Positive Emotion Enhances Impaired Hippocampal Functioning
Claire Lauzon1,2 (email@example.com), Michael Yassa3, R. Shayna Rosenbaum1,2; 1York University, 2Rotman Research Institute, Baycrest Centre, 3University of California, Irvine
Pattern separation, the neurobiological process of making overlapping memory representations more distinct, critically depends on sparse firing in the dentate gyrus (DG), while pattern completion, and the more general ability to retrieve previously learned information, has been shown to depend on CA1. The classic and well-validated finding that episodic memory is enhanced for emotional content has been demonstrated in cases with lesions to the hippocampus, but it is unknown whether this enhancement extends to pattern separation, and if it can survive lesions to specific hippocampal subregions. Here we examine if pattern separation is rescued by emotional content in the face of bilateral DG lesions. Two unique individuals with selective bilateral hippocampal lesions, affecting the DG in case B.L. and the CA1 subfield in case B.R., were tested on a behavioural measure of pattern separation requiring the mnemonic discrimination of positive, negative, and neutral scenes. When their memory for negative and neutral stimuli was compared to that of controls, B.L. and B.R. showed significantly worse mnemonic discrimination and recognition memory, respectively. Despite having lesions that would be expected to interfere with these processes, neither patient was impaired compared to controls when tested on positive stimuli. Findings that otherwise impaired hippocampal processes may be preserved for positive content may reflect the conceptual organizing properties of positive stimuli, whereas negative content, which typically leads to overall enhanced memory following bilateral hippocampal lesions, is not sufficient to restore mnemonic discrimination or retrieval when the dentate gyrus and CA1 subfield, respectively, sustain extensive damage.
Topic Area: LONG-TERM MEMORY: Episodic
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