S74

15 Motor system V Higher motor centers

MONKEY PREMOTOR NEURONS RELATED TO SIMPLE MOVEMENTS OF FOOT, HAND AND MOUTH

JUN TANJI, KIYOSHI KURATA* and KAZUHIKO OKANO* Department of Physiology, School of Medicine, Hokkaido Univers i ty, Sapporo, 060, Japan.

Monkeys were trained to perform e i ther a forel imb or hindlimb movement in a temporally separated manner. The forel imb movement was a key press with the r ight hand and the hindlimb movement was a pedal press with the r igh t foot , both in response to a v i b ro tac t i l e t r igger ing signal. EMG analysis revealed that the key press was performed pr imar i ly with hand and f inger muscles, with modest a c t i v i t i e s in proximal forel imb muscles. The pedal press was per- formed pr imar i ly with ankle f lexors , with addi t ional a c t i v i t i e s in thigh muscles. 51% of task related premotor neurons were active sole ly in re la t ion to the forel imb movement. A major i ty of them was d is t r ibuted at around a focal point located poster io r ly to the genu of the arcuate sulcus. A much smaller number of neurons related to the forel imb movement was d is t r ibuted posteromedial to the focal point. 34 % of p~emotor neurons were related to the hindlimb movement. They were d is t r ibuted mostly at around the precentral dimple, several mm la tera l to the hemispheric midl ine. Very few forel imb- or hindlimb-movement related neurons were recorded at a region medial to the upper limb of the arcuate sulcus. The remaining 26 % of neurons were related to both the forel imb and hindlimb movements. They were scattered among forel imb and hindlimb neurons. Premotor neurons related to orofac ia l movements were located la tera l to the focal point of forel imb neurons and la tera l to the i n f e r i o r limb of the arcuate sulcus.

DRUG SENSITIVITIES OF NEURONS RELATED TO VISUAL REACTION TIME TASK IN THE MONKEY DORSOLATERAL PREFRONTAL CORTEX.

TOSHIYUKI SAWAGUCHI~ MICHIKAZU MATSUMURA W and KISOU KUBOTA, Department of Neurophysiology, Primate Research Institute, Kyoto University, 41 Kanrin, Inuyama, Aichi, 484 Japan.

Effects of iontophoretically applied drugs, such as nordrenaline (NA), dopamine (DA), and acetylcholine (ACh), were investigated in dorsolateral prefrontal neurons which showed activity changes during a visual reaction time task. The task consisted of an initial warning phase (green lamp, variable times of 1.5-3.5 s), a later lever release GO phase (red lamp) and a reward phase. Out of about one handred task-related neurons, 30% were modulated in their discharge rate during warning, 30% during GO, 25% during both phases and 15% were modulated during the reward phase. The activities of warning phase-related neurons were mostly influenced by NA (85%), those of GO-related neurons by DA (88%) and those of neurons with activity changes in both phases by both NA and DA (65%). Activities of reward related neurons were mainly influenced by NA (70%). On the other hand, ACh influenced the all types of activity changes. Further, propranolol diminished the changes in the warning phase and fluphenazine diminished those in the GO phase. Results suggest that NA may be involved in the activity modulations related to visual attention, and DA may in those related to motor performance. ACh may have a more generalized role in modulating changes related to the visual reaction time task.