The impact of low frequency stimulation of the pedunculopontine nucleus region on reaction time in parkinsonism

Wesley Thevathasan (1) , Peter A Silburn (2) , Helen Brooker (3) , Terry J Coyne (4) , Sadaquate Khan (5) , Steven S Gill (5) , Tipu Z Aziz (6) , Peter Brown (1)

1 Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology
2 Centre for Clinical Research, Royal Brisbane and Womens Hospital, University of Queensland
3 Cognitive Drug Research Ltd, Goring-on-Thames
4 St Andrews and Wesley Hospitals, Brisbane
5 Institute of Neurosciences, Frenchay Hospital, Bristo
6 University of Oxford

Objectives: Attentional augmentation and enhanced motor function are potential mechanisms by which stimulation of the region of the pedunculopontine nucleus (PPN) may improve gait in parkinsonism. Here we assess the impact of stimulation of this region on attentional and motor aspects of reaction task performance in patients with parkinsonism. Methods: Eleven patients implanted with PPN stimulators underwent computerised assessment of simple, choice and digit vigilance reaction tasks. Patients were assessed ‘off medication' during stimulation at different frequencies (0Hz, 5Hz, 10Hz and ‘therapeutic' 20-35Hz). There were two primary endpoints: ‘Speed of Reaction' (sum of the mean task reaction times) and ‘Accuracy of Reaction' (reflecting omissions and percentage of correct responses). Baseline performance was compared to aged and sex matched healthy controls. Clinical effects of stimulation were assessed using the Unified Parkinson's Disease Rating Scale and a falls frequency scale. Results: Compared with healthy controls, subjects had significant deficits in ‘Speed of Reaction' and in all mean task reaction times. ‘Accuracy of Reaction' was not different to healthy controls and did not improve with stimulation. ‘Speed of Reaction' significantly improved with stimulation at therapeutic frequencies (20-35Hz). Of the individual tasks, only simple reaction time significantly improved. Simple reaction time distribution analysis revealed a general speeding of responses rather than a selective reduction in outliers. Acute PPN stimulation improved gait and balance but not akinesia scores. Chronic PPN stimulation significantly improved falls frequency. Falls score improvement significantly correlated with changes to simple reaction time with therapeutic stimulation. Conclusion: The pattern of reaction time improvement with stimulation of the PPN area suggests a benefit on motor performance, rather than augmentation of attention.

Mots clés: ELECTRICAL STIMULATION; MOTOR PHYSIOLOGY; PARKINSON'S DISEASE

Wesley Thevathasan, Peter A Silburn, Helen Brooker, Terry J Coyne, Sadaquate Khan, et al.. The impact of low frequency stimulation of the pedunculopontine nucleus region on reaction time in parkinsonism. Journal of Neurology, Neurosurgery and Psychiatry, 2010, 81 (10), pp.1099. ⟨10.1136/jnnp.2009.189324⟩. ⟨hal-00557411⟩