Visual Pathways Fine Tuned Over Time

Marlene Behrmann, Carnegie Mellon University

In adolescents, activation in the ventral visual pathway for the category of “faces” appears at first glance to be adult-like; but, surprisingly, their recognition abilities for individual faces is actually still immature. Now TDLC researchers Marlene Behrmann, K. Suzanne Scherf, Beatriz Luna and Galia Avidan have investigated at the neural level the ability to represent individual faces and houses. In their study, which included children, adolescents and adults, category-selective regions of interest (ROI) in the fusiform gyrus (FG) were individually identified for faces, with sites in the parahippocampal place area (PPA) individually identified for houses. 

Using functional Magnetic Resonance Imaging (fMRI), the magnitude of individual-level adaptation for faces and houses was measured separately in each ROI. Despite finding equal levels of category-selectivity in the ROIs across the three age groups, adults were the only group who exhibited individual-level adaptation bilaterally for faces in the FG and for houses in the PPA. Adolescents did exhibit individual-level adaptation for houses bilaterally in the PPA but for faces only in the left FG. Children exhibited no category-selective individual-level adaptation effects for either faces or houses anywhere in the brain.

These results indicate that category-level neural tuning develops prior to individual-level neural tuning throughout the ventral visual pathway and that face-related cortex is disproportionately slower in this developmental transition than is place-related cortex.

These findings would seem to provide novel evidence that, developmentally, category-level neural tuning precedes individual-level neural tuning throughout the ventral visual pathway: across all three age groups, stimulus-specific neural tuning (i.e., individual-level adaptation) for faces and/or houses was present only if category-level selectivity for these stimulus classes was already established.

“What precedes which: Developmental neural tuning in face- and place-related cortex.” Scherf, K. S., Luna, B., Avidan, G., and Behrmann, M., Cerebral Cortex (in review).