Rhythmic auditory stimulation improves gait more than NDT/Bobath training in near-ambulatory patients early poststroke: a single-blind, randomized trial.

OBJECTIVES: The effectiveness of 2 different types of gait training in stroke rehabilitation, rhythmic auditory stimulation (RAS) versus neurodevelopmental therapy (NDT)/Bobath- based training, was compared in 2 groups of hemiparetic stroke patients over a 3-week period of daily training (RAS group, n = 43; NDT/Bobath group =35). METHODS: Mean entry date into the study was 21.3 days poststroke for the RAS group and 22.3 days for the control group. Patients entered the study as soon as they were able to complete 5 stride cycles with handheld assistance. Patients were closely equated by age, gender, and lesion site. Motor function in both groups was pre-assessed by the Barthel Index and the Fugl-Meyer Scales. RESULTS: Pre- to posttest measures showed a significant improvement in the RAS group for velocity (P = .006), stride length (P = .0001), cadence (P = .0001) and symmetry (P = .0049) over the NDT/Bobath group. Effect sizes for RAS over NDT/Bobath training were 13.1 m/min for velocity, 0.18 m for stride length, and 19 steps/min for cadence. CONCLUSIONS: The data show that after 3 weeks of gait training, RAS is an effective therapeutic method to enhance gait training in hemiparetic stroke rehabilitation. Gains were significantly higher for RAS compared to NDT/Bobath training.

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 brain's computational ability to optimally scale movement parameters across time.

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.

Conscious and preconscious adaptation to rhythmic auditory stimuli: a magnetoencephalographic study of human brain responses.

This study was triggered by the experimental evidence that subjects required to tap in synchrony with a heard rhythm spontaneously time their tapping to variations in rhythm frequency even when these variations are so small that they are not consciously detectable. We performed a series of magnetoencephalographic (MEG) measurements, aimed at investigating whether the response of the auditory cortex discriminates randomly administered series of brief tones differing from each other only by their interstimulus intervals (ISI). Moreover, by combining psychophysical measurements, conscious and preconscious adjustments of tapping to rhythm variations were compared with brain cortical responses. The ISIs were varied by 2% or 20% from a "central" value of 500 ms. Subjects always consciously detected the 20% ISI changes and easily adjusted their tapping accordingly, whereas they never consciously detected the 2% ISI changes, even though they always correctly adjusted their tapping to them. Analysis of the auditory evoked fields (AEFs) showed that the intensity of the M100 component decreased with decreasing ISI both for 20% and 2% variations in a statistically significant manner, despite the fact that the 2% variation was not consciously perceived. The M100 behavior indicated that connections between auditory and motor cortexes may exist that are able to use the information on rhythm variations in the stimuli even when these are not consciously identified by the subject. The ability of the auditory cortex to discriminate different time characteristics of the incoming rhythmic stimuli is discussed in this paper in relation to the theories regarding the physiology of time perception and discrimination.

Analysis of correlations and search for evidence of deterministic chaos in rhythmic motor control by the human brain.

We investigate rhythmic finger tapping in both the presence and the absence of a metronome. We examine both the time intervals between taps and the time lags between the stimulus tones from the metronome and the response taps by the subject. We analyze the correlations in these data sets, and we search for evidence of deterministic chaos, as opposed to randomness, in the fluctuations.

A measure of kinematic limb instability modulation by rhythmic auditory stimulation.

A mathematical method based on computations of residual absolute value sums (RAVS) was developed for the quantitative analysis of tremor-like perturbations of knee angle during the gait cycle. The method was tested on simulation data created by adding sinusoidal tremor of varying frequency and amplitude to the knee-angle graph of a healthy test subject. The method was then applied to compare knee tremor reduction, with and without auditory rhythm, in a group of five traumatically brain-injured patients with gait hemiparesis. Deviations from normal gait performance due to tremor were assessed by using self-comparison to a 17th-degree regression polynomial of each subject's own motion-, time-, and point-normalized knee- angle curve. With rhythmic cueing, the five subjects had a statistically significant RAVS-measured mean tremor reduction of 39.5+/-22.6% (t=-3.91; p=0.017).

Velocity modulation and rhythmic synchronization of gait in Huntington's disease.

