RESUMEN
We studied the activity of single neurons in the pre-supplementary motor area (pre-SMA) of macaque monkeys as they performed two visuomotor tasks, called the visual fixation task and the visual fixation-blink task. Both tasks involved a sequence of three visual stimuli, red followed by yellow and green. The tasks differed in that the latter one had a gap within the period of the red stimulus, called a "blink". The tasks were performed in two modes, one of which included movements of both the arm and eye and the other of which involved only eye movements. In the arm-eye mode, the monkeys had to press a bar and fixate the red stimulus that appeared after bar press. To receive a reward, both the bar press and visual fixation had to be maintained until the green stimulus triggered bar release. In the eye mode, bar press and bar release were eliminated from the task. Of the 42 neurons active during the visual fixation task, 15 showed task-related activity in both arm-eye and eye modes, and our analysis focused on these cells. We found that the introduction of the blink in visual fixation-blink task abolished the task-related activity of these cells over the course of 2-4 trials. This finding suggests a role for the pre-SMA in reflecting progression of trials as an updating of motor instruction.
Asunto(s)
Potenciales de Acción/fisiología , Atención/fisiología , Corteza Motora/citología , Movimiento/fisiología , Neuronas/fisiología , Desempeño Psicomotor/fisiología , Análisis de Varianza , Animales , Brazo/inervación , Parpadeo/fisiología , Fijación Ocular/fisiología , Macaca mulatta , Masculino , Estimulación Luminosa , Tiempo de ReacciónRESUMEN
Area 8B may be treated as part of either the prefrontal cortex or the premotor cortex. Previous investigations showed an involvement of area 8B in both eye and ear motor control and in auditory perception. In this report, we studied 139 neurons in three macaque monkeys of these, 32 neurons showed an activity related to environmental auditory stimuli. Fifteen cells with auditory characteristics (15/32) presented a firing discharge inhibited during the execution of visual fixation. The remaining 107 units presented complex or indefinable behaviour. The presence of auditory environmental cells which activity is related prevalently to the voice of persons (researchers) suggests that area 8B may be an area involved in auditory cross-modal association, in natural behaviour. The inhibitory effects during visual fixation suggest that area 8B is part of the inhibitory network preventing the gaze shift in relation to an auditory stimulus. This may be the consequence of the engagement of attention during fixation that may affect the auditory perception. Both aspects indicate that area 8B is involved in high cognitive processes in auditory and orienting processes.
Asunto(s)
Fijación Ocular/fisiología , Neuronas/fisiología , Corteza Prefrontal/citología , Estimulación Acústica/métodos , Potenciales de Acción/fisiología , Animales , Macaca fascicularis , Inhibición Neural/fisiología , Neuronas/clasificación , Estimulación Luminosa/métodosRESUMEN
A voluntary motor act requires recognition of the informational content of an instruction. An instruction may contain spatial and temporal information. The recently proved role of the monkey frontal cortex in time computation, as well as in motor preparation and motor learning, suggested that we investigate the relationship between premotor neuron discharges and the temporal feature of the visual instructions. To this purpose, we manipulated the duration of an instructional cue in a visuomotor task while recording unit activity. We found two types of premotor neurons characterised by a discharge varying in relation to the duration of the cue: (1) "motor-linked" neurons, with a specific premotor activity constantly bounded to the motor act; (2) "short-term encoders" neurons, with a premotor activity depending on the cue duration. The cue duration was the critical factor in determining the behaviour of the short-term encoders cells: when the cue ranged from 0.5 s to 1 s, they presented a preparatory activity; when the cue was longer, up to 2 s, they lost their preparatory activity; when the cue was blinked the cells anticipated their discharge. The activity changed in few trials. These data confirm and highlight the role of frontal cortex in encoding specific cues with a temporal flexibility, which may be the expression of temporal learning and represent an extended aspect of cortical plasticity in time domain.
Asunto(s)
Potenciales Evocados Visuales/fisiología , Lóbulo Frontal/fisiología , Neuronas Eferentes/fisiología , Desempeño Psicomotor/fisiología , Animales , Brazo/fisiología , Mapeo Encefálico , Señales (Psicología) , Macaca fascicularis , Plasticidad Neuronal/fisiología , Tiempo de Reacción/fisiologíaRESUMEN
The aim of this article was to describe an apparatus, called multipurpose neck robot (MURPO), designed to record both the forces exerted at head level and the head rotations in the horizontal plane in the behaving monkey. It consists of a mechanical device, comprising a cardan joint, a potentiometer, an electromagnetic brake, and four flexion load cells, plus an oleodynamic system allowing head rotation in the horizontal plane between +/- 20o. These components are assembled on a column bolted to the primate's chair. An electrical device provides DC power for the potentiometer and the brake. The apparatus enables us to measure both the force fields and the head movements during training sessions and electrophysiological investigations.