Optimization of Pulse-Triggered fMRI Measurement Delay with Acoustic Stimulation

Abstract

The purpose of the study was to examine whether improvement of activation maps of auditory cortex and brainstem nuclei is possible when the delay between the cardiac induced pulse signal and the measurements is optimized. Subsequently, the comparison of the height of brain activity obtained for different stimuli- classical and rock music. In five healthy, right- handed volunteers (the mean ages 25,4 ± 2,8 years old), musical stimuli were presented binaurally in a block design. Evaluation was performed using ‘Matlab’ and ‘SPM8new’ software with statistical threshold p< 0.001 (auditory cortex, AC) and pu< 0.01 (brainstem). Our results suggest that the manipulation of the trigger delay (TD) time changes the degree of activation in auditory cortex and brainstem nuclei. Detection of auditory cortex was in 16% (TD=0), 30% (TD=200), 8% (TD=400) and 9% (TD=800) higher than without cardiac gating examinations, and correspond to the 41 and 22 Brodmann areas. The 3-selected slices volume included the medial geniculate bodies (MGB), lateral lemniscus nuclei (NLL), superior olivary complex (SOC) and cochlear nuclei (CN). The height of activation depends on duration of trigger delay. Therefore, using various TD time proves that it is possible to increase ability to detect activation in subcortical auditory structures - another method to reduce image signal variability, which was caused by brainstem motion. Examinations with rock type of music bring better than examinations using classical music.