NEURAL DYNAMICS AND THE PERCEPTION OF VISUAL FORM

当灵长类动物观察世界时，它会进行跳眼运动

When a primate views the world it makes a saccadic eye movement, and at the end of this movement the eyes remain more-or-less fixed in position for typically a third of a second, whereupon a new saccadic eye movement is performed. At the end of each saccadic eye movement the different pieces of the images of different objects are brought into the receptive fields of different assemblages of neurons. The visual scene is cluttered, with many objects overlapping and occluding each other. The activity elicited by the appearance of new stimuli in the receptive fields of neurons propagates through a loose hierarchy of cortical visual areas with a particular time course. The coordinated activity of many neurons in the different cortical areas during this interval between saccades is presumably what gives rise to visual perception. A great deal has been learned about the pattern of connections between the various cortical visual areas, and about the single aspects of a visual stimulus for which the individual neurons in each area are most sensitive to. However, less is known about how the visual system deals with complex stimuli, and for what (if many) role the time-varying aspects of neurons in the visual system might play. This study will address these issues by recording from single neurons and pairs of neurons in several cortical visual areas (V1, V2, V4, and IT) of awake behaving rhesus monkeys, using both simple and more complex visual stimuli, exploring the responses of neurons to stimuli that are either flashed on or brought into the receptive fields of neurons via a saccade, and quantifying the variation over time of neuronal responses under these conditions. The results of this project should now only increase our basic understanding of how the brain works, but should also be valuable for such efforts as the design of visual prostheses, where knowledge of the principles of neuronal encoding is vital, and also in the clinical interpretation of visually evoked potentials, which could be improved by a more detailed knowledge of the time course of visual processing.