The response of the central auditory system to nonsense syllables in normal hearing adults with and without HIV/AIDS : an fMRI study

Abstract

AIM : The aim of this study was to apply fMRI to comparatively evaluate any activation in the central auditory nervous system (CANS) to nonsense syllables sound in normal hearing adults with and without HIV/AIDS. OBJECTIVE : To determine the response of the central auditory nervous system (CANS) to nonsense syllables sound in normal hearing adults with and without HIV/AIDS, using fMRI. METHOD : A between-group comparative design was used to determine and compare the response of the CANS to nonsense syllables stimuli of a sample of 15 normal hearing participants without HIV/AIDS and 12 normal hearing participants with HIV/ AIDS. Structural and fMRI images were acquired during a listening task where nonsense syllables were presented binaurally using earphones. Stimuli were presented with a block design with two conditions: silence (baseline) of twenty seconds, and the stimuli task tone of twenty seconds. Each block was repeated four times. The blood oxygen level-dependent (BOLD) technique was employed. RESULTS : Both groups showed activation in all the region of interests (ROIs) of the CANS. The mean percentage signal change in BA41 and BA42 differed significantly between the two groups with a p-value of 0.03. The control group showed a significantly greater increase in neuronal activity caused by cerebral blood flow than the HIV/AIDS group. Conclusions This study indicates that BOLD fMRI provides the possibility to display brain regions responding to specific auditory stimuli applied during the scanning session. These differences could not have been observed with any other basic audiometric test procedure.