Inducing the return of automaticity in gait after stroke through distractions that force the act of walking into the background.
By Mike Studer, PT, DPT, MHS, NCS, CEEAA, CWT, CSST, FAPTA, and Robert Winningham, PhD
Expect this article about post-stroke dual task rehabilitation to surprise, inform, and help to improve your efforts in restoring functional ambulation for persons recovering from stroke. We expect you to learn why and how to use dual task interference (DTI) or cognitive-motor training to help people recover better after a stroke. It may be easiest to understand why we use DTI if we frame it as a constraint. Yes, that’s right, a constraint…similar to using a sling on a less-impaired arm to “force” a more involved arm to be chosen, used, and stimulated to recover.
Imagine it. Place a constraint on your patient’s attention, by using a distraction…causing a person recovering from stroke to reprogram a motor task to operate without as much attentional resources. Movement such as walking must be able to survive in the background without attention, as a “motor memory” or what is scientifically known as a procedural memory.
Accessing Procedural Memories
Among the related questions that we will answer for post-stroke dual task rehabilitation include, “How did walking become procedural?” or “How do we access these memories and motor skills after stroke or injury?” and finally, “How many repetitions of a task are needed to make it ‘automatic’ again after stroke?” Our most pressing and practical question at hand is, “How can rehabilitation interventions most effectively encourage the return of procedural memories?”
Know that the terms automatic, automatized, or expressing that a person has automaticity, are synonymous with having a procedural memory. As for the first question—”How does a movement become procedural?”—we are aware that the procedural memory centers (PMCs) develop in any skill (functional, vocational, craft, or athletic) when we have interest, repetitions, and a demand (stimulus) that the movement operate without full attention. In walking, we need two essential ingredients.
First, we need an environment that allows for predictable locomotion as a primary means of transit (ie, repetitions and a surface with minimal variability). Second, we need an attentional demand (DTI), such as texting, cleaning glasses, counting money, assessing a dynamic environment, engaging in conversation, or preparing for an upcoming interview. Neuroplasticity (learning) comes when sufficient demand pushes the organization of the motor control of gait into the PMCs.
Our recognizable “walk” does evolve during developmental years and, barring injury or change in somatotype (eg, significant weight gain or loss), remains relatively constant through our adult years. To the good fortune of most PwS, the primary PMCs are spared. It is far less likely that a stroke will impact the basal ganglia (BG) or cerebellum, leaving this pathway to access walking intact.
Redefining “Their Walk”
A common problem for most PwS is the reverse: creating movement with conscious attention, generated from the primary motor cortex. So, thinking about moving (internal focus) is often more challenging than moving without thinking (external or goal-directed focus). Walking toward a destination, with a list of items to retrieve from that shelf, is an example of goal-directed movement with DTI. Recognizing that the PMCs largely remain intact leaves therapists and PwS alike with the problem of reclaiming automaticity. This requires neuroplasticity, which includes making and growing new connections as well as reorganization of responsibilities.
PwS can reorganize and redefine “their walk” in the face of a changing set of resources as compared to what they had pre-stroke (hemiplegia, sensory impairments, abnormal tone). Compensated gait can be healthy, automatic, and reliable again. Recall that having a reliable and predictable walk poses a very low demand on attentional resources and is therefore preferable to either of the alternatives of: 1) variable gait that is unpredictable or 2) most every step requiring conscious control to initiate, monitor, and terminate.
Redeveloping Automaticity: Repetitions and Dual Tasking
How many repetitions of a task are needed to make the behavior “automatic” again after stroke? Is there a dosage of intensity that would make repetitions more effective? How can we ensure that DTI will promote carryover in way of tolerance for distractions, or an improved procedural encoding of gait again?
While dual-task demands are everywhere, no two people should be affected by the same environmental and task demands in the same manner. This variability is due to: 1) their past experiences with the proposed task or related tasks; 2) their relative automaticity in a primary motor task (influencing the cognitive resources available); and 3) each person’s tolerance for a specific mode of distraction (eg, cognitive, motor, visual, or auditory). Each person has an individual skill set with both biological and experiential (nature and nurture) influence.
