Effects of Aging and Background Babble Noise on Speech Perception Processing: An fMRI Study

Speech perception processing in a noisy environment is subjected to age-related decline. We used functional magnetic resonance imaging (fMRI) to examine cortical activation associated with such processing across four groups of participants with age ranges of 23–29, 30–37, 41–47 and 50–65 years old. All participants performed a forward repeat task in quiet environment (SQ) and in the presence of multi-talker babble noise (SN; 5-dB signal-to-noise ratio, SNR). Behavioral test results demonstrated a decrease in the performance accuracy associated with increasing age for both SQ and SN. However, a significant difference in the performance accuracy between these conditions could only be seen among the elderly (60–65 years old) subjects. The fMRI results across the four age groups showed a nearly similar pattern of brain activation in the auditory, speech, and attention areas during SQ and SN. Comparisons between SQ and SN demonstrated significantly lower brain activation in the left precentral gyrus, left postcentral gyrus, left Heschly's gyrus, and right middle temporal gyrus under the latter condition. Other activated brain areas showed no significant differences in brain activation between SQ and SN. The decreases in cortical activation in the activated regions positively correlated with the decrease in the behavioral performance across age groups. These findings are discussed based on a dedifferentiation hypothesis that states that increased brain activation among older participants, as compared to young participants, is due to the age-related deficits in neural communication.

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