Publications using TDT

Sexually mature females of multiple mammalian species were previously reported to have increased peripheral auditory sensitivity, often measured as higher auditory brainstem response (ABR) wave I amplitude compared to males. Here, we determined potential hormonal and genetic (i.e., XX- vs. XY-linked genes) contributions to this sex difference by recording ABRs in gonadally intact and gonadectomized female and male wildtype (WT) and four core genotypes (FCG) C57BL/6J mice. WT females at postnatal day 38 (P38) and P65, and FCG mice with ovaries at P65 had higher wave I amplitude than males, and the difference was absent in gonadectomized mice. Furthermore, in WT mice, we addressed the initiation and duration of the sex difference in wave amplitude from pre-pubescence (P25) through maturation from post-pubescent late adolescence to early adulthood (P38, P65, and P95) in both the cochlea and cochlear nucleus. In both female and male mice, wave I amplitude decreased by 50 % from P25 to P95. However, the amplitude in females was 22 % and 11 % higher than males at P38 and P65, respectively. In gonadectomized mice, there was no sex difference in wave I amplitude at any age tested, due to a decrease in gonadectomized females. In contrast, we found that wave II amplitude remains relatively constant over these ages in both sham and gonadectomized WT female and male mice. Together, the data suggest that gonad-derived hormones differentially refine the maturation of wave I, but not wave II, amplitude between late adolescence and early adulthood.

Closed-loop neural control is a powerful tool for both the scientific exploration of neural function and for mitigating deficiencies found in open-loop deep brain stimulation (DBS). Here, we present a protocol for artificial intelligence-guided neural control in rats using deep reinforcement learning (RL) and infrared neural stimulation (INS). We describe steps for integrating RL closed-loop control into neuroscience and neuromodulation studies. We then detail procedures for using and deploying infrared INS in chronic DBS applications. For complete details on the use and execution of this protocol, please refer to Coventry et al.1 and Coventry and Bartlett.2.

Face processing models propose gradually more complex receptive field properties culminating in invariant representations in anterior inferotemporal cortex (aITC), leading to late socio-emotionally relevant encoding in pre- and orbitofrontal cortex (POC). Top-down facilitation models, however, predict that some lower-level POC neurons respond faster than aITC. To resolve this discrepancy, we recorded from 2,459 neurons in fMRI-defined POC and aITC face patches. POC patches are more heterogeneous, containing smaller fractions of face-selective neurons than aITC and a mixture of responses to faces and non-faces. In one POC patch, face responses are surprisingly fast, outpacing those in aITC. Moreover, its responses correlate inversely with stimulus spatial frequency. Hence, our extensive data, with a large diversity of POC neurons, support both models and suggest one POC face patch might be specialized in fast, low-level face processing, which may enable (partially) invariant face representations during subsequent processing stages in inferotemporal cortex (ITC).

Background: Successful seizure onset zone (SOZ) localisation for epilepsy surgery often relies upon intracranial recordings. Accurate delineation requires anatomical detail yet influences of intracranial electrode density on clinical variables have not been systematically studied. Methods: In this experimental study we compared SOZ localisation between spontaneously captured seizures on higher-density depth and grid electrode arrays (4-5 mm inter-electrode spacing) vs. lower-density resampled versions of those same seizures (8-10 mm spacing). Since traditional review of channel traces would reveal density conditions, we instead projected seizure activity data as heatmaps on patient brain reconstructions and hid electrode locations. Using a single-blinded randomised crossover design, six attending-level epileptologists viewed these visualisations from ten patients under both higher-density and lower-density conditions (n = 120 observations) and digitally annotated SOZs. Findings: Inter-rater agreement between epileptologists on annotated margins was moderate (average Cohen's kappa: 0.47) and lower for the lower-density condition (p = 0.021, mixed effects model). Scorer confidence ratings did not differ between higher- and lower-density conditions (p = 0.410). The spatial extents of annotated SOZs for higher-density recordings were 25.4% larger on average (p = 0.011) and always closer to true SOZ extents in computer simulations, relative to lower-density. Interpretation: Epileptologists using higher-density depth and subdural intracranial EEG recordings had higher inter-rater agreement and identified larger extents of SOZs compared to lower-density recordings. While further studies assessing surgical outcomes in more patients are needed, these results suggest higher densities of electrodes on already-implanted hardware may reveal sub-centimetre extensions and clearer functional contiguity of the SOZ(s) for better appraisals of pathophysiological margins in epilepsy surgery. Funding: This work was supported by the National Institutes of Health through NINDS grant K23NS110920 and through a UCSF Weill Institute for Neurosciences Pilot Award.

