Prospective memory in prodromal Alzheimer’s Disease: real world relevance and correlations with cortical thickness and hippocampal subfield volumes

INTRODUCTION: Prospective memory (PM) is a marker of independent living in Alzheimer’s disease. PM requires cue identification (prospective component) and remembering what should happen in response to the cue (retrospective component). We assessed neuroanatomical basis and functional relevance of PM.
METHODS: 84 older participants (53-94 years old, 58% male) with or without Mild Cognitive Impairment (MCI) performed PM tests, Activities of Daily Living (ADL) scale and had a structural MRI of the brain to estimate for cortical thickness and hippocampal subfield volumes. A General Linear Model cluster analysis was carried out using FreeSurfer to determine which cortical regions were correlated with PM scores. 

RESULTS: Both components of PM are impaired in MCI (p<.001). The retrospective component of PM correlates strongly with ADL (p=.005). Prospective component performance correlates positively with cortical thickness of bilateral frontal-temporal-parietal cortex and volume of CA1 of hippocampus. In contrast, the retrospective component performance correlates positively with cortical thickness of a right-lateralised fronto-temporal-parietal network and volumes of subiculum and CA3 hippocampal subfields.

DISCUSSION: Our neuroimaging findings complement and extend previous research into structural correlates of PM. Here, we show that there are distinct, yet, overlapping brain regions correlating with the two components of PM. PM performance provides a window into real-life functional abilities in people at risk of Alzheimer’s disease and could be utilised as a marker of clinically relevant disease.