Neurophysiology of Behaviour

The limbic system is a part of the brain consisting of a band of cortical tissue on the medial sides of the hemispheres and, partly, of deeper structures including the amygdala, the hippocampus and the septal nuclei (Fig. 19.1). The limbic areas are phylogenetically among the oldest parts of the brain. In the course of evolutionary development, they have been more or less covered by the cortex of the cerebrum, but the limbic system has relatively few connections with it. The neocortex has therefore been likened to a rider astride the limbic system but unable to steer it. As our instincts and emotional life seem centred in the limbic system, they appear to be outside the control of the cortex. In electrophysiological studies of the limbic system, single stimuli often give very long-lasting responses, which may explain why emotional reactions may long outlast their stimulus.