Biology subjects

Tseng, H.-a.

Publications and source records attributed to Tseng, H.-a..

17 recordsLinked to original sources

bioRxiv2026

Striatal Cholinergic Interneurons Signal Aversion and Drive Avoidance

Seeking reward and avoiding punishment are essential for survival. However, how the brain learns aversive value and generates avoidance remains poorly understood. We investigate acetylcholine-releasing striatal cholinergic interneurons (ChIs), which exhibit prominent excitation to salient behavioral cues but have largely been postulated to play a permissive role in reinforcement learning. Using voltage imaging in mice performing aversive versus reward conditioning tasks, we reveal learning-mediated changes in both subthreshold membrane voltage and suprathreshold spiking of individual ChIs. Across tasks, ChIs exhibit stronger immediate excitation to conditioned cues predicting negative outcomes than positive outcomes. This valence-dependent response augmentation reflects a learning-induced network change specific to cues predicting negative outcomes. Furthermore, brief optogenetic silencing of this immediate excitation selectively impairs conditioned avoidance, but not conditioned approach. Together, these results reveal that ChIs actively signal evidence for aversion and play a critical role in driving avoidance, highlighting a cholinergic mechanism underlying aversive learning.

neuroscience↗

bioRxiv2026

Deep brain stimulation reduces subthalamic nucleus pathological dynamics and rescues gait deficits associated with dopamine loss

The Subthalamic Nucleus (STN) regulates movement and is an important clinical target for deep brain stimulation (DBS) in Parkinsons Disease (PD). However, it remains unclear how dopamine loss and DBS influence STN gait encoding. We performed simultaneous recordings from multiple neurons and intermittent DBS in the STN of healthy and dopamine depleted PD mice during voluntary locomotion. We found that dopamine loss resulted in gait deficits manifested as altered stride length of both hindlimbs and forelimbs, which were rescued by intermittent DBS. Furthermore, dopamine loss exaggerated movement encoding of STN population dynamics, and elevates individual STN spiking during movement and beta-rhythmic firing at rest. Despite an overall increase in the fraction of neuron activated by movement, individual neurons gait encoding properties remain similar between healthy and PD mice. While DBS suppressed firing in both healthy and PD mice, it selectively reduced STN beta-rhythmic spiking, desynchronized STN networks, and rescued gait deficits associated with the loss of dopamine. These results suggest that pathological activation and beta synchronization of the STN contributes to motor deficits related to PD, and DBS-induced reduction of beta rhythmic spiking and STN network desynchronization contribute to the therapeutic effects of DBS in PD.

neuroscience↗

bioRxiv2026

Subthreshold membrane depolarization powerfully engages intracellular calcium dynamics in the brain

Membrane voltage (Vm) regulates spike timing and intracellular signaling. While Vm is extensively modulated by behavior, it is unclear how subthreshold Vm dynamics engage intracellular signaling in the awake mammalian brain. We developed a bicistronic viral vector to express genetically encoded and color compatible voltage and calcium (Ca2+) indicators in the same neuron, and simultaneously recorded cellular Vm and Ca2+ dynamics in awake mice. We report that prolonged subthreshold Vm depolarization is closely accompanied by prominent large amplitude Ca2+ elevation, whereas isolated spikes are coupled with weak Ca2+ rise. Additionally, individual spikes differentially engage intracellular Ca2+ dynamics depending on post-spiking Vm depolarization, consistent with a prominent role of slow Vm depolarization in regulating cellular signaling. While brief intracranial electrical stimulation consistently leads to Vm depolarization and Ca2+ increase, longer stimulation disrupts Vm and Ca2+ coupling, highlighting a tightly regulated cellular mechanism that relays slow Vm depolarization to intracellular signaling.

neuroscience↗

bioRxiv2025

Relative phase of membrane potential theta oscillations between individual hippocampal neurons code space

The timing of spikes dictates a neurons impact on downstream circuits and behavior, and spike timing is determined by the membrane potential (Vm). However, due to technical challenges, it has been impossible to analyze the relative timing of Vm dynamics between neurons during behavior. Using large scale membrane voltage imaging, we simultaneously recorded Vm from many individual hippocampal neurons in animals engaged in a virtual spatial task. We found that relative phase of Vm theta oscillations across neurons exhibit gradual or discrete shifts depending on spatial position. This finding extends beyond previous studies showing Vm dynamics in single neurons or spiking activity in multiple neurons, revealing previously unknown evidence for consistent coding of space by spike-independent relative phase of Vm theta dynamics between neurons.

