猕猴额叶神经元视辨别机能可塑性的研究

我们曾经提出,额叶神经元的反应,主要不是取决于刺激物的物理属性,而是与信号意义有密切的关系。为了验证这一看法,设计了两套作业,即视延缓辨别作业(作业Ⅰ)和视辨别反应作业(作业Ⅰ),对4只成年猕猴进行实验。两套作业都由1—4期组成,在第2期都有伪随机出现的红绿灯光信号,在第3期都要求动物密切注意随后的灯光信号变化。但是,作业Ⅰ要求动物对第2期出现的红绿灯光进行辨别,作业Ⅰ则要求对第4期的红绿灯光进行辨别。待动物学会作业,正确率达90％以上,在动物进行作业的同时引导额叶神经元放电。共记录作业相关神经元163个。其中作业Ⅰ98个,作业Ⅱ 65个。在作业Ⅰ中,神经元的反应多数出现在第2、3期,占该作业反应总数的70％。而在作业Ⅱ中,反应多数出现在第3、4期,也占该作业反应总数的70％。其次,作业Ⅰ第2期的神经元反应绝大多数对红、绿灯光有明显的特异性,而作业Ⅱ第2期的则没有,只有第4期的反应才有明显的特异性。本实验结果进一步支持了我们的上述看法,并且表明,额叶神经元对信号的反应主要是在学习中逐渐形成的,有很大的可塑性。

FUNCTIONAL PLASTICITY OF FRONTAL NEURONS IN RHESUS MONKEYS DURING PERFORMING VISUAL DISCRIMINATION GO/NO-GO TASK

We previously reported that frontal neurons in monkeys may be essentially responsive to the biological meanings of the stimuli in a task, rather than to their physical attributes. To examine this hypothesis, activity of single neurons was recorded from the frontal cortex of monkeys (Macaca mulatta) while performing a visual delayed discrimination GO/NO-GO task (task I, n = 2) and a visual discrimination response GO/NO-GO task (task II, n = 2), respectively. A green or red light presented in the period 2 of task I and in the period 4 of task II was used as a cue to guide the monkeys' behaviour. The same green/red light was presented in the period 2 of task II as well, but this was not a cue and had no definite meanings in the task. The monkeys were trained to watch attentively the panel in period 3 of both tasks. A total of 163 task-related neurons were recorded: 98 in task I and 65 in task II. Although neuronal responses appeared in all periods of both tasks, the majority of the responses (70% of the total) were in the periods 2 and 3 of task I, and in the periods 3 and 4 of task II. Furthermore, in the period 2 of task I and period 4 of task II, but not in the period 2 of task II, most of neurons were responsive exclusively to either green or red light. The results support the hypothesis stated above, and suggest that the responses of the frontal neurons to signal stimulation are gradually established in the course of learning, and possess highly developed functional plasticity.