Abstract
The conditioned behavior adopted in this study is complicated by combining a conditioned behavior to avoid electric shock with that to choose the place for avoidance. In order to standardize conditions of learning, a programer for conditioned and unconditioned stimuli was used and rat's behaviors in response to those stimuli were automatically recorded. Befor the onset of exposure, the rats had learned the conditioned behavior 61 times once a day. The 16 rats which had made good results in the learning were selected and divided equally into two groups. Exposure group was exposed to 2, 000 p.p.m. of toluene for 8 hours per day during 52 days, and the control group was not exposed to toluene. For 28 days after the onset of exposure, learning process was the same as befor and total learning times were 17 (reinforcement process). From 41 st day to 52 nd day after the onset of exposure, extinction was daily undertaken (extinction process), and for the same term water consumptions of the two groups were measured. As a result of exposure, the following facts were made clear. (1) In the process of reinforcement, any significant difference was not noticed between the results of the two groups. (2) In the process of extinction, the result of the exposure group was significantly wronger than the control group. (P<0.01) (3) In general observations : (a) The water consumption of the exposure group increased by 22% in comparison with the control group. (b) For a while after daily exposure begun, excitability of the exposure group increased and this tendency was remarkble at first and second exposures. (c) In the weight of the rats, any significant difference was not noticed between the two groups.
