Place memory is intact in rats with perirhinal cortex lesions

Area of Science:

• Neuroscience
• Cognitive Psychology
• Animal Behavior

Background:

• The hippocampal formation (HPC) and perirhinal cortex (PRh) are implicated in memory functions.
• Allocentric spatial working memory is crucial for navigation and memory recall.

Purpose of the Study:

• To investigate the roles of the HPC and PRh in allocentric spatial working memory using a delayed matching-to-place task.
• To determine if lesions to these brain regions affect spatial memory performance at varying retention delays.

Main Methods:

• Rats with bilateral HPC or PRh lesions performed a delayed matching-to-place (DMTP) task in a water maze.
• Performance was assessed across retention delays of 4, 30, 120, and 300 seconds.
• Two experiments varied the amount of presurgery training.

Main Results:

• Rats with HPC lesions showed significant deficits in DMTP performance across all delays in both experiments.
• Rats with PRh lesions exhibited normal acquisition and performance on the DMTP task.
• HPC lesions led to increased search times and distances compared to controls.

Conclusions:

• The hippocampal formation (HPC) is critical for allocentric spatial working memory.
• The perirhinal cortex (PRh) does not appear to be essential for this type of spatial memory.
• These findings differentiate the functional roles of the HPC and PRh in memory processes.