Visual information processing during controlled hypoglycaemia in humans

Summary A general impairment of congnitive performance occurs during acute insulin-induced hypoglycaemia, but little objective evidence is available for disruption of more specific cognitive process. The effect of controlled hypoglycaemia on the early stages of visual information processing and contrast sensitivity was examined in a homogeneous group of 20 non-diabetic human subjects. Hypoglycaemia caused a significant disruption in general congnitive performance as assessed by a digit symbol task (P < 0.001) and the trail making B task (P < 0.05). Hypoglycaemia also produced a highly significant deterioration in performance on all of the visual information processing tasks, namely inspection time (IT) (P = 0.01), visual change detection (VCD) (P < 0.005) and visual movement detection (VMD) (P < 0.005). A significant deterioration in contrast sensitivity was observed during hypoglycaemia (P < 0.005). In contrast, no significant effect of hypoglycaemia was demonstrated on standard clinical measures of visual acuity or stereoscopic vision. Thus, although hypoglycaemia caused no detectable deterioration in visual acuity as measured by Snellen-type tests, a marked deterioration occurred in the speed of visual information processing and in constrast sensitivity. As many deceisions are made under conditions of limited perceptual time and low visual contrast (e.g. when driving), the disruptive effect of moderate insulin-induced hypoglycaemia on visual perception will have important practical implications in diabetic humans exposed to this metabolic stress. The present results are congruent with other evidence which shows that the early stages of visual information processing are susceptible to deterioration by general cerebral insults.