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J. A. Droll, J. W. Bisley, T. Pasternak; The delay activity of some MT neurons may signal the remembered direction of motion. Journal of Vision 2001;1(3):20. doi: https://doi.org/10.1167/1.3.20.
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© ARVO (1962-2015); The Authors (2016-present)
The Cortical area MT is known to play an important role in the processing of information about stimulus direction. Recent lesion and microstimulation studies suggest that it may also play a role in the temporary storage of this information. We recently reported that many MT neurons are active during memory for stimulus direction (Droll et al, Soc. for Neurosci., 2000). This activity was present during the early stages of a 1500 ms delay and lasted 100–300msec, with maximal firing rates of 10 – 50 Hz. We now report that the firing rates of this activity were strongly correlated with the maximal response of the neuron to the preferred direction. In a quarter of the cells active during the delay, the activity was present following only the preferred or the null direction. The presence of delay activity in these neurons could signal the direction of the preceding stimulus. However, in more than half of the neurons the delay activity did not differ during the retention of the preferred and null directions. For these neurons, the magnitude of delay activity does not appear to carry information about the direction of the preceding stimulus. We also found that for the majority of neurons, delay activity following the preferred and the null directions occurred at slightly different times. This difference in the time of occurrence of activity between the two directions could also provide information about stimulus direction. The finding that MT neurons are active during the period of retention, and that this activity is correlated with the direction of the remembered stimulus, suggests that MT neurons may contribute to memory for visual motion.
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