Efficient visual recognition is critical for many aspects of our lives, and understanding how il is accomplished is essential for any complete theory of the brain. One primary reason for the efficiency of object recognition is its facilitation by top-down, feedback processes. We have been tasting a top-down facilitation model according to which coarse, low spatial frequency, image is quickly extracted from early visual regions and projected to the orbitofrontal cortex, where this Agisr'information is used to generate predictions about potential stimulus identity. The predictions are then fed back to the object recognition areas in the inferior temporal cortex to aid the boltom-up processing in the ventral visual stream. Our previous studies have already revealed a recognition network in which the spatio-temporal dynamics of cortical events, and the primary information exchanged, are consistent with OUf top-down facilitation model. These findings raise a host of important questions about the structural, functional and communication properties of the top-down facilitation network. In particular, we propose to apply our multimodal imaging approach. capitalizing on the complementary strengths of psychophysical paradigms, functional and diffusion MRI, and magnetoencephalography to achieve the following specifiC aims: 1) To study the nature of the prefrontal cortex representations that participate in faCilitating object recognition; 2) To begin characterizing the properties of the pathways mediating top-down facilitation; and 3) To reveal how top-down predictions are generated and integrated with the bottom-up stream. It is expected that the outcome of the six experiments proposed here will provide the foundations and will subsequently stimulate a critical expansion of these aims. We antiCipate thai the characterization of these mechanisms will inform clinical mOdels underlying several disorders. For example, magnocellular pathway abnormalities have been associated with visual deficits in schizophrenia and dyslexia. In addition the proposed examination of the cortical visual pathways will enhance our understanding of visual impairments such as visual agnOSia and anomia, prosopagnosia and achromatopsia. Lastly, the proposed DTI experiments can contribute insights for the treatment of demyelination diseases, such as multiple sclerosis, Alzheimer's and Parkinson's diseases.
We propose 10 study how perception-basad predictions in the brain help undersland our visual world. This will inform clinical models of visual deficit in schizophrenia and dyslexia, several neurological disorders, and demyelination diseases such as multiple sclerosis, Alzheimer's and Parkinson's diseases.
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