Biology subjects

Kothari, N. B.

Publications and source records attributed to Kothari, N. B..

3 recordsLinked to original sources

bioRxiv2025

Pooled versus structured inhibition drives competitive stimulus interactions across distinct spatial scales of the superior colliculus

Competitive stimulus interactions across the space map in the midbrain superior colliculus (SC) are essential for spatial decision-making. Here, with electrophysiological recordings in intermediate and deep layers of the mouse SC (SCid), we discovered that rules and the spatial profiles of these competitive interactions are different between local, within-RF versus global, across-RF-boundary spatial scales. When one visual stimulus was centered in the receptive field (RF) and a second one was located within the RFs classical inhibitory surround, we found that stimulus interactions followed an averaging rule. This classical surround was spatially restricted, and the strength of inhibition underlying these within-RF interactions decreased with distance from the RF center. By contrast, when the second stimulus was located outside the RF, stimulus interactions followed a divisive rule. Strikingly, this extra-classical inhibitory surround was spatially global, and the strength of competitive inhibition underlying these across-RF-boundary interactions was distance-invariant. Computational modeling revealed that whereas within-RF interactions are well-explained by a divisive normalization-like mechanism driven by pooled inhibition, across-RF-boundary interactions are not, and instead, are well-explained by a winner-take-all-like mechanism driven by structured, donut-like inhibition. Combined, our results offer insights into the mechanistic logic of stimulus competition in the SCid, which critically underlies spatial decision-making in mammals.

neuroscience↗

bioRxiv2025

Sensorimotor dynamics in the superior colliculus of the echolocating bat

To successfully execute natural tasks, animals must continuously monitor and integrate dynamic sensory information to guide behavior. While this process - known as active sensing - is fundamental to goal-directed behavior, the mechanisms by which sensory information supports motor planning, particularly across different behavioral contexts, remains poorly understood. We investigated sensory and motor activity in the superior colliculus (SC) of echolocating bats, a powerful model system to study active sensing behaviors due to their reliance on self-generated sonar signals. We recorded multichannel SC activity while bats performed spatial navigation and target tracking behaviors. We hypothesized that changes in sensory signals (i.e., returning echoes) drive quantifiable adjustments in SC activity related to sonar call production, and that adaptive changes in SC sensorimotor processing are preserved across behavioral contexts. We examined pooled SC activity using a dimensionality reduction technique to isolate the largest changes in firing rates across multichannel SC recordings. We then examined the variation in SC activity from the time of echo arrival (sensory input) to call production (motor output). Our data show that increases in call rate are associated with shorter trajectory lengths in neural state space, reflecting reduced variability and increased efficiency in population activity. Strikingly, when bats cluster calls into sonar sound groups (SSGs, which are rapid bursts of calls to increase sensory sampling), SC activity is distinct from times when bats produce isolated calls. Notably, we find that successive SSGs lead to progressively shorter trajectory lengths, suggesting a refinement of sensorimotor processing across successive SSGs. Together, our findings demonstrate that sensorimotor population dynamics in the SC follow common principles across distinct behavioral tasks. These results support a fundamental role for the SC in adaptive sensing and highlight its contribution to flexible sensorimotor tranformations in natural behaviors.

neuroscience↗

bioRxiv2022

Ancient midbrain inhibitory neurons control selective spatial attention

To behave adaptively in complex environments, animals must selectively process the most important information in space while ignoring distractors. Contrary to the dominant cortico-centric view, we report that an evolutionarily old group of inhibitory neurons in the brainstem, called PLTi, is critical for this function of selective spatial attention. In freely behaving mice performing a human-like spatial attention task, we found that bilateral silencing of PLTi severely disrupted target selection without causing perceptual or motor impairments. PLTis effects depended necessarily on goal-relevant, rather than just physical salience-based signals, together revealing it as a dedicated brain site for priority-driven attentional target selection. PLTis core computational function is its explicit implementation of the abstract cognitive decision boundary separating target from distracters: it controlled the accuracy and categorical precision of this decision boundary, doing so by shaping neural representations of competing stimuli in the superior colliculus, a major sensorimotor hub. PLTi may, therefore, be a conserved brainstem engine across vertebrates for winner-take-all-like spatial decisions in goal-driven behavior.

neuroscience↗