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Anthony Stiliani
Graduate Student

How does the human visual system code changes to the appearance of the world over time?
What neural mechanisms enable us to perceive fast and slow changes in our surroundings?
How does the representation of temporal information differ across parallel visual processing streams in the brain?

To address these questions with functional magnetic resonance imaging (fMRI), we measured brain responses to time-varying stimuli and then used an encoding model to characterize the temporal sensitivity of human visual cortex. Unlike conventional methods, the encoding approach first models neural responses to the stimulus in separate temporal channels from which fMRI responses are derived. Notably, our model predicts responses to images changing on timescales ranging from milliseconds to seconds and also reveals differential contributions of transient and sustained temporal channels across visual cortex. Consistent with classical models, regions in lateral occipitotemporal cortex are dominated by transient responses evoked by the appearance and disappearance of a stimulus. However, regions in ventral occipitotemporal cortex are driven by both transient responses as well as sustained responses, which are maintained for the duration of the stimulus. These findings propose a rethinking of temporal processing in the ventral stream and suggest that transient responses are important for rapidly extracting the content of the visual input. Critically, our encoding approach also has implications for modeling temporal processing in other sensory and cognitive systems because it enables linking non-invasive fMRI measurements to the timescale of neural computations in the living human brain.

Read all about this research in our paper: Encoding model of temporal processing in human visual cortex. Anthony Stigliani, Brianna Jeska, & Kalanit Grill-Spector; PNAS 2017.