Recent studies show that systemic administration of a glucagon-like peptide-1 receptor (GLP-1R) agonist is sufficient to attenuate cocaine seeking. However, the neural mechanisms mediating these effects and the role of endogenous central GLP-1 signaling in cocaine seeking remain unknown. Here, we show that voluntary cocaine taking decreased plasma GLP-1 levels in rats and that chemogenetic activation of GLP-1–producing neurons in the nucleus tractus solitarius that project to the ventral tegmental area (VTA) decreased cocaine seeking. Single-nuclei transcriptomics and FISH studies revealed that GLP-1Rs are expressed primarily on GABA neurons in the VTA. Using in vivo fiber photometry, we found that the efficacy of a systemic GLP-1R agonist to attenuate cocaine seeking was associated with increased activity of VTA GABA neurons and decreased activity of VTA dopamine neurons. Together, these findings suggest that targeting central GLP-1 circuits may be an effective strategy toward reducing cocaine relapse and highlight a functional role of GABAergic GLP-1R–expressing midbrain neurons in drug seeking.

To comprehend the volumetric neural connectivity of a brain organoid, it is crucial to monitor the spatiotemporal electrophysiological signals within the organoid, known as intra-organoid signals. However, previous methods risked damaging the three-dimensional (3D) cytoarchitecture of organoids, either through sectioning or inserting rigid needle-like electrodes. Also, the limited numbers of electrodes in fixed positions with non-adjustable electrode shapes were insufficient for examining the complex neural activity throughout the organoid. Herein, we present a magnetically reshapable 3D multi-electrode array (MEA) using direct printing of liquid metals for electrophysiological analysis of brain organoids. The adaptable distribution and the softness of these printed electrodes facilitate the spatiotemporal recording of intra-organoid signals. Furthermore, the unique capability to reshape these soft electrodes within the organoid using magnetic fields allows a single electrode in the MEA to record from multiple points, effectively increasing the recording site density without the need for additional electrodes.

Varicella zoster virus (VZV) causes chicken pox, and reactivation of this virus later in life causes shingles. Previous work demonstrated that estrogens could reduce VZV‐induced orofacial pain and affect gene expression in the central amygdala. It is known that the central amygdala processes pain signals from the orofacial region and that estrogens produced by the enzyme aromatase within the central amygdala regulate neuronal function. Based on the previous studies, it was hypothesized estrogens produced within the central amygdala attenuate VZV‐induced orofacial pain. To address this hypothesis, male Long–Evans rats were implanted with cannulas terminating in the central amygdala. Through these cannulas, the aromatase inhibitor letrozole or estrogen receptor alpha (ERα) agonist, 4,4′,4″‐(4‐propyl‐[1 H ]‐pyrazole‐1,3,5‐triyl) tris phenol (PPT), was infused in the central amygdala. The whisker pad of each rat was injected with either MeWo cells or MeWo cells containing VZV. One week after VZV injection, letrozole or PPT was infused into the central amygdala, followed by measuring pain behavior, GABA release, and estradiol concentrations. Tissues in the orofacial pain pathway were isolated, and neuronal activity was quantitated by counting c‐Fos‐positive neurons. Letrozole significantly increased the pain response and decreased GABA release. Letrozole also decreased estradiol within the central amygdala. Infusion of PPT reduced pain and increased GABA release. Moreover, letrozole increased the number of active neurons in the lateral parabrachial nucleus and spinal trigeminal nucleus, while PPT reduced the number of active neurons in the trigeminal ganglia, lateral parabrachial nucleus, and spinal trigeminal nucleus. The results suggest aromatase‐derived estradiol interacts with ERα within the central amygdala to attenuate VZV‐induced pain by increasing GABA release and reducing neuronal activity in the pain pathway.

