The postnatal development of open field behaviour of the visually deprived rat

The postnatal development of open field (OF) behaviour of two groups of each 8 male hooded rats (Long-Evans strain) was compared after bilateral eye bulb removal on the seventh postnatal day (pd) in one group and sham-operation on the same day in the other group. Ambulatory activity of the deprived group was much increased (p less than 0.01) in all sessions from the 10th to the 30th pd. Their habituation of responses to the OF was stabilized with delay only on the 21st pd. The deprived rats immediately entered central fields whereas sham-operated controls began this on the 23rd pd. Exploratory behaviour as measured by groups of horizontal head and body turnings, sniffing periods, rearings and wall climbings was significantly enhanced in deprived rats during certain phases of the postnatal development. The timing of the phases was rather identical with those of the sham-operated group and with untreated controls. Grooming activity was enhanced, too. The results indicate a rather quantitative than qualitative difference to rats which can develop visually guided behaviour. The changed OF behaviour of visually deprived rats is hardly explainable in terms of changed emotionality or tendencies to reinstate social contact and attempts to evade predation or any other ethological hypothesis of OF behaviour, but may be related to the role of visual input in the development of goal-directed behaviour.