Fluid Intelligence and Executive Dysfunction in Progressive Supranuclear Palsy

Abstract Background Fluid intelligence ( g ) contributes to executive‐task performance, but its role in progressive supranuclear palsy (PSP) remains unclear. Objectives To examine whether executive deficits in PSP are explained by reductions in g . Methods Thirty‐five PSP patients, 39 Parkinson's disease (PD) patients and 18 healthy controls underwent neuropsychological assessment. G was derived using principal component analysis from non‐executive cognitive measures. Group differences in executive performance were examined before and after controlling for g . Healthy controls provided contextual comparison. Results In PSP versus PD, differences in phonemic fluency and TMT‐B were no longer significant after controlling for g , whereas WCST categories remained significant. In PSP versus healthy controls, WCST and phonemic fluency remained significant after controlling for g . Sensitivity analyses in cognitively preserved participants showed similar results. Conclusions Executive deficits in PSP are partly associated with reduced g , but cognitive flexibility appears to reflect an additional disease‐related impairment.