Biology subjects

Chakravarthi, R.

Publications and source records attributed to Chakravarthi, R..

2 recordsLinked to original sources

bioRxiv2024

Suppressive interactions between nearby stimuli in visual cortex reflect crowding

Crowding is a phenomenon in which visual object identification is impaired by the close proximity of other stimuli. The neural processes leading to object recognition and its breakdown as seen in crowding are still debated. To assess how crowding affects the processing of stimuli in the visual cortex, we recorded steady-state visual evoked potentials (SSVEPs) elicited by flickering target and flanker stimuli while manipulating the spacing of these stimuli (Experiment 1) as well as target similarity (Experiment 2). Participants performed an orientation discrimination task while accuracy and speed of behavioural responses, along with frequency-tagged SSVEPs elicited by target and flanker stimuli, were recorded. Decreasing target-flanker distance reduced both behavioural performance and target-elicited SSVEP amplitudes. Estimates of the critical spacing, a measure of the spatial extent of crowding, from both behavioural data and SSVEP amplitudes were similar. Additionally, manipulating target similarity affected both measures in the same way. These findings establish a clear connection between the suppression of stimulus processing by nearby flankers in the visual cortex and crowding, and demonstrate the usefulness of SSVEPs in studying the cortical mechanisms of visual crowding.

neuroscience↗

bioRxiv2023

Neural and behavioral signatures of the multidimensionality of manipulable object processing.

Understanding how we recognize everyday objects requires unravelling the variables that govern the way we think about objects and the way in which our representations are organized neurally. A major hypothesis is that the organization of object knowledge follows key object-related dimensions, analogously to how sensory information is organized in the brain. Here, we explored, behaviorally and neurally, the multidimensionality of object processing. We focused on within-domain object information as a proxy for the kinds of object decision tasks we typically engage in our daily lives - e.g., identifying a knife from other types of manipulable objects such as spoons, axes or screwdrivers. To do so, we extracted object-related dimensions from subjective human judgments on a set of objects from a particular object domain - i.e., manipulable objects. We demonstrated that the extracted dimensions are cognitively interpretable - i.e., participants are able to label them; are cognitively relevant for manipulable object processing - i.e., categorization decisions are guided by these dimensions; and are important for the neural organization of knowledge - i.e., they are good predictors of the neural signals elicited by manipulable objects. This shows that multidimensionality is a hallmark of the organization of object knowledge in the brain.

neuroscience↗