There is clear evidence for the functional significance of DTI on gait speed, fall frequency, and independence in gait after stroke. Subsequently, there is clear evidence for the efficacy of cognitive-motor training to promote automaticity in PwS. However, the present science does not easily translate into applications, objective tests, or justifications of skilled care.
Applying the Science
While many of these studies have included sufficient numbers of repetitions, they have not always applied sufficient intensity and quite likely insufficient dosage. Dosage built in frequency, intensity, type, and time (FITT principle)56, as well as those principles cited of neuroplasticity and motor learning57,58, lead us to the understanding that it is not the sheer numbers of repetitions or minutes-spent in dual task training, but rather the level of rigor, complexity, challenge, intensity, and ultimately interest (engagement), which has the opportunity to make each repetition meaningful and sufficient to induce measurable change.
Recent studies in stroke rehabilitation have improved the delivery of intensity and respect for the presence of error (difficulty). Kleim and Jones 2008 found that dual task training delivered at a rigorous level induces neuroplasticity when the complexity and intensity are adequate.58 Gait training with dual task overlay is complex, by application, but only intense when applied relative to the learner’s capabilities and readiness.58
As for the application of dual task training, therapists must conduct their efforts in motor learning for the primary task of gait, with a consideration for both individualizing and later integrating dual task overlay. This must be carried out using reasonable expectations based on lesion size and location, age, learning style, and personality.59-69 As McIsaac and colleagues21 wrote, “In aging and disease states, declines in sensorimotor and cognitive functions may lead to reduced postural reserve and cognitive reserve creating overall greater demands for attention to the task.”
While all dual-tasking must be proportional to capabilities, success rates, and personal tolerance as noted above, we must recognize additional trends by diagnosis and age. Therapists must watch for signs of DT overload, including agitation, pathway deviation, foot clearance, steps to turn, dramatic reductions in gait velocity, poor sequencing of assistive device, and increased losses of balance requiring assistance. As stroke is not a heterogeneous condition, clinicians should not assume that all groups have a timetable upon which they are “ready” for dual task interference to be introduced.
Clinical applications of DT training are only as sophisticated as the evidence to date. As it is functionally relevant to focus on ambulation, the task specific nature of DT practice in the clinic often stops there, meaning that the distraction should have specificity, relevance, and person-based interest. Asking patients to perform mathematical calculations, spell words backwards, or name state capitals are cognitive tasks that many clinicians have applied. However, these distractions may not be as intuitive to the learner as they can feel contrived, lacking functional significance and failing to fully engage PwS as they are left to ask two questions that they should not have to face:
1) “Why am I doing this?” and, 2) “Am I improving?”
As we mature in DT applications, clinicians can be seen incorporating cell phones; pulling items from a purse, wallet, or pocket; recalling information delivered prior-to and after a primary task (requiring cognitive rehearsal during); utilizing obstacles for visual distraction; and overlaying relevant auditory distractions during the motor task. When a person endures the overtraining or loading of DT, it is important for them to see and feel the “why.”
As for the second question, we land squarely at the feet of gamification. PwS should know their functional measurements that reflect their capacity to tolerate distractions in activities that reflect their lives, in real numbers. This leaves people with an opportunity to both see their improvement, and to compete against an established baseline. For the sake of this brief article, these are the essential ingredients affording gamification, elevating intensity, and increasing the likelihood of neuroplastic change.
This may leave us with a final question: “How_ _can rehabilitation interventions most effectively encourage the return of procedural memories?” In all, the best DT training takes into consideration the following:
1) Patient’s relative experience or level of automaticity with the primary gait task. Is the patient using a new assistive device? New footwear? Will distractions interfere with motor learning?14,21,23
2) Transfer of training (what are and how can training imitate the environmental demands for this person?42,43)
3) Lesion location/type (what strengths and limitations are superimposed neurologically by the stroke?74)
4) Patient tolerance of error and need for success—consider personality. Will this person improve or become more frustrated by the DT loading?43
5) Specificity. Exposure to one condition/environment of gait or modality of DT condition should not be expected to transfer to skill (tolerance) in another.42
6) Intensity. For dual task experiences to induce change and stimulate procedural processing of a primary task, they must be of sufficient challenge to offer a therapeutic dosage.42,76
7) Autonomy. Has this person been given an opportunity to voice their typical routines, skills, and preferences—as well as their preferred level of challenge?
