Speaker: Christopher Honey, Dept. of Psychology, University of Toronto
Title: Integrating Information Over Time in the Human Cerebral Cortex
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, much less is known about how information is integrated over time. We present functional magnetic resonance imaging (fMRI) and electrocorticographic (ECoG) measurements of brain responses to real-world movies and stories that had been temporally scrambled at different scales. The data suggest that the human brain uses analogous strategies for integrating information over space and over time, a finding that has empirical and theoretical implications for the study of context and memory. Drawing an analogy with the spatial receptive field (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. As with SRFs, the topographical organization of the TRWs is distributed and hierarchical. The organization 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 regions such as the primary auditory or visual cortices have relatively short TRWs (less than 1 second), while the TRWs in higher-order areas can accumulate information over minutes of time. Finally, neural dynamics in long TRW regions change more slowly than in short TRW regions. Overall, these data suggest a joint spatiotemporal information processing hierarchy in the human cerebral cortex, and point toward new models of memory and perception.
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