Critical determinants of nonspatial working memory deficits in rats with conventional lesions of the hippocampus or fornix

• Published in: Behavioral neuroscience Vol. 107; no. 3; p. 420
• Main Authors: Rawlins, J N, Lyford, G L, Seferiades, A, Deacon, R M, Cassaday, H J
• Format: Journal Article
• Language: English
• Published: United States 01.06.1993
• Subjects: Animals; Appetitive Behavior - physiology; Attention - physiology; Brain Mapping; Discrimination Learning - physiology; Hippocampus - physiology; Male; Mental Recall - physiology; Neural Pathways - physiology; Orientation - physiology; Pattern Recognition, Visual - physiology; Problem Solving - physiology; Rats; Rats, Inbred Strains; Retention (Psychology) - physiology
• ISSN: 0735-7044
• DOI: 10.1037/0735-7044.107.3.420

Rats with conventional lesions of the hippocampus or fornix were compared postoperatively with controls on nonspatial memory tasks. Neither lesion impaired delayed matching-to-sample (DMS) performance in a discrete-trial task involving "pseudo-trial-unique" complex stimuli. An impairment emerged if a single pair of complex stimuli was used throughout each day's session, and the greatest impairment was obtained with the use of a single pair of less complex stimuli throughout each day's test. Transfer to a continuous DMS task with no explicit intertrial interval produced a different pattern because both lesion and control levels of performance were depressed when two complex stimuli were used repeatedly. A final, separate discrimination learning experiment showed that hippocampectomized rats readily discriminated between the stimuli associated with the greatest lesion-induced DMS deficit. Hippocampal dysfunction thus produces clear deficits on non-spatial memory tasks under appropriate test conditions.