Episodic memory relies on the formation and retrieval of content-specific memory traces. In addition to their veridical reactivation, previous studies have indicated that traces may undergo substantial transformations. However, the exact time course and regional distribution of reinstatement and transformation during recognition memory have remained unclear. We applied representational similarity analysis to human intracranial electroencephalography to track the spatiotemporal dynamics underlying the reinstatement and transformation of memory traces. Specifically, we examined how reinstatement and transformation of item-specific representations across occipital, ventral visual, and lateral parietal cortices contribute to successful memory formation and recognition. Our findings suggest that reinstatement in temporal cortex and transformation in parietal cortex coexist and provide complementary strategies for recognition. Further, we find that generalization and differentiation of neural representations contribute to memory and probe memory-specific correspondence with deep neural network (DNN) model features. Our results suggest that memory formation is particularly supported by generalized and mnemonic representational formats beyond the visual features of a DNN.

Brain-machine interface performance can be affected by neuroinflammatory responses due to blood-brain barrier (BBB) damage following intracortical microelectrode implantation. Recent findings suggest that certain gut bacterial constituents might enter the brain through damaged BBB. Therefore, we hypothesized that damage to the BBB caused by microelectrode implantation could facilitate microbiome entry into the brain. In our study, we found bacterial sequences, including gut-related ones, in the brains of mice with implanted microelectrodes. These sequences changed over time. Mice treated with antibiotics showed a reduced presence of these bacteria and had a different inflammatory response, which temporarily improved microelectrode recording performance. However, long-term antibiotic use worsened performance and disrupted neurodegenerative pathways. Many bacterial sequences found were not present in the gut or in unimplanted brains. Together, the current study established a paradigm-shifting mechanism that may contribute to chronic intracortical microelectrode recording performance and affect overall brain health following intracortical microelectrode implantation.

The medial prefrontal cortex (mPFC) is critical for learning and decision-making processes, including responding to threats. The protracted maturation of the mPFC extends into early adulthood. Although prominent models suggest that increasing top-down control by the mPFC eventually allows adult behavioral repertoires to emerge, it is unclear how progressive strengthening can produce nonlinear behavioral changes observed across development. We use fiber photometry and optogenetics to establish causal links between frontolimbic pathway activity and threat avoidance strategies in juvenile, adolescent and adult mice. We uncover multiple developmental switches in the roles of mPFC pathways targeting the nucleus accumbens and basolateral amygdala. These changes are accompanied by axonal pruning, strengthening of synaptic connectivity and altered functional connectivity with downstream cell types, which occur in the mPFC-basolateral amygdala and mPFC-nucleus accumbens pathways at different rates. Our results reveal how developing mPFC pathways pass through distinct architectures that may make them optimally adapted to age-specific challenges.

Auditory neuropathies affect the spiral ganglion neurons of the auditory nerve or their synapses with the sensory hair cells, distorting the sound information transmitted from the ear to the brain. Deciphering the underlying pathophysiological mechanisms remains challenging owing to the diversity of spiral ganglion neuron subtypes and associated central auditory circuits. An auditory neuropathy mechanism is unraveled by investigating the origin of auditory hyperexcitability in a mouse model for hereditary congenital deafness. Otogl encodes the large Otogelin‐like protein, which is related to secreted epithelial mucins and is implicated in the mechanical stimulation of cochlear outer hair cells. Heterozygous Otogl +/− mutant mice display auditory hyperexcitability, highlighted by their susceptibility to audiogenic seizures induced by loud sounds. It is shown that Otogl is transiently expressed in a subpopulation of spiral ganglion neurons during cochlear development. Despite their apparently normal hearing, Otogl +/− mice display poor activation of the spiral ganglion neurons processing loud sounds and an elevation of the activation threshold of the middle the ear muscle reflex that attenuates loud sounds. The findings reveal how a neuropathy affecting spiral ganglion neurons specialized in loud sound processing and associated with the middle the ear muscle reflex can manifest itself as auditory hyperexcitability.

