Grant: Discovery Grants Program - Individual

Background: Thanks to the advent of simultaneous electroencephalography and functional neuroimaging techniques (EEG-fMRI), significant advancements have been made in identifying and understanding the systems-level functional neuroanatomical correlates of the characteristic electrophysiological features of sleep, including spindles and slow waves. By comparison, very little is known about the neural correlates of the characteristic features of rapid eye movement (REM) sleep in humans, e.g., rapid eye movements (EMs). REM sleep has been found to be beneficial to memory consolidation for cognitively complex problem solving skills. However, it is not clear whether REM sleep per se is involved in memory trace strengthening via memory trace reactivation and replay. Approach: By leveraging the temporal resolution of EEG and the spatial resolution of MRI, using a unique combination of cognitive-behavioural testing and simultaneous EEG-fMRI, we will identify the functional neuroanatomical correlates of EMs during REM sleep. In addition, we will investigate the functional significance of these activations for offline, sleep-dependent memory consolidation. Objectives & outcomes: 1: Using simultaneous EEG-fMRI recordings during sleep, we will provide for the first time, valuable insight into the neuroanatomical functional correlates of the characteristic EMs during REM sleep and the distinct brain regions that are most active during REM sleep. In addition, Objective 1 will also provide a first look at the network-level functional communication time-locked to EMs during REM sleep. 2: Using simultaneous fMRI during learning, and subsequent EEG-fMRI recordings during sleep, we will for the first time, investigate if EMs during REM sleep are actively involved in the reactivation, strengthening and replay of newly acquired memory traces for procedural skills. The results will not only reveal the neuroanatomical substrates that support optimal memory consolidation during sleep, but also, the nature of the functional communication in the network of brain structures required to learn and perform such skills. Novelty, impact & significance: These studies will: 1) amass one of the largest EEG-fMRI sleep datasets that includes REM sleep, 2) will provide functional neuroanatomical evidence about the functional significance of REM sleep, and 3) will provide for the first time, evidence that sleep-dependent memory consolidation for novel cognitive strategies occurs via the EM-related reactivation and replay of memory traces. These processes ultimately support real-world specialized skills involving cognitive strategies, problem-solving and rule-based learning; such as our ability to become world-class professional athletes, musicians, or computer programmers. A 2023 position paper in the Lancet expressed the desperate need to promote sleep in public policy. This research will help to influence the public, private sector and government policy on the importance of sleep.