Hypoglycemic Brain Function Different in Type 1 Diabetes

More activation of brain regions, less deactivation of default-mode network in type 1 diabetes

FRIDAY, Oct. 14 (HealthDay News) -- During hypoglycemia, patients with type 1 diabetes (T1D) who perform a working-memory task (WMT) have more activation of brain regions and less deactivation of the default-mode network (DMN) than control subjects, according to a study published online Oct. 7 in Diabetes.

Nicolas R. Bolo, Ph.D., from the Harvard Medical School in Boston, and colleagues investigated the effects of acute hypoglycemia on working memory and brain function in patients with T1D. Brain activation responses were compared with WMT during euglycemia (5.0 mmol/L) and hypoglycemia (2.8 mmol/L) using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging during hyperinsulinemic clamp in 16 individuals with T1D and 16 age-matched controls without diabetes. The percentage of correct responses was used to assess behavioural performance.

The investigators found that, in both groups, WMTs activated the bilateral frontal and parietal cortices, insula, thalamus, and cerebellum during euglycemia. Activation decreased in both groups during hypoglycemia, but remained 80 percent larger in patients with T1D. Higher hemoglobin A1c was correlated with reduced activation in the right parahippocampal gyrus and amygdala in individuals with T1D. During hypoglycemia, deactivation of the DMN was 70 percent lower in patients with T1D than in controls. Glycemic conditions or groups did not affect behavioral performance.

"BOLD activation was increased and deactivation was decreased in type 1 diabetic versus control subjects during hypoglycemia. This higher level of brain activation required by type 1 diabetic subjects to attain the same level of cognitive performance as control subjects suggests reduced cerebral efficiency in type 1 diabetes," the authors write.

Abstract
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