BRAIN ENERGY-METABOLISM IN EARLY BLIND SUBJECTS - NEURAL ACTIVITY IN THE VISUAL-CORTEX

As an attempt to better understand the metabolic basis for the previou sly reported increases in glucose metabolism in the visual cortex of c ongenitally blind subjects, cerebral blood flow, oxygen consumption an d glucose utilization were investigated with multitracer positron emis sion tomography. Measurements were carried out in three subjects who b ecame blind early in life and in three age-matched blindfolded control s. Regional analysis of cerebral blood flow, metabolic rates for oxyge n and glucose utilization revealed that these parameters were relative ly higher in the visual cortex in case of early blindness (109.7 +/- 2 .4%; 114.3 +/- 1.5%; 118.0 +/- 5.5%, respectively) than in controls (9 8.1 +/- 3.9%; 108.6 +/- 3.6%; 105.2 +/- 4.8%). There were slight diffe rences, albeit statistically not significant, between early blind and control subjects in terms of oxygen-to-glucose metabolic ratios. The r elatively preserved stoichiometry in the visual areas of blind subject s points to the lack of variation in the yield of glucose oxidation in this cortex. Those observations suggest that the high level of energy metabolism disclosed in early blind visual cortex is related to neura l activity.