Bendiksby Michael S, Platt Michael L
Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.
Neuropsychologia. 2006;44(12):2411-20. doi: 10.1016/j.neuropsychologia.2006.04.011. Epub 2006 Jun 6.
Saccade reaction times decrease and the frequency of target choices increases with the size of rewards delivered for orienting to a particular visual target. Similarly, increasing rewards for orienting to a visual target enhances neuronal responses in the macaque lateral intraparietal area (LIP), as well as other brain areas. These observations raise several questions. First, are reward-related modulations in neuronal activity in LIP, as well as other areas, spatially specific or more global in nature? Second, to what extent does reward modulation of neuronal activity in area LIP reflect changes in visual rather than motor processing? And third, to what degree are reward-related modulations in LIP activity independent of performance-related modulations thought to reflect changes in attention? Here we show that increasing the size of fluid rewards in blocks reduced saccade reaction times and improved performance in monkeys performing a peripherally-cued saccade task. LIP neurons responded to visual cues spatially segregated from the saccade target, and for many neurons visual responses were systematically modulated by expected reward size. Neuronal responses also were positively correlated with reaction times independent of reward size, consistent with re-orienting of attention to the saccade target. These observations suggest that motivation and attention independently contribute to the strength of sustained visual responses in LIP. Our data thus implicate LIP in the integration of the sensory, motor, and motivational variables that guide orienting.
对于朝向特定视觉目标的定向行为，扫视反应时间会随着所给予奖励的大小而缩短，且目标选择的频率会增加。同样，增加对朝向视觉目标的奖励会增强猕猴外侧顶内区（LIP）以及其他脑区的神经元反应。这些观察结果引发了几个问题。首先，LIP以及其他区域中与奖励相关的神经元活动调制在空间上是特定的还是更具全局性？其次，LIP区域中神经元活动的奖励调制在多大程度上反映了视觉处理而非运动处理的变化？第三，LIP活动中与奖励相关的调制在多大程度上独立于被认为反映注意力变化的与表现相关的调制？在这里我们表明，在执行外周线索扫视任务的猴子中，在不同组块中增加液体奖励的大小会缩短扫视反应时间并提高表现。LIP神经元对与扫视目标在空间上分离的视觉线索做出反应，并且对于许多神经元来说，视觉反应会受到预期奖励大小的系统性调制。神经元反应也与反应时间呈正相关，且与奖励大小无关，这与注意力重新定向到扫视目标一致。这些观察结果表明，动机和注意力独立地对LIP中持续视觉反应的强度做出贡献。因此，我们的数据表明LIP参与了引导定向的感觉、运动和动机变量的整合。
