GENDER DIFFERENCES IN CEREBRAL BLOOD-FLOW AS A FUNCTION OF COGNITIVE STATE WITH PET

This study explored the role of cognitive states in gender-based diffe rences in brain function, Methods: We used the O-15-water bolus method to measure cerebral blood flow (CBF) in 14 young normal volunteers wi th PET. Each subject was scanned six times, three during different neu ropsychological tasks linked to the prefrontal cortex and three others during customized sensorimotor control tasks, The prefrontal tasks we re the Wisconsin Card Sorting (WCS) Test, Delayed Alternation task (DA ) and Spatial Delayed Response task (DR), Results: A significant main influence of sex on global CBF (ml/min/100g) was seen, with higher val ues in women, as viewed across all six conditions (means: 60.9 versus 53.2, ANOVA F = 9.35, p < 0.01), Post-hoc contrasts, however, showed t hat this finding was not uniform in all conditions, Differences betwee n men and women were seen during performance of the frontal lobe tasks , but not during the sensorimotor control tasks. Even within the three frontal lobe tasks, results tended to vary: the differences between t he sexes were most significant during the DA and just reached traditio nal levels of significance during the WCS, Therefore, if we had utiliz ed a single task condition to determine whether men and women have dif ferent global CBFs, disparate conclusions would have been reached depe nding upon the task chosen, Conclusion: Although clear sex differences in global CBF can be demonstrated, the cognitive state of the subject s must be controlled and considered when interpreting the differences, Also, variations in the cognitive state might explain some of the dis crepancies in gender studies in the rCBF and cerebral glucose metaboli sm literature.