Electrophysiology publications

Although clinical and experimental evidence highlight the role of the thalamus in voluntary movement production, the involvement of the thalamus in complex motor tasks such as speech production remains to be elucidated. The present study examined neural activity within the bilateral thalamus in 13 participants (seven females) with essential tremor undergoing awake deep brain stimulation implantation surgery, using three speech tasks of varied complexity [vowel vocalization, a diadochokinetic task (DDK), and sentence repetition]. Low-frequency neural activity (delta/theta band) activity was significantly increased during sentence and DDK compared with vowel vocalization in the bilateral motor thalamus and, to a lesser extent, increased for sentence repetition compared with DDK. Moreover, there was prominent prespeech beta band activity, with a greater decrease in the power of beta activity for sentence compared with DDK and vowel vocalization. The greater low-frequency activity in more complex speech tasks may reflect the allocation of additional cognitive resources to monitor the execution of speech motor plans through cortico–thalamo–cortical pathways in a temporally precise manner. The greater decrease in the power of beta activity prior to the onset of sentence repetition may imply greater involvement of the bilateral thalamus in the planning of complex speech tasks. These findings provide new insights into the role of the bilateral thalamus in speech production and may have clinical implications for neurological disorders that affect speech production.

Long-term robust intracortical microelectrode (IME) neural recording quality is negatively affected by the neuroinflammatory response following microelectrode insertion. This adversely impacts brain-machine interface (BMI) performance for patients with neurological disorders or amputations. Recent studies suggest that the leakage of blood-brain barrier (BBB) and microhemorrhage caused by IME insertions contribute to increased neuroinflammation and reduced neural recording performance. Here, we evaluated dexamethasone sodium phosphate-loaded platelet-inspired nanoparticles (DEXSPPIN) to simultaneously augment local hemostasis and serve as an implant-site targeted drug-delivery vehicle. Weekly systemic treatment or control therapy was provided to rats for 8 weeks following IME implantation, while evaluating extracellular single-unit recording performance. End-point immunohistochemistry was performed to further assess the local tissue response to the IMEs. Treatment with DEXSPPIN significantly increased the recording capabilities of IMEs compared to controls over the 8-week observation period. Immunohistochemical analyses of neuron density, activated microglia/macrophage density, astrocyte density, and BBB permeability suggested that the improved neural recording performance may be attributed to reduced neuron degeneration and neuroinflammation. Overall, we found that DEXSPPIN treatment promoted an anti-inflammatory environment that improved neuronal density and enhanced IME recording performance.

Introduction The posterior tail of the striatum receives dense inputs from sensory regions of cortex and thalamus, as well as midbrain dopaminergic innervation, providing a neural substrate for associative sensory learning. Previously, we have demonstrated that developmental hearing loss is associated with aberrant physiological states in striatal medium spiny neurons (MSNs). Methods Here we directly investigated auditory associative learning impairments in the striatum of adult Mongolian gerbils that underwent transient developmental hearing loss or sham hearing loss during the critical period of auditory development. We used electrophysiology to reveal significant changes to neuronal population responses in vivo and intrinsic and synaptic properties to medium spiny neurons in vitro as animals learned an appetitive “Go/No-Go” auditory discrimination task. For in vivo experiments a 64-channel electrode was implanted in the auditory region of the posterior tail of the striatum and neuronal recordings were carried out as animals learned the task. For in vitro experiments, corticostriatal slice preparations were made from animals on each day of training. Results In naïve animals from both groups there was limited to no phase locking to either auditory stimulus in vivo , and long term depression resulted from theta burst stimulation in vitro . Furthermore, intrinsic and synaptic properties in normal hearing animals were unaffected; however, the hearing loss group continued to show lowered synaptic inhibition, synaptic hyperexcitation, and suppressed intrinsic excitability in the hearing loss group. Starting around day 3–4 in both groups, the emergence of striatal medium spiny neuron phase locking to the auditory conditioning stimuli was observed in vivo . This occurred contemporaneous to an increased probability of theta burst induced LTP during MSN whole cell recording in vitro , and acquisition of the task as the correct rejection response significantly increased in the behaving animals. During the acquisition phase MSNs in the normal hearing group showed a significant decrease in synaptic inhibition and increase in synaptic excitation with no change to intrinsic excitability, while the MSNs in the hearing loss group showed a significant increase in synaptic inhibition, reduction of synaptic hyper excitability, and compensatory changes to intrinsic excitability that supported normal action potential generation. In both groups, synaptic properties were resolved to similar level of E/I balance that could be part of a conserved learning state. Discussion These changes to the intrinsic and synaptic properties likely support LTP induction in vivo and the strengthening of synapses between auditory inputs and MSNs that facilitate neuronal phase locking. These findings have significant implications for our understanding of striatal resilience to sensory impairments in early life, in addition to establishing a granular understanding of the striatal circuit changes that support reward driven stimulus–response learning.

