Biology subjects

Gritton, H.

Publications and source records attributed to Gritton, H..

15 recordsLinked to original sources

bioRxiv2026

ABISS: An Open-Source, Low-Cost Platform for Auditory and Visual Intrinsic Optical Signal Imaging

Defining the boundaries of functional cortical areas is increasingly important for targeted electro-physiology, optical imaging, viral delivery, and circuit manipulation. Intrinsic optical signal imaging (IOSI) provides a rapid and minimally invasive approach for mapping stimulus-evoked cortical activity, but its implementation often requires laboratory-specific combinations of stimulus-generation hardware, experiment-control software, synchronization devices, and data-acquisition systems. These requirements limit accessibility and hinder the use of IOSI as a routine functional mapping tool. Here, we present the Arduino-Based Intrinsic Stimulation System (ABISS), an open-source platform that integrates auditory and visual stimulus generation, trial timing, and image-acquisition triggering into a single programmable device. ABISS generates auditory tone stimuli, VGA-based visual stimuli, and tightly synchronized camera-trigger pulses without requiring a dedicated experiment-control system. Stimulus protocols are also fully modifiable in firmware. Performance was evaluated in auditory and visual cortices of mice. Engineering validation demonstrated accurate stimulus generation and synchronization between stimulus delivery and camera triggering over extended recording sessions. Biological validation showed that ABISS output results in auditory and visual intrinsic signal maps comparable to those obtained using highly specialized or commercial platforms. Together, these findings demonstrate the utility of a low-cost open-source platform for experimental control of intrinsic optical signal imaging. By reducing the technical and financial barriers associated with routine intrinsic optical imaging, ABISS facilitates broader adoption of functional cortical mapping as a tool for improved cortical localization in neuroscience experiments. Significance StatementFunctional cortical mapping is an increasingly important element of neuroscience experimental design as anatomical coordinates alone are often insufficient for defining cortical boundaries in individual animals. Intrinsic optical signal imaging provides an effective solution but traditionally requires specialized hardware, commercial stimulus-generation systems, and laboratory-specific synchronization workflows. We developed ABISS, an inexpensive, open-source platform that integrates auditory and visual stimulus generation with synchronized camera triggering in a single programmable device. ABISS produces functional cortical maps comparable to those obtainable with commercial or specialized systems while substantially reducing hardware complexity and cost. By making intrinsic optical signal imaging more accessible, ABISS lowers the practical barriers for routine functional mapping of the brain and promotes adoption of this important neuroscience technique.

neuroscience↗

bioRxiv2026

Parvalbumin and somatostatin interneurons support distinct computations during auditory scene analysis

Auditory scene analysis requires cortical circuits to preserve target-sound representations while suppressing interference from competing sound sources. Although spatial separation between tar{-}get and masker sounds can substantially improve perception, the inhibitory circuit mechanisms that transform spatial separation into improved target sound representations remain poorly un{-}derstood. Here, we used a multi-speaker auditory environment to present target sounds alone (clean) or together with spatially distributed competing white noise (masked) trials while record{-}ing auditory cortical activity in awake mice. By combining electrophysiology, cell-type-specific optogenetic suppression, and spike-distance-based neural classifiers, we examined how parval{-}bumin (PV) and somatostatin (SST) interneurons contribute to spatial processing in complex auditory scenes. PV and SST interneurons made dissociable, context-dependent contributions. PV suppression broadly altered spatial tuning properties, including tuning width, modulation depth, centroid, and sparseness, and reduced target-sound discriminability under clean condi{-}tions. In contrast, SST suppression produced comparatively modest effects on spatial tuning but selectively impaired neural discrimination only during masked trials thereby weakening the im{-}provement in target discrimination normally associated with spatial release from masking. Thus, the interneuron population that most strongly altered spatial tuning was not the population that most strongly disrupted masked discrimination. This reveals a dissociation between cortical in{-}hibitory mechanisms supporting spatial receptive-field structure and those supporting target-masker segregation. Together, these findings suggest that PV-mediated inhibition refines the fi{-}delity of auditory cortical representations, whereas SST-mediated inhibition enhances separation of simultaneously spatially competing sound sources, providing complementary inhibitory mecha{-}nisms for auditory scene analysis.

neuroscience↗

bioRxiv2026

Representations of spatial saliency in auditory cortex are selectively organized through temporal coordination

