Finke C, Ostendorf F, Martus P, Braun M, Ploner C J
Klinik für Neurologie, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, D-13353 Berlin, Germany.
Neuroscience. 2008 Apr 22;153(1):189-95. doi: 10.1016/j.neuroscience.2008.01.053. Epub 2008 Feb 10.
Recent behavioral studies in monkeys and humans have shown that holding an item in spatial working memory may lead to sustained and spatially selective prolongation of reaction times (RTs) to visual stimuli presented during the memory delay. In order to resolve the seeming contradiction between these findings and current theories on the interaction of working memory and attentional orienting, it has been hypothesized that memory-dependent modulation of orienting may be the net effect of superposed facilitatory and inhibitory mechanisms. Their relative strength during the memory delay may determine whether RTs to visual stimuli presented during the memory delay are shortened or prolonged. Here, we expand on this hypothesis by investigating the spatial distribution of memory-dependent inhibition with behavioral data from normal human subjects. The experiment consisted of a combination of an oculomotor spatial working memory task (memory-guided saccade task, 6-s delay) and a visual discrimination task (performed 1500, 2500, or 3500 ms after presentation of the memory cue). RTs to discrimination stimuli were analyzed as a function of memory-guided saccade amplitude. By fitting polynomial approximations to our data we show that the spatial distribution of memory-dependent inhibition of orienting significantly differs from a monotonic gradient across the visual field. Instead, we demonstrate the existence of a central inhibitory peak surrounded by a facilitatory annulus, forming a transient "inverted Mexican hat" profile, which mirror-images findings from recent studies on the spatial distribution of attention. These findings are consistent with the hypothesis of a highly flexible modulation of orienting in which both the signs and spatial distribution of memory-dependent bias signals are adapted to behavioral demands.
近期对猴子和人类的行为研究表明，在空间工作记忆中持有一个物品可能会导致对记忆延迟期间呈现的视觉刺激的反应时间（RTs）持续且在空间上具有选择性地延长。为了解决这些发现与当前关于工作记忆和注意力定向相互作用的理论之间看似矛盾的问题，有人提出假设，即定向的记忆依赖性调制可能是叠加的促进和抑制机制的净效应。在记忆延迟期间它们的相对强度可能决定对记忆延迟期间呈现的视觉刺激的反应时间是缩短还是延长。在这里，我们通过研究来自正常人类受试者的行为数据中记忆依赖性抑制的空间分布来扩展这一假设。该实验由眼动空间工作记忆任务（记忆引导扫视任务，6秒延迟）和视觉辨别任务（在呈现记忆线索后1500、2500或3500毫秒执行）组合而成。对辨别刺激的反应时间作为记忆引导扫视幅度的函数进行分析。通过对我们的数据拟合多项式近似，我们表明定向的记忆依赖性抑制的空间分布与整个视野中的单调梯度有显著差异。相反，我们证明存在一个中央抑制峰值，周围是一个促进性环，形成一个短暂的“倒墨西哥帽”轮廓，这与最近关于注意力空间分布的研究结果互为镜像。这些发现与定向高度灵活调制的假设一致，在这种调制中，记忆依赖性偏差信号的符号和空间分布都适应行为需求。
