Gerald C. McIntosh

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.

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.

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.

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.

Distinct cortico-cerebellar activations in rhythmic auditory motor synchronization

We investigated the role of the cerebellum in differential aspects of temporal control of rhythmic auditory motor synchronization using positron emission tomography (PET). Subjects tapped with their right index finger to metronome tones at a mean frequency of .8 Hz during 5 conditions: (1) an isochronous rhythm condition, (2) random changes in interval durations, and while the duration of rhythmic intervals was continuously time-modulated following a cosine-wave function at (3) 3%, (4) 7%, and (5) 20% of base interval. Anterior lobe cerebellar neuronal populations showed similar motor-associated activity across all conditions regardless of rhythmic time structure in vermal and hemispheric parts ipsilateral to the movements. Neuronal populations in bilateral anterior posterior lobe, especially in the simple lobule, increased their activity stepwise with each increase in tempo modulation from a steady beat. Neuronal populations in other parts of the posterior lobe showed an increase of activity only during the 20% condition, which involved conscious monitoring of rhythmic pattern synchronization, especially on the left side contralateral to the movements. Differential cerebellar activation patterns correspond to those in contralateral primary (primary sensorimotor), ipsilateral secondary (inferior parietal close to the intraparietal sulcus) and bilateral tertiary (dorsolateral prefrontal cortex) sensorimotor areas of the cerebral cortex, suggesting that distinct functional cortico-cerebellar circuits subserve differential aspects of rhythmic synchronization in regard to rhythmic motor control, conscious and subconscious response to temporal structure, and conscious monitoring of rhythmic pattern tracking.

Temporal Entrainment of Cognitive Functions : Musical Mnemonics Induce Brain Plasticity and Oscillatory Synchrony in Neural Networks Underlying Memory

Abstract: In a series of experiments, we have begun to investigate the effect of music as a mnemonic device on learning and memory and the underlying plasticity of oscillatory neural networks. We used verbal learning and memory tests (standardized word lists, AVLT) in conjunction with electroencephalographic analysis to determine differences between verbal learning in either a spoken or musical (verbal materials as song lyrics) modality. In healthy adults, learning in both the spoken and music condition was associated with significant increases in oscillatory synchrony across all frequency bands. A significant difference between the spoken and music condition emerged in the cortical topography of the learning‐related synchronization. When using EEG measures as predictors during learning for subsequent successful memory recall, significantly increased coherence (phase‐locked synchronization) within and between oscillatory brain networks emerged for music in alpha and gamma bands. In a similar study with multiple sclerosis patients, superior learning and memory was shown in the music condition when controlled for word order recall, and subjects were instructed to sing back the word lists. Also, the music condition was associated with a significant power increase in the low‐alpha band in bilateral frontal networks, indicating increased neuronal synchronization. Musical learning may access compensatory pathways for memory functions during compromised PFC functions associated with learning and recall. Music learning may also confer a neurophysiological advantage through the stronger synchronization of the neuronal cell assemblies underlying verbal learning and memory. Collectively our data provide evidence that melodic‐rhythmic templates as temporal structures in music may drive internal rhythm formation in recurrent cortical networks involved in learning and memory.

Effect of Rhythmic Auditory Cuing on Temporal Stride Parameters and EMG. Patterns in Hemiparetic Gait of Stroke Patients

This study investigated the effect of auditory (musical) rhythm on temporal parameters of the stride cycle and electromyographic (EMG) activity in gait of stroke patients. Ten subjects were studied over three trials. Each trial consisted of a baseline walk without rhythm and a walk with rhythm as pacemaker, marched to the step cadence of the baseline walk. Surface EMG on the gastrocnemius muscle and a dual walkway, consisting of pressure-sensitive voltage coded switch mats, were used to record data. Percentage change scores from no-rhythm to rhythm conditions were calculated for statistical analysis. Results showed several significant (p < .05) changes: (a) weight-bearing stance time on the paretic side and stride symmetry improved with rhythmic cuing; (b) magnitude of muscle activation during midstance/pushoff increased on the affected side and decreased on the nonaffected side; (c) variability of integrated amplitude ratios decreased during the midstance/pushoff phase on the affected side; (d) EMG activity during the swing phase also decreased on the affected side; (e) decrease in EMG variability and decrease in muscle activity during the swing phase were positively correlated with improvement in stride symmetry. Specificity of changes in muscle activation and improvement in temporal gait parameters suggest a strong entrainment effect of auditory rhythmic cues on temporal gait control in stroke patients.

Effect of Rhythmic Auditory Cuing on Temporal Stride Parameters and EMG Patterns in Normal Gait

This research investigated the effect of auditory (musical) rhythm on temporal parameters of the stride cycle and electromyographic (EMG) activity in normal gait at three different walking cadences. Sixteen normal subjects were studied. For each walking cadence, a baseline walk without rhythm and a walk with rhythmic cuing, matched to the baseline tempo, were measured. Surface EMG and a dual walkway, consisting of pressure-sensitive switch mats, were used to record data. Results showed several significant (p < 0.05) changes with rhythmic cuing: a) improved stride rhythmicity between right and left lower limbs; b) delayed onset of gastrocnemius EMG; c) shortened duration of gastrocnemius EMG; d) decreased variation in timing of gastrocnemius EMG; e) increased integrated amplitude ratios for gastrocnemius EMG. Data suggest that auditory rhythm as peripheral timing signal improved stride rhythmicity and effected muscle activity by producing more focused motor unit recruitment patterns.

Neurological Conceptualizations of Epilepsy

Epilepsy is a common neurological disorder, currently affecting over two million people in the United States. The generally accepted prevalence rate is five per 1000 when chronic epileptic disorders are considered. Approximately 2.2% of the population will have a single seizure some time in their lives (Epilepsy Foundation of America, 1975). The neurophysiological mechanisms active in epileptogenesis involve changes in membrane conductances and neurotransmitter function (Delgado-Escueta, Ward, Woodburg, & Porter, 1986a), and experimental models have been developed to correlate microstructural alterations with physiological and chemical observations.