Age-related changes in prefrontal oxygenation during memory encoding and retrieval.

Abstract

Memory dysfunction is a major component of age-related cognitive decline, and is a marker of cognitive impairment. Emerging evidence suggests that the prefrontal cortex is required for maintenance of memory functions. The purpose of the present study was to elucidate age-related changes in prefrontal oxygenation during memory encoding and retrieval using near-infrared spectroscopy. We examined 21 young (mean age 24.3 years), 52 young-old (mean age 69.7 years) and 50 old-old (mean age 79.5 years) participants. The concentration of oxyhemoglobin, which is a reliable biomarker of changes in regional cerebral blood flow, in the right and left prefrontal cortex was measured during encoding and delayed retrieval of a list of 10 target words. The average number of correct answers in the retrieval task was used as a measure of task performance. During encoding, oxyhemoglobin was significantly and bilaterally lower in young-old and old-old participants compared with young participants. Meanwhile, during retrieval, only old-old participants showed significantly decreased oxyhemoglobin compared with young and young-old participants. The old-old participants showed fewer correct answers in the retrieval period than the young and young-old participants. Old-old participants showed reduced prefrontal oxygenation during both encoding and retrieval, and decreased memory performance compared with younger participants. It is necessary for the clinical application of near-infrared spectroscopy to consider the effects of demographic variables on cerebral oxygenation. Geriatr Gerontol Int 2016; 16: 1296-1304.