Evidence for a Two-Stage Model of Spatial Working Memory Processing within the Lateral Frontal Cortex: A Positron Emission Tomography Study

TLDR

Frontal cortex is essential for spatial and nonspatial working memory, as shown by primate studies and patients with frontal lobe damage. This study used PET/MRI to identify two distinct subdivisions of the lateral frontal cortex that may support different aspects of spatial working memory. Five spatial memory tasks varying in executive demands were employed to probe these subdivisions. Task‑dependent blood‑flow changes revealed that ventrolateral frontal cortex (area 41) activates during sequence organization and execution, while mid‑dorsolateral frontal cortex (areas 46 and 9) activates during active monitoring and manipulation, supporting a two‑stage model of spatial working memory processing.

Abstract

Previous work in nonhuman primates and in patients with frontal lobe damage has suggested that the frontal cortex plays a critical rolein the performance of both spatial and nonspatial working memory tasks. The present study used positron emission tomography with magnetic resonance imaging to demonstrate the existence, within the human brain, of two functionally distinct subdivisions of the lateral frontal cortex, which may subserve different aspects of spatial working memory. Five spatial memory tasks were used, which varied in terms of the extent to which they required different executive processes. When the task required the organization and execution of a sequence of spatial moves retained in working memory, significant changes in blood flow were observed in ventrolateral frontal cortex (area 41) bilaterally. By contrast, when the task required active monitoring and manipulation of spatial information within working memory, additional activation foci were observed in mid-dorsolateral frontal cortex (areas 46 and 9). These findings support a two-stage model of spatial working memory processing within the lateral frontal cortex.