The roles of prefrontal brain regions in components of working memory: Effects of memory load and individual differences

TLDR

The study aimed to determine how dorsal and ventral prefrontal cortex contribute to encoding, delay, and response components of working memory under varying memory loads. Event‑related fMRI was employed while participants performed a working‑memory task, enabling comparison of PFC activation across low and high load conditions. Higher memory load increased dorsal PFC activity only during encoding, with right‑hemisphere lateralization in the high‑load condition; individual differences in retrieval rate explained variability, showing that slower subjects relied more on dorsal PFC for retrieval, supporting distinct roles for dorsal and ventral PFC in working‑memory components.

Abstract

Using an event-related functional MRI design, we explored the relative roles of dorsal and ventral prefrontal cortex (PFC) regions during specific components (Encoding, Delay, Response) of a working memory task under different memory-load conditions. In a group analysis, effects of increased memory load were observed only in dorsal PFC in the encoding period. Activity was lateralized to the right hemisphere in the high but not the low memory-load condition. Individual analyses revealed variability in activation patterns across subjects. Regression analyses indicated that one source of variability was subjects’ memory retrieval rate. It was observed that dorsal PFC plays a differentially greater role in information retrieval for slower subjects, possibly because of inefficient retrieval processes or a reduced quality of mnemonic representations. This study supports the idea that dorsal and ventral PFC play different roles in component processes of working memory.