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an established treatment for dystonia, yet the neurophysiological mechanisms underlying frequency-dependent effects remain poorly understood. In this study, we investigate how different GPi-DBS frequencies modulate evoked potential (EP) characteristics within the basal ganglia-thalamo-cortical network in pediatric dystonia patients. We evaluated how increasing stimulation frequency alters EP morphology, focusing on peak-to-peak amplitude (PPa), peak-to-peak duration (PPd), and time to peak (TP). This analysis was motivated by clinical observations that higher DBS frequencies often produce distinct therapeutic effects, suggesting underlying differences in how neural circuits respond to varying stimulation rates. We analyzed intracranial electrophysiological recordings from 13 pediatric and young adult dystonia patients undergoing staged DBS implantation. EPs were recorded from the GPi and subthalamic nucleus (STN) of basal ganglia, and ventral oralis (VO) nucleus of the thalamus during unilateral GPi stimulation at 55, 85, 185, and 250 Hz. EP detection and characterization were performed using an automated algorithm, and group-level analyses were conducted using linear mixed effects models to assess frequency-dependent changes across regions. Increasing stimulation frequency significantly decreased PPa and increased PPd and TP, with a clear threshold effect: 55 Hz and 85 Hz produced similar responses, while 185 Hz and 250 Hz elicited significantly greater changes. These frequency-dependent effects were most pronounced in GPi recordings, followed by STN and VO, suggesting that local circuit dynamics are more sensitive to frequency modulation. Our findings highlight the distinct neurophysiological effects of DBS frequency on EP characteristics, emphasizing the need for personalized DBS programming. The pronounced frequency-dependent modulation observed in GPi suggests that optimal stimulation parameters should be tailored to the target region rather than applying uniform settings across patients. Future studies should investigate the clinical relevance of these EP dynamics and explore their potential as biomarkers for DBS optimization in dystonia.

