COGNITIVE FUNCTION DURING INSULIN-INDUCED HYPOGLYCEMIA IN HUMANS - SHORT-TERM CEREBRAL ADAPTATION DOES NOT OCCUR

It has been suggested that cerebral adaptation may occur in response t o short-term hypoglycemia. This was examined in the present; study by measuring serial changes in cognitive function and symptoms after 60 m in of continuous hypoglycemia. Hypoglycemia was induced with a hyperin sulinemic glucose clamp on two separate occasions in 24 non-diabetic h uman subjects. Cognitive function was assessed using the following cog nitive test battery: Paced Auditory Serial Addition Test (PASAT), Rapi d Visual Information Processing (RVIP), Trail-Making B (TMB), Digit Sy mbol Substitution Test (DSST) and Four Choice Reaction Time (CRT). In condition A the blood glucose was maintained at 4.5 mmol/l throughout. On two separate occasions (condition B and condition C) the blood glu cose was stabilised at 4.5 mmol/l for 30 min, lowered to 2.5 mmol/l fo r 60 min and restored to 4.5 mmol/l for 30 min. In each condition the cognitive test battery was performed immediately after stabilisation o f blood glucose at 4.5 mmol/l and the subsequent battery was repeated at different time intervals: condition A - after a further 40 min of e uglycemia; condition B - after 5 min of hypoglycemia; condition C - af ter 40 min of hypoglycemia. Acute hypoglycemia induced a significant d eterioration in cognitive function which was manifest in all tests exc ept TMB (P < 0.05), but performance ability did not differ between con ditions B and C. Symptom scores, assessed by a scaled questionnaire, i ncreased significantly during hypoglycemia (P < 0.001) but no differen ces were detected between the scores at 30 min and 60 min. In non-diab etic humans, no improvement appears to occur either in cognitive funct ion or in symptom score after 40-60 min of hypoglycemia (2.5 mmol/l), suggesting that cerebral adaptation does not occur during this period of time.