Selectivity to limbs in ventral temporal cortex decreases during childhood as selectivity to faces and words increases

Abstract

Ventral temporal cortex (VTC) contains category-selective regions that are involved in perception. Childhood development of VTC is associated with increases in selectivity to behaviorally relevant categories such as faces and words. However, it is unknown whether the increase in selectivity emerges in voxels that are initially weakly specialized or if the selectivity of voxels is being repurposed. To investigate how changes in selectivity to different categories unfold in children over time, we investigated lateral ventral temporal responses to visual categories using longitudinal fMRI measurements spanning 2-5 years in 29 children (ages 5-17) comprising a total of 128 functional sessions. During fMRI participants viewed images of faces (child/adult), body parts (limbs/bodies), characters (words/numbers), objects (cars/guitars), and places (houses/corridors) while performing an oddball task. Longitudinal measurements show a significant increase in the size of face-selective activation, which is larger in the right than left fusiform gyrus (FG), and in the size of word-selective activations in the left occipitotemporal sulcus (OTS, Fig 1). Surprisingly, in the same participants, we find a significant decrease in the size of limb-selective activations in the FG and OTS, bilaterally (Fig 1). However, selectivity to bodies, objects, numbers, and corridors in VTC did not change across childhood. Notably, increasing selectivity to faces and words was coupled with decreasing selectivity to limbs in the developing regions. These results provide evidence that childhood development is not only associated with increased selectivity to socially relevant categories such as faces and words, but also may involve recycling of selectivity: regions that are selective to limbs earlier in childhood become repurposed to represent faces and words.