Biology subjects

Finlayson, N. J.

Publications and source records attributed to Finlayson, N. J..

3 recordsLinked to original sources

bioRxiv2020

Heritability of visual cortex architecture and perception

How much of the functional organization of our visual system is inherited? Here we tested the heritability of retinotopic maps in human visual cortex using functional magnetic resonance imaging. We demonstrate that retinotopic organization shows a closer correspondence in monozygotic (MZ) compared to dizygotic (DZ) twin pairs, suggesting a partial genetic determination. Using population receptive field (pRF) analysis to examine the preferred spatial location and selectivity of these neuronal populations, we estimate a heritability around 30% for polar angle preferences and spatial selectivity, as quantified by pRF size, in extrastriate areas V2 and V3. Our findings are consistent with heritability in both the macroscopic arrangement of visual regions and stimulus tuning properties of visual cortex. This could constitute a neural substrate for variations in a range of perceptual effects, which themselves have been found to be at least partially genetically determined. These findings also add convergent evidence for the hypothesis that functional map topology is linked with cortical morphology. HighlightsO_LIWe analyzed retinotopic maps from monozygotic and dizygotic twin pairs C_LIO_LIVisual field maps in V1-V3 are more similar in monozygotic twins C_LIO_LIHeritability is greater in V1 and V3 for polar angle and population receptive field sizes C_LIO_LIEccentricity maps show lesser degree of heritability C_LIO_LIFurther evidence for link between cortical morphology and topology of retinotopic maps C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/077545v4_ufig1.gif" ALT="Figure 1"> View larger version (77K): org.highwire.dtl.DTLVardef@ceacd6org.highwire.dtl.DTLVardef@b51604org.highwire.dtl.DTLVardef@b860f8org.highwire.dtl.DTLVardef@e67398_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2019

Topographic Signatures of Global Object Perception in Human Visual Cortex

Our visual system readily groups dynamic fragmented input into global objects. How the brain represents such perceptual grouping remains however unclear. To address this question, we recorded brain responses using functional magnetic resonance imaging whilst observers perceived a dynamic bistable stimulus that could either be perceived globally (i.e., as a grouped and coherently moving shape) or locally (i.e., as ungrouped and incoherently moving elements). We further estimated population receptive fields and used these to back-project the brain activity during stimulus perception into visual space via a searchlight procedure. Global perception resulted in non-topographic suppression of responses in lower visual cortex accompanied by wide-spread enhancement in higher object-sensitive cortex. However, follow-up experiments indicated that higher object-sensitive cortex is suppressed if global perception lacks shape grouping, and that grouping-related suppression can be diffusely confined to stimulated sites once stimulus size is reduced. These results speak against a rigid between-area response amplitude code acting as a generic grouping mechanism and point to a within-area response amplitude code mediating the perception of figure and ground.

neuroscience↗

bioRxiv2018

Population receptive field estimates for motion-defined stimuli

The processing of motion changes throughout the visual hierarchy, from spatially restricted local motion in early visual cortex to more complex large-field global motion at later stages. Here we used functional magnetic resonance imaging (fMRI) to examine spatially selective responses in these areas related to the processing of random-dot stimuli defined by differences in motion. We used population receptive field (pRF) analyses to map retinotopic cortex using bar stimuli comprising coherently moving dots. In the first experiment, we used three separate background conditions: no background dots (dot-defined bar-only), dots moving coherently in the opposite direction to the bar (kinetic boundary) and dots moving incoherently in random directions (global motion). Clear retinotopic maps were obtained for the bar-only and kinetic-boundary conditions across visual areas V1-V3 and in higher dorsal areas. For the global-motion condition, retinotopic maps were much weaker in early areas and became clear only in higher areas, consistent with the emergence of global-motion processing throughout the visual hierarchy. However, in a second experiment we demonstrate that this pattern is not specific to motion-defined stimuli, with very similar results for a transparent-motion stimulus and a bar defined by a static low-level property (dot size) that should have driven responses particularly in V1. We further exclude explanations based on stimulus visibility by demonstrating that the observed differences in pRF properties do not follow the ability of observers to localise or attend to these bar elements. Rather, our findings indicate that dorsal extrastriate retinotopic maps may primarily be determined by the visibility of the neural responses to the bar relative to the background response (i.e. neural signal-to-noise ratios) and suggests that claims about stimulus selectivity from pRF experiments must be interpreted with caution.

neuroscience↗