Prefrontal cortex and hippocampus subserve different components of working memory in rats

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Behavioral Neuroscience

Background:

• The medial prefrontal cortex (mPFC) and hippocampus are key brain regions involved in working memory.
• Hypotheses suggest the mPFC handles short-term information (subsecond to seconds), while the hippocampus is critical for longer temporal scales.
• The distinct roles of the mPFC and hippocampus in the informational content of working memory require further investigation.

Purpose of the Study:

• To investigate the specific contributions of the mPFC and dorsal hippocampus (dHPC) to working memory.
• To differentiate the roles of the mPFC and dHPC in processing different temporal scales and informational components of working memory.

Main Methods:

• Temporary inactivation of the mPFC and dHPC in rats using muscimol, a GABA(A) receptor agonist.
• Performance assessment on a delayed alternation task (DAT) using an automated figure-eight maze.
• Testing at varying delay intervals (3, 30, and 60 seconds) to evaluate working memory capacity.

Main Results:

• Inactivation of either the mPFC or dHPC significantly impaired performance on the DAT across all delay intervals.
• mPFC inactivation selectively impaired working memory accuracy without affecting reference memory or response latencies.
• dHPC inactivation increased both reference memory errors and response latencies, and also elevated successive working memory errors.

Conclusions:

• Both the mPFC and dHPC are essential for successful performance on the delayed alternation task.
• The mPFC and dHPC appear to process distinct informational components within working memory.
• Findings suggest a functional dissociation, with the mPFC critical for short-term accuracy and the dHPC involved in longer-term rule adherence and memory consolidation.