Aging Effects of Auditory Cortical Activation during Speech listening in Noise: A Study of Central Presbycusis Using fMRI

• Main Authors: Juen-Haur Hwang, 黃俊豪
• Other Authors: 林凱南
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/54340801035434411265

碩士 === 國立臺灣大學 === 臨床醫學研究所 === 94 === The aging human auditory system is manifested by deterioration of two critical dimension of hearing, namely, reduction in threshold sensitivity and reduction in the ability to understand speech. The deterioration in speech perception ability results not only from the problems of peripheral hearing organs but also affected by the degeneration of central auditory system. Further more, the elderly listener’s difficulties increase dramatically more than the young listeners whenever the speech message is degraded. These difficulties may due to a central integrative and synthesizing hearing disability that reflects a progressive deterioration of the CNS. Twelve subjects aged over 61 with normal peripheral hearing will be included in this study. Another twelve young subjects aged between 21 and 31 will serve as control. Functional MRI will be performed while these subjects were listening to speech (both in quiet and in noise) binaurally using a Bruker’s 3T scanner. A pre-recorded continuous discourse is used as the speech signal. The same signal plus a background white noise (S/N ratio: + 5 dB) serve as the hearing in noise counterpart. Results showed that the SDS and activation patterns were very similar between young adults and elderly people during speech listenig, but the SDS and extent of activation decreased obviously in both groups durning speech listening in white noise, especially in elderly people. The reduced activation was mainly located in the anterior and posterior parts of superior temporal gyrus of both hemispheres, especially in the left side. The IWV of auditory cortex was smaller in elderly subjects than in young subjects, so as to the cluster levels and the voxel levels, especially in cluster levels. In addition, the ratio of the noise-induced masking effect in IWV was much greater in elderly subjects than in young subjects. Both of the cluster levels and voxle levels, especially in cluster levels, were also decreased greatly in elderly subjects. Furthermore, compared to speech listening alone, the activation increased in the left putamen, the anterior part of the right STG (BA 38), pulvinar of right thalamus, right claustrum and left caudate tail during speech listening in noise in younger adults. However, only medial dorsal nuclei of the thalamus of both hemispheres were additionally activated during speech listening in white noise in elderly subjects. To conclude, the early changes of central presbycusis maily located in anterior and posterior parts of the superior temporal gyrus, and suprior part of the middle temporal gysus of both hemispheres. Top-down mechanism during speech listening in noise were reduced in elderly subjects.