Department of Otolaryngology-Head and Neck Surgery, Fuzhou General Hospital of Nanjing Command, PLA, 156 Xihuan Bei Road, Fuzhou 350025, China ; Department of Otolaryngology-Head and Neck Surgery, Dongfang Hospital, Fujian Medical University, Fuzhou 350001, China.
Neural Plast. 2013;2013:735290. doi: 10.1155/2013/735290. Epub 2013 Oct 9.
The aim of this study was to investigate the effects of age on hemispheric asymmetry in the auditory cortex after pure tone stimulation. Ten young and 8 older healthy volunteers took part in this study. Two-dimensional multivoxel 1H-magnetic resonance spectroscopy scans were performed before and after stimulation. The ratios of N-acetylaspartate (NAA), glutamate/glutamine (Glx), and γ -amino butyric acid (GABA) to creatine (Cr) were determined and compared between the two groups. The distribution of metabolites between the left and right auditory cortex was also determined. Before stimulation, left and right side NAA/Cr and right side GABA/Cr were significantly lower, whereas right side Glx/Cr was significantly higher in the older group compared with the young group. After stimulation, left and right side NAA/Cr and GABA/Cr were significantly lower, whereas left side Glx/Cr was significantly higher in the older group compared with the young group. There was obvious asymmetry in right side Glx/Cr and left side GABA/Cr after stimulation in young group, but not in older group. In summary, there is marked hemispheric asymmetry in auditory cortical metabolites following pure tone stimulation in young, but not older adults. This reduced asymmetry in older adults may at least in part underlie the speech perception difficulties/presbycusis experienced by aging adults.
本研究旨在探讨纯音刺激后听觉皮层半球间不对称性随年龄变化的情况。10 名年轻志愿者和 8 名老年志愿者参加了本研究。在刺激前后进行二维多体 1H 磁共振波谱扫描。测定 N-乙酰天冬氨酸(NAA)、谷氨酸/谷氨酰胺(Glx)和γ-氨基丁酸(GABA)与肌酸(Cr)的比值,并比较两组之间的差异。还确定了代谢物在左右听觉皮层之间的分布情况。刺激前,老年组左侧和右侧 NAA/Cr 以及右侧 GABA/Cr 明显低于年轻组,而右侧 Glx/Cr 明显高于年轻组。刺激后,老年组左侧和右侧 NAA/Cr 以及 GABA/Cr 明显低于年轻组,而左侧 Glx/Cr 明显高于年轻组。在年轻组中,刺激后右侧 Glx/Cr 和左侧 GABA/Cr 明显不对称,但在老年组中则没有。总之,在年轻成年人中,纯音刺激后听觉皮层代谢物存在明显的半球间不对称性,但在老年成年人中则没有。这种老年人中对称性的降低至少部分解释了老年人在言语感知方面的困难/老年性聋。