MICROSTIMULATION OF EXTRASTRIATE AREA MST INFLUENCES PERFORMANCE ON A DIRECTION DISCRIMINATION TASK
MICROSTIMULATION OF EXTRASTRIATE AREA MST INFLUENCES PERFORMANCE ON A DIRECTION DISCRIMINATION TASK
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DOI：
10.1152/jn.1995.73.2.437
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发表时间：
1995-02-01
影响因子：
2.5
通讯作者：
NEWSOME, WT
中科院分区：
文献类型：
--
作者：
CELEBRINI, S;NEWSOME, WT
1.单单位记录的证据表明，内侧颞叶上视区(MST)的神经元携带方向信号，影响对运动方向的心理物理判断。我们通过电刺激MST(主要是背内侧亚区)中的方向选择性神经元簇来检验这一假设，而恒河猴则执行两种选择、强制选择的方向辨别任务。我们在两只恒河猴身上进行了46次微刺激实验。视觉刺激是动态随机的点图案，其中相干运动信号的强度可以在心理物理阈值附近连续变化。这些猴子因为正确地报告了连贯运动信号的方向而得到奖励。对随机选择的一半实验进行微刺激，并对心理物理数据进行分析，以确定刺激MST神经元是否会影响猴子的选择。在67%的实验中，微刺激以统计上显著的方式影响了猴子的表现。在所有重要的实验中，除一项外，微刺激使猴子的选择偏向刺激部位MST神经元编码的运动方向。微刺激对心理测量功能的斜率几乎没有影响，这表明刺激诱导的神经活动类似于相对纯粹的运动“信号”，而不是“噪音”。4.只有当视觉刺激位于刺激地点测量的多单位感受野内时，微刺激才对猴子的行为产生强烈影响。这种空间特异性也出现在中颞叶视区(MT)，但MST的感受野通常比MT大得多。因此，MST的微刺激效应具有更粗的空间尺度：在MST中对单个位置的刺激比在MT中的同等刺激可以影响对更大部分视野的判断。当视觉刺激被放置在感受场的一个特别敏感的分区(“热点”)内时，微刺激通常是最有效的。结果表明，MST神经元和MT神经元一样，对方向辨别任务的成绩有很大的影响。MT和MST对决策过程的影响是并行的还是串联的，这一点还有待确定。
1. Evidence from single-unit recordings suggests that neurons in the medial superior temporal visual area (MST) carry directional signals that influence psychophysical judgements of motion direction. We tested this hypothesis by electrically stimulating clusters of directionally selective neurons in MST (the dorsomedial subdivision, primarily) while rhesus monkeys performed a two-alternative, forced-choice direction discrimination task.2. We performed forty-six microstimulation experiments on two rhesus monkeys. The visual stimuli were dynamic random dot patterns in which the strength of a coherent motion signal could be varied continuously about psychophysical threshold. The monkeys were rewarded for reporting correctly the direction of the coherent motion signal. Microstimulation was applied on half the trials, selected randomly, and the psychophysical data were analyzed to determine whether stimulation of MST neurons influenced the monkeys' choices.3. Microstimulation influenced the monkeys' performance in a statistically significant manner in 67% of the experiments. In all but one of the significant experiments, microstimulation biased the monkeys' choices toward the direction of motion encoded by MST neurons at the stimulation site. Microstimulation had little effect on the slopes of the psychometric functions, suggesting that the stimulation-induced neural activity resembled a relatively pure motion ''signal'' rather than ''noise.''4. Microstimulation exerted strong effects on the monkeys' behavior only when the visual stimulus was located within the multiunit receptive field measured at the stimulation site. This kind of spatial specificity has also been observed in the middle temporal visual area (MT), but receptive fields in MST are typically much larger than those in MT. Thus MST microstimulation effects are characterized by a coarser spatial scale: stimulation of a single site in MST can influence judgements over a much larger portion of the visual field than equivalent stimulation in MT.5. Microstimulation was often most effective when visual stimuli were placed within a particularly responsive subregion of the receptive field (a ''hot spot'').6. The results show that MST neurons, like MT neurons, can strongly influence performance on a direction discrimination task. Whether MT and MST influence the decision process in parallel or in series remains to be determined.