Object, tactile, and spatial oddity judgements are impaired in DG-compromised rats but enhanced in CA1-compromised rats

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Krista Mitchnick¹ (mitchnick.k@gmail.com), R. Shayna Rosenbaum², Boyer Winters³; ¹York University, ²Rotman Research Institute at Baycrest, ³University of Guelph

The hippocampus (HPC) is necessary for supporting episodic memory, although HPC subregions might differentially contribute to various underlying component processes. For example, the dentate gyrus (DG) is involved in the orthogonal representation of similar information (i.e., pattern separation) to facilitate precise encoding. Given that this computational process occurs as information enters the DG, the DG might additionally be involved in non-mnemonic, perceptual discrimination. Moreover, although prominent theories of HPC function predict a domain-specific role of the DG in processing space/scenes, it is possible that the DG plays a domain-general role in discriminating other stimulus types that form rich, episodic memories. In contrast, perirhinal cortex (PRh) has been involved in successful domain-specific perceptual discrimination involving objects. Therefore, we assessed performance on visual, spatial, and tactile oddity tasks in rats with compromised DG, PRh, or CA1 functioning, the latter included as a negative control. Our results demonstrate that DG-compromised rats exhibited impairments on all three tasks at an intermediate level of difficulty, but spared performance on the easier level. Conversely, PRh-compromise produced only visual oddity deficits (easy version). Unexpectedly, CA1-compromise enhanced discrimination in all modalities. These results support the domain-general involvement of the DG in difficult perceptual discriminations compared to the domain-specific (object identity) involvement of PRh in this process. Furthermore, our results demonstrate that perceptual discrimination can be enhanced by blocking CA1 activity, possibly due to reduced interference from retrieval processes. Current studies are investigating perceptual discrimination in human cases with damage to the DG or CA1 using analogous oddity tasks.

Topic Area: LONG-TERM MEMORY: Other