Adaptive processing and perceptual learning in visual cortical areas V1 and V4

Neurons in visual cortical areas primary visual cortex (V1) and V4 are
adaptive processors, influenced by perceptual task. This is reflected in
their ability to segment the visual scene into task-relevant and
task-irrelevant stimulus components and by changing their tuning to
task-relevant stimulus properties according to the current top-down
instruction. Differences between the information represented in each area
were seen. While V1 represented detailed stimulus characteristics, V4
filtered the input from V1 to carry the binary information required for
the two-alternative judgement task. Neurons in V1 were activated at
locations where the behaviorally relevant stimulus was placed well outside
the grating-mapped receptive field. By systematically following the
development of the task-dependent signals over the course of perceptual
learning, we found that neuronal selectivity for task-relevant information
was initially seen in V4 and, over a period of weeks, subsequently in V1.
Once the learned information was represented in V1, on any given trial,
task-relevant information appeared initially in V1 responses, followed by
a 12-ms delay in V4. We propose that the shifting representation of
learned information constitutes a mechanism for systems consolidation of
memory.