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Counterfactual cognitive deficit in persons with Parkinson’s disease

Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA

Correspondence to:
Correspondence to:
Dr Patrick McNamara, Department of Neurology (127), VA New England Healthcare System, 150 South Huntington Avenue, Boston, MA 02130, USA;
mcnamar{at}bu.edu

Objective: To test the hypothesis that counterfactual thinking is impaired in some patients with Parkinson’s disease and is linked to frontal dysfunction in these patients.

Methods. Measures of counterfactual processing and frontal lobe functioning were administered to 24 persons with Parkinson’s disease and 15 age matched healthy controls.

Results. Patients with Parkinson’s disease spontaneously generated significantly fewer counterfactuals than controls despite showing no differences from controls on a semantic fluency test; they also performed at chance levels on a counterfactual inference test, while age matched controls performed above chance levels on this test. Performance on both the counterfactual generation and inference tests correlated significantly with performance on two tests traditionally linked to frontal lobe functioning (Stroop colour–word interference and Tower of London planning tasks) and one test of pragmatic social communication skills.

Conclusions: Counterfactual thinking is impaired in Parkinson’s disease. This impairment may be related to frontal lobe dysfunction.

Keywords: counterfactual thinking; Parkinson’s disease; frontal lobe; executive function

Abbreviations: CIT, counterfactual inference test; DSM-III, Diagnostic and Statistical Manual of Mental Disorders, 3rd ed; MMSE, mini-mental state examination; TAS, total achievement score; TOL, Tower of London task; VTA, ventral tegmental area; WAIS, Wechsler adult intelligence scale