This study analyzed the ability of patients with Huntington's disease (HD) to modulate gait velocity without external sensory cues and in response to an auditory rhythmic cue within a frequency entrainment design. Uncued gait patterns of 27 patients were first assessed during normal, slower, and faster self-paced walking. During rhythmic trials, metronome and musical beat patterns were delivered at rates 10% slower and 10-20% faster than baseline cadence to cue gait patterns. After the rhythmic trials, patients were retested at normal gait speed without rhythm. Gait velocities in the patients with HD were below normal reference values in all ranges. Patients were able to significantly (p <0.05) modulate their gait velocity during self-paced and rhythmic metronome cueing but not during music. The ability to modulate gait velocity was retained regardless of the severity of the disease. Gait velocity declined with an increase in disability and chorea score. The disability score differentiated better between gait velocity of moderately and severe patients than chorea score. Slowness of gait was significantly correlated only with disability score and not with chorea. Patients had more difficulty producing adequate step rates than stride lengths during normal and fast walking speeds. After the rhythmic trials, unpaced gait velocity remained significantly (p <0.05) higher than baseline. This carry-over effect was not seen after the uncued trials. Synchronization ability was deficient in all patients, deteriorated with severity of disease, and was already compromised in patients with soft disease signs. Rhythmic tracking of music declined more with severity of disease than metronome tracking. In summary, patients were able to modulate velocity with and without external cues. Velocity adaptations to the external rhythm in music and metronome were achieved without exact synchronization between step cadence and rhythmic stimulus.

Autoregressive moving average modeling for finger tapping with an external stimulus.

We report the Autoregressive Moving Average (ARMA) structures of interresponse interval and interstimulus interval in rhythmic finger tapping and how tapping schemes arise from these structures. The interstimulus interval is chosen to be a metronome cue slightly perturbed from its periodic mode by a zero-mean sine-wave modulated sequence. These metronome sequences were chosen to follow an exact Autoregressive model of the third order and are generated using metronome interval durations of 400, 500, and 600 msec. At each frequency, four different perturbation rates were presented to seven subjects: 1, 3, 5, and 7% of the base interval. Synchronization error, i.e., tap-to-beat phase deviations, induced by these ARMA models are stable and thus were bounded. This framework is useful in characterizing the relationship between motor control variables, interresponse interval, synchronization error, and interstimulus interval. Also, several known models can be easily derived and analyzed in this setting.

The connection between rhythmicity and brain function.

Although rhythm and music are not entirely synonymous terms, rhythm constitutes one of the most essential structural and organizational elements of music. When considering the effect of music on human adaptation, the profound effect of rhythm on the motor system strongly suggests that the time structure of music is the essential element relating music specifically to motor behavior. Why the motor system appears so sensitive to auditory priming and timing stimulation can only be partially answered so far. The high-performance function of the auditory system regarding processing of time information makes good functional sense within the constraints of auditory sensory processing. Thus, the motor system sensitivity to auditory entrainment may simply be an evolutionary useful function of taking advantage of the specific and unique aspects of auditory information processing for enhanced control and organization of motor behavior; e.g, in the time domain. Unlike processes in the motor system, many other physiological processes cannot be effectively entrained by external sensory stimuli. For example, there is probably a very good protective reason why other cyclical physiological processes (e.g., autonomic processes such as heart rate) have only very limited entrainment capacity to external rhythmic cues. Some of the basic auditory-motor arousal connections may also have their basis in adaptive evolutionary processes related to survival behavior; e.g., in fight or flight reactions. Much of the "why" in auditory-motor interactions, however, remains unknown heuristically. In the absence of this knowledge, great care should be taken to not compensate for this lack of understanding of specific cause and effect processes by assigning anthropomorphic descriptions to the behavior of biological and physical systems. The unraveling of the perceptual, physiological, and neuroanatomical basis of the interaction between rhythm and movement has been, and continues to be, a fascinating endeavor with important ramifications for the study of brain function, sensory perception, and motor behavior. One of the most exciting findings in this research, however, may be the evidence that the interaction between auditory rhythm and physical response can be effectively harnessed for specific therapeutic purposes in the rehabilitation of persons with movement disorders.

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

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.

Auditory vs visual speech timing cues as external rate control to enhance verbal intelligibility in mixed spastic-ataxic dysarthric speakers: a pilot study.

