Event-related fMRI of the auditory cortex

An event-related protocol was designed to permit auditory fMRI studies mini mally affected by the echoplanar noise artifact; a long time interval (TR = 10 s) between each cerebral volume acquisition was combined with strobosco pic data acquisition, and event-related curves were reconstructed with a 1- s resolution. The cerebral hemodynamic-response time course to a target aud itory stimulus was measured in five individual subjects using this method. Clear bell-shaped event-related responses were observed bilaterally in all individuals in primary auditory cortex (A1) as well as in laterally extendi ng secondary cortical fields. Group-average event-related curves attained t heir maxima (0.5-0.7%) 3 s after stimulus onset in Al (4 s for more anterio r and lateral regions of auditory cortex), and signal had returned to near- baseline level 6 s after stimulus onset. The stroboscopic event-related met hod appeared effective in minimizing effects of the interaction between sca nning noise and experimental auditory stimulation; it adds useful temporal information to the spatial resolution afforded by fMRI in studies of human auditory function, while allowing presentation of auditory stimuli on a sil ent background. (C) 1999 Academic Press.