Document Type

Dissertation

Date of Award

1978

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Subject Heading(s)

Memory; Memory transfer; Strychnine

Abstract

An attempt was made to determine the effects of post-training strychnine treatment on the retention of specific memory attributes over extended temporal intervals. Heterogeneous strain (Binghamton HET) mice were given two training trials (1 trial per day) on a discrimination problem for which there was two relevant redundant stimulus cues, a brightness cue and a spatial-sequence cue. Immediately after the second training trial, mice were administered intraperitoneal injections of either strychnine sulphate (1 . 0 mg/kg) or physiological saline. After retention intervals of either 1, 3, or 27 day s, mice were tested under either complete cue reversal (both training cues were reversed), partial cue reversal (one training cue was reversed while the other cue remained unchanged ) , or relearning conditions (both training cues were unchanged) . On the oasis of subjects' performance upon initial exposure (first retention test trial) to cue reversal conditions, it was shown that stry chnine had enhanced the memory of specific rather t han more general-contextual aspects of the training situation. Stry chninetreated mice exhibited significantly greater impairment of initial test performaT-ce than saline-treated mice, VThen both cues were reversed during retention testing. Secondly, strychnine was shown to selectively enhance the memory of the brightness cue; the initial test performance of strychnine-treated mice was more i~paired when the brightness cue rather than the spatial-sequence cue was reversed during retention testing. No significant differences in initial test performance were observed between saline-treated mice as a function of which cue reversed during retention testing. Thirdly, the effects of post-training strychnine treatment appeared to be relatively short-lived or, at least, masked by whatever ~orgetting may have occurred over t he 7 and 21 Day retention intervals. It was suggested that, while strychnine treatment may have strengthened specific memory attributes, strychnine may not have other-vrise aff ected the rate of forgetting of specific memo!"'J attributes. The possibility was also raised that strychnine treatment may bias the manner in which the memory of a learning event is processed, in such a way that t h e memory may be less accessible for retrieval after long retention intervals. Finally, because a progressive decrease in negative t ransf er '\vas observed, as a function of retention interval duration, when mice were tested under cue reversal conditions, it was suggested that forgetting of specific memory attributes had occurred. In comparison, relatively little f orgetting was indicated by the performance of mice on a relearning task. The discrepancy b et>veen these findings I•Ias argued to reflect the relative insensitivity of a relearning task as a measure of retention.

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