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Abstract:
We trained monkeys to identify objects in the presence of varying amounts of visual noise in a delayed-matching-to-sample paradigm. After attaining fixation, monkeys were presented with a brief sample, which could be either a novel or familiar object at one of several stimulus levels ranging from 0 (visual noise) to 100 (undegraded object). After a brief delay, an undegraded test object was presented and monkeys had to release a lever if the sample matched this test object. We used large (8º×8º), colored images of natural scenes, faces, etc. presented at the center of gaze. Experience with a particular set of objects allowed monkeys to identify them in the presence of greater amounts of noise compared to novel objects. We have previously shown that object-selective neurons in macaque prefrontal cortex reflect this behavioral improvement (RainerMiller, Neuron 27:179-189 2000).
By recording the activity of single neurons and local field potentials from eight electrodes simultaneously placed in parafoveal extrastriate area V4, we aim to describe the role of these neurons in communicating information about degraded objects, and examine if and how this information is modified by visual learning. We have preliminary data from 83 neurons from one monkey. Many neurons reliably communicated information about both novel and familiar degraded objects. In addition, we observed a tendency for familiar objects to elicit more activity than novel objects. These findings suggest that visual experience can modify the properties of neurons in extrastriate area V4. We shall quantify these experience-dependent changes and discuss their relation to the monkeys’ improvements in behavioral performance.
