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Brad C. Motter; Sensitivity of V4 neurons to sequences of letter-like stimuli. Journal of Vision 2005;5(8):909. doi: 10.1167/5.8.909.
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© ARVO (1962-2015); The Authors (2016-present)
During active visual search, visual receptive fields are faced with a new view of the scene about every 200 milliseconds. The neuronal coding of the visual information in these views may be a function not only of the classic receptive field properties and spatial crowding conditions surrounding the receptive field, but also of the temporal history of receptive field stimulation.
The neural dynamics associated with a 5–8 item sequence of flashed letter-like stimuli were investigated in macaque extrastriate area V4 neurons while the monkeys performed a standard maintained fixation task. As the interstimulus interval (ISI) is reduced to durations mimicking saccade durations (55ms or less), the neural coding of sequences of identical stimuli undergo major changes in both amplitude and latency of activation. The initial transient response of many neurons is completely suppressed and the resulting response profile is shifted to longer latencies. At ISI's of 100 ms the response profiles are partially restored although ISI's of several hundred ms are needed to return to baseline responsiveness. Re-emergence of the transient response phase is seen in sequences of mixed stimulus types, although this is dependent on the stimulus selectivity of the neuron. The dampening of responsiveness at saccade like timing intervals as seen in V4 may be a basic factor in controlling the stability of vision across saccades. Supported by the VA Medical Research Program.
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