Biology subjects

O'Shea, R. T.

Publications and source records attributed to O'Shea, R. T..

3 recordsLinked to original sources

bioRxiv2025

Impaired thalamic burst firing in Fragile X syndrome

The thalamus performs a critical role in sensory processing by gating the flow of sensory information to the neocortex and directing sensory-driven behaviors; functions which are disrupted in people with autism spectrum disorders (ASD). We have identified cellular changes in thalamic neurons in a mouse model of Fragile X syndrome (FX), the leading monogenic cause of ASD, that alter how the thalamus transmits sensory information to neocortical circuits. In awake animals, thalamic relay cells gate input by shifting between two firing modes: burst and tonic. Relay cells in FX mice, however, do not shift between these modes and instead operate primarily in the tonic mode. We demonstrate that the lack of burst mode firing is caused by a shift in the voltage sensitivity for the Ca2+-dependent low threshold spike, which underlies normal burst firing.

neuroscience↗

bioRxiv2024

Synchrony dynamics underlie irregular neocortical spiking

Cortical neurons are characterized by their variable spiking patterns. We challenge prevalent theories for the origin of spiking variability. We examine the specific hypothesis that cortical synchrony drives spiking variability in vivo. Using dynamic clamp, we demonstrate that intrinsic neuronal properties do not contribute substantially to spiking variability, but rather spiking variability emerges from weakly synchronous network drive. With large-scale electrophysiology we quantify the degree of synchrony and its time scale in cortical networks in vivo. We demonstrate that physiological levels of synchrony are sufficient to generate irregular responses found in vivo. Further, this synchrony shifts over timescales ranging from 25 to 200 ms, depending on the presence of external sensory input. Such shifts occur when the network moves from spontaneous to driven modes, leading naturally to a decline in response variability as observed across cortical areas. Finally, while individual neurons exhibit reliable responses to physiological drive, different neurons respond in a distinct fashion according to their intrinsic properties, contributing to stable synchrony across the neural network.

neuroscience↗

bioRxiv2024

Luminance invariant encoding in primary visual cortex

The retina maintains sensitivity over a large range of luminance intensities by switching between rod and cone photoreceptors. This luminance adaptation has been shown to alter the receptive fields and interneuronal correlations of retinal ganglion cells (RGCs). While these adaptations allow the retina to encode visual information across environmental conditions, they present a challenge to downstream processing areas for which it is important that representations are invariant to light level. We measured the effects of scotopic versus photopic luminance adaptation on thalamic and cortical activity by tracking neuronal populations across light levels. While changes in the output of the retina are evident in the lateral geniculate nucleus (LGN), the representation in primary visual cortex (V1) is largely invariant to the changes in luminance. We show that an invariant V1 code can emerge through the integration of parallel functional pathways at the geniculocortical synapse.

neuroscience↗