Lack of LTP-like plasticity in primary motor cortex in Parkinson's disease

• Published in: Experimental neurology Vol. 227; no. 2; pp. 296 - 301
• Main Authors: Suppa, A., Marsili, L., Belvisi, D., Conte, A., Iezzi, E., Modugno, N., Fabbrini, G., Berardelli, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.02.2011; Elsevier
• Subjects: Aged; Aged, 80 and over; Biological and medical sciences; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dyskinesias; Electromyography - methods; Female; Humans; Long-Term Potentiation - physiology; Male; Medical sciences; Middle Aged; Motor Cortex - physiology; Neurology; Neuronal Plasticity - physiology; Parkinson Disease - physiopathology; Parkinson's disease; Plasticity; Primary motor cortex; TMS; Transcranial Magnetic Stimulation - methods; Dyskinesias; PAS; Parkinson's disease; M1; TDCS; LTP; FDI; cTBS; STP; LIDs; ANOVA; Plasticity; NMDA; UPDRS; EMG; MEPs; TBS; AMT; UDysRS; iTBS; Primary motor cortex; PD; SNr; RMT; H&Y; MVC; TMS; LTD; rTMS; Nervous system diseases; Motor pathway; Central nervous system; Parkinson disease; Encephalon; Involuntary movement; Cerebral disorder; Motor cortex; Central nervous system disease; Degenerative disease; Neurological disorder; Extrapyramidal syndrome; Dyskinesia
• ISSN: 0014-4886; 1090-2430; 1090-2430
• DOI: 10.1016/j.expneurol.2010.11.020

In this study in patients with Parkinson's disease (PD), off and on dopaminergic therapy, with and without L-dopa-induced dyskinesias (LIDs), we tested intermittent theta-burst stimulation (iTBS), a technique currently used for non-invasively inducing long-term potentiation (LTP)-like plasticity in primary motor cortex (M1). The study group comprised 20 PD patients on and off dopaminergic therapy (11 patients without and 9 patients with LIDs), and 14 age-matched healthy subjects. Patients had mild-to-moderate PD, and no additional neuropsychiatric disorders. We clinically evaluated patients using the Unified Parkinson's Disease Rating Scale (UPDRS) and the Unified Dyskinesia Rating Scale (UDysRS). The left M1 was conditioned with iTBS at 80% active motor threshold intensity. Twenty motor evoked potentials (MEPs) were recorded from right first interosseous muscle before and at 5, 15 and 30 min after iTBS. Between-group analysis of variance (ANOVA) testing healthy subjects versus patients with and without LIDs, on and off therapy showed a significant interaction between factors “Group” and “Time”. After iTBS, MEP amplitudes in healthy subjects increased significantly at 5, 15 and 30 min (p < 0.01 at all time-points) but in PD patients with and without LIDs, on and off therapy, remained unchanged. In PD patients with and without LIDs, on and off therapy iTBS fails to increase MEP responses. This finding suggests lack of iTBS-induced LTP-like plasticity in M1 in PD regardless of patients' clinical features. ► Reduced LTP-like plasticity in primary motor cortex in Parkinson's disease. ► L-dopa leaves the reduced LTP-like plasticity in Parkinson's disease unchanged. ► Reduced LTP-like plasticity is present in patients with and without dyskinesias.