Frontal lobe involvement in spatial span: converging studies of normal and impaired function

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Prefrontal cortex (PFC) involvement in working memory is established in monkeys and neuroimaging, but patient studies show inconsistencies.
• Discrepancies may stem from insensitive patient testing measures or task variations between study types.

Purpose of the Study:

• To investigate the necessity of the prefrontal cortex for spatial working memory using a more sensitive measure.
• To reconcile conflicting findings between monkey lesion studies, neuroimaging, and human patient data regarding PFC function in working memory.

Main Methods:

• Utilized a sensitive spatial working memory span task with structured and unstructured spatial arrays.
• Confirmed prefrontal cortex activation using Positron Emission Tomography (PET) in healthy subjects.
• Administered the same tasks to patients with frontal lobe lesions and matched controls.

Main Results:

• Patients with large frontal lesions showed significant spatial working memory impairments.
• Damage specifically to the right dorsolateral prefrontal cortex correlated with particularly severe deficits.
• Both structured and unstructured spatial array tasks activated the prefrontal cortex in healthy individuals.

Conclusions:

• The prefrontal cortex is demonstrably necessary for normal spatial working memory, even in relatively simple tasks.
• Observed patient deficits are likely attributable to strategic or goal-based processing dysfunction, not solely storage limitations.