Brown Alyse, Corner Molly, Crewther David, Crewther Sheila
School of Psychological Science and Public Health, La Trobe University, Melbourne, VIC, Australia.
Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, VIC, Australia.
Front Aging Neurosci. 2019 Jan 18;10:430. doi: 10.3389/fnagi.2018.00430. eCollection 2018.
As the visual system ages, flicker sensitivity decreases and the latencies of cortical visual evoked potentials (VEP) increase. However, the extent to which these effects reflect age-related changes in the magnocellular (M) and or parvocellular (P) pathways remain unclear. Here, we investigated the relation between flicker fusion frequencies and VEP non-linearities induced by rapid stimulation, as a function of age over 6 decades. The approach, using Wiener kernel analysis of multifocal flash (mf)VEP, allows the extraction of signatures of both M and P processing and hence establishing a neural basis of the known decline in flicker fusion threshold. We predicted that, in a sample of 86 participants, age would be associated with a latency increase in early mfVEP response components and that flicker fusion thresholds, for both low and high contrast stimuli, would relate to the temporal efficiency of the M-generated VEP component amplitudes. As expected, flicker fusion frequency reduced with age, while latencies of early second order peaks of the mfVEP increased with age, but M temporal efficiency (amplitude ratio of first to second order peaks) was not strongly age-related. The steepest increases in latency were associated with the M dominated K2.1 (second order first slice) N70 components recorded at low and high contrast (6.7 and 5.9 ms/decade, respectively). Interestingly, significant age-related latency shifts were not observed in the first order responses. Significant decreases in amplitude were found in multiple first and second order components up to 30 years of age, after which they remained relatively constant. Thus, aging and decline in visual function appears to be most closely related to the response latencies of non-linearities generated by the M pathway.
随着视觉系统老化，闪烁敏感度下降，皮层视觉诱发电位（VEP）的潜伏期增加。然而，这些影响在多大程度上反映了大细胞（M）和/或小细胞（P）通路中与年龄相关的变化仍不清楚。在这里，我们研究了闪烁融合频率与快速刺激诱发的VEP非线性之间的关系，作为六个十年间年龄的函数。该方法使用多焦点闪光（mf）VEP的维纳核分析，能够提取M和P处理的特征，从而建立已知闪烁融合阈值下降的神经基础。我们预测，在86名参与者的样本中，年龄将与早期mfVEP反应成分的潜伏期增加相关，并且低对比度和高对比度刺激的闪烁融合阈值将与M产生的VEP成分振幅的时间效率相关。正如预期的那样，闪烁融合频率随年龄降低，而mfVEP早期二阶峰值的潜伏期随年龄增加，但M时间效率（一阶与二阶峰值的振幅比）与年龄的相关性不强。潜伏期增加最陡峭的情况与在低对比度和高对比度下记录的M主导的K2.1（二阶第一切片）N70成分相关（分别为6.7和5.9毫秒/十年）。有趣的是，在一阶反应中未观察到与年龄相关的显著潜伏期变化。在30岁之前，多个一阶和二阶成分的振幅显著下降，之后它们保持相对稳定。因此，视觉功能的老化和衰退似乎与M通路产生的非线性反应潜伏期最为密切相关。
