Assessing the effects of apneusis on brain functional magnetic resonance imaging with symbolic dynamics

Abstract

Symbolic dynamics was used to investigate the effect of breath-holding on brain functional Magnetic Resonance Imaging (fMRI). Data from 5 subjects, available as an open Internet database, were used. Three conditions were compared: resting (RS), breath-holding (BH) and sensorimotor-finger tapping (SM), the last two with on-off task period of 30 seconds. A symbolic dynamics parameter P(n), equal to the proportion of brain voxels with positive derivatives at each scan in a run, was calculated from the blood oxygenation level dependent (BOLD) signal. The robustness of P(n) was assessed by comparing the results of the original data to those with preprocessed data, as well as with the data split into odd and even slices. Statistical analyses of P(n) in the frequency domain indicated global, periodic effects at the BH frequency in all 20 BH runs, in 3 out of the 20 RS runs and in 10 out of the 40 SM runs. The technique may be useful in the analysis of brain activity and vasoreactivity. © 2008 Springer-Verlag.