Mutations in MYO7A , the gene encoding the unconventional myosin 7a, cause hereditary deafness in mice and humans. In the cochlea, MYO7A is present in the sensory hair cells from embryonic stages of development, and plays a critical role in the development and maintenance of the mechanosensitive hair bundles composed of actin‐rich stereocilia. Shaker‐1 mutant mice ( Myo7a Sh1/Sh1 ), the murine model of Usher 1B syndrome, exhibit a progressive loss of the stereocilia, subsequent degeneration of the sensory epithelium and ultimately profound deafness. In addition to the hair bundle defects, we found that the shaker‐1 mutation prevented both inner hair cells (IHCs) and outer hair cells (OHCs) from acquiring their fully mature basolateral current profile. Delivering exogenous Myo7a to newborn Myo7a Sh1/Sh1 mice using dual‐adeno‐associated virus 8 (AAV8)‐ Myo7a or dual‐AAV9‐PhP.eB‐ Myo7a , which primarily target IHCs, led to a substantial rescue of their hair bundle structure. The rescued bundles regained their ability to generate mechanoelectrical transducer (MET) currents in response to fluid jet displacement. Although the average MET current was smaller than in control IHCs, the normal resting open probability of the MET channel was fully restored. The IHCs of the treated cochlea also regained a mature basolateral membrane current profile. Functionally, rescue of the IHC structure and function, but not that of OHCs, leads to an average improvement of 20–30 dB in hearing thresholds across most frequencies. These results support dual AAV‐induced gene replacement therapy as an effective strategy to recover hair‐cell function in Myo7a Sh1/Sh1 mice. image Key points Shaker‐1 mutant mice ( Myo7a Sh1/Sh1 ), which carry a mutation in the unconventional myosin MYO7A and are the murine model of Usher 1B syndrome, become profoundly deaf at 1 month of age or soon after. In the mammalian cochlea, MYO7A is expressed in the hair cells, including within their actin‐rich stereociliary bundles. We show that hair cells of Myo7a Sh1/Sh1 mice progressively lose their transducing stereocilia and mechanoelectrical transduction, and fail to acquire their fully mature basolateral current profile. Delivering exogenous Myo7a to newborn Myo7a Sh1/Sh1 mice using dual‐adeno‐associated virus (AAVs) led to a substantial rescue of the bundle structure and function of inner hair cells, including mechanoelectrical transduction. This functional rescue led to a 20–30 dB improvement in hearing thresholds across most frequencies. These results support dual AAV‐induced gene replacement therapy as an effective strategy to recover the hair‐cell function in Myo7a Sh1/Sh1 mice.

Layer 6 corticothalamic neurons (CTs) provide strong feedback input that is crucial to perception and cognition in normal and pathological states; however, the synaptic properties of this input remain largely unknown, especially in pathology. Here, we examined the synaptic properties of CT axon terminals in the medial geniculate body (MGB), the auditory thalamus, in normal hearing male and female mice and in a mouse model of noise-induced hearing loss (NIHL), also in male and female mice. In normal hearing mice, we found that the amplitude of CT-evoked excitatory postsynaptic current (EPSC) to the core-type ventral subdivision of the auditory thalamus (MGv), which mainly conveys rapid sensory information, is larger compared with the amplitude of CT-evoked EPSC to the matrix-type dorsal subdivision of the auditory thalamus (MGd), which likely conveys higher-order internal state information. This is due to higher axonal density and/or axonal recruitment in CT→MGv compared with CT→MGd synapses. After noise trauma, we observed enhanced short-term facilitation in CT→MGd but not CT→MGv synapses. Our findings reveal a previously unknown mechanism of short-term synaptic plasticity after NIHL via which CTs enhance the throughput of matrix-type thalamus, likely to improve perceptual recovery via higher-order contextual modulation.

Peripheral damage drives auditory cortex (ACtx) plasticity, but the underlying synaptic and cellular mechanisms remain poorly understood. We used a combination of in vitro slice electrophysiology, optogenetics, and in vivo two-photon imaging to investigate layer 5 extratelencephalic (ET) and layer 6 corticothalamic (CT) neuronal plasticity in mice, following noise-induced hearing loss (NIHL). Thalamocortical input was initially balanced between CTs and ETs but shifted to CT-dominant 1 day post-NIHL and then normalized by day 7. This transient shift was accompanied by increased quantal size and suprathreshold excitability in CTs, with minimal changes in ETs. In vivo, CTs exhibited persistent elevation in sound intensity thresholds, while ETs showed a transient shift in frequency tuning and reduced high-frequency responsiveness that recovered within a week. These findings reveal distinct, cell type–specific plasticity mechanisms in deep-layer ACtx neurons following peripheral damage and highlight potential targets for treating hearing loss–related disorders such as tinnitus and hyperacusis.

The neural representations of acoustic features that differ in the location or timbre of the emitter elicit similar perceptions, suggesting the existence of a robust stimulus‐response function between complex sounds and the activity of neural populations at all stages of the auditory system. This hypothesis is tested by decoding a random sound stream, using spike trains from a biophysical model of the auditory nerve and from large‐scale recordings in the inferior colliculus, the auditory thalamus, and the auditory cortex of awake mice. At the level of individual neurons, the reliability of temporal and rate codes is found to decrease along the ascending auditory pathways. Rate coding is progressively favored with increasing independence of neuron frequency tuning. Firing in the auditory cortex is found to be synergistic, whereas that in subcortical areas is more redundant. Finally, combinatorial codes involving neural firing and neural silence within neuron pairs are shown to efficiently encode sound information, particularly in the auditory cortex. Overall, these findings reveal a progressive transformation of the neural code from an individual, redundant, and temporal code at the periphery to a more distributed rate‐based code in the auditory cortex.