Selective processing of behaviorally relevant sounds in complex environments requires dynamic modulation of auditory representations. Here, we show that behaviorally relevant sound locations selectively organize auditory cortical activity through temporal coordination rather than changes in firing rate. Using laminar electrophysiology in mice, we recorded activity in primary auditory cortex (A1) activity during a task in which reward was associated with a specific sound location while neutral, non-rewarded sounds were presented across multiple spatial positions. Neurons exhibited increased response reliability, temporal precision, and spike-field coupling to gamma oscillations selectively for sounds presented from behaviorally relevant locations, even when those sounds were unrewarded. These effects were absent during passive listening. Neurons with stronger gamma coupling also had sharper spatial tuning and greater trial-to-trial reliability, linking temporal coordination to representational fidelity. These findings identify gamma-mediated synchronization as a mechanism through which spatial relevance dynamically reshapes auditory encoding.

neuroscience↗

bioRxiv2026

Reduced MOV10 reveals novel functional cortical connections in an increased fear response

The RNA helicase MOV10 is highly expressed in developing brain, is present in synapses and is required for embryonic viability. A murine brain-specific knockout of MOV10 (Mov10 Deletion) has a thickened cortex, abnormal dendritic arborization and enhanced fear memory. In human studies, MOV10 is among the loci that is correlated with enhanced cortical brain volumes and is also significantly associated with substance dependence by epigenetic profiling. Here we demonstrate that Mov10 Deletion mice show enhanced fear learning that is aligned with impaired structural connectivity of canonical fear circuits revealed by Diffusion Tensor Imaging. We propose a model where MOV10 loss leads to increased GABRA2 expression in the hippocampus and reduced anatomical connectivity that drives augmented fear learning. Memory reactivation is observable during fear memory retrieval as an overall increase in fMRI functional activity in cortical regions. Taken together, this framework identifies that enhanced fear in the MOV10 model is driven via a "corticalized" fear response during re-exposure to the training context that is not driven by the canonical fear circuit. These findings support a molecular basis for non-traditional enhanced learning mechanisms activated by fearful events that shed light on the intractability of fear memories with the potential to inform PTSD and substance dependence disorders.

neuroscience↗

bioRxiv2025

Living Neurosheets: Engineering readily deployable neural architectures

Inspired by the ability of brain structures to support cognitive processing, the need for reliable queryable neural models, and emerging biohybrid applications, we present Living Neurosheets: practical, malleable, modular, and scalable systems for realizing living neural architectures, bio-inspired or beyond evolutionary precedent. By innervating porous sheets, paper-like substrates are endowed with neural function while retaining exceptional versatility. Pre-programmed porosity anchors deposited neurons for reliable spatial control. Cutting, folding, and stacking allow intuitive design, modular composition, and batch fabrication (by the hundreds) of complex neural motifs that preserve geometry and function for months. Reversible integration with tissue-matched optoelectronics enables both sample reuse across hardware and hardware multiplexing across samples, for high-throughput, multimodal investigations. We illustrate these aspects across tissue topologies, gyri-inspired manifolds, and laminar cortical mimics, attaining control over entrainment, synchronization, propagation, suppression, and augmentation dynamics--key features of in vivo neural activity. Finally, via cross-instrument portability, we fuse spatial transcriptomics and electrophysiology, linking gene programs to emergent dynamics.

neuroscience↗

bioRxiv2025

Ventral Hippocampal Temporoammonic and Schaffer Collateral Pathways Differentially Control Fear- and Anxiety-Related Behaviors

The ventral hippocampus plays a crucial role in regulating anxiety- and fear-related behaviors. Previously, we demonstrated that diazepam reduces anxiety-like behavior by inhibiting the dentate gyrus and CA3 principal neurons via 2-GABAARs, while inhibition of CA1 pyramidal neurons is necessary to suppress fear-related responses. This study investigated the role of inputs from ventral CA3 (vCA3) and entorhinal cortex to ventral CA1 (vCA1) in anxiety- and fear-like behavior using bidirectional optogenetic modulations. Adult C57BL/6J male and female mice were subjected to bilateral stereotaxic injection of a viral vector expressing channelrhodopsin or halorhodopsin into vCA3 or into layers II-III of lateral entorhinal cortex, followed by bilateral implantation of fiberoptic ferrules into vCA1. After four weeks of recovery, mice were assessed for anxiety-like behavior in the novel open field, elevated plus maze, and Vogel conflict tests, and by contextual and trace fear conditioning for fear. The behavior of the mice was recorded under laser ON and OFF conditions in all experiments. The activation of vCA3 to vCA1 projections (i.e., Schaffer collateral pathway) increased anxiety- and fear-related behaviors, whereas inhibition reduced such behaviors. In contrast, optogenetic activation or inhibition of EC to vCA1 projections (i.e., temporoammonic pathway) had no effect on anxiety-related behavior but positively or negatively modulated fear-related behavior, respectively. These results suggest that while fear-related behavior is modulated by both inputs to vCA1, modulation of anxiety-related behavior is input-specific for the vCA3 to vCA1 projection. In summary, this study offers mechanistic insights into the complex organization of hippocampal circuitry underlying fear and anxiety. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=183 SRC="FIGDIR/small/690696v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1a3a0d7org.highwire.dtl.DTLVardef@194b96forg.highwire.dtl.DTLVardef@11a62b7org.highwire.dtl.DTLVardef@1471977_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Beta-frequency sensory stimulation enhances gait rhythmicity through strengthened coupling between striatal networks and stepping movement

