Hippocampal place cells encode intended destination, and not a discriminative stimulus, in a conditional T-Maze task

Online ISSN: 1098-1063The firing of hippocampal place cells encodes instantane-ous location but can also reflect where the animal is heading (prospec-tive firing), or where it has just come from (retrospective firing). The current experiment sought to explicitly control the prospective firing of place cells with a visual discriminada in a T-maze. Rats were trained to associate a specific visual stimulus (e.g., a flashing light) with the occur-rence of reward in a specific location (e.g., the left arm of the T). A dif-ferent visual stimulus (e.g., a constant light) signaled the availability of reward in the opposite arm of the T. After this discrimination had been acquired, rats were implanted with electrodes in the CA1 layer of the hippocampus. Place cells were then identified and recorded as the ani-mals performed the discrimination task, and the presentation of the vis-ual stimulus was manipulated. A subset of CA1 place cells fired at dif-ferent rates on the central stem of the T depending on the animal’s intended destination, but this conditional or prospective firing was inde-pendent of the visual discriminative stimulus. The firing rate of some place cells was, however, modulated by changes in the timing of presen-tation of the visual stimulus. Thus, place cells fired prospectively, but this firing did not appear to be controlled, directly, by a salient visual stimulus that controlled behaviorSistemų analizės katedraVytauto Didžiojo universiteta