Characterising Sleep Dependent Memory in Mild Cognitive Impaired Subtypes
Mild Cognitive Impaired (MCI) and Sleep disorders
Research Project Description
The aim of this study is to identify alterations in sleep microarchitecture as possible clinical biomarkers and modifiable risk factors for cognitive decline and dementia. Differences between MCI and controls sleep dependent memory consolidation are examined using novel verbal and spatial navigation memory tasks, and their relationship with NREM and REM neurophysiology. In addition, to investigate the relationship between sleep dependent memory and structural brain integrity, and to what extent these key brain regions required for optimal sleep and memory mediate the relationship between sleep neurophysiology and overnight memory consolidation.
Sleep plays a crucial role in the overnight consolidation of newly learnt information in young adults, however the sleep-cognition relationship in older adults is less understood. Age-associated memory decline as well as sleep disturbances are a concern for up to 60% of older people. It is of critical importance to uncouple this relationship between sleep, memory and key brain functions, and how these processes are affected by age. Crucial features of non-rapid eye movement (NREM) sleep neurophysiology have been identified as promoting memory consolidation, in particular declarative memory, that include slow wave activity and spindles. However, sleep neurophysiology during rapid eye movement (REM) sleep has not been well explored in older adults. This research study looks at 3 main components.
Sleep dependent memory consolidation
Overnight memory consolidations are assessed on the night of an overnight sleep study (polysomnography) across several different memory domains. Firstly, neuropsychological tests of verbal and visuospatial memory are administered pre-and post-sleep. Secondly, novel tasks of lexical integration and spatial navigation memory are used in order to further delineate how sleep impacts various components memory, and how this differs between those with mild cognitive impairment, and its subtypes, compared to healthy controls.
Overnight EEG is examined on the night of the polysomnography assessed across varying stages of sleep. In addition, a subset of participants’ neural oscillations are examined, as well as their pre- and post resting wake EEG using a 256-channel high density EEG.
Finally, the research study looks to investigate structural brain integrity, particularly in key regions such as the medial prefrontal cortex and hippocampal subfields, regions important for sleep and memory, as well as task specific regions, their relationship with overnight memory consolidation and how this may potentially mediate the relationship between sleep neurophysiology and memory consolidation.
The research study intends to fill a gap in the literature in better understanding how microarchitecture change in those ‘at risk’ of dementia underpin sleep dependent memory consolidation. Age-appropriate sleep dependent memory tasks have been developed in order to allow for a greater understanding of sleeps effect on memory consolidation in order to develop targeted interventions specifically for older adults. In addition, the implications of these findings speak to new potential biomarkers that can be detected 10-15 years before disease onset and to determine the impact and functions of sleep as a modifiable risk factor.