Cerebral Cortex Advance Access published online on November 26, 2008
Cerebral Cortex, doi:10.1093/cercor/bhn221
Aging Affects the Neural Representation of Speed in Macaque Area MT
1 Vision Research Laboratory, School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, China, 2 Laboratory of Primate Cognitive Neuroscience, Kunming Institute of Zoology, Chinese Academy of Science, Kunming, Yunnan 650223, China, 3 Department of Neurobiology and Anatomy, School of Medicine, University of Utah, Salt Lake City, UT 84132, USA, 4 State key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, China
Address correspondence to Dr Yifeng Zhou, School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, China. Email: zhouy{at}ustc.edu.cn.
Human perception of speed declines with age. Much of the decline is probably mediated by changes in the middle temporal (MT) area, an extrastriate area whose neural activity is linked to the perception of speed. In the present study, we used random-dot patterns to study the effects of aging on speed-tuning curves in cortical area MT of macaque visual cortex. Our results provide evidence for a significant degradation of speed selectivity in MT. Cells in old animals preferred lower speeds than did those in young animals. Response modulation and discriminative capacity for speed in old monkeys were also significantly weaker than those in young ones. Concurrently, MT cells in old monkeys showed increased baseline responses, peak responses and response variability, and these changes were accompanied by decreased signal-to-noise ratios. We also found that speed discrimination thresholds in old animals were higher than in young ones. The foregoing neural changes may mediate the declines in visual motion perception that occur during senescence.
Key Words: aging • area MT • degradation • inhibition • macaque • speed
Yun Yang and Jie Zhang contributed equally to this work.