Neural Mechanisms of the Development of Face Perception
Colloquium | February 12 | 12:15-1:30 p.m. | Tolman Hall, Beach Room (3105)
Kalanit Grill-Spector, Stanford University
How do brain mechanisms develop from childhood to adulthood? There is extensive debate if brain development is due to pruning of excess neurons, synapses, and connections, leading to reduction of responses to irrelevant stimuli, or if development is associated with growth of dendritic arbors, synapses, and myelination leading to increased responses and selectivity to relevant stimuli. Our research addresses this central debate using cutting edge multimodal imaging, obtaining multiple measurements of brain function using functional magnetic resonance imaging (fMRI), and brain anatomy using quantitative MRI (qMRI) and diffusion MRI (dMRI) in children (ages 5-12) and adults (ages 22-28). We use the face recognition system as a model system to study brain development as it is a well understood cortical system that shows particularly protracted development throughout childhood and adolescence, into adulthood.
Both anatomical and functional measurements provide compelling empirical evidence supporting the growth hypothesis. Anatomically, we find age-related increases in macromolecular tissue volume in face-selective regions, which we validate in histological slices of postmortem brains. Critically, this tissue development is correlated with specific increases in functional selectivity to faces, as well as improvements in face recognition. Functionally, results reveal (1) age-related increases in responsiveness to faces rather than decreased responses to nonfaces, (2) age-related increases in neural sensitivity to face identity, which are correlated with better perceptual discriminability of faces, and (3) age-related increases in the visual field coverage and foveal bias by receptive fields tiling face-selective regions. Together our data propose a new model by which emergent brain function and behavior during childhood result from cortical tissue growth and increases in responses and selectivity to relevant stimuli rather than from pruning and decreases in responses to irrelevant stimuli.
This research has been done together with Jesse Gomez, Vaidehi Natu, Kevin Weiner, Michael Barnett, and Brianna Jeska