Single cell activities were recorded from both the supplementary and precentral motor areas (SMA and PCM) of individual monkeys in order to compare their relation to performance. In the first series of experiments, monkeys were trained to perform a simple movement of key pressing in response to sensory signals of three different modalities: visual, auditory and somatosensory. It was found that the intensity of the movement associated neuronal activity was smaller in SMA than in PCM, and that onsets of neuronal activity in SMA were not as well correlated with the animal's movement onsets as those in PCM. These findings suggest that SMA is more remote from the peripheral motor apparatus than PCM. On the other hand, SMA seems to be closer to visual and auditory inputs. In the second series of experiments, monkeys were trained in a behavioural paradigm where instructions required them to predetermine their motor response to a signal of a particular sensory modality. In one situation, an instruction required the animal to be prepared to start a movement promptly in response to a forthcoming tone burst but to remain motionless if the signal was vibrotactile. In a second situation, a different instructional signal required the animal to be prepared to execute the movement if the vibrotactile, but not the tone burst, was presented. Striking differences in the instruction-induced activities in the two motor areas were found, indicating that SMA plays a more important role than PCM in a preparatory process leading to correct initiation on suppression of movement performance.

Animals↗

PubMedDate not supplied

Relation of neurons in the nonprimary motor cortex to bilateral hand movement.

In the primate cerebral cortex there are at least two somatotopically organized, nonprimary motor fields rostral to the primary motor area. To understand the functions of these multiple motor representations we have compared the neuronal activity in each of these fields while monkeys performed a trained motor task, using right, left or both hands. In the nonprimary motor cortex, activity in a number of neurons was related to the movement the animal chose and performed, whereas in the primary motor cortex, changes in the firing of most neurons were simply related to activity in the contralateral muscles. This result indicates that the nonprimary motor cortex is involved in higher-order coding of the laterality of the motor response, implying that it exerts its motor control function at a higher hierarchical level than its counterpart in the primary motor cortex.

Animals↗

PubMedDate not supplied

Involvement of NMDA and non-NMDA receptors in motor task-related activity in the primary and secondary cortical motor areas of the monkey.

The involvement of the NMDA and non-NMDA receptors in the task-related neuronal activity of the primary motor cortex (MI), premotor cortex (PM), supplementary motor area (SMA), and an area rostral to the SMA (pre-SMA) of two monkeys (Macaca fuscata) was examined during performance of a trained motor task. The selective NMDA antagonist D-2-amino-5-phosphonovaleric acid (APV) and the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were iontophoretically applied to motor task-related neurons. A total of 568 task-related neurons (435 movement related, 83 set related, 50 mixed type) were recorded from the MI, PM, SMA, and pre-SMA, and the effects of APV and CNQX were examined in the individual neurons. In many neurons, APV selectively or preferentially suppressed the spontaneous discharge rather than movement-related activity. In many neurons, the movement-related activity was more selectively or effectively suppressed by CNQX than by APV. However, the set-related activity was affected by both APV and CNQX. The neurons in layers I and II were affected more strongly by APV and CNQX than those in layers V and VI. No correlation was found between the magnitude of task-related activity in the control (no drug application) period and the effectiveness of APV or CNQX. These results indicate that both NMDA and non-NMDA glutamate receptors are involved in motor task-related neuronal activity of both primary and secondary motor areas, although the contribution of these two receptors to individual neuronal activity varies a great deal.

2-Amino-5-phosphonovalerate↗