P. Vanni

Mechanisms underlying mirror movements in Parkinson's disease: A transcranial magnetic stimulation study

The neural mechanisms underlying unintended mirror movements (MMs) of one hand during unimanual movements of the other hand in patients with Parkinsons disease (PD) are largely unexplored. Here we used surface electromyographic (EMG) analysis and focal transcranial magnetic stimulation (TMS) to investigate the pathophysiological substrate of MMs in four PD patients. Surface EMG was recorded from both abductor pollicis brevis (APB) and first dorsal interosseous (FDI) muscles. Cross‐correlation EMG analysis revealed no common motor drive to the two APBs during intended unimanual tasks. Focal TMS of either primary motor cortex (M1) elicited normal motor‐evoked potentials (MEPs) in the contralateral APB, whereas MEPs were not seen in the ipsilateral hand. During either mirror or voluntary APB contraction, focal TMS of the contralateral M1 produced a long‐lasting silent period (SP), whereas stimulation of the ipsilateral M1 produced a short‐lasting SP. During either mirror or voluntary finger tapping, 5 Hz repetitive TMS (rTMS) of the contralateral M1 disrupted EMG activity in the target FDI, whereas the effects of rTMS of the ipsilateral M1 were by far slighter. During either mirror or voluntary APB contraction, paired‐pulse TMS showed a reduction of short‐interval intracortical inhibition in the contralateral M1. These findings provide converging evidence that, in PD, MMs do not depend on unmasking of ipsilateral projections but are explained by motor output along the crossed corticospinal projection from the mirror M1.

Surface electromyography shows increased mirroring in Parkinson's disease patients without overt mirror movements

Patients with Parkinsons disease (PD) may present mirror movements (MM). Transcranial magnetic stimulation data indicate that these movements reflect an abnormal enhancement of the “physiological mirroring” that can be observed in healthy adults during complex and effortful tasks. It was hypothesized that, in PD, enhanced mirroring is caused by a failure of basal ganglia output to support the cortical network that is responsible for the execution of strictly unimanual movements. If so, it is likely that subtle alterations of voluntary unimanual motor control are also present in PD patients without overt MM. We tested this hypothesis by using surface electromyographic (EMG) techniques in 12 mildly to moderately affected PD patients without overt MM, and in 2 control groups (12 age‐matched and 10 young healthy volunteers). Subjects performed unilateral phasic thumb abduction during a sustained tonic contraction of the opposite abductor pollicis brevis. All patients were tested on dopaminergic therapy. On a separate day, 7 of 12 patients were re‐tested after withdrawal of medication. During this task, involuntary mirror‐like increase in surface EMG of the tonically abducting thumb was significantly larger in PD patients than in age‐matched or young healthy volunteers. Off therapy, mirroring was slightly greater than on medication, although this difference was not significant. Our findings suggest that dysfunction of unimanual motor control is a general feature of PD. It is likely that this deficient movement lateralization contributes to an impairment of nonsymmetrical bimanual movements in PD.

Automatic identification of dysprosody in idiopathic Parkinson's disease

Abstract Parkinsons disease (PD) involves impairments of voice and speech (hypokinetic dysarthria). Dysprosody is one of the most common features of PD speech that includes alterations of rhythm and velocity of articulation. The aim of this study is the evaluation of dysprosody patterns in Parkinsonian patients during a sentence repetition task by means of a fully automated tool. Twenty PD patients (14 male and 6 female) and 19 healthy controls (9 male and 10 female) were tested. Results show significant differences between the two groups as far as the time interval between each sentence repetition (Tinter), the percent of speech time with respect to sentence duration (D%) and the Net Speech Rate (NSR – defined as the number of syllables of the sentence divided by the effective speech time) are concerned. In particular, Tinter is larger in PD patients while D% is higher in the control group. These results show that PD patients may exhibit longer pauses between each sentence repetition and a lower percentage of “speech time” during a whole repetition period. Thus, the decrease of D% leads to an increase of NSR. Other acoustic parameters (noise and F0 variability) did not show any significant difference. This study confirms that speech in PD patients is characterized by short rushes followed by unorthodox pauses. These results may lead to the development of a system for the automatic acoustic analysis which could significantly reduce the processing time in particular during pre-processing, that to date is a time-consuming and operator-dependent step especially in case of recordings of long duration.