neuroscience↗

bioRxiv2025

Transcranial ultrasound stimulation modulates neuronal membrane potentials across broad timescales in the awake mammalian brain

BackgroundTranscranial ultrasound stimulation (TUS) offers noninvasive neuromodulation with high spatial and temporal precision, but its cellular-level effects in the awake brain remain poorly understood. ObjectiveWe investigated how low-intensity TUS modulates membrane voltage dynamics in single cortical neurons in awake mice. MethodsUsing the genetically encoded voltage indicator SomArchon, we performed high-speed kilohertz voltage imaging in awake head-fixed mice. TUS was delivered with a 0.35 MHz transducer at 10 or 40 Hz pulse repetition frequency with a 20% duty cycle, at intensities below the estimated threshold for auditory brainstem activation. We analyzed changes in membrane potential (Vm), spiking, and coordination across simultaneously recorded neurons. ResultsTUS evoked rapid (<10 ms) Vm depolarizations in 42.8% of neurons, while only 20.5% showed increased spiking, highlighting a direct effect of TUS on modulating synaptic inputs. Many neurons were entrained at both PRFs (20.8% at 10 Hz; 12.7% at 40 Hz) with Vm exhibiting significant phase-locking to individual TUS pulses. Vm entrainment was accompanied by increased temporal coordination across neurons and reset network synchrony. Furthermore, TUS-evoked cellular responses adapted over time, often transitioning from membrane depolarization to hyperpolarization upon repeated exposures, demonstrating prominent response depression. ConclusionBy resolving single-neuron responses, our results demonstrate that TUS directly activates individual cortical neuron with a latency shorter than 10 ms. TUS pulsed at physiologically relevant frequencies of 10 and 40 Hz robustly entrains neural dynamics, alters network coordination and evokes neuronal plasticity. These results highlight the therapeutic potential of designing TUS pulsing patterns to target specific neural circuit dynamics.

neuroscience↗

bioRxiv2024

Ultrasound pulse repetition frequency preferentially activates different neuron populations independent of cell type

Transcranial ultrasound activates mechanosensitive cellular signaling and modulates neural dynamics. Given that intrinsic neuronal activity is limited to a couple hundred hertz and often exhibits frequency preference, we examined whether pulsing ultrasound at physiologic pulse repetition frequencies (PRFs) could selectively influence neuronal activity in the mammalian brain. We performed calcium imaging of individual motor cortex neurons, while delivering 0.35 MHz ultrasound at PRFs of 10, 40, and 140 Hz in awake mice. We found that most neurons were preferentially activated by only one of the three PRFs, highlighting unique cellular effects of physiologic PRFs. Further, ultrasound evoked responses were similar between excitatory neurons and parvalbumin positive interneurons regardless of PRFs, indicating that individual cell sensitivity dominates ultrasound-evoked effects, consistent with the heterogeneous mechanosensitive channel expression we found across single neurons in mice and humans. These results highlight the feasibility of tuning ultrasound neuromodulation effects through varying PRFs.

neuroscience↗

bioRxiv2022

Membrane Voltage Dynamics of Parvalbumin Interneurons Orchestrate Hippocampal Theta Rhythmicity

Hippocampal network activity at theta frequencies (5-10Hz) is important for behavior. However, it remains unclear how behaviorally-relevant network theta rhythms arise and interact with cellular dynamics to dictate spike timing. We performed membrane voltage (Vm) imaging of individual CA1 pyramidal cells and parvalbumin interneurons with simultaneous local field potential (LFP) recordings in mice during locomotion. We found that Vm theta rhythms organize spike timing in both cell types regardless of behavioral conditions, but the Vm of parvalbumin interneurons is better synchronized with LFP. The temporal relationships between spikes and LFP theta reliably reflect the Vm-LFP relationships in parvalbumin cells, but not in pyramidal cells. Thus, cellular theta rhythms broadly organize spike timing in CA1 neurons, and parvalbumin interneurons are critical in coordinating network theta rhythms. One-Sentence SummaryCellular membrane voltage of parvalbumin interneurons organizes spiking and network dynamics in the hippocampus.

neuroscience↗

bioRxiv2022

The autism spectrum disorder risk gene NEXMIF alters hippocampal CA1 cellular and network dynamics