Aging disrupts brain network integration and is a significant risk factor for cognitive decline and neurological diseases, yet the circuit-level mechanisms underlying these changes remain unclear. Most previous studies have utilized cross-sectional or acute approaches, limiting insights into the longitudinal dynamics of the neural network. In this study, we chronically recorded laminar electrophysiological activity in both the primary visual cortex (V1) and hippocampal CA1 region of young (2-month-old) and aged (13-month-old) mice over 16 weeks. This approach allowed us to directly assess how aging modulates functional connectivity within hierarchically connected cortical and hippocampal circuits. We found that single-unit spiking activity and the signal-to-noise ratio were largely preserved in aged versus young mice, suggesting intact neuronal firing properties. However, aged mice showed global reductions in local field potential (LFP) power and a selective decrease in coherence across delta, alpha-beta, and gamma frequency bands within and between cortical layers and V1-CA1 pathways, while phase amplitude coupling remained unaffected. Interestingly, population level excitatory activity in CA1 was increased in aged animals. These findings indicate that aging selectively impairs network-level synchrony and temporal coordination in specific frequency bands and regions, with minimal loss of single-neuron function. Our results highlight the necessity of longitudinal, multi-region measurements to uncover the multi-scale vulnerabilities of the aging brain. Understanding the depth- and region-dependent circuit changes will guide strategies to preserve cortical-hippocampal communication and cognitive function in aging, as well as enhance neural interface technologies for older populations. NEW & NOTEWORTHY Aging non-uniformly degrades cortico-hippocampal networks, leading to region- and frequency-specific breakdowns in coordinated activity. While single-neuron activity remains preserved, disruptions in frequency-selective synchrony (delta and alpha-beta) were observed in aged mice, indicating impaired V1-CA1 communication as a marker of aging rather than neuronal degeneration. By separating single-neuron activity and large-scale dynamics, we reveal that aging alters communication between sensory and memory systems, underscoring the need for longitudinal approaches to capture age-related impairments in laminar connectivity.

How the brain organizes discrete actions into fluid sequences is a central problem in motor neuroscience. Competing models of basal ganglia (BG) function propose that BG neurons either signal sequence boundaries or encode movements across ordinal positions. Prior studies have largely examined fixed sequences with end-of-sequence rewards, leaving open whether such findings generalize to more naturalistic conditions. We trained four rhesus macaques to perform a visuomotor sequence task requiring four or five out-and-back joystick movements to peripheral targets. Sequences were completed under two conditions: a random condition, in which target order varied across trials, and a fixed condition, in which order was predictable and consistent. Rewards were delivered after each movement, dissociating reward timing from sequence completion. We recorded single-unit activity in arm-related regions of the globus pallidus (GP; n = 458) and primary motor cortex (M1; n = 306). Regression analyses revealed that many neurons in both GP and M1 encoded ordinal position within a sequence. Order effects were more frequent in the fixed condition, but were also present during random sequences. We found no evidence for preferential encoding of sequence initiation or termination in overlearned sequences, in contrast to prior studies reporting start/stop signals in basal ganglia. Weak effects appeared under the random condition in one animal pair, but these did not generalize across animals or conditions. Instead, neurons exhibited heterogeneous order-related responses spanning the full sequence. These results demonstrate that GP neurons, like those in M1, encode ordinal position throughout a sequence rather than acting solely as sequence initiators or terminators. This challenges boundary-specific models of BG function and highlights the BG’s broader role in representing serial order during motor sequence production.

