Anstey Kaarin J, Mack Holly A, Christensen Helen, Li Shu-Chen, Reglade-Meslin Chantal, Maller Jerome, Kumar Rajeev, Dear Keith, Easteal Simon, Sachdev Perminder
Centre for Mental Health Research, Australian National University, Australian Capital Territory, Australia.
Neuropsychologia. 2007 Apr 9;45(8):1911-20. doi: 10.1016/j.neuropsychologia.2006.11.020. Epub 2007 Jan 22.
Intra-individual variability in reaction time increases with age and with neurological disorders, but the neural correlates of this increased variability remain uncertain. We hypothesized that both faster mean reaction time (RT) and less intra-individual RT variability would be associated with larger corpus callosum (CC) size in older adults, and that these associations would be stronger in adults with mild cognitive disorders. A normative sample (n=432) and a sample with mild cognitive disorders (n=57) were compared on CC area, RT mean and RT variability adjusting for age, sex, education, APOE genotype, smoking, alcohol consumption, grip strength, visual acuity, handedness and lung function. Samples did not differ in CC area or intra-cranial volume. In the normative sample, simple RT (SRT) and choice RT (CRT) were negatively associated with CC area but there were minimal associations between CC area and intra-individual RT variability. In the mild cognitive disorders sample, SRT, CRT and intra-individual variability on the SRT task were associated with CC area. Increased RT variability explained up to 12.7 percent of the variance in CC area in the sample with mild cognitive disorders, but less than 1 percent of the variance in CC area in the normative sample. There were no associations with APOE genotype. We conclude that intra-individual variability is associated with CC area in mild cognitive disorders, but not in normal aging. We propose that biological limits on reserve capacity must occur in mild cognitive disorders that result in stronger brain-behavior relationships being observed.
反应时间的个体内变异性会随着年龄增长和神经疾病而增加，但这种变异性增加的神经关联仍不明确。我们假设，在老年人中，更快的平均反应时间（RT）和更小的个体内RT变异性都与更大的胼胝体（CC）大小相关，并且在患有轻度认知障碍的成年人中，这些关联会更强。在调整了年龄、性别、教育程度、APOE基因型、吸烟、饮酒、握力、视力、利手和肺功能后，对一个正常样本（n = 432）和一个患有轻度认知障碍的样本（n = 57）进行了CC面积、RT平均值和RT变异性的比较。两个样本在CC面积或颅内体积上没有差异。在正常样本中，简单反应时间（SRT）和选择反应时间（CRT）与CC面积呈负相关，但CC面积与个体内RT变异性之间的关联极小。在轻度认知障碍样本中，SRT、CRT以及SRT任务中的个体内变异性与CC面积相关。在患有轻度认知障碍的样本中，RT变异性增加最多可解释CC面积方差的12.7%，但在正常样本中，RT变异性增加解释的CC面积方差不到1%。与APOE基因型没有关联。我们得出结论，个体内变异性在轻度认知障碍中与CC面积相关，但在正常衰老中并非如此。我们提出，在轻度认知障碍中，储备能力的生物学限制必然存在，这导致观察到更强的脑-行为关系。
