Biology subjects

Trenholm, S.

Publications and source records attributed to Trenholm, S..

6 recordsLinked to original sources

bioRxiv2025

RetINaBox: A hands-on learning tool for experimental neuroscience

An exciting aspect of neuroscience is developing and testing hypotheses via experimentation. However, due to logistical and financial hurdles, the experiment and discovery component of neuroscience is generally lacking in classroom and outreach settings. To address this issue, here we introduce RetINaBox: a low-cost open-source electronic visual system simulator that provides users with a hands-on tool to discover how the visual system builds feature detectors. RetINaBox features an LED array for generating visual stimuli and a photodiode array that acts as a mosaic of model photoreceptors. Custom software on a Raspberry Pi computer reads out responses from model photoreceptors and allows users to control the polarity and delay of the signal transfer from model photoreceptors to model retinal ganglion cells. Interactive lesson plans are provided, guiding users to discover different types of visual feature detectors--including ON/OFF, center-surround, orientation selective, and direction selective receptive fields--as well as their underlying circuit computations.

neuroscience↗

bioRxiv2024

Visual objects refine head direction coding

Animals use visual objects to guide navigation-related behaviors, from hunting prey, to escaping predators, to exploring the world. However, little is known about where visual objects are encoded in the mouse brain or how they impact processing in the spatial navigation system. Using functional ultrasound imaging in mice, we conducted a brain-wide screen and identified brain areas that were preferentially activated by images of objects compared to scrambled versions of the same images. While visual cortical areas did not show a significant preference, regions associated with spatial navigation were preferentially activated by visual objects. Electrophysiological recordings in postsubiculum, the primary cortical area of the head direction (HD) system, further confirmed a preference for visual objects, which was present in both HD cells and fast-spiking interneurons. Finally, we found that visual objects dynamically modulated HD cells, selectively increasing firing rates of HD cells aligned with a visual landmarks direction, while decreasing activity in HD cells coding for other directions. These results reveal that visual objects refine population-level coding of head direction.

neuroscience↗

bioRxiv2023

Efficient and sustained optogenetic control of nervous and cardiac systems

Optogenetic control is used to manipulate the activity of specific cell types in vivo for a variety of biological and clinical applications. Here we report ChReef, an improved variant of the channelrhodopsin ChRmine. ChReef offers minimal photocurrent desensitization, a unitary conductance of 80 fS and closing kinetics of 30 ms, which together enable reliable optogenetic control of cells at low light levels with good temporal fidelity and sustained stimulation. We demonstrate efficient and reliable red-light pacing and depolarization-block of ChReef-expressing cardiomyocyte clusters. We used AAV-based gene transfer to express ChReef in retinal ganglion cells, where it restores visual function in blind mice with light sources as weak as an iPad screen. Toward optogenetic hearing restoration, ChReef enables stimulation of the auditory pathway in rodents and non-human primates with nano-Joule threshold, enabling efficient and frequency-specific stimulation by LED-based optical cochlear implants.

biophysics↗

bioRxiv2023

The feature landscape of visual cortex

Understanding computations in the visual system requires a characterization of the distinct feature preferences of neurons in different visual cortical areas. However, we know little about how feature preferences of neurons within a given area relate to that areas role within the global organization of visual cortex. To address this, we recorded from thousands of neurons across six visual cortical areas in mouse and leveraged generative AI methods combined with closed-loop neuronal recordings to identify each neurons visual feature preference. First, we discovered that the mouses visual system is globally organized to encode features in a manner invariant to the types of image transformations induced by self-motion. Second, we found differences in the visual feature preferences of each area and that these differences generalized across animals. Finally, we observed that a given areas collection of preferred stimuli ( own-stimuli) drive neurons from the same area more effectively through their dynamic range compared to preferred stimuli from other areas ( other-stimuli). As a result, feature preferences of neurons within an area are organized to maximally encode differences among own-stimuli while remaining insensitive to differences among other-stimuli. These results reveal how visual areas work together to efficiently encode information about the external world.

neuroscience↗

bioRxiv2022

Flexible cue anchoring strategies enable stable head direction coding in both sighted and blind animals

Vision plays a crucial role in instructing the brains spatial navigation systems. However, little is known about how vision loss affects the neuronal encoding of spatial information. Here, recording from head direction (HD) cells in the anterior dorsal nucleus of the thalamus in mice, we find stable and robust HD tuning in blind animals. In contrast, placing sighted animals in darkness significantly impairs HD cell tuning. We find that blind mice use olfactory cues to maintain stable HD tuning and that prior visual experience leads to refined HD cell tuning in blind adult mice compared to congenitally blind animals. Finally, in the absence of both visual and olfactory cues, the HD attractor network remains intact but the preferred firing direction of HD cells continuously drifts over time. We thus demonstrate remarkable flexibility in how the brain uses diverse sensory information to generate a stable directional representation of space. HighlightsO_LIHead direction (HD) cell tuning in ADn is robust in blind animals, but unstable in sighted animals placed in the dark C_LIO_LIBlind mice use olfaction to stabilize HD cell tuning C_LIO_LIPrior visual experience leads to refined HD cell tuning in blind adult mice C_LIO_LIIn the absence of both vision and olfaction, the HD attractor network in ADn remains intact but the preferred firing direction of HD cells continuously drifts C_LI

neuroscience↗

bioRxiv2020

High resolution visual information via a gap junction-mediated spike order code

Gap junctions promote correlated spiking between coupled neurons. Recording from pairs of coupled retinal ganglion cells, we find that differences in firing rate between coupled neurons dictates which cell leads correlated spike-pairs, and that the precise temporal order of spike activity between pairs of cells changes depending on the spatial position of a visual stimulus. We thus demonstrate a spike order spatial code for encoding sensory information.

neuroscience↗