Impaired procedural memory in narcolepsy type 1

Objectives Sleep enhances the consolidation of memories. Here, we investigated whether sleep-dependent memory consolidation differs between healthy subjects and narcolepsy type 1 (NT1) patients. Material and Methods We recruited 18 patients with NT1 and 24 healthy controls. The consolidation of spatial (declarative memory; 2-dimensional object location) and procedural (non-declarative memory; finger sequence tapping) memories was examined across one night of at-home sleep. Sleep was measured by an ambulatory sleep recording device. Results The overnight gain in the number of correctly recalled sequences in the finger-tapping test was smaller for NT1 patients than healthy subjects (+8.1% vs. +23.8% from pre-sleep learning to post-sleep recall, p = .035). No significant group differences were found for the overnight consolidation of spatial memory. Compared to healthy subjects, the sleep of NT1 patients was significantly more fragmented and shallow. However, no significant correlations were found between sleep parameters and overnight performance changes on the memory tests in the whole group. Conclusion The sleep-dependent consolidation of procedural but not spatial memories may be impaired among patients with NT1. Therefore, future studies are warranted to examine whether sleep improvement, for example, using sodium oxybate, can aid the sleep-dependent formation of procedural memories among NT1 patients.