Facilitating Implicit Learning to Improve Neurorehabilitation in Stroke
Condition: Cerebral Stroke
MeSH terms: Stroke
Study type: Interventional

Summary: 
      Stroke is one of the leading causes of chronic disability in Veterans. Stroke is associated
      with significant loss of mobility, increased risk of falling, cardiovascular disease,
      depression and neuro-cognitive impairment. These deficits negatively impact the independent
      completion of the Activities of Daily Living (ADLs). Task-oriented training has emerged as
      the dominant therapeutic intervention in the rehabilitation of chronic stroke victims. The
      effectiveness of these interventions may be enhanced through facilitation of implicit
      knowledge rather than explicit knowledge. Specifically, implicit learning increases retention
      and improves transfer of the improved motor function outside of the lab environment.
      Moreover, implicit motor control reduces the burden imposed on cognitive resources as the
      skill is performed automatically (i.e. do not have to 'think' about it). The amount and type
      of feedback individuals receive while learning a new task (or relearning in the case of
      rehabilitation) has been shown to influence the type of learning (i.e. implicit or explicit).
      Thus the purpose of the current study is to determine the effect of different types of
      feedback during motor learning on the learning type and the resultant impact on functional
      outcomes (i.e. motor performance, retention, and cognitive workload) in chronic stroke
      patients.
    

Detailed description: 
      Someone has a stroke in the US every 45 seconds, resulting in over 700,000 new strokes every
      year and stroke is the leading cause of disability in Veterans (American Heart Association
      Statistics Committee and Stroke Statistics Sub-Committee). The vast majority of these cases
      result in motor impairments, which frequently cause individuals to become dependent on others
      for daily functioning (modified Rankin Scale 3-5, see Lees et al., 2006). Specifically, upper
      extremity hemiparesis is the leading cause of functional disability after stroke and upper
      arm function explains about 50% of the variability in reported quality of life (Wyller et al,
      1997). As such optimizing upper arm neurorehabilitation is a critical problem to address in
      the aging Veteran population.

      "Rehabilitation, for patients, is fundamentally a process of relearning how to move to carry
      out their needs successfully" (Carr & Shepherd, 1987). This statement posits that at its core
      neurorehabilitation is motor learning, but despite this principle, research in motor learning
      has had little impact on stroke rehabilitation (Krakauer, 2006). Recently there has been an
      interest in developing and testing new methods to optimize upper extremity rehabilitation.
      Investigators at the Baltimore VAMC have pioneered task oriented training paradigms to
      improve mobility (Macko et al., 2005) in those with chronic stroke. As part of this
      programmatic approach novel upper extremity robotics training programs have been developed to
      improve reaching, and limb coordination. However, the majority of these interventions rely on
      error-based learning strategies during rehabilitation, which foster task-related explicit
      knowledge. However, a corpus of motor learning research indicates that this may not be the
      best strategy to optimize motor learning, and thus neurorehabilitation.

      Error-based learning involves receiving continual feedback of movement with the intent that
      the learner will make corrections to the movement in real time. Thus learning occurs through
      a series of repetitions in which the learner continually reduces the discrepancy between the
      ideal behavior and the observation of their own behavior. In other words, error-based
      learning fosters an adaptation to achieve the desired behavior. In contrast, operant
      conditioning learning strategies consists of the learner only receiving feedback about the
      quality of their movement at the end of the behavior. Thus, learning occurs through a series
      of reinforcement of the desired behavior in its entirety, which is more model-free than the
      adaptation incurred during error-based learning. A primary distinction between these two
      learning strategies is that error-based learning fosters explicit knowledge of the task,
      whereas operant conditioning fosters implicit knowledge (Krakauer & Mazzoni, 2011). These two
      types of knowledge have drastic implications for functional outcomes (i.e. motor performance,
      cognitive workload, and retention).

      Prior to stroke, upper arm functions such as reaching and grasping were largely done without
      the use of explicit knowledge. In other words, healthy individuals devote little conscious
      effort about how they are controlling their limbs, they just 'do it'. Although, using
      explicit strategies during learning can facilitate the rate of learning, if given enough
      time, individuals who have limited explicit knowledge will perform equally well (Maxwell et
      al, 1999). Despite a slower rate of learning, the payoff of reducing explicit knowledge of
      the task can be very advantageous during motor performance. Notably, retention of the learned
      behavior is greater in individuals who learned under conditions that inhibit explicit
      knowledge. For example Malone and Bastian (2010) had individuals learn a novel walking task
      (split belt treadmill where the belts move at different rates) and in those in which explicit
      knowledge was limited exhibited learning that persisted longer than those who relied on
      explicit knowledge during learning. In addition, limiting explicit knowledge during motor
      learning may result in reduced cognitive workload and maintained performance under conditions
      of challenge (Zhu et al., 2011). In conclusion, promoting explicit knowledge during
      rehabilitation rather than unconscious control (limiting explicit knowledge) reduces
      sustainability of the newly acquired motor skill, and consumes cognitive resources, which
      need to be available for other demands. As such, automatic control of these behaviors is
      critical to perform daily activities, suggesting operant conditioning (which limits explicit
      knowledge) as superior to error-based learning.

      Those with stroke are able to learn tasks implicitly, although the rate of learning may be
      delayed as compared to healthy controls (Pohl et al., 2001) and delayed further as a function
      of stroke severity (Boyd et al., 2007). Further, simply providing explicit information about
      an implicit task has been shown to reduce the learning rate and retention in those with basal
      ganglia stroke (Boyd et al., 2004; Boyd et al., 2006) and damage to sensorimotor areas (Boyd
      et al., 2003; Boyd et al., 2006; Winstein et al., 2003). While these studies highlight the
      importance limiting explicit knowledge during learning they were done in the context of
      learning implicit sequences rather than the development of skill, which while related, rely
      on different aspects of motor learning (Krakauer & Mazonni, 2011, Yarrow et al., 2009). In
      the context of functional skill learning, the timing/ type of feedback have been robustly
      shown to affect the learning rate as well as retention and have been implicated to affect
      knowledge type (Levin et al., 2010). Specifically, providing feedback about task performance
      less frequently and after performance rather than during (i.e. delayed) have been shown to
      increase learning retention and likely facilitate implicit learning (Cirstea et al., 2006;
      Winstein et al., 1996). Additionally, feedback about the results (knowledge of results)
      rather than the performance (knowledge of performance) has shown to increase retention and
      limit explicit knowledge (Cirstea el al., 2006; Sidaway et al., 2008; Winstein, 1991).
      Accordingly, the current proposal will attempt to foster implicit knowledge during the
      development of motor skill by manipulating when feedback is given and type of feedback.

      The aim of the current study is to determine the effect of error-based learning versus
      operant conditioning learning on critical outcomes of neurorehabilitation (i.e. performance
      after learning, generalizability, cognitive workload imposed by the task, and retention).
    

Intervention name(s): Reaching Task
Intervention type(s): Behavioral
Intervention description(s): Learn a reaching task that requires coordination of the arm segments
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Stroke; Cerebral Infarction