NEUROCONTROL - ASSESSMENT AND STIMULATION: Visual information and motor control strategy
*NEURAS-V*

A highly prevalent disease like stroke may affect key organ systems involved in
motor control (e.g., the central nervous system, the musculoskeletal system,
and the senses). The observed motor dysfunction in this condition results from
an interplay between primary damage, secondary decline and development of
compensatory strategies. Therefore, the clinical community is in great need for
assessment methods that allow for high resolution quantitative and valid
measures of factors contributing to motor dysfunction to guide selection of the
optimal strategy for treatment. For moving and interacting with our
environment, it is essential to properly adapt the motor control strategy to
fluctuating environmental conditions and task demands. Against this background,
emerging technologies such as haptic robots and virtual or augmented reality
provide new opportunities to identify various contributors to movement
disorders. For meaningful use of a virtual reality surrounding in a clinical
setting (e.g., in stroke patients), however, it is essential to understand the
extent and manner in which control strategy and task performance are influenced
by visual information in healthy subjects

The primary objective of this study is to determine if and how specific
characteristics of visual information influence the motor control strategy
adopted by healthy subjects during a visuomotor tracking task. Changes in wrist
joint impedance (i.e., the resistance to movement) due to specific
manipulations of the visual scenery related to task demands (i.e., tolerance,
velocity, preview) and related to presentation of visual information (i.e.,
gain, optical flow density, preview) are quantified using System Identification
and Parameter Estimation (SIPE) techniques in order to assess feed-forward and
feedback motor control strategies. Secondary objective of this study is to
evaluate whether the assessment can be used to examine the (expected lack of
adaptability of) motor control strategy in stroke patients.

Observational study, single session. Subjects will perform a visuomotor
tracking task (presented on a LED tv screen) under different visual conditions.
In experiment 1, three features of the visual scenery will be manipulated to
systematically vary the task demands: tolerance (3 levels), velocity (3
levels), preview (3 levels). In experiment 2, three features of the visual
scenery will be manipulated to vary the visual presentation without changing
the task demands: visual gain (3 levels), optical flow density (2 levels),
preview (3 levels). During this visuomotor tracking task, which comprises very
small movements (5 degrees flexion/extension of the wrist joint), a haptic
manipulator applies small torque perturbations to the wrist, which allows for
identification of motor control strategies using SIPE techniques.
Neuromechanical properties of the wrist (e.g., joint stiffness, joint damping,
and reflexes) and tracking performance will be compared between the
abovementioned visual conditions.

Expected duration of the protocol is 60 minutes for healthy subjects and 75
minutes for stroke patients. Actual measurements will take no longer than 25
minutes. Active task performance is warranted, but will only involve submaximal
effort and small movements. Additional rest periods will be offered if
necessary. Perturbation torques will be adjusted to each individual participant
in order to elicit angular perturbations of approximately 1°. For patients, if
possible, the measurement will be combined with a regular visit to the LUMC
outpatient clinic, such that no extra travelling is required.

The risks of the assessment are minimal. The haptic manipulator is safe guarded
against displacements larger than the wrist ROM of each individual participant.
The motor and other moving or fragile parts are sufficiently insulated and
equipment will be certified according to local regulations.