Prefrontal Lobe Gray Matter, Cognitive Control and Episodic Memory in Healthy Cognition

Objective: We combined neuropsychological and structural magnetic resonance imaging (MRI) measures to examine the neural and informational processes underlying episodic memory in healthy participants. Method: The Doors-and-People Test (DPT) provided a detailed assessment of episodic memory, including recall and recognition tasks of matched difficulty for social (e.g., people) and non-social (e.g., shape) content. The Wisconsin Card Sorting (WCS) test provided a measure of category learning that relies heavily on executive control and inhibition. A subset of participants also had available high-resolution, 3-T MRI gray matter volume studies of prefrontal cortex (PFC) parcellated into four regions: 1) frontal pole; 2) superior frontal gyrus; 3) middle frontal gyrus; and 4) inferior frontal gyrus. Results: Bivariate neuropsychological correlations revealed a highly statistically significant relationship of reduced WCS perseverative errors and stronger recall for people but not for shapes. By contrast, WCS perseveration did not correlate with any recognition measures. Hierarchical regression revealed that perseverative errors and people recall test scores combined to account for approximately 29.98% to 57.78% of the variance in left PFC gray matter volume. Conclusions: These results may point to an important role of the PFC in mnemonic process of retrieval inhibition in episodic memory for recall of social content in healthy participants.