Object Responses in the Ventral and Dorsal Pathway of Human Infants

Abstract

Recently we reported fMRI studies in infants showing selectivity for faces, scenes, and bodies in the ventral visual pathway (Kosakowski et al., VSS 2020). But in adults, visual stimuli also elicit strong responses in the dorsal pathway, in parietal regions that have long been implicated in visually guided action, and more recently in intuitive inferences about the physical world (Fischer et al., 2016). Further, behavioral evidence indicates infants understand the basic physical properties of objects from birth and continue to build an intuitive physical understanding throughout infancy (Baillergeon, 1998). Thus, we tested the hypotheses that regions of the dorsal pathway in infants might show a) strong responses to objects and b) functional response profiles resembling those in regions implicated in intuitive physical inference in adults (namely, objects>bodies>scenes>faces). With fMRI data from awake infants (2-9 months, n=30), we successfully identified regions responding to objects (more than the average of faces, scenes, and bodies) in both ventral and dorsal pathways. We further characterized the response of these regions in held out data. In the ventral pathway, the “object” voxels responded to inanimate, relative to animate conditions (objects≈scenes>faces≈bodies). Conversely, the regions in the dorsal pathway, particularly in the parietal cortex, showed a distinct profile (objects>bodies>>faces>scenes), similar to responses in the adult dorsal pathway. Thus, beyond the category-selective responses to faces, bodies, and scenes in the ventral visual pathway, infants also show robust responses to objects, including activations in the dorsal pathway that resemble the responses implicated in intuitive physical inference in adults.