Functional MRI mapping of dynamic visual features during natural viewing in the macaque

Abstract

The ventral visual pathway of the primate brain is specialized to respond to stimuli in certain categories, such as the well-studied face selective patches in the macaque inferotemporal cortex. To what extent does response selectivity determined using brief presentations of isolated stimuli predict activity during the free viewing of a natural, dynamic scene, where features are superimposed in space and time? To approach this question, we obtained fMRI activity from the brains of three macaques viewing extended video clips containing a range of social and nonsocial content and compared the fMRI time courses to a family of feature models derived from the movie content. Starting with more than two dozen feature models extracted from each movie, we created functional maps based on features whose time courses were nearly orthogonal, focusing primarily on faces, motion content, and contrast level. Activity mapping using the face feature model readily yielded functional regions closely resembling face patches obtained using a block design in the same animals. Overall, the motion feature model dominated responses in nearly all visually driven areas, including the face patches as well as ventral visual areas V4, TEO, and TE. Control experiments presenting dynamic movies, whose content was free of animals, demonstrated that biological movement critically contributed to the predominance of motion in fMRI responses. These results highlight the value of natural viewing paradigms for studying the brain’s functional organization and also underscore the paramount contribution of magnocellular input to the ventral visual pathway during natural vision.

Whole-agent selectivity within the macaque face-processing system

“…Although whole-agent integration emerges across the face patches-bolstering recent evidence that these patches represent social information beyond face form (15,36)-this integration does not develop along the same ventral-to-dorsal trajectory as natural motion selectivity, but rather the posterior-to-anterior axis of the face processing system (Fig. 5): Subadditive responses in posterior patches PL and ML gave way to additive responses in MD and MF and, eventually, a superadditive response in AF (and likely AL).…”

Data-driven approaches in the investigation of social perception

“…Specific subsystems-such as those involved in face or voice perception-thus operate during natural viewing as in more controlled experiments (see also [25] for similar results in macaques). On the fMRI end, it is also possible to use the pattern of activation across multiple voxels as the response, rather than the more typical mass-univariate response, which averages over voxels.…”

Three-Dimensional Digital Template Atlas of the Macaque Brain

“…8. Further methodological detail about the functional MR scanning is provided in Russ and Leopold (2015).…”