The effects of estrogen on temporal and numerical processing in ovariectomized female rats

Ovariectomized rats were trained to discriminate discrete sound sequences t hat varied in time or number. On time trials, the number of sounds was held constant at four, and the duration of the sound sequences was either 2 or 8 sec. On number trials, the duration of the sound sequence was a constant 4 sec, and the number of sounds was two or eight. After reaching criterion, half the rats received injections of 17-beta -estradiol 3-benzoate (8 mug per kg bodyweight) for a period of 2 weeks. In Experiment 1, estradiol trea tment significantly decreased both the number of training trials completed and discrimination accuracy. For the ovariectomized control rats, the psych ophysical functions for time and number had properties that were consistent with those in the previous literature. For the ovariectomized estradiol-tr eated rats, the psychophysical functions were initially flatter, but as tim e since estradiol exposure increased, they approached those of control rats . The points of subjective equality were equivalent for estradiol-treated a nd control rats, and both groups performed with higher accuracy on time tri als than on number trials. In Experiment 2, prefeeding the rats before a se ssion decreased the number of trials completed but had no significant effec t on discrimination accuracy. Therefore, estradiol's effect on the accuracy of time and number discriminations in Experiment 1 was not due to its effe ct on food motivation. These findings are discussed in terms of the interna l clock model, their relation to studies of spatial processing, and implica tions for human health.