Michael H. Thaut

Rhythmic auditory-motor facilitation of gait patterns in patients with Parkinson's disease.

OBJECTIVES: The effect of rhythmic auditory stimulation (RAS) on gait velocity, cadence, stride length, and symmetry was studied in 31 patients with idiopathic Parkinsons disease, 21 of them on (ON) and 10 off medication (OFF), and 10 healthy elderly subjects. METHOD: Patients walked under four conditions: (1) their own maximal speed without external rhythm; (2) with the RAS beat frequency matching the baseline cadence; (3) with RAS 10% faster than the baseline cadence; (4) without rhythm to check for carry over from RAS. Gait data were recorded via a computerised foot switch system. The RAS was delivered via a 50 ms square wave tone embedded in instrumental music (Renaissance style) in 2/4 metre prerecorded digitally on a sequencer for variable tempo reproduction. Patients on medication were tested in the morning 60-90 minutes after medication. Patients off medication were tested at the same time of day 24 hours after the last dose. Healthy elderly subjects were tested during the same time of day. RESULTS: Faster RAS produced significant improvement (P < 0.05) in mean gait velocity, cadence, and stride length in all groups. Close synchronisation between rhythm and step frequency in the controls and both Parkinsons disease groups suggest evidence for rhythmic entrainment mechanisms even in the presence of basal ganglia dysfunction. CONCLUSIONS: The results are consistent with and extend prior reports of rhythmic auditory facilitation in Parkinsons disease gait when there is mild to moderate impairment, and suggest a technique for gait rehabilitation in Parkinsons disease.

Comparison of linear, nonlinear, and feature selection methods for EEG signal classification

The reliable operation of brain-computer interfaces (BCIs) based on spontaneous electroencephalogram (EEG) signals requires accurate classification of multichannel EEG. The design of EEG representations and classifiers for BCI are open research questions whose difficulty stems from the need to extract complex spatial and temporal patterns from noisy multidimensional time series obtained from EEG measurements. The high-dimensional and noisy nature of EEG may limit the advantage of nonlinear classification methods over linear ones. This paper reports the results of a linear (linear discriminant analysis) and two nonlinear classifiers (neural networks and support vector machines) applied to the classification of spontaneous EEG during five mental tasks, showing that nonlinear classifiers produce only slightly better classification results. An approach to feature selection based on genetic algorithms is also presented with preliminary results of application to EEG during finger movement.

The connection between rhythmicity and brain function

We first present some clinical research results involving rhythmic facilitation and motor control. We then discuss synchronization strategies for sensorimotor coupling pertaining to rhythmic entrainment mechanisms; followed by trajectory cuing and optimization models as they relate to rhythmic entrainment and movement control; and, finally, the outlook for applications that may help rehabilitate motor function. Our interest in the study of the connections between rhythm, time, and the control of movement was stimulated from three directions: (a) the study of high-level motor control in musicians and the effect of rhythmic cues on muscle activity in cello performance; (b) the evidence that auditory rhythmic patterns exert a strong magnet effect on the timing of motor responses; and (c) the clinical observation that music-therapy techniques that were originally designed for socio-emotional needs elicited motor responses in neurologically impaired patients that were not readily accessible by other therapies.

Neural Basis of Rhythmic Timing Networks in the Human Brain

Abstract: The study of rhythmicity provides insights into the understanding of temporal coding of music and temporal information processing in the human brain. Auditory rhythms rapidly entrain motor responses into stable steady synchronization states below and above conscious perception thresholds. Studying the neural dynamics of entrainment by measuring brain wave responses (MEG) we found nonlinear scaling of M100 amplitudes generated in primary auditory cortex relative to changes in the period of the rhythmic interval during subliminal and supraliminal tempo modulations. In recent brain imaging studies we have described the neural networks involved in motor synchronization to auditory rhythm. Activated regions include primary sensorimotor and cingulate areas, bilateral opercular premotor areas, bilateral SII, ventral prefrontal cortex, and, subcortically, anterior insula, putamen, and thalamus. Within the cerebellum, vermal regions and anterior hemispheres ipsilateral to the movement became significantly activated. Tracking temporal modulations additionally activated predominantly right prefrontal, anterior cingulate, and intraparietal regions as well as posterior cerebellar hemispheres. Furthermore, strong evidence exists for the substantial benefits of rhythmic stimuli in rehabilitation training with motor disorders.

Components of EMG symmetry and variability in parkinsonian and healthy elderly gait

Variability and bilateral symmetry of EMG gait-cycle profiles were studied in parkinsonian and healthy elderly subjects in the gastrocnemius, tibialis anterior, and vastus lateralis muscles. Components reflecting shape and timing were defined by the magnitude and phase of the cross-correlation function between individual stride profiles and the latency corrected ensemble average (LCEA) (variability), and between bilateral LCEAs (symmetry). Statistical significance was set at a confidence level of 0.01 reflecting a Bonferroni adjustment due to multiple measures. Parkinsonian gait was significantly different from the healthy elderly in several measures: increased shape variability and asymmetry in the gastrocnemius and tibialis anterior muscles, and reduced timing variability in the gastrocnemius. A portion of the parkinsonian group participated in a 3 week therapy program where they walked to rhythmic auditory stimulation. Gait parameters shifted toward healthy elderly values in each measure where population differences were found. Significant changes were observed in decreased tibialis anterior shape variability and asymmetry, and gastrocnemius shape variability. Strong trends were also observed in increased gastrocnemius timing variability and reduced bilateral asymmetry. In addition to the expected decreased in variability and asymmetry of healthy elderly, increased timing variability in the gastrocnemius was associated with a more normal gait, possibly reflecting feedback adaptability of muscle activity which may be useful in generating stable locomotion.

