Table 1.

Increased duration of contextual freezing time in socially isolated mice

No. electric foot shocks during training session	Freezing during training test, seconds per 5-minute period		Freezing during contextual test, seconds per 5-minute period
	Group housed	Socially isolated	Group housed	Socially isolated
1	15.0 ± 3.3	12.8 ± 1.7	37 ± 9.7	60 ± 1.11*
3	38.3 ± 7.1	33.2 ± 1.9	68 ± 9.9	121 ± 5.6*
6	137 ± 20	138 ± 14	94 ± 9.3	161 ± 9.6*

Freezing involved the absence of all movement, except for respiratory-related movements while the mouse was in a stereotyped crouching posture. Each value is the mean ± SEM of five animals.

*, P < 0.01, freezing time of socially isolated mice compared to group-housed mice (Student's t test).