8) Safety (perceived). Intensity, error (consequence), and ultimately carryover are impacted by patients’ perception of safety. Recall that fear is a cognitive distractor. Using a safety harness or body weight support as a safety net can mitigate some of these concerns as patients engage in their initial DT experiences.
9) Measurement. As stated above, gamification can enhance engagement and intensity. Intensity is required for neuroplasticity. Measure patient performance in single task and immediately follow this with dual task. Share numbers. Remeasure. Compete.
10) Awareness. The ultimate indicator for DT prognosis in recovery. Does this person:
a. Recognize dual task conflict? Are they able to perceive and independently recognize reduction in primary performance?
b. Recognize as they are being distracted?
c. Independently re-prioritize attention for their own safety, attempting to extinguish or filter-out distractions?
It is through these 10 considerations that we can both guide our dual task intervention and individualize care, providing each person the greatest opportunity to recover.
For stroke survivors, the evidence is irrefutable and conclusive; dual task gait training can be and often is beneficial for when adhering to principles of task specificity and intensity at the least. Many authors have postulated the mechanism by which this is true, with the most common theme being one of motor learning, specifically engaging the learner to re-automatize the primary task of walking, by organizing the effort of gait on external feedback. In other words, gait training by itself may be beneficial, yet this approach allows the learner to internalize the focus of attention on the movement itself. Dual task training forces an external focus of attention, which has proven to be a superior form of training for stroke and many other impaired and un-impaired (athletics, developmental learning, etc) conditions.75,81,82
Evidence suggests that stroke survivors can make new procedural memories. The extent to which these memories are identical to pre-stroke patterns of gait, or are well-reinforced and novel iterations of post-stroke gait, is based on the type of stroke, the location of the stroke, access to rehabilitation, comorbidities, social support, personal traits, and many more factors, as suggested by the International Classification of Functioning.85 Creating dual task interference during gait training has the proven capacity to take the recovery of gait from a conscious-control frontal lobe process and make it subcortical again.
Limitations of this line of research to date can be found in the lack of respect for principles of task specificity and intensity. Additionally, most dual task research has been designed to prove the presence of dual task cost, or its relationship to fall risk, rather than the potential benefits in applications in rehabilitating the automaticity of gait. As noted above, it is time to mature from the notion of rehabilitating dual task tolerance in the activity of gait, to the more sophisticated and functionally relevant notion of rehabilitating gait, through the application of dual task interference. Readers may utilize the 10 recommendations above to improve their efficacy of DT interventions.
Mike Studer, PT, DPT, MHS, NCS, CEEAA, CWT, CSST, FAPTA, is the owner of Northwest Rehabilitation Associates in Salem, Ore. He is also an adjunct professor at Oregon State University’s DPT program in Bend, Ore, where he leads the coursework on motor control and assists the national network of neurologic PT residencies (Neuroconsortium). He is also part of the clinical team for SMARTfit.
Robert Winningham, PhD, has more than 25 years of experience researching human memory and has largely focused on older adults and ways to enhance their mental functioning and quality of life. He currently serves as provost and vice president for Academic Affairs at Western Oregon University, where he has been a professor of Psychology and Gerontology, chair of the Behavioral Sciences Division, and interim dean of the College of Liberal Arts and Sciences. He is also part of the clinical team for SMARTfit. For more information, contact [email protected]
The following companies provide products that are useful in treating stroke and neurological conditions:
Allard USA Inc
Biodex Medical Systems Inc
Bionik Laboratories Corp
CIR Systems Inc/GAITRite
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