Rhythmic Auditory Stimulation RAS w Developed primarily by

Rhythmic Auditory Stimulation (RAS) w Developed primarily by Thaut, Mc. Intosh, & Rice at the CBRM at Colorado State University w NMT technique utilizing the physiological effects of rhythm on the motor system to increase the efficiency of controlled movement patterns during rehabilitation. w Enhancement of gait is mediated by an entrainment effect where movement frequencies and motor programs entrain to rhythm through anticipatory cuing of functional movement patterns.

RAS Uses w Immediate entrainment stimulus providing rhythmic cues during movement. w Listen to music with strong rhythmic pulse while walking to enhance walking tempo, balance, and control of muscles and limbs. w Stimulus for training where patients train with RAS for a prescribed period of time in order to achieve more functional gait patterns which they then transfer to walking without rhythmic facilitation.

Mechanisms w Rhythmic Entrainment w Priming of the Auditory Pathway w Cuing of the Movement Period w Step-Wise Limit Cycle Entrainment

Rhythmic Entrainment w Physiological basis for the perception of rhythm is the detection of periodicity patterns in amplitude modulations of sound w External rhythm serves as an external oscillator which has a “magnet” effect on one’s internal timekeeper. w Strength of the effect is substantiated by the observation that motor responses can be entrained by rhythmic patterns even at levels that are imperceptible.

Auditory-Spinal Facilitation w Physiological entrainment of muscle activation through rhythm perception takes place via reticulospinal pathways. w Neurons in the spinal cord become excited as a result of auditory perception. w Support for these concepts were observed in research when many components of the neural synchronization network were already activated and “entrained” simply by listening to rhythm. w One result of neuronal excitement is the “priming” or “readying” of muscle groups utilized in movement, which has a facilitative effect on subsequent motor functioning.

Cuing of the Movement Period w Period Synchronization - adaptation of the movement duration to the rhythmic stimulus duration w Phase Synchronization - ISI and IRI are closely matched although period synchronization is not behaviorally observable. w Kinematic models show that period (or frequency) entrainment results in enhanced kinematic stability through the stabilization of the following parameters: acceleration, velocity, trajectory).

Step-Wise Limit Cycle Entrainment (SLICE) w RAS frequencies (tempi) need to be set initially at a pt. s ‘resonant’ (current or intrinsic) frequency of movement. w Limit cycles are frequencies at which any moving system performs optimally (developed in the fields of engineering, physics) w Hence, RAS frequencies should be adapted to a person’s current limit cycle, i. e. the current step cadence.

SLICE cont’d w Initial purpose of RAS is to stabilize movement parameters at a pt. s current limit-cycle. w New limit cycles can be gradually entrained through a step-wide incremental process to approximate a pt. s pre-morbid limit-cycle. w Ex. When using RAS to increase cadence of PD pt. s, stride lengths will increase also due to the mechanical properties of the gait generating system.

SLICE cont’d w In the case of pt. who has a nearly normal cadence with shortened stride length, RAS is used to match the current cadence or a slightly slower one in order to increase stride length through added kinematic stability which is present due to the entrainment process. w SLICE - most commonly used RAS protocol in the treatment of gait disorders.

RAS Gait Training Procedures w Assessment w Resonant Frequency Entrainment w Frequency Modulation w Advanced Adaptive Gait w Fading w Reassessment

Cadence Assessment w Cadence - steps/minute w Client walks for 60 seconds while you count each step; walks for 30 seconds then multiply steps by 2) w This is unaccompanied by music. w Avg. cadence for an adult is 105 -120 steps/min but is age related.

Velocity Assessment w Velocity - Meters/minute or feet/minute w Measure distance across time w Pt. walks for 60 seconds and you measure how many meters or feet they walked (multiply by 2 if walking for only 30 seconds) w Difficult to do because of space limitations. w Hospitals usually have 1 -foot floor tiles. Count the tiles to get a feet/min measurement, then divide by 3. 281 for meters/min (1 meter = 3. 281 ft. )

Velocity Assessment cont’d w Measure off 10 meters on the floor. w Time the number of seconds it takes a pt. to walk 10 meters. *Have them start a few ft. before and continue going for a few ft. past the line. w Divide the number of seconds by 60 (60 sec/min) w Divide 10 meters by the number of minutes which gives you the meters/minute value. w Ex. Pt. walks 10 meters in 7 seconds w 7 sec/60 sec/min =. 117 minutes w 10 meters/. 117 minutes = 85. 5 meters/minute w Avg. normal velocity in adults is 80 m/m, but is age dependent.

Stride Length w Divide velocity by cadence. w This will provide the number of meters for each step. (*This in inaccurate if there is uneven step length between the right and left legs) w Multiply this figure by 2 and this will give you the average stride length. w Ex. 70 meters/min (velocity) / 80 steps/min (cadence) =. 875 meters/step w. 875 meters/step x 2 steps/stride = 1. 75 meters avg. stride length.

Step 2 Resonant Frequency Entrainment w Match RAS frequency (music tempo) to gait cadence and walk with patient. w Pt. s who are not ready for sustained walking exercises can practice specific pre-gait exercises, e. g. weight shifting - front to back, side to side, etc. 6/8 tempo usually more preferable w Therapist may need to cue proper gait mechanics, e. g. stride length, arm swing, posture, toe clearance, heel strike, etc.

Step 3 Frequency Modulation w Increase tempo by no less than 5% ~ an increase that still allows them to maintain proper mechanics. w Again use verbal cues, but feedback should be kept to a minimum as you may interfere with rhythm perception and its subsequent effects w Clients who have attention problems may need enhancing verbal cues initially, e. g. left-right, 1 -2 w Generally, frequencies (tempi) that are more closely aligned with a pt. s pre-morbid state tend to more have the strongest effect on overall gait patterns. w In some cases, a deceleration in RAS frequency is indicated for pt. groups who have the proclivity for unsafe walking patterns.

Considerations w 2/4 or 4/4 meter with strong beat accents (1 & 3) w If a pt. utilizes an assistive device, cane or walker, a 3 -step pattern may be more useful, e. g. step, walker w The motivational quality of music is a bonus secondary effect ~ client preferences. Note that some diagnoses do not perceive complex acoustic patterns well so very simple music or simply a metronomic click would work best.