The role of Basal ganglia circuits in data processing is unknown. They are widely distributed and share a common structure despite serving a range of data modalities. It is likely that basal ganglia circuits perform a data processing task that can apply to any data modality. One universal data processing task is the separation of signal from background noise. Patients with advanced Parkinson’s disease without dementia represent a unique model to study the data processing role of basal ganglia circuits. The same individual within one dose cycle experiences dramatic changes in the state of basal ganglia activity making it possible to create an internally controlled experiment.
Face and voice recognition amongst distractors were tested in 16 advanced Parkinsons patients with motor fluctuations and no evidence of dementia. Similar tests were administered in the same patients when mobile and dyskinetic ‘ON’ or rigid and akinetic ‘OFF’ within one dose cycle.
A criterion shift was observed between states. When ‘ON’ patients had a more liberal criterion then when ‘OFF’ (p<0.00001) and when compared to age matched controls, in both face and voice recognition tests. When ‘OFF’ patients had a more conservative criterion than controls in the face recognition test (p<0.01). Accuracy was similar whether ‘OFF’ or ‘ON’ but less than controls (p<0.01)
This criterion shift may explain a variety of published results of cognitive deficits in non demented Parkinson’s patients, and has implications for understanding data processing within basal ganglia circuits.