猕猴执行痛、热延缓辨别作业时额叶神经元及肌电活动的观察

为研究额叶神经元对躯体痛、热刺激出现反应的机能意义,设计了痛、热延缓辨别作业对猕猴进行实验。痛和热仅在暗示期给予,要求动物对此不立即作出行为反应。而是暂时记住这个信号,等到行动期再作出反应。待作业正确率连续三天达90%以上,记录额叶神经元和两侧上肢肌肉的电活动.以观察神经元活动与信号刺激以及肌肉活动之间的关系。在记录的142个作业相关神经元中,与痛、热刺激相关者87个(66.4%)。其中22个仅对痛刺激、18个仅对热刺激起反应,47个对痛、热刺激都起反应(其中4个反应方向相反)。此外,有21个对痛、热、视都出现反应。其余仅对视觉刺激起反应。这些神经元主要位于额叶弓状沟上支内侧,包括前额叶和运动前区皮层。在两侧上肢12块肌肉中,除操作侧指总伸肌、尺侧腕屈肌和桡侧腕屈肌在压放杠杆时,可记录到短暂的肌电活动外,在作业的其它时期和其它肌肉均未记录到规律的肌电活动。这表明痛热刺激在暗示期引起的神经元反应与行为动作的发动没有直接关系,从而支持关于额叶皮层这一区域的神经元在对刺激物信号意义的辨别机制中,可能起着重要作用的假说。

OBSERVATIONS ON NEURONAL ACTIVITY IN FRONTAL CORTEX AND EMG_s IN MONKEYS DURING PERFORMING NOXIOUS AND INNOCUOUS HEAT DISCRIMINATION GO/NO-GO TASK

To study the functional implication of neuronal responses in frontal cortexto noxious and innocuous heat stimuli,experiments were carried out on twomonkeys(Macaca mulatta)during performing a delayed discrimination GO/NO-GO task.The animals were trained to hold a lever for at least 3 s in the responseperiod when an innocuous heat stimulus had been applied to theforearm in the cue period,or release it within 1 s with a noxious one.After a cri-terion of 90% of correct responses in 3 successive days was reached,single neuronalactivity was recorded from the frontal cortex along with EMGs from six musclesin both arms.Of 142 task-related neurons recorded,87(66.4%)were related toheat,34 to visual,and 21 to both visual and heat stimuli.Among the heat-relatedneurons,22 were responsive to noxious heat,18 to innocuous heat,and 47 to both.Of the neurons responding to both noxious and innocuous heat stimuli,4 neuronsshowed changes in discharge rates,depending on the type of stimuli.In mostcases,muscular activities just appeared at the moment of lever pressing and/orreleasing in m.extensor digitorium communis,m.flexor carpi ulnaris and m.flexor carpi radialis of the performing arm.No regular muscular activities ap-peared in other muscles and in other periods of the task.The results showed thatthe neuronal responses in frontal cortex elicited by heat stimuli in the cue period werenot related directly to the initiation and modulation of behaviours.Most of the heat-related neurons were located in a circumscribed area medial to the superior ramusof arcuate sulcus,including prefrontal and premotor cortex.It is suggested thatfrontal neurons in this area may be involved in discriminating the biological mean-ings of cue heat stimuli.