DNA repair mechanisms are essential for cellular development and function. This is particularly true in post-mitotic neurons, where deficiencies in DNA damage response proteins can result in severe neurodegenerative and neurodevelopmental disorders. One highly conserved factor involved in DNA repair is Mut-S Homolog 2 ( Msh2 ), which is responsible for correcting base-base mismatches and insertion/deletion loops during cell proliferation. However, its role in mature neuronal function remains poorly understood. This study investigates the impact of Msh2 loss on sensory processing in a mouse model. Using electrophysiological and molecular assays, we identified significant deficits in cortical and thalamic sound processing in Msh2 -/- mice. These deficits were linked to dysfunction of the thalamic reticular nucleus (TRN), a brain region that critically regulates corticothalamic and thalamocortical activity. Our findings revealed increased oxidative damage, aberrant neuronal activity, and elevated parvalbumin (PV) expression in PV + interneurons in the TRN of Msh2 -/- mice. Additionally, we observed the presence of connexin plaques, indicating that disrupted gap junction formation may contribute to impaired TRN function. These results underscore the critical role of Msh2 in supporting the functionality of PV + interneurons in the TRN, thereby profoundly influencing sensory processing pathways. This study provides new insights into the importance of DNA repair mechanisms in neuronal development and function, potentially contributing to our understanding of their role in neurological disorders.

Value-based decision–making involves multiple cortical and subcortical brain areas, but the distributed nature of neurophysiological activity underlying economic choices in the human brain remains largely unexplored. Specifically, the nature of the neurophysiological representation of reward-guided choices, as well as whether they are represented in a subset of reward-related regions or in a more distributed fashion, is unknown. Here, we hypothesize that reward choices, as well as choice-related computations (win probability, risk), are primarily represented in high-frequency neural activity reflecting local cortical processing and that they are highly distributed throughout the human brain, engaging multiple brain regions. To test these hypotheses, we used intracranial recordings from multiple areas (including orbitofrontal, lateral prefrontal, parietal, cingulate cortices as well as subcortical regions such as the hippocampus and amygdala) from neurosurgical patients of both sexes playing a decision-making game. We show that high-frequency activity (HFA; ɣ and HFA) represents both individual choice-related computations (e.g., risk, win probability) and choice information with different prevalence and regional representation. Choice-related computations are locally and unevenly present in multiple brain regions, whereas choice information is widely distributed and more prevalent and appears later across all regions examined. These results suggest brain-wide reward processing, with local HFA reflecting the coalescence of choice-related information into a final choice, and shed light on the distributed nature of neural activity underlying economic choices in the human brain.

The striatum is the primary input nucleus of the basal ganglia, integrating a dense plexus of inputs from the cerebral cortex and thalamus to regulate action selection and learning. Neuroanatomical mapping of the striatum and its subcompartments has been carried out extensively in rats and mice, nonhuman primates, and cats allowing comparative neuroanatomy studies to derive heuristics about striatal composition and function. Here, we systematically map corticostriatal topography from motor, somatosensory, auditory, and visual cortices as well as thalamostriatal parafascicular (PfN) inputs in the Mongolian gerbil. We also map a pathway reported in mice from medial vestibular nucleus to the PfN that could convey vestibular information to the striatum. Our findings align with those of similar studies in other rodents, indicating homologous neuroanatomical connectivity patterns within the corticostriatal projectome across Rodentia. We observed corticostriatal peaks of dense labeling for each input with a diffuse projection throughout striatal subregions from each cortical region, suggesting a global integration of all cortical information by the striatum. Thalamostriatal projections from PfN covered most of the striatum with a peak of PfN-specific compartmentalized labeling similar to other sensory and motor systems. We also confirm the connection from the medial vestibular nucleus to PfN thalamus, indicating that vestibular information may be widely integrated throughout the striatum. The findings build upon our body of knowledge on striatal connectivity across mammalian species and provide a foundation for striatal research focusing on vestibulothalamostriatal circuits in Rodentia.

