Gail Alexander, Andersen Richard A
Bernstein Center for Computational Neuroscience Göttingen, German Primate Center, 37077 Göttingen, Germany.
J Neurosci. 2006 Sep 13;26(37):9376-84. doi: 10.1523/JNEUROSCI.1570-06.2006.
We investigated the neural dynamics of sensorimotor transformations in the parietal reach region (PRR) of monkeys. To dissociate sensory from motor goal representations, we used a memory-guided anti-reach task. The monkeys had to reach either to a visually instructed, memorized peripheral target position (pro-reach) or to a diametrically opposed position (anti) while keeping central ocular fixation. Pro- and anti-reaches were randomly interleaved and indicated by a color instruction from the beginning of each trial. We analyzed spatiotemporal single-cell tuning and performed time-resolved population decoding to quantify the dynamic representation of the spatial visual cue, the reach goal, and the currently valid task rule (pro/anti mapping). Sensory information regarding the visual cue position was represented weakly during a short period of cue visibility. PRR predominantly encoded the reach goal from the end of the cue period on. The representation of the reach goal in the memory task evolves later for the anti- compared with pro-reaches, consistent with a 40-50 ms difference in reaction time between the two task rules. The task rule could be decoded before the appearance of the spatial cue, which indicates that abstract rule information is present in PRR that is independent of spatial cue or motor goal representations. Our findings support the hypothesis that PRR immediately translates current sensory information into reach movement plans, rather than storing the memorized cue location in the instructed-delay task. This finding indicates that PRR represents integrated knowledge on spatial sensory information combined with abstract behavioral rules to encode the desired movement goal.
我们研究了猴子顶叶够物区域(PRR)中感觉运动转换的神经动力学。为了区分感觉表征与运动目标表征,我们采用了记忆引导的反向够物任务。猴子必须在保持中央注视的同时,朝着视觉指示的、记忆中的外周目标位置(正向够物)或完全相反的位置(反向够物)进行够物。正向和反向够物随机交错出现,并在每个试验开始时通过颜色指示来表明。我们分析了时空单细胞调谐,并进行了时间分辨群体解码,以量化空间视觉线索、够物目标和当前有效的任务规则(正向/反向映射)的动态表征。在视觉线索可见的短时间内,关于视觉线索位置的感觉信息表征较弱。从线索期结束开始,PRR主要编码够物目标。与正向够物相比,记忆任务中反向够物的够物目标表征出现得更晚,这与两种任务规则之间40 - 50毫秒的反应时间差异一致。任务规则可以在空间线索出现之前被解码,这表明PRR中存在独立于空间线索或运动目标表征的抽象规则信息。我们的研究结果支持这样的假设,即PRR会立即将当前的感觉信息转化为够物运动计划,而不是在指令延迟任务中存储记忆的线索位置。这一发现表明,PRR代表了关于空间感觉信息与抽象行为规则相结合的综合知识,以编码期望的运动目标。