Selective processing of food words during insulin-induced hypoglycemia in healthy humans

Rationale. Hypoglycemia leads to undernutrition of the brain. Favoring selective processing of food stimuli would be an adaptive cognitive strategy. However, hypoglycemia is known to impair several aspects of cognitive function, and it is unknown whether selective cognitive processing of food stimuli occurs during insulin-induced hypoglycemia. Methods. In a single-blind repeated measures design, healthy young adults (n=12, six female, mean age 28 years; mean body mass index 22.5 kg/m(2)) performed a standard Stroop word-color test, as well as a variant with food words designed to detect selective processing of food cues. Two sessions were scheduled with a 4-week interval. In each session, a hyperinsulinemic clamp method produced a normoglycemic (plasma glucose: 4.7 mmol/l) period, followed on 1 day by a hypoglycemic (2.7 mmol/l) testing period, and on the other day a second normoglycemic testing period (counterbalanced order). Results. Color naming verbal reaction time (RT) increased during hypoglycemia (P<0.0001). The extent of the Stroop cognitive interference was independent of plasma glucose level. The key finding is that RT for food words increased more than for non-food control words (P<0.004), and this effect was not predicted by hunger ratings. Conclusions. Our data provide new evidence that during hypoglycemia, attention is directed selectively to food-relevant stimuli. The results are discussed in terms of adaptation.