Fig. 2

Abnormal SICI in PD patients. Example of recordings from representative subjects are shown in a. The top row represents the recordings with test stimulus alone and other five rows are recordings for paired-pulse stimulation at different interstimulus intervals. SICI was tested at the interstimulus intervals where short interval intracortical facilitation was at its peaks and troughs. An additional interval of 1 ms was also tested. Note that SICI was decreased at facilitatory peaks and troughs in the PD OFF medication state, and this was normalized in the PD ON state. The group data analysis is shown in b. The abscissa indicates the interstimulus interval. The ordinate indicates the degree of SICI. It represents the amplitude of paired-pulse induced MEP expressed as a percentage of the MEP amplitude induced by test stimulus alone. Values more than 100 % indicate facilitation and those less than 100 % indicate inhibition. Filled circles indicate MEP in PD patients OFF medication. Triangles indicate MEP in PD patients ON medication. Open circles indicate MEP in healthy controls. * p < 0.05, ** p < 0.01, comparing PD OFF to control. # p < 0.05, comparing PD OFF to PD ON. “S” p < 0.05, comparing PD ON to control. SICI was reduced in PD OFF compared to controls at an ISI of 1 ms, at short interval intracortical facilitation peak 1, trough 1, peak 2 and peak 3. Reduced SICI in PD OFF compared to PD ON group was only found at facilitatory peaks. SICI for PD ON was still decreased compared to controls at ISI of 1 ms and at facilitatory trough 1. MEP = motor evoked potential, PD = Parkinson’s disease, SICI = short interval intracortical inhibition. Modified from Ni et al., Increased motor cortical facilitation and decreased inhibition in Parkinson disease, Neurology 2013, 80:1746-1753 [11]. Promotional and commercial use of the material in print, digital or mobile device format is prohibited without the permission from the publisher Wolters Kluwer Health. Please contact healthpermissions@wolterskluwer.com for further information