Short-interval intracortical inhibition (SICI), intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF)were assessed in the cortical motor area of the first dorsal interosseous muscle (FDI) of 16 healthy subjects. Paired-pulse TMS was delivered to the left hemisphere at the following interstimulus intervals (ISIs): 2 and 3 ms for SICI, 10 and 15 ms for ICF and 1-5 ms for SICF. Motor-evoked potentials were recorded from the resting and active right FDI. The effects exerted on SICI and ICF by four intensities (60-90% of active motor threshold, AMT) of the conditioning stimulus (S1) and by three levels of muscle contraction (10%, 25%, 50% of maximal voluntary contraction, MVC) were evaluated. The effects exerted on SICF were evaluated with two intensities (90% and 70% of AMT) of the test stimulus (S2) and with the same levels of muscle contraction. Results showed that: (i) during 10% MVC, maximum SICI was observed with S1 = 70% AMT; (ii) the amount of SICI obtained with S1 = 70% AMT was the same at rest as during 10% MVC, but decreased at higher contraction levels; (iii) ICF was observed only at rest with S1 = 90% AMT; (iv) SICF was facilitated at 10% and 25% MVC, but not at 50% MVC. We conclude that during muscle activation, intracortical excitability reflects a balance between activation of SICI and SICF systems. Part of the reduction in SICI during contraction is due to superimposed recruitment of SICF. Low intensity (70% AMT) conditioning stimuli can test SICI independently of effects on SICF at low contraction levels.

Interhemispheric interactions between the primary motor cortices (M1) have been described with a variety of TMS methods. Here we give a detailed description of the interhemispheric interactions of a period of theta burst simulation (TBS), a rapid method of producing long lasting after-effects on the excitability of the stimulated M1. A total of 18 right handed healthy subjects participated. In most experiments, continuous and intermittent TBS (cTBS and iTBS) were delivered over the right M1 using a coil orientated to induce antero-posterior followed by postero-anterior (AP-PA) currents in the brain. The intensity of stimulation was 80% of active motor threshold (AMT), and a total of 600 pulses were applied. The effects on the amplitude of motor evoked potentials (MEPs), short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were evaluated in the left and right M1 before and at three different times after TBS. We also tested long-interval intracortical inhibition (LICI) in right M1 and interhemispheric inhibition (IHI) from right to left M1. Finally, to explore the effect of different polarities of cTBS over dominant and non-dominant hemisphere we delivered AP-PA and postero-anterior followed by antero-posterior (PA-AP) cTBS over either right or left M1 and tested MEPs in both hemispheres. In the stimulated hemisphere, cTBS reduced MEPs and SICI whereas iTBS increased MEPs and SICI. In the non-stimulated hemisphere cTBS increased MEPs and reduced SICI, while iTBS reduced MEPs and increased SICI. There were no effects on ICF, LICI or IHI. Although both AP-PA cTBS and PA-AP cTBS reduced MEPs in the stimulated M1, the former increased MEPs from non-stimulated M1 whereas the latter did not. There was no difference in the effect of cTBS on the dominant or non-dominant hemisphere.

Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.

Abstract. OBJECTIVE:To explore the effects of Dance Therapy (DT) and Traditional Rehabilitation (TR) on both motor and cognitive domains in Parkinson's Disease patients (PD) with postural instability. METHODS: Sixteen PD patients with recent history of falls were divided in two groups (Dance Therapy, DT and Traditional Rehabilitation, TR); nine patients received 1-hour DT classes twice per week, completing 20 lessons within 10 weeks; seven patients received a similar cycle of 20 group sessions of 60 minutes TR. Motor (Berg Balance Scale -BBS, Gait Dynamic Index -GDI, Timed Up and Go Test -TUG, 4 Square-Step Test -4SST, 6-Minute Walking Test -6MWT) and cognitive measures (Frontal Assessment Battery -FAB, Trail Making Test A & B -TMT A&B, Stroop Test) were tested at baseline, after the treatment completion and after 8-week follow-up. RESULTS: In the DT group, but not in the TR group, motor and cognitive outcomes significantly improved after treatment and retained after follow-up. Significant changes were found for 6MWT (p = 0.028), TUG (p = 0.007), TMT-A (p = 0.014) and TMT-B (p = 0.036). CONCLUSIONS: DT is an unconventional physical therapy for PD patients which effectively impacts on motor (endurance and risk of falls) and non-motor functions (executive functions).

Brainstem degeneration in Parkinson's disease (PD) may explain the occurrence of many non-motor symptoms in this condition. Purposes of the present work were to investigate brainstem function in PD through a battery of vestibular-evoked myogenic potentials (VEMP) allowing a comprehensive brainstem exploration and to correlate VEMP findings with symptoms related to brainstem involvement. Cervical (cVEMP), masseter (mVEMP) and ocular (oVEMP) VEMPs were investigated in 24 PD patients and compared with those recorded in 24 age-matched controls. Presence of symptoms ascribable to brainstem dysfunction, such as daytime sleepiness, REM sleep behavior disorder and depression, was investigated through Epworth Sleepiness Scale, Parkinson's Disease Sleep Scale, REM Sleep Disorder Screening Questionnaire (RBD-SQ) and Geriatric Depression Scale. Postural instability was additionally assessed through mini-BESTest. The frequency of alteration of VEMPs in patients was 83.3 % when considering the whole set and 41.7 % for cVEMP, 66.7 % for mVEMP and 45.8 % for oVEMP. This was significantly different from controls, with absence being the prevalent alteration in PD. A significant inverse correlation between the number of altered VEMPs and mini-BESTest and a direct correlation with RBD-SQ were found. The VEMP battery under study allowed the identification of brainstem dysfunctions in PD patients, which correlated with clinical tests suggestive of postural and REM sleep disorders. VEMPs might represent a valuable tool of brainstem assessment in PD.

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Averaged responses to loud clicks were recorded in the unrectified and rectified masseter electromyogram (EMG) of 18 healthy subjects. Unilateral clicks (0.1 ms, 3 Hz, 70-100 dB NHL), delivered during a steady masseter contraction, evoked bilateral responses that appeared to consist of 2 components on the basis of threshold, latency, and their appearance in rectified EMG. The lowest threshold response appeared as a p16 wave (onset 11-13 ms) in the unrectified EMG and corresponded with a 10- to 12-ms period of inhibition in the rectified EMG. Higher-intensity clicks recruited an earlier p11 response in the unrectified EMG (onset 7.0-9.2 ms) that sometimes appeared as an initial increase in the rectified EMG before suppression. The amplitude of the p11 wave scaled with background EMG level and was asymmetrically modulated by 30 degrees tilt of the whole body. The threshold of the early p11/n15 wave in masseter was the same as the threshold for click-induced vestibulocollic reflexes. Single motor unit recordings demonstrated that responses in masseters corresponded to a silent period in unit firing that began earlier and lasted longer at 100 dB than at 80 dB. We propose that loud clicks induce 2 partially overlapping short-latency reflexes in masseter muscle EMG: a p11/n15 response, which we suggest is of vestibular origin, and a p16/n21 response, which we suggest is equivalent to the previously described jaw-acoustic reflex.

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