Table 2.

Results of the principal component analysis.

Test/essay measure	A) Loadings on the first five factors extracted by PCA, varimax rotation					B) Loadings on the first five factors extracted by PCA, varimax rotation, after correction for strain effects: residuals
	Factor 1	Factor 2	Factor 3	Factor 4	Factor 5	Factor 1	Factor 2	Factor 3	Factor 4	Factor 5
open field
Time in corners (mean 5 days)				0.73	-0.50				-0.78
Line crossings (mean 5 days)	-0.92					-0.87
Rearings (mean 5 days)	-0.91					-0.90
elevated plus maze
Percent time open arms (day 1)					0.86				0.83
Percent entries open arms (day 1)					0.89				0.87
Rearings (day 1)	-0.69					-0.64
circular Light-dark box
Time in dark (mean 3 days)		-0.56		0.59				0.68
Line crossings (mean 3 days)				-0.62				-0.71
Rearings (mean 3 days)	-0.50			-0.67		-0.63		-0.67
standard MWM
Distance swum (mean 5 days)	0.64					0.72
Distance swum (linear trend)			0.79				0.62
Probe trial time training annulus			-0.74							-0.55
repeated acquisition MWM
Delta (odd minus even trials)	-0.51									0.75
passive avoidance
Log latency entry dark, retention			-0.57				-0.60
serotonin
5-HT turnover in hippocampus	-0.51
5-HT cortex		0.90					-0.81
5-HIAA cortex		0.85					-0.75
Variance explained (%)	32.0	12.3	11.5	9.0	8.0	24.4	15.1	12.4	10.0	8.1

Loadings, higher than 0.5, on the first five factors extracted by principal component analysis (PCA), after varimax rotation (A), and of residuals obtained after correction for the effect of strain (B), of measures of emotional reactivity, spatial learning and memory in the standard and the repeated acquisition versions of the MWM task, the passive avoidance task, and serotonergic measures in hippocampus and cortex of 32 rats. The percent of total variation explained by each factor is also shown.