The effects of feedback-mode upon instrumental learning of heart rate changes were examined in 20 rats which were deeply curarized and maintained by artificial respiration. Ten rats were randomly assigned to the following two feedback-mode groups. In 1RR Group, Ss were presented a continuous feedback on the basis of 1 beat unit, on the other hand, information about heart rate changes was fed back to Ss on the basis of 5 beats unit in 5RR Group. Furthermore, in each of the two groups, half the Ss were randomly rewarded for increase of heart rate and the other half for decrease. The trial of instrumental learning of heart rate changes was started by the onset of a tone (2000 Hz, 82 dB), and the training of 300 trials was carried on VI schedule with a mean intertrial interval of 30 sec. Heart rate and blood pressure responses recorded during a test trial in which a tone was presented for 5 sec in every 10th trial were analyzed. As can be seen in Fig. 2 and 3,each group of the Ss learned to increase or decrease their heart rate, respectively, in order to escape and/or avoid the mild electric shocks consisting of a , 2 sec rectangular pulse of .3 ma which were delivered to S's tail. Differences of the changes for the opposite directions were significant in 1 RR Group (F=5.37,df=1/56 , P>.025) and in 5 RR Group (F=59.43,df=1/56,P<.005). And in case of the heart rate deceleration, difference of the heart rate changes between 1RR and 5RR Groups was not significant. On the other hand, however, 5 RR Group showed a highly significant heart rate acceleration than 1 RR Group in the case of acceleration (F=l4.11,df=1/56,P<.005). From the above mentioned results, it is suggested that feedback-mode is an important factor to determine the degree of heart rate changes in this kind of learning. And this facts indicate that the acquisition of heart rate speeding and slowing appears to involve different psychophysiological mechanisms as were shown in our pharmacological studies.
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