Abstract 3021: Areas of Chronic Infarct Associated with Impaired Verbal Working Memory
Background: Functional imaging studies consistently show activation of Broca's area (Brodmann's area 44 and 45) in verbal working memory (VWM) tasks such as backward digit span, indicating that this area is an important node in the network underlying VWM. We have recently shown acute infarcts in Brodmann’s area (BA) 45 are associated with impaired VWM. However, there is surprising little evidence that chronic lesions of Broca's cause deficits in VWM, although there are case reports and small series of patients with both with normal and impaired VWM. Other areas of the brain might assume this function during recovery. We tested the hypothesis that chronic infarcts in BA 44 and 45 are associated with reduced backward digit span.
Methods: Patients had tests of backward digit span and MRI at least 6 months after first left supratentorial ischemic stroke. Technicians blinded to digit span results analyzed FLAIR sequences for infarct in BA 4, 6, 10, 11, 19, 20, 21, 22, 37, 38, 39, 40, 44, 45, anterior and posterior insula. Associations between between VWM and ROIs were identified using Fisher's exact tests for dichotomous data. Differences in mean span length between those with and without lesions in each area were identified with t-tests. Additionally, using linear regression analysis (adjusted for age and education level), we determined which areas, when infarcted, predicted backward span length.
Results: 79 patients (mean age 57.2 years; mean education 13.6 years) were included. Reduced VWM (defined as backward digit span <3) was associated with infarct in BA 44 (p=0.002) and BA 45 (p=0.001). Patients with infarct in Broca’s area had significantly shorter backward digit spans than those without (BA 44: 1.3 vs 4.2; p=.003; BA 45: 1.0 vs 4.15; p= 0.006). Using linear regression, infarct in BA 44 was associated with, on average, 2.5 fewer digits on digit span backwards compared to cases without BA 44 infarct (adjusted beta=-2.5; 95% CI -3.4, -1.7), BA 45 (beta=-2.8, 95% CI -3.6, -2.0). BA 39 (adjusted beta=-1.8, 95% CI -2.9, -0.7) or BA 40 (adjusted beta=-2.1, 95% CI -3.0, -1.1) also predicted digit span backwards.
Conclusion: Left BA 44, 45 (Broca’s area) and 39 and 40 (inferior parietal lobule) are crucial brain regions for recovery of VWM.
- © 2012 by American Heart Association, Inc.