The Neurophysiology of Visual Search: Oculomotor and Visual Mechanisms

描述（由申请人提供）：人的表现不是恒定的。我们都有好日子和坏日子，我们工作或行动有效率的时候，我们效率低下的时候。以往的研究往往通过改变奖励的数量或等待奖励的时间来研究动机，但从未从正面研究动机的内部波动的影响 和顶叶皮层。该实验室的初步结果表明，猴子的外侧顶内区（LIP）有一个信号，它不是描述猴子看到或将要做什么，而是与猴子在当前试验中的成功概率相关。 这是一项困难的任务，因此符合唤醒或激励信号的标准，而不是感觉信号。这种信号可能是上行通路的皮层表现，如果是这样，它应该在其他视觉和眼神经区域中发现，并且应该具有与调节相关的药理学特性，而不是感觉运动处理。 在一个困难的视觉搜索任务中，在搜索阵列出现之前，猴子开始注视固定点500 ms，在固定期间LIP中神经元的基线活动预测了猴子在任务中成功或失败的概率，以及瞬态的强度。 对阵列开始的视觉反应。在一次又一次的试验中， 根据猴子的成功或失败历史，最近加权指数，当猴子最近表现不佳时增加，当猴子表现良好时减少。基线不预测目标在即将到来的阵列中的位置，并且它与猴子的空间注意力轨迹无关，所述空间注意力由猴子在线索视觉反应时间任务中的反应确定。这个建议的第一个目的是验证这个信号在LIP，广告，然后看看它是否存在于其他两个视觉领域，额眼场（FEF）和前纹状体区V4的行为相关的，空间非特异性信号在LIP的进一步证据来自研究噪声相关性在觅食任务。不共享兴奋性感受野的神经元仍然表现出显着的噪声相关性，这是最大的在pretarget固定期间，也与猴子的成功和失败的历史成反比。本提案的第二个目的是在搜索任务中验证这些发现，并将其扩展到FEF和V4。 调节信号的特点是它应该可以被与上行通路相关的神经递质改变。乙酰胆碱（Acetylcholine，ACh）可增加LIP的基线和视觉瞬时信号，而ACh烟碱受体拮抗剂美加明可抑制这些信号，提示烟碱胆碱能信号在LIP感觉运动活动的调节中起重要作用。第三个目标是在LIP中验证这些结果，并将其推广到FEF和V4。大多数与行为相关的药物作用于调节系统。了解调节系统影响视觉处理的机制对于了解这些药物的作用机制至关重要，并将有助于设计新的更好的药物。

DESCRIPTION (provided by applicant): Human performance is not a constant. We all have good days and bad days, times when we work or act efficiently and times when we are inefficient. Motivation has often been studied by changing the amount or the waiting time for reward, but the effect of internal fluctuations of motivation has never been studied in the frontal and parietal cortex of the monkey. Preliminary results from this laboratory indicate that the monkey lateral intraparietal area (LIP) has a signal which, rather than describing what the monkey sees or will do, correlates with the monkey's probability of success on the current trial of a difficult task, and therefore fits the criteria for an arousal or motivational signal rather thana sensoriomotor signal. This signal may be the cortical manifestation of ascending pathways, and if so it should be found in other visual and oculomotor areas, and should have pharmacological properties related to modulatory as opposed to sensorimotor processing. In a difficult visual search task, which begins with the monkey looking at a fixation spot for 500 ms before the search array appears, the baseline activity of neurons in LIP during the fixation period predicts both the monkey's probability of success or failure in the task, and the intensity of the transient visual response to the array onset. The baseline activity correlates inversely, on a trial-by-trial basis, with a recency-weighted index of the monkey's history of success or failure, increasing when the monkey has recently has done poorly and decreasing when the monkey has done well. The baseline does not predict the location of the target in the impending array, and it is unrelated to the monkey's locus of spatial attention as determined by the monkey's response in a cued visual reaction time task. The first aim of this proposal is to verify this signal in LIP, ad then see if it exists in two other visual areas, the frontal eye field (FEF) and prestriate area V4 Further evidence for a behaviorally relevant, spatially non-specific signal in LIP comes from studying noise correlation in a foraging task. Neurons that do not share excitatory receptive fields nonetheless exhibit significant noise correlation, which is maximal during the pretarget fixation period, and also varies inversely with the monkey's history of success and failure. The second aim of this proposal is to verify these findings in the search task and extend them to FEF and V4. The hallmark of a modulatory signal is that it should be modifiable by neurotransmitters associated with ascending pathways. Acetylcholine (ACh) increases the baseline and visual transient signals in LIP, and mecamylamine, an ACh nicotinic receptor antagonist, suppresses the signals, suggesting that nicotinic cholinergic signals are important in modulating sensorimotor activity in LIP. The third aim is to verify these results in LIP, and extend them to FEF and V4. Most behaviorally relevant drugs work on modulatory systems. Understanding the mechanism by which modulatory systems affect visual processing is critical to understanding the mechanism of action of these drugs, and will facilitate the design of new and better agents.