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Carvalho, J.

Publications and source records attributed to Carvalho, J..

2 recordsLinked to original sources

Predictive masking is associated with a system-wide reconfiguration of neural populations in the human visual cortex

The human visual system masks the perceptual consequences of retinal or cortical lesion-induced scotomas by predicting what is missing from nearby regions of the visual field. To reveal the neural mechanisms underlying this remarkable capacity, known as predictive masking, we used fMRI and neural modeling to track changes in cortical population receptive fields (pRFs) and connectivity in response to the introduction of an artificial scotoma (AS). Consistent with predictive masking, we found that extrastriate areas increased their sampling of the V1 region outside the AS projection zone. Moreover, throughout the visual field and hierarchy, pRFs shifted their preferred position towards the AS border. A gain field model, centered at this border, accounted for these shifts, especially for extrastriate areas. This suggests that a system-wide reconfiguration of neural populations in response to a change in visual input is guided by extrastriate signals and underlies the predictive masking of scotomas.

neuroscience

Micro-probing enables high-resolution mapping of neuronal subpopulations using fMRI

The characterization of receptive field (RF) properties is fundamental to understanding the neural basis of sensory and cognitive behaviour. The combination of non-invasive imaging, such as fMRI, with biologically inspired neural modeling has enabled the estimation of population RFs directly in humans. However, current approaches require making numerous a priori assumptions, so these cannot reveal unpredicted properties, such as fragmented RFs or subpopulations. This is a critical limitation in studies on adaptation, pathology or reorganization. Here, we introduce micro-probing (MP), a technique for fine-grained and assumption free characterisation of subpopulation RFs. Without specific stimuli or adapted models, MP mapped the bilateral RFs characteristic of observers with a congenital pathway disorder. Moreover, in healthy observers, MP revealed voxels that capture the activity of multiple neuronal subpopulations. Thus, MP provides a versatile framework to visualize, analyze and model, without restrictions, the diverse RFs of cortical subpopulations in health and disease.

neuroscience