep-layer neurons in the pIns directly bridge the auditory thalamus to a midbrain vocal gating region. Therefore, the pIns is a site that encodes vocal expression and reception in a manner that depends on social context.

Aminoglycoside antibiotics remain indispensable despite their ototoxicity. Like other sensorineural forms, aminoglycoside-induced hearing loss (AGIHL) has no effective pharmacotherapy. Oxidative stress, apoptosis, excitotoxicity and inflammation are key pathological factors of the disease. We hypothesised that selegiline, an irreversible monoamine oxidase-B (MAO-B) inhibitor used in Parkinson’s disease, could be repurposed as an otoprotective agent against AGIHL and its effect on dopamine (DA) release from lateral olivocochlear (LOC) fibres, the efferent division of a protective feedback loop plays a major role in the protection against excitotoxicity. Selegiline mitigated AGIHL in BALB/c mice in a dose-dependent manner at different auditory brainstem response frequencies, including 16 kHz, the hearing sensitivity optimum of the animals. It also enhanced the action potential-evoked DA release from LOC efferents in mouse cochlear preparation dose-dependently. Inhibition of DA reuptake contributed to its basic effect of saving DA from metabolism. Among four selegiline analogues tested, the one that increased LOC DA release also provided otoprotection. In contrast, neither safinamide (a reversible MAO-B inhibitor) nor LJP-1207 (a selective semicarbazide-sensitive amine oxidase/vascular-adhesion protein 1 (SSAO/VAP1) inhibitor) prevented AGIHL, despite their antioxidant and anti-inflammatory properties. The reversibility or lack of MAO-B inhibition in safinamide and LJP-1207, respectively, as well as the absence of the propargylamine moiety with known intrinsic neuroprotective activity in both molecules, may explain their ineffectiveness. Selegiline, or certain propargylamine analogues of it, offer a promising therapy against AGIHL by addressing its multifactorial pathology through antioxidant, antiapoptotic, neuroprotective, and anti-inflammatory actions, while enhancing endogenous DAergic protective mechanisms.

Affective and consumption circuits in the brain are intertwined, with changes in each domain often affecting the other. Therapeutic interventions that reduce consumption, thereby facilitating weight loss, have tended to increase anxiety and depression. Obesity is a major risk factor for poor health; thus, it is important to understand the circuits and signals that regulate consummatory and affective behavior. Neurons expressing Urocortin-1 (Ucn) in the Edinger-Westphal (EW) nucleus have been hypothesized to play an important role in regulating both consummatory and affective behavioral domains and responses to stress. We generated UcnCre mice to allow measurement of Ucn neuron calcium activity and to directly activate these neurons during consummatory behaviors and repeated restraint stress. Our findings provide evidence for Ucn neuron regulation of consummatory behaviors and some affective behaviors.

During sleep, behavioral responsiveness to external stimuli is decreased. This classical definition of sleep has been applied effectively across the animal kingdom to identify this common behavioral state in a growing list of creatures, from mammals to invertebrates. Yet, it remains unclear whether decreased behavioral responsiveness during sleep is necessarily associated with decreased responsiveness in brain activity, especially in insects. Here, we performed long-term multichannel electrophysiology in tethered Drosophila melanogaster flies exposed continuously to repetitive visual stimuli. Flies were still able to sleep under these visual stimulation conditions, as determined by traditional immobility duration criteria for the field. Interestingly, we did not find any difference between responses to repetitive visual stimuli during sleep compared with wake when we recorded local field potentials (LFPs) across a transect of the fly brain from optic lobes to the central brain. However, we did find LFP responses to be altered when visual stimuli were variable and of lower probability, especially in the central brain. Central brain responses to less predictable or ‘deviant’ stimuli were lower during the deepest stage of sleep, a time of quiescence characterized by more regular proboscis extensions. This shows that the sleeping fly brain processes low-probability visual stimuli in a different way from more repeated stimuli, and presents Drosophila as a promising model for studying the potential role of sleep in regulating predictive processing.