Impaired long-term potentiation-like motor cortical plasticity in progressive supranuclear palsy

To elucidate long-term potentiation (LTP)-like effects on the primary motor cortical (M1) in progressive supranuclear palsy (PSP) and its relationships with clinical features.

Participants were 18 probable/possible PSP Richardson syndrome (PSP-RS) patients and 17 healthy controls (HC). We used quadripulse stimulation (QPS) over the M1 with an interstimulus interval of 5 ms (QPS-5) to induce LTP-like effect and analyzed the correlations between the degree of LTP-like effect and clinical features. We also evaluated cortical excitability using short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and short interval intracortical facilitation (SICF) in 15 PSP patients and 17 HC.

LTP-like effect after QPS in PSP was smaller than HC and negatively correlated with Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) score, especially bradykinesia, but not with either age or any scores of cognitive functions. The SICI was abnormally reduced in PSP, but neither ICF nor SICF differed from those of normal subjects. None of these cortical excitability parameters correlated with any clinical features.

LTP induction was impaired in PSP. The degree of LTP could reflect the severity of bradykinesia. The bradykinesia may partly relate with the motor cortical dysfunction.

The degree of motor cortical LTP could relate with the severity of motor symptoms in PSP.