Multivariate analysis of the modifications induced by an environmental acoustic cue on rat exploratory behavior

The aim of the present paper is to study by means of a multivariate analysis the modifications induced by an environmental acoustic cue on the structure of rat exploratory behavior. Adult male Wistar rats were observed during the exploration of a soundproof observation box. Each rat was acoustically stimulated after 150 s from the beginning of the experimental session, lasting 300 s, and recorded through a digital videocamera. A frame by frame analysis was thereafter carried out using a professional video-recording system. Thirteen behavioral patterns were selected: immobility, immobile-sniffing, walking, rearing, climbing, chewing, paw-licking, face-grooming, body-grooming, head-turning, tuning, oriented-sniffing, focusing. Both descriptive and multivariate analyses (cluster, stochastic, adjusted residuals) were carried out. Through descriptive statistical analysis, latencies and per cent distribution of each pattern were studied. A multivariate cluster analysis revealed the presence of three main behavioral clusters, an additional one being identified following acoustic stimulation. Multivariate stochastic analysis showed that all the patterns converged on immobile-sniffing which could represent a key component in behavioral switching processes related to environmental exploration. Moreover, through adjusted residuals, the degree of relationship among different patterns was shown according to statistic Z-distribution. Our data assign new ethological meanings to different behavioral patterns. Notably, head-turning is suggested to be considered as a generic directional search and tuning as a subtle activity of stimulus localization.