Facial paralysis is characterized by an injury to the facial nerve, causing the loss of the functions of the structures that it innervates, as well as changes in the motor cortex. Current models have some limitations for the study of facial paralysis, such as movement restriction, the absence of studying awake animals in behavioral contexts, and the lack of a model that fully evaluates facial movements. The development of an algorithm capable of automatically inferring facial paralysis and overcoming the existing limitations is proposed in this work. In C57/BL6J mice, we produced both irreversible and reversible facial paralysis. Video recordings were made of the faces of paralyzed mice to develop an algorithm for detecting facial paralysis applied to mice, which allows us to predict the presence of reversible and irreversible facial paralysis automatically. At the same time, the algorithm was used to track facial movement during gustatory stimulation and extracellular electrophysiological recordings in the anterolateral motor cortex (ALM). In the basal state, mice can make facial expressions, whereas the algorithm can detect this movement. Simultaneously, such movement is correlated with the activation in the ALM. In the presence of facial paralysis, the algorithm cannot detect movement. Furthermore, it predicts that the condition exists, and the neuronal activity in the cortex is affected with respect to the evolution of facial paralysis. This way, we conclude that the facial paralysis algorithm applied to mice allows for inferring the presence of experimental facial paralysis and its neuronal correlates for further studies.

Numerous studies have shown that neuronal representations in sensory pathways are far from static but are instead strongly shaped by the complex properties of the sensory inputs they receive. Adaptation dynamically shapes the neural signaling that underlies our perception of the world yet remains poorly understood. We investigated rapid adaptation across timescales from hundreds of milliseconds to seconds through simultaneous multielectrode recordings from the ventro-posteromedial nucleus of the thalamus (VPm) and layer 4 of the primary somatosensory cortex (S1) in male and female anesthetized mice in response to controlled, persistent whisker stimulation. Observations in VPm and S1 reveal a degree of adaptation that progresses through the pathway. Under these experimental conditions, signatures of two distinct timescales of rapid adaptation in the firing rates of both thalamic and cortical neuronal populations were revealed, also reflected in the synchrony of the thalamic population and in the thalamocortical synaptic efficacy that was measured in putatively monosynaptically connected thalamocortical pairs. Controlled optogenetic activation of VPm further demonstrated that the longer timescale adaptation observed in S1 is likely inherited from slow decreases in thalamic firing rate and synchrony. Despite the degraded sensory responses, adaptation induced by the controlled repetitive stimulation presented here resulted in a shift in coding strategy that favors theoretical discrimination over detection across the observed timescales of adaptation. Overall, although multiple mechanisms contribute to rapid adaptation at distinct timescales, they support a unifying framework on the role of adaptation in sensory processing.

Our movements result in predictable sensory feedback that is often multimodal. Based on deviations between predictions and actual sensory input, primary sensory areas of cortex have been shown to compute sensorimotor prediction errors. How prediction errors in one sensory modality influence the computation of prediction errors in another modality is still unclear. To investigate multimodal prediction errors in mouse auditory cortex, we used a virtual environment to experimentally couple running to both self-generated auditory and visual feedback. Using two-photon microscopy, we first characterized responses of layer 2/3 (L2/3) neurons to sounds, visual stimuli, and running onsets and found responses to all three stimuli. Probing responses evoked by audiomotor (AM) mismatches, we found that they closely resemble visuomotor (VM) mismatch responses in visual cortex (V1). Finally, testing for cross modal influence on AM mismatch responses by coupling both sound amplitude and visual flow speed to the speed of running, we found that AM mismatch responses were amplified when paired with concurrent VM mismatches. Our results demonstrate that multimodal and non-hierarchical interactions shape prediction error responses in cortical L2/3.