We developed an extended reciprocity theorem approach to model neuron signals which handles heterogeneous dielectric environments and arbitrary electrode shapes, and use it to study analytically the single fiber action potential. We then established a semi-analytic model that also uses hybrid electromagnetic-electrophysiological simulations to model evoked compound action potential (eCAP) signals from multi-fascicular nerves populated with heterogeneous fiber populations. For validation, model predictions were compared with cuff electrode recordings of activity induced by vagus nerve stimulation in in vivo porcine experiments. The semi-analytic model produces signals that approximate the shape and amplitude of in vivo measurements. It can account for the important variation in the recorded eCAP due to changes in the shape and placement of the stimulus and recording electrodes. We find that partially activated fascicles contribute particularly to the signal, as eCAP contributions from smoothly varying fiber calibers in fully activated ones partially cancel. As a result, eCAP magnitude does not depend monotonically on the stimulation current and recruitment level. Our method can be used to rapidly assess new stimulation and recording setups involving complex nerves and neurovascular bundles, e.g., to maximize signal information content, for closed-loop control in bioelectronic medicine applications, and potentially to non-destructively reconstruct structural and functional nerve topologies through inverse problem solving. In a proof-of-concept study, we demonstrate that parameter optimization can recover the ground-truth distribution of fiber diameters in a simplifed variant of our model.

Brain-computer interfaces (BCIs) enable direct communication between the brain and computers. However, their long-term functionality remains limited due to signal degradation caused by acute insertion trauma, chronic foreign body reaction (FBR), and biofouling at the device-tissue interface. To address these challenges, we introduce a multifunctional surface modification strategy called targeting-specific interaction and blocking nonspecific adhesion (TAB) coating for flexible fiber, achieving a synergistic integration of mechanical compliance and biochemical stability. The coating combines brain-derived neurotrophic factor (BDNF) conjugation and a lubricant-infused surface. This dual-functional design enables selective interaction with neurons and astrocytes while preventing nonspecific adhesion. Notably, high-quality single-unit neural signals were stably recorded for more than 12 months after implantation, demonstrating exceptional long-term recording performance. Integrating mechanical compatibility, antifouling properties, and selective neural cell interaction, the TAB-coated multifunctional fiber represents a transformative approach for neural implants, bridging biological systems with computational systems.

The locus coeruleus–norepinephrine (LC-NE) system regulates arousal and awakening; however, it remains unclear whether the LC does this in a global or circuit-specific manner. We hypothesized that sensory-evoked awakenings are predominantly regulated by specific LC-NE efferent pathways. Anatomical, physiological, and functional modularities of LC-NE pathways involving the mouse basal forebrain (BF) and pontine reticular nucleus (PRN) were tested. We found partial anatomical segregation between the LC → PRN and LC → BF circuits. Extracellular NE dynamics in BF and PRN exhibited distinct sound-evoked activation during sleep, including a fast sound-evoked NE peak specific to PRN. Causal optogenetic interrogation of LC efferent pathways, by retro-channelrhodopsin (ChR2) activation or Platynereis dumerilii ciliary opsin (PdCO) silencing of synapses in target regions, revealed a role for early LC → PRN activity in driving arousal and sound-evoked awakenings. Together, our results uncover a role for early LC-NE PRN activity in connecting sensory and arousal pathways and establish LC heterogeneity in regulating arousal.