Perturbations in autism spectrum disorder (ASD) risk genes disrupt neural circuit dynamics and ultimately lead to behavioral abnormalities. To understand how ASD-implicated genes influence network computation during behavior, we performed in vivo calcium imaging from hundreds of individual hippocampal CA1 neurons simultaneously in freely locomoting mice with total knockout of NEXMIF. NEXMIF is an ASD risk gene most highly expressed in the hippocampus, and NEXMIF knockout in mice creates a range of behavioral deficits, including impaired hippocampal-dependent memory. We found that NEXMIF knockout does not alter the overall excitability of individual neurons but exaggerates movement-mediated neuronal responses. At the network level, NEXMIF knockout creates over-synchronization of the CA1 circuit, quantified by pairwise correlation and network closeness centrality. These neuronal effects observed upon NEXMIF knockout highlight the network consequences of perturbations in ASD-implicated genes, which have broad implications for cognitive performance and other ASD-related behavioral disruptions.

neuroscience↗

bioRxiv2022

Single and complex spikes relay distinct frequency-dependent circuit information in the hippocampus

Hippocampal neurons generate either single spikes or stereotyped bursts of spikes known as complex spikes. Although single and complex spikes co-occur in the same neuron, their contribution to information processing remains unclear. We analyzed hippocampal CA1 neurons in awake mice and in behaving rats, combining cellular membrane voltage imaging with optogenetics and extracellular recordings. We found that network-driven subthreshold membrane rhythms in the theta versus gamma frequencies preferably entrained complex versus single spikes in individual neurons. Optogenetic membrane perturbation revealed a causal link between subthreshold theta and gamma power and the initiation of complex versus single spikes. Further, single and complex spikes exhibited different place field properties and frequency-dependent coding during spatial navigation. Thus, individual hippocampal neurons do not integrate theta and gamma rhythms into a combined spike timing code, but instead, transmit frequency-specific information as distinct output modes of single versus complex spikes during spatial cognition.

neuroscience↗

bioRxiv2021

Large-scale voltage imaging in the brain using targeted illumination

Recent improvements in genetically encoded voltage indicators enabled optical imaging of action potentials and subthreshold membrane voltage dynamics from single neurons in the mammalian brain. To perform high speed voltage imaging, widefield microscopy remains an essential tool for recording activity from many neurons simultaneously over a large anatomical area. However, the lack of optical sectioning makes widefield microscopy more prone to background signal contamination, and thus far voltage imaging using fully genetically encoded voltage indicators remains limited to simultaneous sampling of a few cells over a restricted field-of-view. We here demonstrate a strategy for large scale voltage imaging using the fully genetically encoded voltage indicator SomArchon and targeted illumination. We implemented a simple, low-cost digital micromirror device based targeted illumination strategy to restrict illumination to the cells of interest, and systematically quantified the improvement of this microscopy design theoretically and experimentally with SomArchon expressing neurons in single layer cell cultures and in the brains of awake mice. We found that targeted illumination, in comparison to widefield illumination, increased SomArchon signal contrast and reduced background cross-contamination in the brain. Such improvement permitted the reduction of illumination intensity, and thus reduced fluorescence photobleaching and prolonged imaging duration. When coupled with a high-speed, large area sCMOS camera, we routinely imaged tens of spiking neurons simultaneously over minutes in the brain. Thus, the widefield microscopy design with an integrated targeted illumination system described here offers a simple solution for voltage imaging analysis of large neuron populations in behaving animals.

neuroscience↗

bioRxiv2020

High-contrast multifocus microscopy with a single camera and z-splitter prism

We present a multifocus imaging strategy based on the use of a simple z-splitter prism that can be assembled from off-the-shelf components. Our technique enables a widefield image stack to be distributed onto a single camera and recorded simultaneously. We exploit the volumetric nature of our image acquisition by further introducing a novel extended-volume 3D deconvolution strategy to suppress far-out-of-focus fluorescence background to significantly improve the contrast of our recorded images, conferring to our system a capacity for quasi optical sectioning. By swapping in different z-splitter configurations, we can prioritize high speed or large 3D field-of-view imaging depending on the application of interest. Moreover, our system can be readily applied to a variety of imaging modalities in addition to fluorescence, such as phase-contrast and darkfield imaging. Because of its simplicity, versatility, and performance, we believe our system will be a useful tool for general biological or biomedical imaging applications.

bioengineering↗

bioRxiv2019

Precision calcium imaging of dense neural populations via a cell body-targeted calcium indicator

