Abnormal experimentally- and behaviorally-induced LTP-like plasticity in focal hand dystonia

• Published in: Experimental neurology 2013-02, Vol.240, p.64-74
• Main Authors: Belvisi, Daniele, Suppa, Antonio, Marsili, Luca, Di Stasio, Flavio, Parvez, Ahmad Khandker, Agostino, Rocco, Fabbrini, Giovanni, Berardelli, Alfredo
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Diseases of striated muscles. Neuromuscular diseases; Dystonia; Dystonic Disorders - physiopathology; Early motor learning; Evoked Potentials, Motor - physiology; Female; Hand - innervation; Hand - physiopathology; Humans; Long-Term Potentiation - physiology; Male; Medical sciences; Middle Aged; Motor Cortex - physiology; Motor Cortex - physiopathology; Neurology; Neuronal Plasticity - physiology; Plasticity; Primary motor cortex; TMS; Transcranial Magnetic Stimulation - methods; Young Adult
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2012.11.003

Idiopathic focal hand dystonia (FHD) arises from abnormal plasticity in the primary motor cortex (M1) possibly reflecting abnormal sensori-motor integration processes. In this transcranial magnetic stimulation (TMS) study in FHD, we evaluated changes in motor evoked potentials (MEPs) after intermittent theta burst stimulation (iTBS) and paired associative stimulation (PAS), techniques that elicit different forms of experimentally-induced long-term potentiation (LTP)-like plasticity in M1. We also examined behaviorally-induced LTP-like plasticity as reflected by early motor learning of a simple motor task. We studied 14 patients with FHD and 14 healthy subjects. MEPs were recorded before and after iTBS and PAS at the 25ms interstimulus interval (PAS25) in separate sessions. Subjects did a simple motor task entailing repetitive index finger abductions. To measure early motor learning we tested practice-related improvement in peak velocity and peak acceleration. In FHD patients iTBS failed to elicit the expected MEP changes and PAS25 induced abnormally increased MEPs in target and non-target muscles. In the experiment testing early motor learning, patients lacked the expected practice-related changes in kinematic variables. In FHD, the degree of early motor learning correlated with patients' clinical features. We conclude that experimentally-induced (iTBS and PAS) and behaviorally-induced LTP-like plasticity are both altered in FHD. ► In FHD LTP-like plasticity is abnormal (reduced after iTBS and increased after PAS25). ► FHD reduces early motor learning and motor retention. ► Simple writer's cramp patients move faster than dystonic writer's cramp patients. ► The degree of early motor learning correlates with dystonia duration and severity. ► Experimentally- and behaviorally-induced LTP-like plasticity are altered in FHD.