Mammillary body (MB) is traditionally viewed as a structural node of an anatomic circuit for emotion and memory. However, little is known about its molecular and cellular organizations. Here, a discovery that MB contains four subtypes of neurons that occupy different spatial subregions is reported. Of these, two subtypes of neurons are tagged by parvalbumin (PV) and dopamine receptor‐D2 (Drd2) markers. PV neurons are spontaneously active, whereas Drd2 neurons are inactive at rest and generate rebound bursts. These two distinct electrophysiological properties are encoded by Kcnn4 and Cacna1h . PV and Drd2 neurons generate two distinct cell‐type specific circuits by receiving inputs from two discrete subiculum neuronal classes. Gain‐ and loss‐of‐function studies on these cortical‐subcortical circuits demonstrate their differential roles for place and object recognition memory. This finding provides a comprehensive molecular and structural atlas of MB neurons at single‐cell resolution and reveals that MB contains molecularly, structurally, and functionally dissociable streams within its serial architecture.

CRISPR-Cas13 systems have therapeutic promise for the precise correction of point mutations in RNA. Using adenosine deaminase acting on RNA (ADAR) effectors, A-I base conversions can be targeted using guide RNAs (gRNAs). We compare the Cas13 effectors PspCas13b and Cas13bt3 for the repair of the gene USH2A , a common cause of inherited retinal disease and Usher syndrome. In cultured cells, we demonstrate up to 80% efficiency for the repair of the common c.11864 G > A and its murine equivalent c.11840 G > A, across different gRNAs and promoters. We develop and characterize a mouse model of Usher syndrome carrying the c.11840 G > A mutation designed for the evaluation of base editors for inherited retinal disease. Finally, we compare Cas13 effectors delivered via AAV for the repair of Ush2a in photoreceptors. Mean RNA editing rates in photoreceptors across different constructs ranged from 0.32% to 2.04%, with greater efficiency in those injected with PspCas13b compared to Cas13bt3 constructs. In mice injected with PspCas13b constructs, usherin protein was successfully restored and correctly localized to the connecting cilium following RNA editing. These results support the development of transcriptome targeting gene editing therapies for retinal disease.

Electrophysiological recording of neurons in deep brain regions using optogenetic stimulation is a powerful method for understanding and regulating the role of complex neural activity in biological behavior and cognitive function. Optogenetic techniques have significantly advanced neuroscience research by enabling the optical manipulation of neural activities. Because of the significance of the technique, constant advancements in implantable optrodes that integrate optical stimulation with low-noise, large-scale electrophysiological recording are in demand to improve the spatiotemporal resolution for various experimental designs and future clinical applications. However, robust and easy-to-use neural optrodes that integrate neural recording arrays with high-intensity light emitting diodes (LEDs) are still lacking. Here, we propose a neural optrode based on Gallium Nitride (GaN) on sapphire technology, which integrates a high-intensity blue LED with a 5 × 2 recording array monolithically for simultaneous neural recording and optogenetic manipulation. To reduce the noise interference between the recording electrodes and the LED, which is in close physical proximity, three metal grounding interlayers were incorporated within the optrode, and their ability to reduce LED-induced artifacts during neural recording was confirmed through both electromagnetic simulations and experimental demonstrations. The capability of the sapphire optrode to record action potentials has been demonstrated by recording the firing of mitral/tuft cells in the olfactory bulbs of mice in vivo. Additionally, the elevation of action potential firing due to optogenetic stimulation observed using the sapphire probe in medial superior olive (MSO) neurons of the gerbil auditory brainstem confirms the capability of this sapphire optrode to precisely access neural activities in deep brain regions under complex experimental designs.