Space and time are two fundamental properties of our physical and psychological realms. We recently proposed that the brain uses similar strategies for integrating information over space and throughout time. It is well established that neurons along visual cortical pathways have increasingly large spatial receptive fields (SRFs). This is a basic organizing principle of the visual system; neurons in higher-level visual areas receive input from low-level neurons with smaller receptive fields, thereby accumulating information over space. Drawing a parallel with SRF, we defined the temporal receptive window (TRW) of a neuron as the length of time prior to a response during which sensory information may affect that response. We argue that, as with SRFs, the topographical organization of the TRWs is distributed and hierarchical. The accumulation of information over time is distributed in the sense that each brain area has the capacity to accumulate information over time. The processing is hierarchical because the capacity of each TRW increases from early sensory areas to higher order perceptual and cognitive areas. Early sensory cortices such as the primary auditory or visual cortex have relatively small SRFs and short TRWs (up to hundreds of milliseconds), while higher-order areas have relatively large SRFs and long TRWs (i.e. can accumulate information over long periods of time). The goal of this proposal is to test this novel hypothesis by characterizing TRWs throughout the cortical hierarchy using temporally extended naturalistic stimuli. Using two complementary methods, functional magnetic resonance imaging (fMRI) and intracranial electroencephalography (iEEG), we will develop novel experimental paradigms and analytic tools to measure processing time scales and to probe the underline neural mechanisms by which brain areas accumulate information over time. A better understanding of how the brain accumulates and integrates information over time may shed light on various cognitive disorders as ADHD, learning impairments, and schizophrenia, which often involve difficulties with synthesizing information over time.
Space and time are two fundamental properties of our physical and psychological realms. While much is known about the integration of information across space within the visual system, little is known about the integration of information over time. This proposal sets out a novel method for characterizing the time scales of neural processing evoked within different brain areas by naturalistic stimuli, and provides a new neurologically based integrative model for how the brain accumulates information over time. Difficulties in the accumulation and integration of information over time may be associated with various cognitive disorders such as ADHD, learning impairments, and schizophrenia, which often involve difficulties with synthesizing information over time.
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