Download or read book Circuits Underlying Visual Attention in Primate Neocortex written by Nicholas A. Steinmetz and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Humans and many other species attend to only a small portion of available visual information at any given moment. They enhance perception of the attended stimulus either overtly, making an eye or head movement to orient toward it, or covertly, without any such movements. The neural circuits that underlie these two types of attention behaviors, and the relationship between them, remain unclear. To investigate the interdependence of them we trained monkeys on a task that behaviorally dissociated the location of covert attention from the location of a saccade target. Recordings in extrastriate visual cortical area V4 surprisingly revealed that enhanced firing rates and other modulations of neural activity accompanied both covert attention and saccade preparation. These results suggested a hypothesis about the circuits that could mediate the control of both behaviors. We recorded neurons in the frontal eye field, an area involved in controlling both behaviors, and found evidence contradicting our hypothesis. Separately, we examined the circuit underlying the integration of attention-related feedback signals with visual information in visual cortex by recording from distinct neuron populations, defined by laminar depth, within V4 during the covert attention task. We found that all neuron populations were modulated indistinguishably during attention. Finally, we constructed a large-scale model of FEF and V4 on neuromorphic hardware and used it to investigate a novel hypothesis about the way feedback from FEF influences V4, namely, via NMDA synapses. This model makes predictions for future experiments that could help uncover the mechanism of attention-related modulation of visual cortex. Taken together, these results have helped to elucidate our understanding of the circuits within and between frontal and visual cortical areas underlying attention.