Simple versus complex performance impairments at three blood glucose levels.

By using a visual reaction time paradigm, we sought to determine if disruption of relatively simple responding (finger tapping or letter recognition) or more complex responding (choice reaction time) would occur in response to blood glucose deviations. Glucose levels were maintained in 24 male diabetics to within 4% of the following targeted concentrations: 55 mg/dl (hypoglycemia), 110 mg/dl (euglycemia/control), and 300 mg/dl (hyperglycemia). The results indicate that simple motor and perceptual skills were not affected by blood glucose alterations, while more complex cognitive processing required significantly longer response latencies during hypoglycemia. Performance impairments occurred independently of disease duration and control, and without documented neuropathy, underscoring the sensitivity of some cognitive skills to acute glucose fluctuations.