An Experiment Using Functional Near-Infrared Spectroscopy and Robot-Assisted Multi-Joint Pointing Movements of the Lower Limb

Summary

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.

Abstract

Stroke affects approximately 17 million individuals worldwide each year and is a leading cause of long-term disability. Robotic therapy has shown promise in helping stroke patients regain lost motor functions. One potential avenue for increasing the understanding of how motor recovery occurs is to study brain activation during the movements that are targeted by therapy in healthy individuals. Functional Near-Infrared Spectroscopy (fNIRS) has emerged as a promising neuroimaging technique for examining neural underpinnings of motor function. This study aimed to investigate fNIRS neural correlates of complex lower limb movements in healthy subjects. Participants were asked to perform cycles of rest and movement for 6 min using a robotic device for motor rehabilitation. The task required coordinated knee and ankle joint movements to point to targets displayed on a computer screen. Two experimental conditions with different levels of movement assistance provided by the robot were explored. The results showed that the fNIRS protocol effectively detected brain regions associated with motor control during the task. Notably, all subjects exhibited greater activation in the contralateral premotor area during the no-assistance condition compared to the assisted condition. In conclusion, fNIRS appears to be a valuable approach for detecting changes in oxyhemoglobin concentration associated with multi-joint pointing movements of the lower limb. This research might contribute to the understanding of stroke motor recovery mechanisms and might pave the way for improved rehabilitation treatments for stroke patients. However, further research is needed to fully elucidate the potential of fNIRS in studying motor function and its applications in clinical settings.

Introduction

Epidemiological data indicates that worldwide there are ~17 million new cases of stroke each year, with an increase in incidence in low- and middle-income countries¹. The number of new cases is estimated to increase to 77 million by 2030². Motor impairment due to stroke often affects patient's mobility and participation in daily life activities, contributing to a low quality of life. Traditional motor rehabilitation includes manual therapy, but over the past few decades, robotic systems for rehabilitation have been developed. These systems can deliver therapy at high intensity, dose, quantifiability, reliability, rep....

Protocol

This study was approved by the local Ethics Review Board of the UNICEP (Centro Universitario Paulista). All participants provided informed consent following all institutional guidelines and federal norms regarding scientific research involving humans. They received no financial compensation, as required by Brazilian federal regulations.

1. fNIRS system

1. Prepare the cap using 16 optodes: 8 light sources (760 nm and 850 nm) and 8 light detectors (see

Discussion

In this proof-of-concept study, the feasibility of making inferences on brain activation mapping using fNIRS data from healthy subjects while they exercised with different types of movements using a robot for lower limb rehabilitation was investigated. Typical fNIRS recording sessions in adults are longer than 6 min⁵⁴. However, to make recordings feasible in the context of a rehabilitation setting, the overall duration of the experiment must be minimized to avoid unnecessary fatigue and effort for.......

Materials

Name	Company	Catalog Number	Comments
32 inch Smart TV	Samsung	N/A	TV connected to robot via HDMI cable
8-detector silicon photodiode (SiPD) optodes for optical detection with dual tip	NIRx Medical Technologies (Glen Head, NY, USA)	https://nirx.net/nirsport
8-source optodes bundle for optical illumination with dual tip	NIRx Medical Technologies (Glen Head, NY, USA)	https://nirx.net/nirsport
Aurora acquisition software	NIRx Medical Technologies (Glen Head, NY, USA)	https://nirx.net/nirsport
Laptop Precision XPS 13	Dell Technologies (Round Rock, TX, USA)
nirsLAB fNIRS Analysis software	NIRx Medical Technologies (Glen Head, NY, USA)	https://nirx.net/nirsport
NIRSports2 fNIRS acquisition system	NIRx Medical Technologies (Glen Head, NY, USA)	https://nirx.net/nirsport	It has two different continuous wave optics (760 and 850 nm), 8 dual-ended LED sources and 8 dual-ended active detectors.
R	R-project.org (open source software)	https://www.r-project.org/
Standard cut cap, black color for up to 128 holders.	Easycap GmbH (Wörthsee, Germany)	https://www.easycap.de/
Vivax Assistive Rehabilitation Machine (ARM)	Vivax Ltda (São Paulo, Brazil)	https://vivaxbr.com/home/	It is a portable robot designed to deliver lower limb rehabilitation. It has a 3D reachable workspace and is compact and light, weighing about 35 lb., which makes it easy to transport and to install.