Methods for one-photon fluorescent imaging of calcium dynamics in vivo are popular due to their ability to simultaneously capture the dynamics of hundreds of neurons across large fields of view, at a low equipment complexity and cost. In contrast to two-photon methods, however, one-photon methods suffer from higher levels of crosstalk between cell bodies and the surrounding neuropil, resulting in decreased signal-to-noise and artifactual correlations of neural activity. Here, we address this problem by engineering cell body-targeted variants of the fluorescent calcium indicator GCaMP6f. We screened fusions of GCaMP6f to both natural as well as engineered peptides, and identified fusions that localized GCaMP6f to within approximately 50 microns of the cell body of neurons in live mice and larval zebrafish. One-photon imaging of soma-targeted GCaMP6f in dense neural circuits reported fewer artifactual spikes from neuropil, increased signal-to-noise ratio, and decreased artifactual correlation across neurons. Thus, soma-targeting of fluorescent calcium indicators increases neuronal signal fidelity and may facilitate even greater usage of simple, powerful, one-photon methods of population imaging of neural calcium dynamics.

neuroscience↗

bioRxiv2019

Distinct Oscillation Dynamics Selectively Coordinate Excitatory and Inhibitory Neurons in Prefrontal Cortex during Sensory Discrimination

Prefrontal cortex (PFC) spike activity and local field potential (LFP) oscillation dynamics are broadly linked to various aspects of behavior. PFC neurons can encode the identity of sensory stimuli and related behavioral outcome in a range of sensory discrimination tasks. However, it remains largely unclear how different neuron subtypes and related LFP oscillation features are modulated in mice during sensory discrimination. To understand how excitatory and inhibitory neurons in PFC are selectively engaged during sensory discrimination and how they relate to LFPs oscillations, we used tetrode devices to probe well isolated individual PFC neurons, and LFP oscillations, in mice performing a three-choice auditory discrimination task. We found that a majority of the PFC neurons, 78% of a total of 711 individual neurons, exhibited sensory evoked responses that are context and task-progression dependent. Using spike waveforms, we classified these responsive neurons into excitatory and inhibitory neurons, and found that both neuron subtypes were transiently modulated, with individual neurons responses peaking throughout the entire task duration. While the number of responsive excitatory neurons remain largely constant throughout the task, an increasing fraction of inhibitory neurons were gradually recruited as trial progressed. Further examination of the coherences between individual neurons and LFPs revealed that inhibitory neurons in general exhibit higher spike-field coherence with LFP oscillations than excitatory neurons, first at higher gamma frequencies at the beginning of the task, and then at theta frequencies during the task, and finally across theta, beta and gamma frequencies at task completion. Together, our results demonstrate that while PFC excitatory neurons are continuously engaged during sensory discrimination, PFC inhibitory neurons are preferentially engaged as task progresses and selectively coordinated with distinct LFP oscillations. These results demonstrate increasing involvement of inhibitory neurons in shaping the overall PFC network dynamics as sensory discrimination progressed towards completion.

neuroscience↗

bioRxiv2019

Population imaging of neural activity in awake behaving mice in multiple brain regions

A longstanding goal in neuroscience has been to image membrane voltage, with high temporal precision and sensitivity, in awake behaving mammals. Here, we report a genetically encoded voltage indicator, SomArchon, which exhibits millisecond response times and compatibility with optogenetic control, and which increases the sensitivity, signal-to-noise ratio, and number of neurons observable, by manyfold over previous reagents. SomArchon only requires conventional one-photon microscopy to achieve these high performance characteristics. These improvements enable population analysis of neural activity, both at the subthreshold and spiking levels, in multiple brain regions - cortex, hippocampus, and striatum - of awake behaving mice. Using SomArchon, we detect both positive and negative responses of striatal neurons during movement, highlighting the power of voltage imaging to reveal bidirectional modulation. We also examine how the intracellular subthreshold theta oscillations of hippocampal neurons govern spike output, finding that nearby cells can exhibit highly correlated subthreshold activities, even as they generate highly divergent spiking patterns.

neuroscience↗

bioRxiv2018

Optoacoustic brains stimulation at submillimeter spatial precision

Low-intensity ultrasound is an emerging modality for neuromodulation. Yet, piezo-based transducers offer poor spatial confinement of excitation volume, often bigger than a few millimeters in diameter. In addition, the bulky size limits their implementation in a wearable setting and prevents integration with other experimental modalities. Here, we report spatially confined optoacoustic neural stimulation through a novel miniaturized Fiber-Optoacoustic Converter (FOC). The FOC has a diameter of 600 m and generates omnidirectional ultrasound wave locally at the fiber tip through the optoacoustic effect. We show that the optoacoustic wave can directly activate individual cultured neurons and generate intracellular Ca2+ transients. The FOC activates neurons within a radius of 500 m around the fiber tip, delivering superior spatial resolution over conventional piezo-based low-frequency transducers. Combining FOC with electrophysiology, direct and spatially confined neural stimulation of mouse brain is achieved in vivo.

neuroscience↗

bioRxiv2018

Automatic Cell Segmentation by Adaptive Thresholding (ACSAT) for large scale calcium imaging datasets