Target engagement determines therapeutic efficacy. In spinal cord stimulation (SCS), efficacy depends on the attributes of the electrodes used to deliver stimulation, particularly their position, interelectrode distance, size, and current orientation. We tested the effects of these electrode parameters using cervical stimulation to elicit forelimb muscle responses in the rat. We implanted devices over the C6 dorsal root entry zone (DREZ) in eight rats and measured responses in six forelimb muscles. We used custom designed electrode arrays to systematically vary position, distance, and size with linear arrays, and current orientation with circular arrays. Stimulation consisted of biphasic and pseudomonophasic pulse shapes with bipolar or distant return, and a high-definition montage with four returns surrounding a central contact to increase local current density. Efficacy was calculated from the motor thresholds of recruitment curves, and parameters were compared using linear mixed models. For position, stimulation over the DREZ was most effective, reducing thresholds by 25.9% ( p = 0.0002) relative to the midline; efficacy decreased as the electrode was positioned medial or lateral to the DREZ. For distance, placing the electrodes farther apart significantly improved efficacy ( p = 0.0022). For size, large electrodes increased SCS efficacy, reducing thresholds by 21.5% ( p = 0.0026) relative to small electrodes. After accounting for position and distance, current orientation did not affect SCS efficacy. Lastly, the high-definition montage decreased efficacy, increasing thresholds by 16.7% ( p = 0.003) relative to monopolar stimulation with a distant return. In conclusion, electrode position, distance, and size had the greatest effect on SCS efficacy, with the optimal parameters combining large electrodes at the DREZ position with a distant return. These results have the potential to lower the current needed to engage cervical spinal circuitry and to inform the design of SCS systems to improve dexterity in people with neurological injury or disease.

Layer 6 corticothalamic (L6CT) neurons project to both cortex and thalamus, inducing multiple effects including the modulation of cortical and thalamic firing, and the emergence of high gamma oscillations in the cortical local field potential (LFP). We hypothesize that the high gamma oscillations driven by L6CT neuron activation reflect the dynamic engagement of intracortical and cortico-thalamo-cortical circuits. To test this, we optogenetically activated L6CT neurons in NTSR1-cre mice (both male and female) expressing channelrhodopsin-2 in L6CT neurons. Leveraging the vibrissal pathway in awake, head-fixed mice, we presented ramp-and-hold light at different intensities while recording neural activity in the primary somatosensory barrel cortex (S1) and the ventral posteromedial nucleus (VPm) of the thalamus using silicon probes. We found that the activation of S1 L6CT neurons induces high-frequency LFP oscillations in S1 that are modulated in frequency, but not in amplitude, across light intensities and over time. To identify which neuronal classes contribute to these oscillations, we examined the temporal evolution of firing rate in S1 and VPm. While most S1 neurons were steadily suppressed, VPm and S1 layer 4 fast spiking (L4 FS) neurons evolved from being suppressed to facilitated within 500 ms, suggesting differential recruitment of the intracortical versus cortico-thalamo-cortical pathways. Finally, we found that LFP frequency selectively correlates with VPm firing rate. Taken together, our data suggests that L6CT neurons sculpt the frequency of S1 LFP oscillations through cortico-thalamo-cortical circuits, linking the recurrent interactions mediated by L6CT neurons to the high gamma oscillations observed across physiological and pathological conditions.

Early sensory experience can exert lasting perceptual consequences. For example, a brief period of auditory deprivation early in life can lead to persistent spatial hearing deficits. Some forms of hearing loss (i.e., conductive; CHL) can distort acoustical cues needed for spatial hearing, which depend on inputs from both ears. We hypothesize that asymmetric acoustic input during development disrupts auditory circuits that integrate binaural information. Here, we identify prolonged maturation of the binaural auditory brainstem in the guinea pig by tracking auditory evoked potentials across development. Using this age range, we induce a reversible unilateral CHL and ask whether behavioral and neural maturation are disrupted. We find that developmental CHL is associated with alterations in a brainstem readout of binaural function, an effect that was not observed in a separate cohort with adult-onset CHL. Startle-based behavioral measures suggest that Early CHL animals exhibit reduced spatial resolution for high-frequency sound sources. Finally, single-unit recordings of auditory midbrain neurons reveal significantly poorer neural acuity to a sound location cue that largely depends on high-frequency sounds. Thus, these findings show that unilateral deprivation can disrupt developing auditory circuits that integrate binaural information and may give rise to lingering spatial hearing deficits.

