Impaired sleep-related memory consolidation in primary insomnia--a pilot study

STUDY OBJECTIVES: To compare sleep-related consolidation of procedural memory in patients with primary insomnia and healthy controls. DESIGN: Controlled comparison pilot study. SETTING: Sleep Laboratory of the Department of Psychiatry and Psychotherapy, University of Freiburg, Germany. PATIENTS OR PARTICIPANTS: Seven patients with primary insomnia and 7 sex-, age-, and IQ-matched healthy controls. INTERVENTIONS: Subjects spent 1 night in the sleep laboratory with polysomnographic monitoring. Performance on a mirror tracing task was measured before and after sleep. MEASUREMENTS AND RESULTS: Polysomnography revealed a trend toward disturbed sleep in the patients, compared with the control group, without reaching significance. Performance in the mirror tracing task before sleep did not differ between the groups. Both groups performed significantly better in the retest condition after sleep. Healthy controls showed an improvement of 42.8% +/- 5.8% in the mirror tracing draw time, whereas patients with insomnia showed an improvement of 20.4% +/- 14.8% (multivariate analyses of variance test session x group interaction: F(3,10) = 10.9, p = .002). CONCLUSIONS: These preliminary findings support the view that sleep-associated consolidation of procedural memories may be impaired in patients with primary insomnia.