Measuring the Temporal Coupling of Slow Oscillations, Spindles, and Hippocampal Ripples in Relation to Procedural Memory in Humans
Abstract number :
3.081
Submission category :
2. Translational Research / 2A. Human Studies
Year :
2021
Submission ID :
1826401
Source :
www.aesnet.org
Presentation date :
12/6/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:54 AM
Authors :
Megan Thompson, PhD - Massachusetts General Hospital; Bryan Baxter - Massachusetts General Hospital; Kristi Kwok - Massachusetts General Hospital; Bailey Driscoll - Massachusetts General Hospital; Rudra Patel - Massachusetts General Hospital; Catherine Chu - Massachusetts General Hospital; Dara Manoach - Massachusetts General Hospital
Rationale: Cortical slow oscillations, thalamocortical sleep spindles, and hippocampal ripples are implicated in sleep-dependent memory consolidation. Triple coupling of these oscillations has been demonstrated to improve memory in rodents but has not yet been shown in humans. Using simultaneous scalp EEG and invasive hippocampal recordings in epilepsy patients, we are investigating triple coupling between spindles, ripples and slow oscillations in relation to sleep-dependent memory consolidation. Here we present validation of a novel ripple detector and coupling data from three participants.
Methods: Patients with epilepsy undergoing phase II presurgical evaluations, including simultaneous 21-channel scalp and intracranial EEG with hippocampal contacts, were recruited from the MGH Epilepsy Monitoring Unit. Participants trained on the finger tapping Motor Sequence Task (MST) at night and were tested the following morning. Slow oscillations and spindles during stage 2 NREM (N2) sleep were detected in scalp EEG using validated algorithms. Hippocampal ripples were detected using a fully automated detector the threshold of which was optimized using expert validation of 8606 candidate ripple events (Fig 1). Coupling was defined as the temporal co-occurrence of spindles with slow oscillations, hippocampal ripples, or both (triple coupling) (Fig 1). We measured spindles and slow oscillations overlying motor cortex (scalp electrode C3 or C4) and ripples in anterior hippocampal contacts in the hemisphere contralateral to the hand that performed the task.
Results: Our hippocampal ripple detector performed with high specificity across subjects (all specificity > 0.83). Based on data from three participants, the ripple rate was 50.6/min (range: 27.4-85.4), which falls within the wide range of average ripple rates reported in the literature (J Neurophysiol 2002; 88:1743-52; J Neurosci 2019; 39(44): 8744-61). Ripple-coupled spindles occurred at an average rate of 2.3/min (range: 1.2-3.7). Triple-coupled spindles occurred at a rate of 0.26/min (range: 0.13-0.56).
Conclusions: We detected coupling between cortical and hippocampal sleep oscillations as a first step to evaluating the relationship between memory consolidation and coupling. Ongoing work includes continued data acquisition, extending our analyses to N3, and comparing coupling in the hemispheres contralateral and ipsilateral to the hand that performed the task to look for lateralized changes in sleep oscillations. This work will indicate whether coupled spindles may be a superior biomarker of sleep-dependent memory consolidation than all spindles (the standard measure) and provide better targets for treatment development for clinical populations with impaired sleep-dependent memory consolidation.
Funding: Please list any funding that was received in support of this abstract.: McKnight Research Scholarship, UG3 MH125273, T32 5T32HL007901.
Translational Research