Basal ganglia neural activity during operant feeding behavior in the monkey: relation to sensory integration and motor execution.

The activity of single neurons in the caudate nucleus (CD), globus pallidus (GP), substantia nigra pars reticulata (SNr), and ventral tegmental area (VTA) was recorded during an operant feeding task in the monkey. The task had three phases: recognition of the food or nonfood stimulus (1st phase), bar pressing to obtain access to the stimulus (2nd phase), and ingestion (3rd phase). Data were collected from 351 neurons in CD, 344 in GP, 261 in SNr, and 275 in VTA. Neurons in the dorsolateral part of the CD, GP, and SNr responded primarily to motor events of feeding, i.e., extension/flexion of the arm, bar pressing, chewing, grasping or gazing. Neurons in the ventromedial part of the CD and rostroventral part of the GP exhibited differential responses to the presentation of food and nonfood during the recognition and bar pressing phases of the task. Neurons in the VTA increased their firing early in the bar pressing phase and then decreased their firing during ingestion. The data suggest that the dorsolateral part of the basal ganglia is involved mainly in motor function, while the ventromedial part may reflect the connection between motivation and motor output.