Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC 3010, Australia.
Monash Biomedical Imaging, Monash University, Clayton, VIC 3800, Australia.
Sci Rep. 2017 Oct 27;7(1):14231. doi: 10.1038/s41598-017-14577-5.
Several studies have attributed certain visual perceptual alterations in older adults to a likely decrease in GABA (Gamma Aminobutyric Acid) concentration in visual cortex, an assumption based on findings in aged non-human primates. However, to our knowledge, there is no direct evidence for an age-related decrease in GABA concentration in human visual cortex. Here, we estimated visual cortical GABA levels and Glx (combined estimate of glutamate and glutamine) levels using magnetic resonance spectroscopy. We also measured performance for two visual tasks that are hypothesised to be mediated, at least in part, by GABAergic inhibition: spatial suppression of motion and binocular rivalry. Our results show increased visual cortical GABA levels, and reduced Glx levels, in older adults. Perceptual performance differed between younger and older groups for both tasks. When subjects of all ages were combined, visual cortical GABA levels but not Glx levels correlated with perceptual performance. No relationship was found between perception and GABA levels in dorsolateral prefrontal cortex. Perceptual measures and GABA were not correlated when either age group was considered separately. Our results challenge current assumptions regarding neurobiological changes that occur within the aging human visual cortex and their association with certain age-related changes in visual perception.
几项研究将老年人某些视觉感知改变归因于视觉皮层中 GABA（γ-氨基丁酸）浓度的可能降低，这一假设基于老年非人类灵长类动物的研究结果。然而，据我们所知，没有直接证据表明人类视觉皮层的 GABA 浓度与年龄有关。在这里，我们使用磁共振波谱法估计了视觉皮质 GABA 水平和 Glx（谷氨酸和谷氨酰胺的综合估计）水平。我们还测量了两种假设至少部分由 GABA 能抑制介导的视觉任务的表现：运动的空间抑制和双眼竞争。我们的结果表明，老年人的视觉皮质 GABA 水平增加，Glx 水平降低。两个任务的年轻组和老年组的知觉表现都不同。当所有年龄组的受试者结合在一起时，视觉皮质 GABA 水平但不是 Glx 水平与知觉表现相关。在背外侧前额叶皮质中未发现感知和 GABA 之间存在关系。当分别考虑每个年龄组时，感知测量和 GABA 之间没有相关性。我们的结果挑战了当前关于衰老过程中人类视觉皮层内发生的神经生物学变化及其与某些与年龄相关的视觉感知变化的关联的假设。
