认知与发展心理学研究室知识库

    工作记忆是一种存储容量有限的认知系统，它负责短暂保持信息以便进一步加工处理。患有注意力缺失过动症的人群通常表现出工作记忆容量的下降，而注意力缺失过动症是儿童常见的一种精神失调，主要表现为注意力散涣或集中困难，活动量过多以及自制力弱。在大脑分区中，外侧内顶叶区(LIP)被认为是与工作记忆及注意相关的脑区，并与额叶眼动区(FEF)及上丘(CSC)共同组成了注意控制的神经通路。前人的研究表明，额叶眼动区的萎缩是注意力缺失过动症形成的重要原因，而在己报导的注意力缺失过动症脑成像研究中，并未特别发现外侧内顶叶皮层受到与额叶眼动区同等程度的萎缩。本研究设想:C1) LIP在工作记忆中扮演积极作用;C2)在因FEF功能不全使得注意控制功能受损时，通过调控LIP神经元活动的方式，能实现对下行的SC的信号传递，进而恢复或增强大脑的注意控制功能。本实验以非人灵长类动物称猴为研究对象，以光遗传调控的方式选择性地激活LIP兴奋性神经元，并检验神经调控对称猴工作记忆及注意控制所产生的影响。实验主要采用记忆引导的视觉扫视实验范式作为行为任务，即猴子被训练能在保持盯住中心注视点的同时，记住外周快速闪现的目标的位置，并在中心注视点消失之后能通过一次快速扫视正确指示己经消失的外周目标的位置。猴子需要维持记忆的时间段，即从视觉刺激消失到中央注视点消失，被定义为工作记忆发生的关键时期。实验发现，通过光遗传技术在记忆早期施予光照刺激激活L工P神经元，会使称猴对呈现在感受野对侧的目标产生的眼跳幅度缩小，表现为对眼跳反应的抑制;在记忆中期施予光照刺激，会加快称猴对感受野右侧和感受野对侧的目标的反应时;在记忆晚期施予光照刺激，当目标呈现在感受野位置时，称猴不仅反应时缩短了并且准确率还上升了，而在感受野右侧的位置，称猴的准确率有所下降。此外，加长记忆期间光照刺激的时间并不能明显增强对称猴行为产生的影响。我们的结果表明，称猴外顶叶内侧区的部分神经元在工作记忆编码及执行中确实起到关键作用，而且有可能影响注意加工。

    Working memory is a cognitive system with limited capacity, which is crucial for holding temporal information for further processing. People with attention deficit hyperactivity disorder (ADHD), which is a common mental disorder in children,normally involve some deficits in working memory as well. Symptoms of ADHD include difficulty in paying attention, hyperactivity, and difficulty in self-control. In the brain, lateral intraparietal area (LIP) is thought to be involved with attention processing. Together with frontal eye field (FEF) and superior colliculus (SC), these key nodes constitute the network of attention processing in the brain. Previous studies indicate that the atrophy in FEF is one of the major causes for ADHD, but there is no evidence that people with ADHD show the same degree of atrophy in LIP. Therefore,we hypothesize that: (1)LIP plays an important role in regulating working memory;(2) in order to recover or even enhance the function of attending from attention deficit due to FEF impairment, it is possible to directly activate the LIP-SC pathway through artificially activating LIP neurons. In this study, we used the optogenetic technique to selectively activate the excitatory neurons in LIP to investigate its function in regulating working memory and attention in a primate model. The experiment mainly used the classical memory-guided saccade task as the behavioral paradigm, in which monkeys were trained to maintain fixating while memorizing the location of a peripheral target that presented briefly. The monkeys were rewarded after making a saccade to the cued location upon receiving the go cue. The period monkeys had to hold memory (from the offset of the visual target to the go cue of saccade) was defined as memory period. We found that optogenetically modulating the early phase of the memory period reduced the saccade amplitude when the targets were displayed at the locations opposite to receptive field (RF); Optogenetically modulating the middle stage of the memory period shortened saccadic reaction times when the targets appeared  at locations  450 counterclockwise or opposite to  RF. Optogenetically modulating the late stage of the memory period not only shortened saccadic reaction times but also increased accuracy when targets appeared at the RF locations. However,the  effect on  accuracy  was  reversed  when  targets  appeared  at locations  450 counterclockwise to the RF. Besides, we observed no evidence that extending the duration of optogenetic stimulation during the memory period could induce stronger behavioral effects in primates. Our results suggest that part of LIP neurons do play an important role in the coding and execution of working memory, and potentially in the processing of attention as well.