Internal motive states, such as sexual arousal, drive behaviour in response to social cues. However, little is known about how internal states and external cues are integrated to release appropriate behaviours at the correct moment during a social interaction, such as the transition from the appetitive to the consummatory phases of mating 1,2 . Here we identify a neural circuit in male mice that gates the onset of consummatory reproductive behaviours on contact with a mating partner. Stimulating MPOA Esr1 ∩ Vgat hypothalamic neurons promotes mounting of conspecifics and three-dimensional dummy objects 3 . We find that such mounting depends on mechanosensory but not visual cues. Through a large-scale electrophysiological screen, we identify neurons in the subparafascicular thalamic nucleus that nonlinearly integrate medial preoptic area of the hypothalamus (MPOA) and mechanosensory input to encode contact with a potential mate. Circuit tracing and perturbations demonstrated that this conjunctive coding occurs by means of convergent disinhibition from MPOA and excitation from the spinal trigeminal nucleus. Functional manipulations and calcium recordings showed these social-contact neurons, marked by parathyroid hormone 2, were essential for and able to promote mounting. These data indicate that subparafascicular thalamic nucleus-parathyroid hormone 2 neurons integrate internal drive with social touch to trigger mounting at opportune moments during mating. More generally, our findings uncover a brain mechanism whereby an internal state can attribute a social quality to a generic touch to initiate purposeful reproductive actions.

This study compared the behavioral minimum audible angle (MAA) and the electrophysiological acoustic change complex (ACC) elicited by an azimuthal shift in sound location. To examine age effects, 63 participants with normal or near-normal hearing were divided into three age groups (Young, Mid-Aged, and Older). The stimuli were narrow bands of noise centered at 500 Hz to facilitate reliance on primarily binaural temporal cues. Putative spatial location was manipulated by means of head-related transfer functions under headphones. MAA results showed that performance was dependent on the reference location, with performance becoming poorer as the reference location shifted away from midline. The Young group had smaller MAAs than the Older group, and performance of the Mid-Age group was intermediate. Measurement of the ACC was restricted to shifts away from midline, and results showed no ACC for shifts of 4.5° and 9° but present ACCs for shifts of 13.5°, 18°, and 36°. The robustness of the ACC, as measured with the intertrial phase coherence metric, grew with increasing azimuthal shift. For shifts of 13.5° and 18°, Young participants had more robust ACCs than Older participants. Although age-related deficits were found in both the MAA and in the robustness of the ACC, no associations were observed at the individual level between MAA and ACC measures. Further work is necessary to evaluate the ACC elicited by shifts from off-midline reference locations before a firm conclusion can be reached that the ACC is not a viable objective proxy for the MAA.

An adverse gestational environment is a risk factor for the development of psychiatric disorders. Although studies have implicated modifications in neuronal DNA and chromatin, how these changes come about and lead to abnormal behaviors is not known. We sought to identify persistent DNA/chromatin and transcriptomic signatures induced by a proinflammatory gestational environment in the ventral dentate gyrus (vDG), a hippocampal region linked to anxiety. A proinflammatory environment shifted DNA methylation of enhancers and promoters and altered synapse-related gene expression, resulting in transcriptional heterogeneity in the vDG. In animals with prior adversity, exposure to a threatening environment recruited vDG neurons with the greatest transcriptional changes, notably in synapse-relevant genes that also tended to be differentially methylated. Finally, vDG activity was increased during transition from a safe to a threatening environment in animals with prior adversity but not in controls, suggesting their enhanced perception of a potential threat. Our data outline a proinflammatory gestational environment-induced neurobiological sequence that leads to anxiety.

The ability to recognize speakers by their voice despite acoustical variation plays a substantial role in primate social interactions. Although neurons in the macaque anterior temporal lobe (ATL) show invariance to face viewpoint, whether they also encode abstract representations of caller identity is not known. Here, we demonstrate that neurons in the voice-selective ATL of two macaques support invariant voice identity representations through dynamic population-level coding. These representations minimize neural distances across different vocalizations from the same individual while preserving distinct trajectories for different callers. This structure emerged from the coordinated activity of the broader neuronal ensemble, although a small subset of highly identity-selective neurons carried high identity information. Our findings provide a neural basis for voice identity recognition in primates and highlight the ATL as a key hub for integrating perceptual voice features into higher-level identity representations.