与作业无关的新异刺激对猕猴额叶神经元延缓期反应的作用

在猕猴执行延缓辨别作业和单纯辨别作业时,观察了与作业无关的新异刺激对额叶神经元延缓期放电的影响。在这两种作业中,延缓期在1—4s之间随机变化。此时,动物必须高度注意信号的变化,稍不注意即导致操作错误。此外,在延缓辨别作业中,动物在延缓期还要暂时记住暗示期的信号,单纯辨别作业则无此要求。在203个与作业相关的神经元中,有70个神经元在延缓期出现放电频率变化,其中见于延缓辨别作业者41个,见于单纯辨别作业者29个。实验结果表明,在这两种作业的延缓期所出现的神经元放电增多的反应,有着许多相同的特点。与课题无关的声、光、触、痛等刺激引起分心时,神经元的延缓期反应出现明显的变化,随之出现操作错误。多数神经元的反应受到抑制,但也有出现反应增强者,而且同一神经元对不同感觉模式的无关刺激可出现不同的效应,表现出不同程度的感觉模式特异性。此外,无关刺激在延缓期和在测试间歇期可产生不同甚至相反的效应。上述在延缓期出现反应的神经元主要位于额叶弓状沟上支内侧部的一定范围内。本文对实验结果进行了讨论,认为额叶神经元的延缓期反应,可能在很大程度上与注意有关。额叶神经元感觉模式各种程度的特异性可能是注意的通道选择性的神经基础。额叶的背内侧部,包括前额叶后部和运动前区前部

EFFECTS OF TASK-UNRELATED STIMULI ON FRONTAL NEURON RESPONSES IN DELAY PERIOD OF PERFORMING MONKEYS

The effects of task-unrelated novel stimuli on frontal neuron responses in delayperiod were studied on awake monkeys (Macaca mulatta) during performing delayeddiscrimination task and simple discrimination task. The duration of delay period ofboth tasks was set pseudo-randomly between 1--4 s in order that the monkey had towatch the signal panel attentively to make a correct response. In delayed discri-mination task, the monkey had to remember the cue signal throughout the wholedelay period, but this was not required in simple discrimination task. Of 203task-related neurons recorded, a total of 70 showed changes in discharge rate indelay period (41 in delayed discrimination task, 29 in simple discrimination task).The feature of the neuron responses in both tasks was similar. The monkey per-formed a mistaken response when he was distracted by visual, auditory, tastile, andpain stimuli unrelated to the tasks, with decreased responses in delay period in mostneurons. However, facilitation was also observed in a few neurons. In some cases,facilitation and inhibition appeared even in the same neurons depending on sensorymodalities of unrelated stimuli, suggesting that the effects may be somewhat modalityspecific. Moreover, in some neurons, different effects could be produced with thesame task-unrelated stimuli applied during delay period or during intertrialintervalperiod. Most neurons studied were located in a circumscribed area medial to thesuperior ramus of arcuate sulcus in the frontal cortex. It is suggested that theneuron responses in delay period may be involved in selective attention. Thedorsomedial portion of the frontal cortex, including prefrontal and premotor areas,may play an important role in attention control.