Learning Motion Discrimination with Suppressed MT
Hongjing Lu, Ning Qian, and Zili Liu, Vision Research
2004, 44:1817-1825.
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Abstract
We studied perceptual learning in motion discrimination when the
brain's middle temporal area (MT/V5) was functionally suppressed. This
was achieved by using the ``paired-dots'' motion stimulus where the
two dots in a pair always move in counter-phase over a short distance
[J. Neurosci. 14 (1994) 7357]. The motion directional signal of the
stimulus is therefore always 0 on average. As a result, this stimulus
activates MT in Rhesus monkeys no more than flicker noise does
[J. Neurosci. 14 (1994) 7367]. We added a new manipulation to
eliminate the Glass pattern in the original stimulus that would have
otherwise provided a static orientation cue. Two such new motion
stimuli were presented sequentially, in a 2AFC task. Subjects decided
if the global motion- axis of the stimuli changed clockwise or
counter-clockwise. When the task difficulty was set at 60% correct,
none of the subjects could learn with feedback, even though their
performance was well above chance. However, when the task difficulty
was set instead at 70% correct, a new group of subjects was able to
learn. Hence, learning motion discrimination was possible when MT was
presumably eliminated.
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