Reverse Correlation Mapping in Face Patches

Harvard Medical School, Boston MA

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Abstract

DESCRIPTION (provided by applicant): The project goal is to explore the relationship between experience, expertise, and modular organization in the temporal lobe. During the last 4 years this laboratory has explored the functional anatomy and mechanisms of face detection and recognition, and the present proposal is to extend these studies to simple shapes and to the role of intensive early experience in generating anatomically distinct functionally specialized domains. There are distinct regions of the brain, reproducible from one person to the next, specialized for processing the most universal forms of human expertise; e.g., face processing, speech processing, and reading. Face-selective regions in the temporal lobe have been identified using functional magnetic resonance imaging (fMRI) in both humans and macaques, and in humans visual recognition of letters and words is also localized, to the same part of the temporal lobe, but more lateral and posterior and in the opposite hemisphere. Because of the importance of social interactions in primates, one could imagine a face-specific region being generated by natural selection, but it is unlikely that a cortical region specific for written words could have evolved, given that humans have been using written language for only a few thousand years, and literacy has been widespread for at most a few hundred years. The fact that most people have intensive early experience with both faces and symbols prompted the question of whether intensive early experience could cause monkeys to develop anatomical specializations for processing stimuli they never naturally use. After intensive training, juvenile monkeys learned symbols faster than adult monkeys and developed more fluency in responding to them. Furthermore fMRI revealed that juveniles, but not adults, develop regions in their temporal lobes selectively responsive to the learned symbols, but not to visually similar but unfamiliar symbols. This provides the unique opportunity to study the physiology and functional organization of a training-induced cortical module selective for simple shapes not normally experienced by monkeys, and to compare this region to the same cortical region in untrained and late-trained animals. Single-unit electrophysiology and fMRI will be used in parallel and in conjunction to explore the functional specialization in these training-induced symbol recognition regions and to explore the differences in the same parts of the temporal lobe in early versus late trained animals. Differences in response properties in this region between untrained, late trained, and early trained animals will illuminate how experience interacts with maturational gradients during development. The learned symbols are simple shapes, with simple features shared among the learned symbol set, therefore single unit physiology should reveal how training affects the way shape selective cells combine simple features to generate more complex shape selectivity. The proposed study should lead to a deeper understanding of how early social and educational experience or deprivation affects the developing brain.