An Experiment Using Functional Near-Infrared Spectroscopy and Robot-Assisted Multi-Joint Pointing Movements of the Lower Limb
June 7th, 2024
It is estimated that 1 in 6 individuals worldwide will have a stroke in their lifetime, causing long-term disability, whose rehabilitation mechanisms are still poorly understood. This study proposes a protocol to evaluate brain activation by functional near-infrared spectroscopy (fNIRS) during a lower limb robotic therapy session.
In this study, we aim to investigate the feasibility of an experimental protocol involving movements of the lower limb attached to a robotic device and simultaneous acquisition of functional near-infrared spectroscopy, fNIRS data. Few studies have employed fNIRS to study brain activation in stroke, motor recovery and lower limb movements focusing mainly on single joint actions, walking or cycling. Our study pioneers in exploring, multi-joints, lower limb training for target rehabilitation.
Functional near-infrared spectroscopy, fNIRS, effectively measures temporal chains in brain blood oxygenation, serving as an indirect brain activity indicator, aching to functional MRI signals. Unlike FMRI, fNIRS is compatible with robotic hardware, portable and more robust to motion artifacts. There are two main channel.
The first is to synchronize the robotic device movements with fNIRS data. The second is to retain enough data to achieve the statistical power to detect hemodynamic changes in only six minutes. Our study confirmed the feasibility of the protocol and the yield, anticipated the results.
And the assisted condition only to subject exhibit significant brain activation. The unassisted exercise requiring more effort showed greater HbO concentration change. Then, as is once, with notable difference in the contra atrial PNC.
Begin by preparing the functional near-infrared spectroscopy or fNIRS system. Prepare the cap using 16 optods, eight light sources having wavelengths of 760 and 850 nanometers and eight light detectors. Attach the eighth detector to the short distance adapter, which is connected to each of the source optods.
Open the fNIRS acquisition software and load the montage with the placement of each optod. Set the fNIRS signal temporal sampling rate at 10.17 hertz. Briefly explain the research relevance and the experimental protocol to the participant.
Instruct the volunteer to sit on an armchair in front of the robot, positioned approximately 150 centimeters away from the computer monitor. After removing the shoes, comfortably attach the participant's foot to the robot arm with Velcro straps. Place the fNIRS cap with the optods on the participant's head and securely fasten with the hook and loop fastener below the chin.
Place the over cap onto the optod cap to reduce the interference of ambient light. Proceed to begin the data acquisition after preparing the participant for the lower limb robotic therapy session. Instruct each participant not to make sudden head movements to minimize the risk of movement artifacts.
Calibrate the functional near-infrared spectroscopy, or fNIRS system, for optimal signal quality. Ensure that all channels are of good quality as shown by the interface. If not, try to remove the hair between the scalp and the optod tip.
Explain to the participant how to play the game by moving the foot attached to the robot to reach the targets indicated on the screen. Explain that there will be two conditions:Without and with robotic assistance. After initialization of the operational system, the first game interface appears.
Position the robotic arm in the standard location and wait to receive the robotic arm positioned correctly feedback message. Enter descriptive data about the participant and experimenter into the system to log into the robot gaming interface. In the game selection interface, configure the session time to six minutes with 30-second rest intervals.
Select the appropriate leg to be used by the participant. Select Picnic game and click on Go to play the game. For each subject, the maps associated with HbO changes should statistically significant activation in the experimental condition with no robot assistance.
While only two subjects showed statistically significant activation in the experimental condition with robot assistance. Regarding HbR, four subjects presented statistically significant activation in both conditions, albeit in fewer channels as compared to HbO. Only the left premotor cortex displayed a statistically significant increase in HbO activation during the game or play without robotic assistance relative to the rest.
In addition, this ROI presented a greater activation in the condition without robotic assistance in comparison to the condition with robotic assistance.
Overview
This study investigates the feasibility of using functional near-infrared spectroscopy (fNIRS) to evaluate brain activation during lower limb robotic therapy sessions for stroke rehabilitation. A protocol was developed to synchronize fNIRS data acquisition with robotic movements, allowing insights into brain activity during multi-joint movements that are crucial for motor recovery.
Key Study Components
Area of Science
- Neuroscience
- Rehabilitation
- Robotics
Background
- Stroke rehabilitation mechanisms are not well understood.
- Previous studies focused on single joint actions rather than multi-joint rehabilitation.
- fNIRS is a portable and robust imaging technique compatible with robotic systems.
Purpose of Study
- To evaluate brain activation during robotic-assisted lower limb training.
- To explore the differences in brain activation between assisted and unassisted conditions.
- To confirm the feasibility of the experimental protocol.
Methods Used
- Functional near-infrared spectroscopy (fNIRS) was employed to measure brain blood oxygenation.
- Participants performed movements while attached to a robotic device, allowing control of movement conditions.
- Data were collected over a duration of six minutes with careful calibration of the fNIRS system.
- Two conditions were tested: with and without robotic assistance.
Main Results
- Significant brain activation was observed in unassisted exercises compared to assisted ones.
- Increased HbO concentration changes were recorded primarily in the left premotor cortex.
- Four subjects showed activation in both conditions, with a notable difference in results between assisted and unassisted tasks.
Conclusions
- This study demonstrates the potential of fNIRS to monitor brain activity during robotic rehabilitation.
- The findings highlight the importance of unassisted movements for eliciting greater brain activation.
- The study contributes to the understanding of neuronal mechanisms involved in motor recovery after stroke.
