Impairment and recovery of elementary cognitive function induced by hypoglycemia in type-1 diabetic patients and healthy controls

Although neuroendocrine changes after induction of hypoglycemia, in patient s with diabetes and healthy persons, are thoroughly investigated, cognitive adaptation processes are still insufficiently understood.: Changes in cogn itive functions are mainly investigated by psychometric tests, which repres ent a summation of different cognitive processes. We aimed at dissecting co gnitive adaptation into single components, i.e. stimulus selection, respons e choice, and reaction speed during a hyperinsulinemic hypoglycemic clamp i n patients with type-1 diabetes and matched healthy controls. Using novel n europhysiological analyses, the event-related potentials of early stimulus selection (selection negativity) and response selection (lateralized readin ess potential) were studied, in addition to reaction time (RT). A total of 12 diabetic patients and 12 normal volunteers were studied while receiving a hyperinsulinemic hypoglycemic clamp. RTs and the event-related potentials related to stimulus selection and response selection: were significantly d elayed during hypoglycemia in both groups, whereas early evoked potentials (P100) were unaltered. This suggests that hypoglycemia delays stimulus sele ction, with the consequence that also central and motor processing are dela yed. In addition, patients with diabetes showed an earlier negative shift o ver the frontal cortex, which, when compared with the controls, reveals bet ter adaptation to hypoglycemia in frontal cortical brain regions. After res toration of euglycemia stimulus selection, response selection and RT return ed to baseline level in the type-1 group. In the control group, however, re sponse selection and RTs were still delayed. This suggests that type-1 pati ents, possibly because of the past occurrence of hypoglycemic events, might be able to better cope with the hypoglycemic state than healthy volunteers who lack such a history. In summary, our data demonstrate, for the first t ime, that cognitive adaptation processes to an experimental hypoglycemic ep isode can clearly be dissected into their single components.