Kinematic optimization of spatiotemporal patterns in paretic arm training with stroke patients.

The effect of rhythmic cueing on spatiotemporal control of sequential reaching movements of the paretic arm was studied in 21 hemispheric stroke patients. Reaching movements were studied with and without rhythmic metronome cuing in a counterbalanced design. Metronome frequencies were entrained to the naturally selected frequency of the patient. Results indicate statistically significant (P<0.05) improvements of spatiotemporal arm control during rhythmic entrainment. Variability of timing and reaching trajectories were reduced significantly. Time series analysis of sequential movement repetitions showed an immediate reduction in variability of arm kinematics during rhythmic entrainment within the first two to three repetitions of each trial. Rhythm also produced significant increases in angle ranges of elbow motion (P<0.05). Analysis of acceleration and velocity profiles of the wrist joint showed significant kinematic smoothing during rhythmic cuing. The link between rhythmic sensory timing and spatiotemporal motor control was investigated using a mathematical optimization model with minimization of peak acceleration as criterion. Rhythmically cued acceleration profiles fit the predicted model data significantly closer (P<0.01) than the self-paced profiles. Since velocity and acceleration are mathematical derivatives of position-time trajectories, the model data suggest that enhanced timing precision via temporal phase and period coupling of the motor pattern to the rhythmic time timekeeper enhances the brains computational ability to optimally scale movement parameters across time.

Multiple synchronization strategies in rhythmic sensorimotor tasks: phase vs period correction

Abstract. To characterize synchronisation strategies in the tracking of auditory rhythm with rhythmic finger tapping, the adaptation process after unexpected step changes of an interstimulus interval (ISI) of 500 ms was investigated. Step changes of 2% (10 ms), 4% (20 ms), and 10% (50 ms) of ISI were applied to the stimulus sequence. Synchronisation patterns of 5 subjects were analyzed based on synchronisation error (SE) and interresponse intervals (IRI). A strategy shift contigent upon the size of the introduced step change was detected. After small ISI changes, rapid IRI matching to the new ISI was accompanied by temporarily enlarged SE values, which slowly returned to preferred SE values before the step change. Large ISI changes showed quick SE adaptations accompanied by a temporary overcorrection of IRI. Response asymmetry between ISI decreases and increases emerged, showing a stronger adaptation during ISI increases. A two-dimensional difference equation was formulated to simulate the time series of intertap intervals and explain the control process during IRI and SE adjustments. The system constants were optimized to minimalize the deviations between the computed and the observed response trajectories, consisting of the time series of SE and IRI. It was shown that a successful model fit using a linear two-dimensional difference equation was based on the size and direction of the ISI changes. MANOVA procedures showed that differences in equation parameters during small and large step changes were statistically significant (P<0.05). It is therefore suggested that a uniform model accounting for synchronization responses to all step changes would require the introduction of nonlinear system properties.

Effect of auditory rhythmic cuing on gait kinematic parameters of stroke patients

Abstract The emotional and psychological benefits of musical experiences for human behavior are well documented by research in music therapy and psychology of music. It is also documented that music and rhythm have been utilized universally to accompany motor activity. The effect, however, of music and rhythm on motor activity including mechanics of hemiparetic gait has not been investigated. The purpose of this study was to investigate the effect of auditory rhythmic cuing on gait kinematic parameters of stroke patients. Eight subjects were studied over three trials. For each trial, a baseline walk without rhythm and a walk with rhythm as pacemaker, matched to the step cadence of the baseline walk, was videotaped with two 60 Hz videocameras. Three dimensional coordinates of ten body points were calculated by combining the images of the two cameras utilizing the direct linear transformation (DLT) method. The raw position data was digitally smoothed before being submitted to further analysis. Repeated measures ANOVA and paired t-tests revealed positive modifications in gait patterns due to musical rhythmic cues; specifically: (1) the stride lengths and hip joint range of motion (ROM) of the affected/non-affected sides became more symmetrical; and (2) center of mass (CM) vertical displacement decreased. These results support the presence of an entrainment effect of auditory rhythmic cuing on hemiparetic gait.

Neurologic music therapy improves executive function and emotional adjustment in traumatic brain injury rehabilitation.

This study examined the immediate effects of neurologic music therapy (NMT) on cognitive functioning and emotional adjustment with brain‐injured persons. Four treatment sessions were held, during which participants were given a pre‐test, participated in 30 min of NMT that focused on one aspect of rehabilitation (attention, memory, executive function, or emotional adjustment), which was followed by post‐testing. Control participants engaged in a pre‐test, 30 min of rest, and then a post‐test. Treatment participants showed improvement in executive function and overall emotional adjustment, and lessening of depression, sensation seeking, and anxiety. Control participants improved in emotional adjustment and lessening of hostility, but showed decreases in measures of memory, positive affect, and sensation seeking.

Conscious and subconscious sensorimotor synchronization--prefrontal cortex and the influence of awareness.

One of the most compelling challenges for modern neuroscience is the influence of awareness on behavior. We studied prefrontal correlates of conscious and subconscious motor adjustments to changing auditory rhythms using regional cerebral blood flow measurements. At a subconscious level, movement adjustments were performed employing bilateral ventral mediofrontal cortex. Awareness of change without explicit knowledge of the nature of change led to additional ventral prefrontal and premotor but not dorsolateral prefrontal activations. Only fully conscious motor adaptations to a changing rhythmic pattern showed prominent involvement of anterior cingulate and dorsolateral prefrontal cortex. These results demonstrate that while ventral prefrontal areas may be engaged in motor adaptations performed subconsciously, only fully conscious motor control which includes motor planning will involve dorsolateral prefrontal cortex.