The Neural Dynamics of Visual Processing in Monkey Extrastriate Cortex: A Comparison between Univariate and Multivariate Techniques
Understanding the brain mechanisms underlying invariant visual recognition has remained a central tenet of cognitive neuroscience. Much of our current understanding of this process is based on knowledge gained from visual areas studied individually. Previous electrophysiology studies have emphasized the role of the ventral stream of the visual cortex in shape processing and, in particular, of higher level visual areas in encoding abstract category information. Surprisingly, relatively little is known about the precise dynamics of visual processing along the ventral stream of the visual cortex. Here we recorded intracranial field potentials (IFPs) from multiple intermediate areas of the ventral stream of the visual cortex in two behaving monkeys engaged in a rapid face categorization task. Using multivariate pattern analysis (MVPA) techniques, we quantified at millisecond precision the face category information conveyed by IFPs in areas of the ventral stream. We further investigate the relationship between the selectivity and latency of individual electrodes as estimated with classical univariate vs. multivariate techniques and conclude on the similarity and differences between the two approaches.
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