Changes in cortical functioning with acute hypoglycemia and hyperglycemia in type I diabetes

In this study, 18 type I (insulin-dependent) diabetic subjects aged 22-35 yr (mean age 29.3) and within 10 yr of diagnosis (mean 7.7) performed a battery of cognitive and psychomotor tasks under conditions of hypoglycemia (50 mg/dl), normoglycemia (100 mg/dl), and hyperglycemia (300 mg/dl). Blood glucose levels during testing were precisely maintained at the preselected level via a Biostator insulin/glucose-infusion system. The order of glycemic level was counterbalanced across subjects in a single-blinded design. Performance on tasks requiring visual tracking, visuomotor speed, concentration, and planning ability (pursuit rotor and trails B) were significantly impaired under conditions of hypoglycemia compared with normoglycemic levels. Visual reaction time was not significantly impaired under conditions of hypoglycemia or hyperglycemia.