Septal neuronal responses related to spatial representation in monkeys

Neuronal activity in the monkey septal nuclei was recorded during performance of a place-dependent go/no-go task in which reward contingencies of the objects were variable with reference to the spatial location of a monkey's cab in one of four places in an experimental room. Of 430 septal neurons recorded, 58 responded differentially to views outside the cab at the four locations of the monkey (place-differential neurons). To investigate the possibility that an ensemble of place-differential neurons represents a space by encoding different scenes (views), responses of the 58 place-differential neurons were analyzed by multidimensional scaling (MDS). The MDS transformed relationships among the four places, expressed as correlation coefficients between all possible pairs of two places based on the 58 place-differential responses, into geometrical relationships in a two-dimensional virtual space. The four places distributed at relative positions in a two-dimensional virtual space derived from the MDS were similar to those in the real experimental room. Furthermore, these correlation coefficients derived from 58 place-differential responses significantly and negatively correlated to behavioral performance in the discrimination of the four places. The results suggest that the ensemble of place-differential responses in the septal nuclei may predict behavioral performance to discriminate places and may represent a space based on the scenes viewed from different locations.