Selective Impairment of Optic Flow Perception in Amnestic Mild Cognitive Impairment: Evidence From Event-Related Potentials

Article type: Research Article

Authors: Yamasaki, Takao^{a; b; *} | Goto, Yoshinobu^c | Ohyagi, Yasumasa^d | Monji, Akira^e | Munetsuna, Shinji^f | Minohara, Motozumi^{b; d} | Minohara, Katsuko^g | Kira, Jun-ichi^d | Kanba, Shigenobu^e | Tobimatsu, Shozo^a

Affiliations: [a] Department of Clinical Neurophysiology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan | [b] Department of Neurology, Minkodo Minohara Hospital, Fukuoka, Japan | [c] Department of Occupational Therapy, Faculty of Rehabilitation, International University of Health and Welfare, Okawa, Japan | [d] Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan | [e] Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan | [f] Department of Brain Science and Engineering, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan | [g] Department of Neuropsychiatry, Minkodo Minohara Hospital, Fukuoka, Japan

Correspondence: [*] Correspondence to: Takao Yamasaki, M.D., Ph.D., Department of Clinical Neurophysiology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Tel.: +81 92 642 5542; Fax: +81 92 642 5545; E-mail: yamasa@neurophy.med.kyushu-u.ac.jp.

Abstract: Alzheimer's disease (AD) patients have visuospatial deficits due to parietal dorsal stream dysfunction. Two distinct dorsal flows have been proposed: the inferior parietal (ventro-dorsal (v-d)) and superior parietal (dorso-dorsal (d-d)) streams. We aimed to elucidate how the two dorsal streams are altered in patients with amnestic mild cognitive impairment (aMCI) and AD. Thus, the psychophysical threshold measurements and visual event-related potentials (ERPs) were recorded in patients with aMCI and AD, and in healthy old and young adults. The visual stimuli included radial optic flow (OF) derived from the v-d stream and horizontal (HO) motion conveyed from the d-d stream. The motion thresholds between aMCI patients and old adults were comparable. However, AD patients showed significantly higher motion thresholds for both stimuli compared with other groups. In lower-level ERPs, there were no significant differences in P1 (100 ms) and N1 (130 ms) for both stimuli among the groups. For higher-level ERPs, aMCI patients showed the prolonged latency of OF-specific P200 (v-d origin) and comparable latency of motion-related N170 (V5/MT origin) for both stimuli compared with old adults. In AD patients, both N170 and P200 latencies were significantly prolonged compared with other groups. P200 latency was closely correlated with the Mini-Mental State Examination score. These findings indicate that the v-d function related to OF perception is selectively impaired in aMCI, whereas AD has impairment of the distributed higher-level dorsal stream. Therefore, OF-specific P200 can be useful for detecting early functional changes of the brain in aMCI.

Keywords: Aging, Alzheimer's disease, coherent motion perception, dorsal visual stream, event-related potentials, mild cognitive impairment, optic flow

DOI: 10.3233/JAD-2011-110167

Journal: Journal of Alzheimer's Disease, vol. 28, no. 3, pp. 695-708, 2012