Functional Organization of Visual Object Processing

Massachusetts General Hospital, Boston MA

Investigators

Linked publications & trials

Abstract

[unreadable] DESCRIPTION (provided by applicant): At high levels of the primate visual system (e.g. those involved in visual object processing, in the 'ventral stream' including inferotemporal cortex), we do not fully understand the neural processing. Existing evidence is based largely on 1) single unit recordings from macaque monkey, or from 2) functional magnetic resonance imaging (fMRI) in humans. Because such evidence arises from quite different techniques, in different primates, with different historical backgrounds, it can be difficult to integrate this information into a coherent understanding of how visual objects are processed in brain. Such information is especially important for the eventual understanding of autism, prosopagnosia and other agnosias, and schizophrenia. Here we propose to use functional magnetic resonance imaging (fMRI) in both humans and macaque monkeys, and anatomical techniques in monkeys, to narrow this information gap and to define the common functional architecture of 'primate' ventral stream. Among many possible object stimuli, we focus on specialized neural regions which appear to process faces. In aim #1, we will use a novel fMRI approach to map the activity produced by faces (and other objects), in humans and monkeys, to test how specific stimulus variations are mapped across the cortical topography. Current fMRI information on this topic is instead based on responses to multiple stimuli (object categories) and/or adaptation effects - rather than direct, high-resolution maps of activity produced by individual stimuli. In aim #2, we quantitatively compare the fMRI maps for face- and object-selective activity in humans and monkeys, to further test which of these cortical regions 'match' each other in the two species, and which do not. After testing and confirming that these face- and object-selective regions 'match', we can study them further using classical neurobiological techniques in the macaque (e.g. aims #3 and 4), as a model for corresponding regions in humans. In aim #3, we will use novel MRI-based techniques to map the neural connections to-and-from the face-selective cortical regions, relative to nearby regions which are activated by different objects. In aim #4, we will measure face perception using psychophysics in monkeys, and make lesions in the fMRI-defined face-selective regions, to test whether damage to the face-selective regions may explain the clinical syndrome of prosopagnosia (facial 'blindness') in human patients. [unreadable] [unreadable] [unreadable]