Dependence of short-latency ocular following and associated activity in the medial superior temporal area (MST) on ocular vergence 追従眼球運動及びそれに関したサルMST野のニューロン活動に対する両眼輻輳の影響
Dependence of short-latency ocular following and associated activity in the medial superior temporal area (MST) on ocular vergence
Motion of a large-field pattern elicits short-latencyocular following responses (OFR) in the monkey, whichare mediated at least in part by the medial superior temporalarea of the cortex (MST). The magnitude of the OFR isknown to be inversely related to viewing distance, and weinvestigated the dependence of OFR and the associated neuronalactivity in the MST on a major cue to viewing distance,ocular vergence, in alert monkeys (Macaca fuscata).The vergence angle, expressed in terms of the apparentviewing distance, ranged from infinity to 16.6 cm (0-6 m-1). The magnitude of the initial OFR increased monotonicallywith increases in convergence at a mean (±SD)rate of 19.6±4.5%/m-1 in four monkeys (over the range0-4 m-1). In two monkeys, we recorded the single unit activityof 160 MST neurons that responded to motion of alarge-field pattern with directional selectivity. The mean latency(±SD) of the MST discharges elicited by large-fieldmotion was 50±7.5 ms (n=115), which preceded the onsetof OFR by an average of 10±9.9 ms. The discharge modulationelicited by large-field motion showed a significant dependenceon vergence in 91/160 neurons (57%), 72 ofwhich (79%) increased their firing rate with increasing convergence("near" neurons), and the remainder increasingtheir firing rate with decreasing convergence ("far" neurons).However, on average, the sensivity of these MSTneurons to vergence was only about 30% of that shownby the OFR. It could be that only those neurons that are verysensitive to vergence angle contribute to the OFR, but it is also possible that much of the modulation of OFR with vergenceoccurs downstream from the MST or in alternativepathways (yet to be discovered) that contribute to OFR.
Thesis (Ph. D. in Medical Sciences)--University of Tsukuba, (A), no. 2182, 1999.3.25
Joint authors: A. Takemura ... et al.
Off print. Originally published in: Experimental brain research, v. 121, pp. 135-144, 1998
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