Neural responses to naturalistic movies in the common marmoset using electrocorticography and fMRI

Abstract

The common marmoset (Callithrix jacchus) is a New World monkey that has shown promise as a model for visual neuroscience. Recently we identified several face-selective patches along the occipitotemporal cortex whose configuration resembles those of macaque. Here we investigated neural responses inside and outside face patches during free viewing of naturalistic stimuli. Three awake marmosets actively viewed dynamic videos of socially interacting monkeys as their eye position was monitored. In two animals, electrocorticography (ECoG) was used to measure neural activity over an uninterrupted swath of the visual cortex spanning V1 to TE. In the other monkey, whole brain fMRI was carried out during the viewing of the same movies. The ECoG and fMRI data were recorded over multiple repetitions of 15-minute movies. In the main analysis, we created low-level (e.g. luminance, contrast, motion) and high-level (e.g. faces, bodies, scenes) feature models extracted from the evolving content in each of the movies. We then generated functional maps, based on the similarity between neural/hemodynamic time courses and feature models. This analysis revealed robust principles of cortical processing based on both ECoG and fMRI results. First, a subset of areas in the early ventral visual pathway were driven strongly by the changing contrast of the videos, with the proportion of variance explained by this factor falling off in a posterior to anterior gradient. Second, motion signals drove large regions of the visual cortex, particularly in regions dorsal to the contrast-driven regions in and around the shallow superior temporal sulcus. Third, several face patches could be extracted in the fMRI data based on the face feature time course. We will present these and related findings as part of a larger exploration of the brain activation under naturalistic viewing conditions.

Meeting abstract presented at VSS 2015