OS_16.1 - Impaired implicit sequence learning under dual task conditions in freezing of gait patients

Vandenbossche, J. ^{1, 2} , Deroost, N. ¹ , Soetens, E. ¹ , Coomans, D. ¹ , Nieuwboer, A. ³ & Kerckhofs, E. ^{1, 2}

1 Cognitive Psychology, Vrije Universiteit Brussel, Brussels, Belgium
2 Neurological Rehabilitation, Vrije Universiteit Brussel, Brussels, Belgium
3 Rehabilitation Sciences, Katholieke Universiteit Leuven, Leuven, Belgium

We examined whether implicit sequence learning, with or without additional working memory load, is impaired in patients with freezing of gait (FOG), a major disturbing symptom in Parkinson’s disease (PD). Fourteen freezers, 14 non-freezers and 14 matched healthy controls performed a serial reaction time (SRT) task with a deterministic stimulus sequence under single (SRT-ST) and dual task (SRT-DT) conditions. The increase in reaction times for random as compared to sequenced trials was used as a measure of implicit sequence learning. Scales for Outcomes in PD-cognition (SCOPA-COG) and tests for cognitive flexibility and set shifting were used as neuropsychological measures of cognitive functioning. Only non-freezers and healthy controls showed significant implicit sequence learning effects, whereas freezers only demonstrated a tendency to learn sequence-specific information in the SRT-ST task. In the SRT-DT task, no sequence learning occurred in FOG. Set-shifting and cognitive flexibility did not correlate with SRT learning, however, scores on the revised Freezing Of Gait Questionnaire (NFOGQ), assessing the severity of FOG, correlated positively with SRT-DT task performance. These results show that implicit sequence learning under dual task conditions is impaired in freezers, and provide more insight into the mechanisms of compensation for deficient motor automaticity in FOG.