A FAIR study of motor cortex activation under normo- and hypercapnia induced by breath challenge

In this study an arterial spin-tagging technique based on flow-sensitive al ternating inversion recovery (FAIR) with single-shot spiral data acquisitio n was used to study how the basal cerebral blood how (CBF) elevated by brea th holding affects the regional cerebral blood flow (rCBF)response to focal brain activation in the motor cortex. Six subjects were examined using thr ee types of activation studies. These were (a) bilateral finger tapping pac ed at 4 Hz under normal breathing, (b) repeated expiration breath holding o f 30 s, and (c) simultaneous breath holding and finger tapping. It was foun d that in five of six subjects the prevailing CBF level adjusted by breath challenge and the increase in rCBF in motor cortex associated with bilatera l finger tapping were completely additive. This finding from FAIR-based fun ctional magnetic resonance imaging is in accordance with that reported from published positron emission tomography studies. The results indicate that in the majority of the subjects examined the regulatory mechanisms for vaso dilatory reaction to CO2 and rCBF response to neural activation in motor co rtex region are independent. (C) 1999 Academic Press.