Advances in calcium imaging have made it possible to record from an increasingly larger number of neurons simultaneously. Neuroscientists can now routinely image hundreds to thousands of individual neurons. With the continued neurotechnology development effort, it is expected that millions of neurons could soon be simultaneously measured. An emerging technical challenge that parallels the advancement in imaging such a large number of individual neurons is the processing of correspondingly large datasets, an important step of which is the identification of individual neurons. Traditional methods rely mainly on manual or semi-manual inspection, which cannot be scaled to processing large datasets. To address this challenge, we have developed an automated cell segmentation method, which is referred to as Automated Cell Segmentation by Adaptive Thresholding (ACSAT). ACSAT includes an iterative procedure that automatically calculates global and local threshold values during each iteration based on image pixel intensities. As such, the algorithm is capable of handling morphological variations and dynamic changes in fluorescence intensities in different calcium imaging datasets. In addition, ACSAT computes adaptive threshold values based on a time-collapsed image that is representative of the image sequence, and thus ACSAT provides segmentation results at a fast speed. We tested the algorithm on wide-field calcium imaging datasets in the brain regions of hippocampus and striatum in mice. ACSAT achieved precision and recall rates of approximately 80% when compared to individual neurons that are verified by human inspection. Additionally, ACSAT successfully detected low-intensity neurons that were initially undetected by humans.\n\nSignificanceACSAT automatically segments cells in large scale wide-field calcium imaging datasets. It is based on adaptive thresholding at both global and local levels, implemented in an iterative process to identify individual neurons in a time-collapsed image from an image sequence. It is therefore capable of handling variation in cell morphology and dynamic changes between different calcium imaging datasets at a fast speed. Based on tests performed on two datasets from mouse hippocampus and striatum, ACSAT performed comparable to human referees and was even able to detect low-intensity neurons that were initially undetected by human referees.

neuroscience↗

bioRxiv2017

Mechanisms of generation of membrane potential resonance in a neuron with multiple resonant ionic currents

Neuronal membrane potential resonance (MPR) is associated with subthreshold and network oscillations. A number of voltage-gated ionic currents can contribute to the generation or amplification of MPR, but how the interaction of these currents with linear currents contributes to MPR is not well understood. We explored this in the pacemaker PD neurons of the crab pyloric network. The PD neuron MPR is sensitive to blockers of H- (IH) and calcium-currents (ICa). We used the impedance profile of the biological PD neuron, measured in voltage clamp, to constrain parameter values of a conductance-based model using a genetic algorithm and obtained many optimal parameter combinations. Unlike most cases of MPR, in these optimal models, the values of resonant- (fres) and phasonant- (f{varphi}=0) frequencies were almost identical. Taking advantage of this fact, we linked the peak phase of ionic currents to their amplitude, in order to provide a mechanistic explanation the dependence of MPR on the ICa gating variable time constants. Additionally, we found that distinct pairwise correlations between ICa parameters contributed to the maintenance of fres and resonance power (QZ). Measurements of the PD neuron MPR at more hyperpolarized voltages resulted in a reduction of fres but no change in QZ. Constraining the optimal models using these data unmasked a positive correlation between the maximal conductances of IH and ICa. Thus, although IH is not necessary for MPR in this neuron type, it contributes indirectly by constraining the parameters of ICa.\n\nAuthor SummaryMany neuron types exhibit membrane potential resonance (MPR) in which the neuron produces the largest response to oscillatory input at some preferred (resonant) frequency and, in many systems, the network frequency is correlated with neuronal MPR. MPR is captured by a peak in the impedance vs. frequency curve (Z-profile), which is shaped by the dynamics of voltage-gated ionic currents. Although neuron types can express variable levels of ionic currents, they may have a stable resonant frequency. We used the PD neuron of the crab pyloric network to understand how MPR emerges from the interplay of the biophysical properties of multiple ionic currents, each capable of generating resonance. We show the contribution of an inactivating current at the resonant frequency in terms of interacting time constants. We measured the Z-profile of the PD neuron and explored possible combinations of model parameters that fit this experimentally measured profile. We found that the Z-profile constrains and defines correlations among parameters associated with ionic currents. Furthermore, the resonant frequency and amplitude are sensitive to different parameter sets and can be preserved by co-varying pairs of parameters along their correlation lines. Furthermore, although a resonant current may be present in a neuron, it may not directly contribute to MPR, but constrain the properties of other currents that generate MPR. Finally, constraining model parameters further to those that modify their MPR properties to changes in voltage range produces maximal conductance correlations.

biophysics↗