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Daniel Zaksas, Tatiana Pasternak; Activity of MT neurons is affected by remote visual stimuli used in a memory for motion task. Journal of Vision 2002;2(7):417. doi: 10.1167/2.7.417.
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© ARVO (1962-2015); The Authors (2016-present)
Neurons in area MT have localized receptive fields representing the contralateral hemifield and play an important role in processing of visual motion. We recorded the activity of these neurons during a working memory task in which the remembered (sample) and the comparison (test) random-dot stimuli, separated by a temporal delay, were presented in opposite hemifields. This allowed us to determine whether the activity of MT neurons during the performance of this task is generated locally within MT or reflects top-down influences of cortical areas with access to the information from the entire visual field.
In nearly half of the recorded neurons (n = 45), activity during every epoch of the trial was altered by the presentation of stimuli at a remote contralateral location. Following a sample placed in the receptive field, many neurons showed transient activation early in the delay. A remote sample often induced inhibition, and was almost never followed by the early delay activity. Excitation and inhibition were equally likely responses during a remote test. These effects were present even when both sample and test were presented at a location remote from the receptive field.
Since area MT is strongly retinotopic, neural activity associated with remote stimuli is unlikely to be generated by local connections. Rather, such effects may be indicative of top-down influences of cortical areas with access to information from the entire visual field. These areas, along with area MT, may form the circuitry underlying the ability to remember visual motion.
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