Journal of Neuroscience, Vol 15, 1683-1703, Copyright © 1995 by Society for Neuroscience
Place and contingency differential responses of monkey septal neurons during conditional place-object discrimination
T Kita, H Nishijo, S Eifuku, K Terasawa and T Ono
Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
To elucidate spatial and cognitive function of the septal nuclei, neural
activity was recorded from alert monkeys during performance of a
place-dependent go/no-go (PGN) task. Response/reinforcement contingencies
of given objects were conditional upon the location of a motorized, movable
device (cab) containing a monkey in one of four places. The task was
initiated by presentation of the outside view (place phase) followed by
presentation of an object (object phase) selected from a total of four. A
lever press was reinforced only if the correct object was seen in its
corresponding place, and the same object was never reinforced in any of the
other three places. Of 430 septal neurons recorded, the responses during
the place phase in the four places were significantly different in 58
neurons. Responses of eight of these neurons were also place-differential
during the object phase as well as the place phase. Furthermore, when the
outside view was not presented before the object phase, differential
responses in the object phase disappeared. Responses of 91 neurons in the
object phase were differential in terms of go/no-go responses and reward
availability. Of these 91 neurons, 72 were further tested on a
place-independent asymmetrical go/no-go (AGN) task, which required no
conditional discrimination. Forty-three neurons responded differentially
only in the PGN task. It is thus concluded that this PGN-specific activity
reflected conditional place-object relations. Of the remaining 29 neurons
that responded differentially in both tasks, 21 were further tested by a
place-independent symmetrical go/no-go task (no-go responses were also
rewarded). Responses of 19 of these 21 neurons were related to the
reward/nonreward contingency but not to the response contingency. The
results suggest that septal nuclei are involved in integrating spatial
information, conditional place-object relations, and reward/nonreward
contingency.