Male mice of 4 strains (C57BL/6, DBA/2, C3H/He, and I20/Se) were individually run for 24 hr in home cages with an activity wheel under normal (LD) and reversed (DL) conditions of light-dark cycle. LD condition was in light from 08 : 30 to 20 : 30, and DL condition was in light from 20 : 30 to 08 : 30, alternating with 12 hr of darkness in each condition. Brightness in the light period was about 330 lux. Each strain consisted of 4 groups (3, 5, 7, and 9 weeks of age at the beginning of the experiment) of 10 mice.
As shown in Figures 1 and 2, the onset of the activities of mice in LD condition, as compared with those in DL condition, synchronized with their transition from light-on to light-off. Especially, those of the mice of DBA and I20 strains synchronized markedly. Moreover, it can be observed in the mice of all strains that transition from light-off to light-on in the time of night has a drifting effect on the onset of activity.
Transformed data on the total activity for 24 hr shown in Table 1 were analyzed by 3-factorial analysis of variance. Significant values of F were obtained only in the main effects of strain (F=6. 314, df=3/288), conditions of light-dark cycle (F=13. 904, df=1/288), and age (F=3. 931, df=3/288). It can be observed from Table 2 that there are very clear differences among strains of mice in the alternation of the active and inactive periods synchronized with light-dark cycle. From these results it is suggested that the activities of DBA and I20 mice synchronize with light-dark cycle of both conditions, whereas the activities of C57BL and C3H mice do not so much synchronize with those conditions. The age-related activity changes could not be observed in the present study.
We conclude from these results that the activity synchronizes with a light-dark cycle, and thus periodicity of the activity is achieved by onset response to light-off and drifting response to light-on. However, further researches are needed to determine whether the 24 hr-periodicity of activity is controlled either by light-dark cycle or by a circadian rhythmic clock.

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The purposes of the present study were to examine the effects of nonreinforced preexposure to the discriminative stimuli on the discrimination learning in goldfish (Exp. I), and to investigate the relation of length of daily preexposure time to preexposure effects (Exp. II).
The experiment consisted of adaptation and pretraining period (5 days), nonreinforced preexposure period (10 days), and simultaneous discrimination learning period. In Exp. I, 16 goldfish were divided into two groups and preexposed for 22 hours a day in preexposure period : one group (N=8) was preexposed to the discriminative stimuli (Fig. 2, A) while the other group (N=8) was preexposed to the irrelevant stimuli to later discrimination (Fig. 2, B). In Exp. II, 32 goldfish were divided into three groups and preexposed to the discriminative stimuli in preexposure period : one group (N=10) was preexposed for 22 hours a day, the second group (N=12) was preexposed for 30 minutes a day, and the third group (N=10) as a control was not preexposed.
The main results were as follows : (1) the groups preexposed to the discriminative stimuli were habituated to those stimuli (Table 1, 2); (2) the groups preexposed to the discriminative stimuli were inferior on the discrimination to the groups not preexposed to the discriminative stimuli (Table 1, 2); (3) the group preexposed to the irrelevant stimuli was superior in performance of discrimination to the group preexposed to the discriminative stimuli and to the control group (Table 1, 2); and (4) the longer the daily preexposure time was, the stronger the preexposure effects (habituation to the discriminative stimuli and inferiority on discrimination learning) became (Table 2).

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The present investigation was designed to clarify relationship between mother-infant distance (0. 5m) and filial locomotion in the Japanese monkeys. The subjects used in the present investigation were three multiparous adult females and their male infants. Each pregnant female was housed in a cage of 60 × 93 × 125cm which denied visual and tactile access with other monkeys. Observations in this living-cage began immediately after parturition and throughout the first six months of the infants' lives. Mother-infant interactions were observed for 15 min with 5-sec intervals once or twice a week. The results suggest that the 0.5m distance between mother and infant is affected directly by infant's locomotion, and indirectly by maternal behavior, because the 0.5m distance between mother and infant tended to change in accordance with filial locomotion, which is affected by maternal behaviors (5) in the first six months of the infant's life (Fig. 1-4).

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[in Japanese]

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