Sleep-dependent motor sequence memory consolidation in individuals with periodic limb movements

Publication date: Available online 28 September 2017
Source:Sleep Medicine
Author(s): Valya Sergeeva, Jeremy Viczko, Laura B. Ray, Adrian M. Owen, Stuart M. Fogel
Periodic limb movements (PLMs) during sleep increase with age and are associated with striatal neurodegeneration and dopamine deficiency. Limb movements are often associated with disruptions to non-rapid eye movement (NREM) sleep. Motor skill memory consolidation recruits the striatum, and learning-dependent striatal activation is associated with NREM sleep. Therefore, we investigated whether de novo individuals who experience significantly elevated levels of PLMs but have not been formally diagnosed with periodic limb movement disorder had learning and sleep-related memory deficits, and if these deficits related to sleep quality and symptom severity.Fourteen adults with significantly elevated PLMs (PLM condition); fifteen aged-matched controls (CTRL); and fourteen age-matched "disturbed" sleep (via induced leg movements) controls (CTRL-ES) participated. Participants were trained (PM) and retested (AM) on procedural motor sequence learning (MSL) and declarative paired associates memory tasks.Baseline sleep quality was significantly worse in the PLM vs. CTRLs. Despite the continued presence of PLMs in the PLM condition on the experimental night, remarkably, sleep quality was improved and arousals were reduced vs. baseline, and did not differ from CTRL. MSL was significantly slower in the PLM condition compared to CTRL at training, but surprisingly, did exhibit overnight performance gains; which correlated with reduced arousals. As predicted, CTRL but not CTRL-ES had overnight gains in MSL. Together, suggesting that, in the PLM condition, sleep quality was normalized following MSL, where they derived the same benefit of sleep to procedural memory consolidation as CTRL. Sleep did not benefit declarative memory.Although preliminary, these results suggest that motor sequence learning in individuals with PLMs may provide a benefit to sleep, which in turn, may benefit memory consolidation.



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