Influence of Timing on Motor Learning

In humans, the acquisition of a new task seems to be based on an error-feedback paradigm,
where motor command error generated in the first phase of learning is gradually corrected
using peripheral feedback. Learning a new skill involves various brain structures and
typically brain activation increases with the difficulty of the movement to be learned. To
find ways to promote greater neuromotor adaptation during learning, some studies have tried
to determine if subjecting individuals to a robot-generated force field that enhances
movement error in the course of skill acquisition would improve learning. This premise could
thus be used as a training paradigm during rehabilitation following a neurological insult
such as a stroke. Results have shown that during training in an enhanced error situation,
healthy individuals adapt to the presented perturbation and when this perturbation is
removed, a greater improvement in performance is observed. It has been demonstrated that
following a stroke, this adaptation still occurs, although to a lower extent than normal.
Thus, stroke individuals present greater improvement in their motor performance after
experiencing error-enhanced training with a robotic device than when receiving assistance in
moving in the intended way. It seems that the impact of such robotic training on brain
function is still unclear.

During the acquisition of a new task, not only the motor sequence of the action is crucial,
but also the timing of the action. Most of the studies evaluating learning and the related
brain structures mediating the acquisition of a new task have focused mainly on the motor
sequence of the action and a paucity of them have assessed the timing of the action. Timing
of an action plays a crucial role in the proper accomplishment of daily activities such as
driving or playing tennis. Studies have found that, with practice, subjects are able to
learn and anticipate the correct timing of a task and become more accurate in performing it.
However, little is known about the effect of learning a new timing task on motor learning
and brain related changes when individuals are subjected to a robotic error-enhanced timing
of action.

The aim of the current project is to evaluate, in healthy and stroke individuals, the effect
of introducing a change in movement timing or a feedback of movement timing that will either
help or hinder individuals in accomplishing a new timing-based task, in order to determine
which form of error modification will best induce motor learning as well as favorable brain
plasticity. We hypothesize that the introduction of error amplification and error feedback
during the practice of a timing-based task will provide the greatest benefit for motor
learning and brain plasticity by providing the individuals with a constant error signal that
will drive adaptation. Using a range of different devices, we will test the hypothesis that
providing auditory and other types of feedback related to timing errors helps in learning
timing tasks.

Inclusion Criteria:

- Age 18 to 80 years of age

- Sustained a single stroke affecting the arm, at least three months prior to
enrollment

- Minimal to moderate lost motor control of the arm after stroke

- No active major psychiatric problems, or neurological/orthopedic problems affecting
the stroke-affected upper extremity

- No active major neurological disease other than the stroke

- Absence of pain in the stroke-affected upper extremity

Exclusion Criteria:

- Severe tone at the affected upper extremity

- Severe aphasia

- Severe reduced level of consciousness

- Severe sensory/proprioception deficit at the affected upper extremity

- Currently pregnant

- Difficulty in understanding or complying with instructions

- Inability to perform the experimental task that will be studied

- Increased pain with movement of the stroke-affected upper extremity