Analysis of facial expressions in parkinson's disease through video-based automatic methods

BACKGROUND The automatic analysis of facial expressions is an evolving field that finds several clinical applications. One of these applications is the study of facial bradykinesia in Parkinsons disease (PD), which is a major motor sign of this neurodegenerative illness. Facial bradykinesia consists in the reduction/loss of facial movements and emotional facial expressions called hypomimia. NEW METHOD In this work we propose an automatic method for studying facial expressions in PD patients relying on video-based METHODS: 17 Parkinsonian patients and 17 healthy control subjects were asked to show basic facial expressions, upon request of the clinician and after the imitation of a visual cue on a screen. Through an existing face tracker, the Euclidean distance of the facial model from a neutral baseline was computed in order to quantify the changes in facial expressivity during the tasks. Moreover, an automatic facial expressions recognition algorithm was trained in order to study how PD expressions differed from the standard expressions. RESULTS Results show that control subjects reported on average higher distances than PD patients along the tasks. COMPARISON WITH EXISTING METHODS This confirms that control subjects show larger movements during both posed and imitated facial expressions. Moreover, our results demonstrate that anger and disgust are the two most impaired expressions in PD patients. CONCLUSIONS Contactless video-based systems can be important techniques for analyzing facial expressions also in rehabilitation, in particular speech therapy, where patients could get a definite advantage from a real-time feedback about the proper facial expressions/movements to perform.

Markerless Analysis of Articulatory Movements in Patients With Parkinson's Disease.

OBJECTIVES A large percentage of patients with Parkinsons disease have hypokinetic dysarthria, exhibiting reduced peak velocities of jaw and lips during speech. This limitation implies a reduction of speech intelligibility for such patients. This work aims at testing a cost-effective markerless approach for assessing kinematic parameters of hypokinetic dysarthria. STUDY DESIGN Kinematic parameters of the lips are calculated during a syllable repetition task from 14 Parkinsonian patients and 14 age-matched control subjects. METHODS Combining color and depth frames provided by a depth sensor (Microsoft Kinect), we computed the three-dimensional coordinates of main facial points. The peak velocities and accelerations of the lower lip during a syllable repetition task are considered to compare the two groups. RESULTS Results show that Parkinsonian patients exhibit reduced peak velocities of the lower lip, both during the opening and the closing phase of the mouth. In addition, peak values of acceleration are reduced in Parkinsonian patients, although with significant differences only in the opening phase with respect to healthy control subjects. CONCLUSIONS The novel contribution of this work is the implementation of an entirely markerless technique capable to detect signs of hypokinetic dysarthria for the analysis of articulatory movements during speech. Although a large number of Parkinsonian patients have hypokinetic dysarthria, only a small percentage of them undergoes speech therapy to increase their articulatory movements. The system proposed here could be easily implemented in a home environment, thus, increasing the percentage of patients who can perform speech rehabilitation at home.

75. Automatic detection of dysprosody patterns in patients with idiopathic Parkinson’s disease

Dysprosody is characterized by alterations of rhythm and speed of speech and represents one of the most frequent alteration of speech in patients with Parkinson’s disease (PD). Our aim was to identify the presence of rhythmic alterations in the parameters related to speech rate in PD patients with no or mild hypophonia during a sentence repetition task. Twenty PD patients (6 women) and 19 healthy controls (10 women) were tested. The task consisted in the repetition of a standardized Italian vocalic sentence (“Il bambino ama le aiuole della mamma”) at least 10 times at comfortable loudness. Audio analysis is based on a newly developed automatic voiced-unvoiced segmentation to calculate net speech rate and the percentage of voiced segments with respect to the sentence duration. The analysis showed that in PD patients the speech is characterized by short rushes followed by inappropriate pauses, as revealed by the reduction of the sentence duration and the increase in net speech rate. PD patients tend to repeat the same sentence in a shorter time period than controls, but with a longer recovery time. Current data suggest that rhythmic alterations of speech may be detectable in patients using a sentence repetition task.