Metronome, singing, and board pacing were used as external rate control techniques for the purpose of comparing the effectiveness of auditory and visual speech timing cues for reducing speech rate and increasing intelligibility in three traumatically brain injured mixed spastic-ataxic dysarthric speakers. A single system design with baseline reversal (ABACAD) was used in this preliminary investigation. Results demonstrated statistically significant (p < 0.05) changes in increased speech intelligibility during all three pacing conditions for the two more involved subjects. Differences between treatment conditions were not statistically significant. However, auditory metronome cuing showed the best results for the two subjects who benefited from rate control. Lower baseline intelligibility was strongly correlated with higher benefit from rate control. Furthermore, the two auditory rhythmic pacing conditions exhibited a close synthronization effect between the frequency rate of the cue and speech rate. Significant correlation coefficients between decreased speech rate and increased intelligibility were only found for the two more involved subjects. These findings suggested a differential benefit of slowing speech rate to improve intelligibility contingent upon severity of speech deficits.

Rhythmic facilitation of gait training in hemiparetic stroke rehabilitation.

Experimental and control groups of 10 hemiparetic stroke patients each underwent a 6 week, twice daily gait training program. The control group participated in a conventional physical therapy gait program. The experimental group trained in the same basic program with the addition of rhythmic auditory stimulation (RAS). Patients entered the study as soon as they could complete 5 strides with hand-held assistance. The training program had to be completed within 3 months of the patients' stroke. In the experimental group RAS was used as a timekeeper to synchronize step patterns and gradually entrain higher stride frequencies. Study groups were equated by gender, lesion site, and age. Motor function was assessed at pretest using Barthel, Fugl-Meyer, and Berg Scales. Walking patterns were assessed during pre- and post-test without RAS present. Pre- vs post-test measures revealed a statistically significant (P<0.05) increase in velocity (164% vs 107%), stride length (88% vs 34%), and reduction in EMG amplitude variability of the gastrocnemius muscle (69% vs 33%) for the RAS-training group compared to the control group. The difference in stride symmetry improvement (32% in the RAS-group vs 16% in the control group) was statistically not significant. The data offer evidence that RAS is an efficient tool to enhance efforts in gait rehabilitation with acute stroke patients.

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 Parkinson's 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 Parkinson's 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 Parkinson's disease gait when there is mild to moderate impairment, and suggest a technique for gait rehabilitation in Parkinson's disease.

Rhythmic auditory stimulation in gait training for Parkinson's disease patients.

Rhythmic auditory stimulation (RAS) was used as a pacemaker during a 3-week home-based gait-training program for Parkinson's disease (PD) patients (n = 15). Electromyogram (EMG) patterns and stride parameters were assessed before and after the test without RAS to evaluate changes in gait patterns. Data were compared with those of two control groups (n = 11), who either did not participate in any gait training or who participated in an internally self-paced training program. RAS consisted of audiotapes with metronome-pulse patterns embedded into the on/off beat structure of rhythmically accentuated instrumental music. Patients who trained with RAS significantly (p < 0.05) improved their gait velocity by 25%, stride length by 12%, and step cadence by 10% more than self-paced subjects who improved their velocity by 7% and no-training subjects whose velocity decreased by 7%. In the RAS-group, timing of EMG patterns changed significantly (p < 0.05) in the anterior tibialis and vastus lateralis muscles. Evidence for rhythmic entrainment of gait patterns was shown by the ability of the RAS group to reproduce the speed of the last training tape within a 2% margin of error without RAS.

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.

Measuring musical responsiveness in autistic children: a comparative analysis of improvised musical tone sequences of autistic, normal, and mentally retarded individuals.

This study provided a systematic analysis of improvised tone sequences of autistic children, as compared to musical improvisations by normal and mentally retarded control subjects. The data indicate that autistic children's tone patterns, analyzed and scored for rhythm, restriction, complexity, rule adherence, and originality, almost reached the scores of normal children. The highest individual total score in the study was achieved by an autistic child. Autistic children scored significantly higher than a control group of mentally retarded individuals. The autistic children's tone sequences showed high scores on the rhythm, restriction, and originality scales which support the notion of unusual musical responsiveness and abilities when compared to results in other performance and behavioral areas. In terms of complexity and rule adherence, autistic children's tone sequences resembled those of the mentally retarded by being rather short and repetitive.

Visual versus auditory (musical) stimulus preferences in autistic children: a pilot study.

This study investigated perceptual preferences of autistic children comparing responses to auditory musical and visual stimuli. The results indicated a weak preference of autistic children for the auditory musical stimulus, however, without the data approaching statistical significance. The autistic children spent significantly more time with the musical stimulus than the two control groups of normal children, equated by chronological and developmental age, respectively. Implications of these findings for a music therapy treatment concept are discussed.