Ward Laura McKernan, Aitchison Ross Thomas, Tawse Melisa, Simmers Anita Jane, Shahani Uma
Department of Vision Sciences, Glasgow Caledonian University, Glasgow, United Kingdom.
PLoS One. 2015 Apr 24;10(4):e0125012. doi: 10.1371/journal.pone.0125012. eCollection 2015.
The effect of healthy ageing on visual cortical activation is still to be fully explored. This study aimed to elucidate whether the haemodynamic response (HDR) of the visual cortex altered as a result of ageing. Visually normal (healthy) participants were presented with a simple visual stimulus (reversing checkerboard). Full optometric screening was implemented to identify two age groups: younger adults (n = 12, mean age 21) and older adults (n = 13, mean age 71). Frequency-domain Multi-distance (FD-MD) functional Near-Infrared Spectroscopy (fNIRS) was used to measure absolute changes in oxygenated [HbO] and deoxygenated [HbR] haemoglobin concentrations in the occipital cortices. Utilising a slow event-related design, subjects viewed a full field reversing checkerboard with contrast and check size manipulations (15 and 30 minutes of arc, 50% and 100% contrast). Both groups showed the characteristic response of increased [HbO] and decreased [HbR] during stimulus presentation. However, older adults produced a more varied HDR and often had comparable levels of [HbO] and [HbR] during both stimulus presentation and baseline resting state. Younger adults had significantly greater concentrations of both [HbO] and [HbR] in every investigation regardless of the type of stimulus displayed (p<0.05). The average variance associated with this age-related effect for [HbO] was 88% and [HbR] 91%. Passive viewing of a visual stimulus, without any cognitive input, showed a marked age-related decline in the cortical HDR. Moreover, regardless of stimulus parameters such as check size, the HDR was characterised by age. In concurrence with present neuroimaging literature, we conclude that the visual HDR decreases as healthy ageing proceeds.
健康衰老对视皮层激活的影响仍有待充分探索。本研究旨在阐明视皮层的血流动力学反应（HDR）是否因衰老而改变。向视力正常（健康）的参与者呈现简单视觉刺激（反转棋盘格）。进行全面的验光筛查以确定两个年龄组：年轻成年人（n = 12，平均年龄21岁）和老年人（n = 13，平均年龄71岁）。使用频域多距离（FD-MD）功能近红外光谱（fNIRS）来测量枕叶皮质中氧合血红蛋白[HbO]和脱氧血红蛋白[HbR]浓度的绝对变化。采用慢事件相关设计，让受试者观看全视野反转棋盘格，并进行对比度和方格大小操作（15和30分视角，50%和100%对比度）。两组在刺激呈现期间均表现出[HbO]增加和[HbR]减少的特征性反应。然而，老年人产生的HDR变化更大，并且在刺激呈现和基线静息状态期间，[HbO]和[HbR]水平通常相当。无论显示何种类型的刺激，年轻成年人在每次调查中[HbO]和[HbR]的浓度均显著更高（p<0.05）。与这种年龄相关效应相关的[HbO]平均方差为88%，[HbR]为91%。在没有任何认知输入的情况下被动观看视觉刺激，显示出皮层HDR明显的年龄相关下降。此外，无论方格大小等刺激参数如何，HDR都具有年龄特征。与当前神经影像学文献一致，我们得出结论，随着健康衰老的进展，视觉HDR会降低。
