Prospective memory in mild cognitive impairment and subjective cognitive impairment

The aim of this study is to investigate prospective memory and its related resting state functional connectivity of individuals with pre-dementia cognitive impairment continuum. Another goal is to examine the relationship between connectivity and cerebrospinal fluid markers. Thirty subjects with mild cognitive impairment and 30 subjects with subjective cognitive impairment participated in the study. The Virtual Week Test(VWT) and the Memory for Intentions Screening Test(MIST) were used to assess prospective memory. Functional connectivity was investigated with Network Based Statistics using MIST prospective memory scores as regressor. Participants were divided into two groups according to their connectivity characteristics. The groups were compared in terms of connectivity values, neuropsychological evaluations, and cerebrospinal fluid values. The relationship of connectivity with education and amyloid-beta(Aβ) level was examined. As a result of connectivity analysis, middle frontal gyrus, supramarginal gyrus and anterior cingulate gyrus areas were determined as central seed regions. Interconnection of the middle frontal gyrus and supramarginal gyrus with each other and with the posterior cingulate cortex was observed. The high connectivity group performed better on prospective memory measurement and some neuropsychological assessments. The results of VWT proportion of miss task indicate that the low connectivity group suffered more impairment in tasks that required spontaneous retrieval. The high connectivity group had higher brain Aβ accumulation. Additionally, it was observed that connectivity increased in relation to Aβ accumulation and this increase was associated with higher education level. This suggests a compensatory mechanism associated with high cognitive reserve against the deteriorating effect of Aβ accumulation.