Verbal and spatial memory spans in mild cognitive impairment.

Area of Science:

• Neuropsychology
• Cognitive Neuroscience
• Neurology

Background:

• Working memory (WM) deficits may indicate early stages of cognitive decline in mild cognitive impairment (MCI).
• Standard WM tasks like verbal and visuospatial span tests are underutilized in MCI assessment.
• Distinguishing between MCI subtypes, especially those progressing to Alzheimer's disease (AD), is crucial for early intervention.

Purpose of the Study:

• To investigate the sensitivity of verbal and visuospatial span tasks in detecting cognitive impairment in MCI patients.
• To determine if specific WM components are differentially affected in MCI, particularly in preclinical AD.
• To assess the utility of WM tasks in differentiating MCI patients who convert to AD (MCIc) from those who do not (MCIs).

Main Methods:

• 99 amnesic MCI patients underwent Digit Span Forward (DSF), Digit Span Backward (DSB), and Corsi span (CS) tests.
• Patients were followed for two years to track conversion to AD (MCIc) or stabilization (MCIs).
• Performance differences and ratio indexes (DSF to DSB, DSF to CS) were analyzed between groups.

Main Results:

• Digit Span Forward (DSF) performance did not differ between MCI patients and controls.
• Digit Span Backward (DSB) and Corsi span (CS) performance, along with ratio indexes, significantly differentiated MCI patients from healthy controls.
• Ratio indexes also significantly discriminated between MCIc and MCIs individuals, indicating differential decline in central executive resources.

Conclusions:

• MCI patients exhibit reduced central executive resources, impacting WM performance.
• The phonological loop appears intact, suggesting specific WM component vulnerability.
• WM task ratio indexes show promise for identifying MCI patients at higher risk of AD progression.