Reorganization of finger coordination patterns through motor exploration in individuals after stroke
Ranganathan Journal of NeuroEngineering and Rehabilitation
Reorganization of finger coordination patterns through motor exploration in individuals after stroke
Rajiv Ranganathan 0
0 Department of Kinesiology, Michigan State University , 308 W Circle Dr Rm 126, East Lansing, MI 48824 , USA
Background: Impairment of hand and finger function after stroke is common and affects the ability to perform activities of daily living. Even though many of these coordination deficits such as finger individuation have been well characterized, it is critical to understand how stroke survivors learn to explore and reorganize their finger coordination patterns for optimizing rehabilitation. In this study, I examine the use of a body-machine interface to assess how participants explore their movement repertoire, and how this changes with continued practice. Methods: Ten participants with chronic stroke wore a data glove and the finger joint angles were mapped on to the position of a cursor on a screen. The task of the participants was to move the cursor back and forth between two specified targets on a screen. Critically, the map between the finger movements and cursor motion was altered so that participants sometimes had to generate coordination patterns that required finger individuation. There were two phases to the experiment - an initial assessment phase on day 1, followed by a learning phase (days 2-5) where participants trained to reorganize their coordination patterns. Results: Participants showed difficulty in performing tasks which had maps that required finger individuation, and the degree to which they explored their movement repertoire was directly related to clinical tests of hand function. However, over four sessions of practice, participants were able to learn to reorganize their finger movement coordination pattern and improve their performance. Moreover, training also resulted in improvements in movement repertoire outside of the context of the specific task during free exploration. Conclusions: Stroke survivors show deficits in movement repertoire in their paretic hand, but facilitating movement exploration during training can increase the movement repertoire. This suggests that exploration may be an important element of rehabilitation to regain optimal function.
Stroke; Hand; Finger; Learning; Coordination; Exploration; Variability
Background
Stroke often results in impairments of upper extremity,
including hand and finger function, with 75% of stroke
survivors facing difficulties performing activities of daily
living [
1, 2
]. Critically, impairments after stroke not only
include muscle- and joint-specific deficits such as
weakness, and changes in the kinetic and kinematic workspace
of the fingers [
3, 4
], but also coordination deficits such as
reduced independent joint control [
5
] and impairments in
finger individuation and enslaving [
6–9
]. Therefore,
understanding how to address these coordination deficits
is critical for improving hand rehabilitation.
Typical approaches to hand rehabilitation emphasize
repetition [
10
] and functional practice based on
evidence that such experience can cause reorganization
in the brain [
11
]. Although this has proven to be
reasonably successful, functional practice (such as
repetitive grasping of objects) does not specify the
coordination pattern to be used when performing the
tasks. As a result, because of the redundancy in the
human body, there is a risk that stroke survivors may
adopt atypical compensatory movements to perform
tasks [
12
]. These compensatory movements have been
mainly identified during reaching [
13, 14
], but there
is evidence that they are also present in finger
coordination patterns during grasping [15]. Although there
is still debate over the role of compensatory
movements in rehabilitation [
16
], there is at least some
evidence both in animal and humans that continued
use of these compensatory patterns may be
detrimental to true recovery [
17–19
].
To address this issue, there has been a greater focus
on directly facilitating the learning of new coordination
patterns. Specifically, in hand rehabilitation, virtual tasks
(such as playing a virtual piano) have been examined as
a way to train finger individuation [
20, 21
]. In these
protocols, individuation is encouraged by asking
participants to press a particular key with a finger, while
keeping other fingers stationary. A similar approach to
improve hand dexterity was also adopted by developing
a glove that could be used as a controller for a popular
guitar-playing video game [22]. However, directly
instructing desired coordination patterns to be produced
becomes challenging as the number of degrees of
freedom involved in the coordination pattern increase. For
example, the hand has approximately 20 kinematic
degrees of freedom, and providing verbal, visual or
auditory feedback for simultaneously controlling all
these degrees of freedom would be a major chall (...truncated)