The hemispheric lateralization of the auditory cortex after being stimulated by pure tone: a 1H-MRS study

Abstract

Objective To explore the asymmetry of metabolic products of the auditory cortex in normal human brain after being stimulated by the pure tone with the proton magnetic resonance spectroscopy(1 H-MRS). Methods Twelve healthy volunteers, including 7 males and 5 females, were performed MRS tests before and after the stimulation of the pure tone of 90 dB in intensity and 1000 Hz in frequency. The the metabolites peak of the N-acetylaspartate (NAA) ,creatine(Cr) ,choline( Cho) , glutamine/glutamate ( Glx) and GABA in auditory cortex were investigated, The content of metabolic products were conducted with half-quantitative analysis. The differences of the NAA/( Cho + Cr) ,Glx/Cr and GABA/ Cr ratios before and after pure tone stimulation in the bilateral auditory cortex were analyzed. The difference of distribution of the metabolic products between the left and right auditory cortex was also analyzed to explore the asymmetry of the auditory cortex. Results The NAA/( Cho + Cr) and GABA/Cr ratios increased,the Glx/Cr ratio decreased in the left auditory cortex after being stimulated by the pure tone. There were significant differences in the NAA/( Cho + Cr) , Glx/Cr and GABA/Cr ratios before and after pure tone stimulation (P 0.05). There were statistically significant differences in the Glx/Cr ratio of the auditory cortex between two sides after being stimulated by the pure tone. Conclusion The metabolic lateralization exists in auditory cortex of normal human brain after being stimulated by the pure tone, which may be the bases of the functional asymmetry. Key words: Proton magnetic resonance spectroscopy; Auditory cortex; Pure tone stimulation; Hemispheric laterality