Spikiness and animacy as potential organising principles of human ventral visual cortex

Considerable research has been devoted to understanding the fundamental
organising principles of the ventral visual pathway. A recent study
revealed a series of 3–4 topographical maps arranged along the macaque
inferotemporal (IT) cortex. The maps articulated a two-dimensional space
based on the spikiness and animacy of visual objects, with
‘inanimate-spiky’ and 'inanimate-stubby’ regions of the maps
constituting two previously unidentified cortical networks. The goal of
our study was to determine whether a similar functional organisation might
exist in human IT. To address this question, we presented the same object
stimuli and images from ‘classic’ object categories (bodies, faces,
houses) to humans while recording fMRI activity at 7 Tesla. Contrasts
designed to reveal the spikiness-animacy object space evoked extensive
significant activation across human IT. However, unlike the macaque, we
did not observe a clear sequence of complete maps, and selectivity for the
spikiness-animacy space was deeply and mutually entangled with
category-selectivity. Instead, we observed multiple new stimulus
preferences in category-selective regions, including functional
sub-structure related to object spikiness in scene-selective cortex. Taken
together, these findings highlight spikiness as a promising organising
principle of human IT and provide new insights into the role of
category-selective regions in visual object processing.