Hippocampal place units in the freely moving rat: Why they fire where they fire
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Place units in the dorsal hippocampus of the freely-moving rat signal the animal's position in an environment (place field). In the present experiments, thirty four place units were recorded in two different environments: one, a small platform where the rat had received neither training nor reward; the other, an elevated T-maze inside a set of black curtains where the rat had been trained on a place discrimination. The places within the curtained enclosure were specified by four cues (a light, a card, a fan, and a buzzer) in addition to the food. Other cues were eliminated by rotating the maze and the four controlled cues relative to the external world from trial-to-trial.
Some units had place fields in both environments while others only had a place field in one. No relationship could be seen between the place fields of units with fields in both environments.
All twelve units tested extensively in the controlled enclosure had place fields related to the controlled cues. Probe experiments in which only some of the controlled cues were available showed that some of these units were being excited by one or two cues while others were influenced in a more complex way. The fields of these latter units were maintained by any two of the 4 cues and were due to inhibitory influences which suppressed the unit firing over the rest of the maze.
Key wordsHippocampus Place units Unit recording Sensory cues Rat
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- Ainsworth, A., O'Keefe, J.: A lightweight microdrive for the simultaneous recording of several units in the awake, freely moving rat. J. Physiol. (bond.) 269, 8–10P (1977)Google Scholar
- Best, P.J., Ranck, J.B., Jr.: Reliability of the relationship between hippocampal unit acitivity and behaviour in the rat. Neurosci. Abstr. 1, 538 (1975)Google Scholar
- Branch, M.H., Olton, D.S., Best, P.J.: Spatial characteristics of hippocampal unit activity. Neurosci. Abstr. 2, 368 (1976)Google Scholar
- Czopf, J., Karmos, G., Bauer, M., Grastyan, E.: Simultaneous elaboration of approach and avoidance conditioning in the same experimental situation for cats. Acta physiol. Acad. Sci. hung. 25, 53–60 (1964)Google Scholar
- Hill, A.J.: Neuronal activity in hippocampus during a spatial alternation task. Neurosci. Abstr. 2. 388 (1976)Google Scholar
- Marey, E.J.: Le Mouvement. Paris: G. Masson Editeur 1894Google Scholar
- O'Keefe, J.: Place units in the hippocampus of the freely moving rat. Exp. Neurol. 51, 78–109 (1976)Google Scholar
- O'Keefe, J., Conway, D.: Sensory inputs to the hippocampal place units (abstract). Neurosci. Letters 3, 103–104 (1976)Google Scholar
- O'Keefe, J., Dostrovsky, J.: The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat. Brain Res. 34, 171–175 (1971)Google Scholar
- O'Keefe, J., Nadel, L.: The hippocampus as a cognitive map. Oxford: Clarendon Press (in press)Google Scholar
- Ranck, J.B., Jr.: Studies on single neurons in dorsal hippocampal formation and septum in unrestrained rats. Exp. Neurol. 41, 461–555 (1973)Google Scholar