Stepping movement is delta (1-4 Hz) rhythmic and depends on sensory inputs. In addition to delta rhythms, beta (10-30 Hz) frequency dynamics are also prominent in the motor circuits and are coupled to neuronal delta rhythms both at the network and the cellular levels. Since beta rhythms are broadly supported by cortical and subcortical sensorimotor circuits, we explore how beta-frequency sensory stimulation influences delta-rhythmic stepping movement, and dorsal striatal circuit regulation of stepping. We delivered audiovisual stimulation at 10 Hz or 145 Hz to mice voluntarily locomoting, while simultaneously recording stepping movement, striatal cellular calcium dynamics and local field potentials (LFPs). We found that 10 Hz, but not 145 Hz stimulation prominently entrained striatal LFPs. Even though sensory stimulation at both frequencies promoted locomotion and desynchronized striatal network, only 10 Hz stimulation enhanced the delta rhythmicity of stepping movement and strengthened the coupling between stepping and striatal LFP delta and beta oscillations. These results demonstrate that higher frequency sensory stimulation can modulate lower frequency dorsal striatal neural dynamics and improve stepping rhythmicity, highlighting the translational potential of non-invasive beta-frequency sensory stimulation for improving gait.

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

Differential Inhibitory Responses to Temporal Features Enhance Cortical Coding of Dynamic Stimuli: A Network Model

Cortical circuits feature both excitatory and inhibitory cells that underlie the encoding of dynamic sensory stimuli, e.g., speech, music, odors, and natural scenes. While previous studies have shown that inhibition plays an important role in shaping the neural code, how excitatory and inhibitory cells coordinate to enhance encoding of temporally dynamic stimuli is not fully understood. Recent experimental recordings in mouse auditory cortex have shown that optogenetic suppression of parvalbumin neurons results in a decrease of neural discriminability of dynamic stimuli. Here, we present a multilayer model of a cortical circuit that mechanistically explains these results. The model is based on parvalbumin neurons which respond to both stimulus onsets and offsets, as observed experimentally, and incorporates characteristic shortterm synaptic plasticity profiles of excitatory and parvalbumin neurons. We reveal that by tuning the relative strengths of onset and offset inputs to parvalbumin neurons, the model generates different regimes of coding dominated by rapid firing rate modulations or spike timing. Moreover, the model replicates the experimentally observed reduction in neural discrimination performance during optogenetic suppression of parvalbumin neurons. These results suggest that distinct onset and offset inputs to parvalbumin neurons enhance cortical discriminability of dynamic stimuli by encoding distinct temporal features, enhancing temporal coding, and reducing cortical noise. New & NoteworthyHere we propose a model for the mechanisms that underlie neuron responses in the auditory cortex. This study focuses on single channel tuning of simple interactions between neurons. Using physiologically relevant parameters that underly parvalbumin and excitatory neurons, in the proposed artificial network, we show that we can recreate observed results in live studies.

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↗

bioRxiv2018

A Teensy microcontroller-based interface for optical imaging camera control during behavioral experiments

BackgroundSystems neuroscience experiments often require the integration of precisely timed data acquisition and behavioral monitoring. While specialized commercial systems have been designed to meet various needs of data acquisition and device control, they often fail to offer flexibility to interface with new instruments and variable behavioral experimental designs. New methodWe developed a Teensy 3.2 microcontroller-based interface that offers high-speed, precisely timed behavioral data acquisition and digital and analog outputs for controlling sCMOS cameras and other devices. ResultsWe demonstrate the flexibility and the temporal precision of the Teensy interface in two experimental settings. We first used the Teensy interface for reliable recordings of an animals directional movement on a spherical treadmill, while delivering repeated digital pulses that can be used to control image acquisition from a sCMOS camera. In another example, we used the Teensy interface to control temporally precise delivery of an auditory stimulus and a gentle eye puff in a trace conditioning eye blink behavioral paradigm, while delivering repeated digital pulses to initiate camera image acquisition. Comparison with existing methodsThis interface allows high-speed and temporally precise digital data acquisition and device control during diverse behavioral experiments. ConclusionThe Teensy interface, consisting of a Teensy 3.2 and custom software functions, provides a temporally precise, low-cost, and flexible platform to integrate sCMOS camera control into behavioral experiments.

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↗