Neuronal activity in the medial orbitofrontal cortex of the behaving monkey: modulation by glucose and satiety.

To investigate neuronal responses to interoceptive information, single neuron activity of the orbitofrontal cortex (OBF) of the behaving monkey was recorded during glucose injection, natural feeding and an operant bar press feeding task. Intravenous glucose injection had almost no effect on rates of spontaneous firing, but tended to attenuate neuronal responses during the bar press and reward periods. In about half of the neurons tested, the spontaneous firing rate changed for a relatively long period after the animal ate to satiety. The results suggest that blood glucose concentration is a modulatory factor in neuronal processing for feeding, but other interoceptive information generated by satiety strongly affects the activity of OBF neurons.