Age-dependent alteration of metabolic response to photic stimulation in the human brain measured by P-31 MR-spectroscopy

Effects of photic stimulation (PS) on energy metabolism were examined in th e occipital cortex of 25 healthy volunteers aged 23-69 years old using phos phorus-31 magnetic resonance spectroscopy (P-31-MRS). A significant effect of photic stimulation was found only for intracellular pH (p < 0.05 by repe ated measures analysis of variance) but not for any peak area ratios, An in teraction between intracellular pH and age were statistically significant ( p < 0.005), and the interaction between phosphocreatine and age was close t o significance (p =0.06). In subjects aged more than 40 years old, phosphoc reatine was significantly decreased during the photic stimulation (p < 0.05 , multiple comparison by Dunnett's method), and intracellular pH tended to be elevated just after the stimulation (p = 0.07). There were no significan t changes in these values in younger subjects. These results suggest that n o significant effect of photic stimulation on brain energy metabolism was f ound in younger subjects, and that significant effects of photic stimulatio n on intracellular pH and phosphocreatine were found in middle-aged subject s. Metabolic response of the human brain to photic stimulation may be depen dent on age. (C) 1999 Elsevier Science B.V. All rights reserved.