Perception and Production of time duration around 10 seconds by rats: a cascaded delay model

[Speaker] Okanoya, Kazuo:1
[Co-author] Nixima, Ken'ichi:1, Tanaka, Tomohiro:1, Kurotani, Toru:2
1:The University of Tokyo (Japan), 2:ERATO, JST (Japan)

Perception and production of time duration around 10 sec is crucial in animals' survival. We trained rats to acquire a trace conditioning in which US occurred after 15 sec of the CS offset. We also trained rats to produce 15 seconds by pressing a lever in an operant box. Neurons in the granular retrosplenial cortex (GRS) in rats exhibit a curious architecture: neurons in the shallow layer show extraordinary long latency for firing when stimulated electrically. These neurons make horizontal cascade. Input from sensory thalamus enters into the shallow layer and input from the hippocampus enters into a deep layer and integrated. We hypothesized that this neural architecture, cascaded delay, can enable time buffering. Lesioning the GRS abolished the trace conditioning suggesting that time buffering is performed by this circuitry. We are further examining electrophysiological properties of GRS neurons in freely moving rats. (Supported by Kakenhi #26119509 and JST-ERATO)
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