Lateralisation of striatal function: evidence from 18F-dopa PET in Parkinson’s disease
- 1Medical Research Council Clinical Sciences Centre, and Division of Neuroscience, Faculty of Medicine, Imperial College, Hammersmith Hospital, London, UK
- 2Cambridge Centre for Brain Repair and Department of Neurology, Cambridge, UK
- 3Department of Experimental Psychology, University of Cambridge, Cambridge, UK
- 4Medical Research Council Cognition and Brain Sciences Unit, Cambridge, UK
- Correspondence to: Dr A Cheesman Medical Research Council Clinical Sciences Centre, Imperial College, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK;
- Received 29 September 2004
- Accepted 18 December 2004
- Revised 1 December 2004
Objectives: The aetiology of the cognitive changes seen in Parkinson’s disease (PD) is multifactorial but it is likely that a significant contribution arises from the disruption of dopaminergic pathways. This study aimed to investigate the contribution of the dopaminergic system to performance on two executive tasks using 18F-6-fluorodopa positron emission tomography (18F-dopa PET) in PD subjects with early cognitive changes.
Methods: 16 non-demented, non-depressed PD subjects were evaluated with the Tower of London (TOL) spatial planning task, a verbal working memory task (VWMT) and 18F-dopa PET, all known to be affected in early PD. Statistical parametric mapping (SPM) localised brain regions in which 18F-dopa uptake covaried with performance scores. Frontal cortical resting glucose metabolism was assessed with 18F-fluoro-2-deoxy-d-glucose (18F-FDG) PET.
Results: SPM localised significant covariation between right caudate 18F-dopa uptake (Ki) and TOL scores and between left anterior putamen Ki and VWMT performance. No significant covariation was found between task scores and 18F-dopa Ki values in either limbic or cortical regions. Frontal cortical glucose metabolism was preserved in all cases.
Conclusions: These findings support a causative role of striatal dopaminergic depletion in the early impairment of executive functions seen in PD. They suggest that spatial and verbal executive tasks require integrity of the right and left striatum, respectively, and imply that the pattern of cognitive changes manifest by a patient with PD may reflect differential dopamine loss in the two striatal complexes.
- CMRGlc, cerebral metabolic rate for glucose
- 18F-dopa PET, 18F-6-fluorodopa positron emission tomography
- 18F-FDG, 18F-fluoro-2-deoxy-d-glucose
- Ki, 18F-dopa storage capacity
- PD, Parkinson’s disease
- SPM, statistical parametric mapping
- TOL, Tower of London
- VWMT, verbal working memory task
This project was jointly funded by the Medical Research Council and the Parkinson’s Disease Society, UK.
Competing interests: none declared