Spatial and behavioral correlates of striatal neurons in rats performing a self-initiated navigation task

To investigate the spatial and behavioral correlates of striatal neurons during displacement movements, the rostromedial dorsal striata (AP 1.0-2.2, ML 1.5-2.0) of five rats were surgically implanted with advanceable bundles of fine wire electrodes. After recovery, the rats were deprived of water and trained in a square-walled open field in a dark room. The behavioral task required alternating visits to water reservoirs in the center and in the four corners. A certain corner contained the first reward for each trial; after this reward, a cue card appeared in this corner for the rest of the trial. The firing rates of striatal units were compared as the rat moved between the center and the four corners of the arena. Analyses were made of 30 units. Eight of these had firing rates that significantly increased or decreased by 62-480% while the rat was in one or more quadrants of the arena. Six of these manifested such firing rate changes only as the rat performed certain behavioral sequences in the quadrant. Three other units fired as the rat's head was in a certain orientation relative to the arena walls, in all parts of the arena. To determine the principal controlling cues and hence the frame of reference of spatial selectivity of these units, the arena, while the rat was still inside, was rotated in total darkness. The first water reward was then presented at the same position relative to the outside room as before the rotation. The cue card was then illuminated in this corner as a visual cue for the extra-arena reference frame. All 11 neurons demonstrated spatial selectivity that rotated with the arena; thus, this activity was in the frame of reference of the arena and was not controlled by the visual cue. Six other units fired at rates up to six times their resting discharge or stopped firing completely in synchrony with initiation or execution of displacement movements, and two of these were also location selective. Four other units were silent as the rat performed the task, but fired tonically following arena rotations or other interruptions of the session, independent of the rat's location or movements. Nine analyzed units had very low firing rates (< 1 impulse/sec) and showed no discernible changes in activity as the rat performed the task. These patterns of unit activity indicate that fundamental informational components required for navigation are coded in the striatum.(ABSTRACT TRUNCATED AT 400 WORDS)