Mapping of sensory-responsive cells in the septal area of the rat.

A study of sensory-responsive characteristics of single cells of the septal area of male rats was undertaken to determine the distribution of stimulation-induced changes in septal activity. Single cells were systematically sampled in six planes transecting the rostral-caudal axis of the septal area and were tested for responsiveness to visual, auditory, tactual, gustatory and olfactory stimuli. Approximately 50% of the sampled population of septal cells was responsive to at least one stimulus. Most of the responses of septal cells to stimulation were excitatory and occurred at the onset of stimulation. Regions of concentration of sensory-responsiveness cells in the system were found to lie in medial areas of the septum consisting of the dorsomedial portion of the lateral septal nucleus, the medial septal nucleus and the ventral portions of the medial and lateral nuclei. Visual, auditory and tactual stimuli were most effective in producing changes in spontaneous activity of units in these regions. On the basis of relationships of the medial septal region to other limbic areas having sensory-responsive properties, it is concluded that the medial septal area is one component of a limbic sensory system.