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Tetsuo Ogino, Kenji Ohtsuka; Effects of Superior Colliculus Inhibition on Visual Motion Processing in the Lateral Suprasylvian Visual Area of the Cat. Invest. Ophthalmol. Vis. Sci. 2000;41(3):955-960.
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purpose. To clarify whether visual inputs of the tectothalamocortical pathway
influence motion processing within the lateral suprasylvian (LS) area
of the cat.
methods. This study was conducted in five cats. Tungsten microelectrodes were
used for recording visual evoked potentials. The electrodes were
introduced into the LS area. An array of 120 randomly located dots was
projected onto the stimulus field (40° × 40°) in front of the
animal by a slide projector. The dots were moved rightward and leftward
alternatively with interstimulus intervals by a mirror attached to a
galvanometer, the movements of which were controlled by a
microcomputer. Each motion sequence consisted of an abrupt onset of
motion that continued for 100 msec followed by an abrupt offset and a
stationary phase of 900 msec; the total duration of each sequence was
thus 1000 msec. The velocity of the motion was varied in 12 steps. The
onset of motion was used as the trigger for recording evoked
potentials. Single or multiple injections (two to three) of muscimol
were made, mainly into the rostral superior colliculus (SC). The
amplitudes of evoked potentials before and after the muscimol injection
results. A large negative wave (N1) with the peak latency of 89.80 ± 16.39
msec (mean ± SD, n = 191) was recorded
consistently. The amplitude of N1 was not altered by the muscimol
injection into the SC when the velocity of motion was 50 deg/sec or
less. When the velocity of motion was 75 deg/sec or more, however, the
amplitude of N1 was reduced to 62% to72% of that noted before the
conclusions. These findings suggest that the LS area processes the visual motion
inputs reaching through the two parallel pathways, the geniculostriate
pathway and the tectothalamocortical pathway, when the velocity of
visual motion is 75 deg/sec or more.
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