Monitoring the motor cortex hemodynamic response function in freely moving walking subjects: a time-domain fNIRS pilot study.

Michele Lacerenza,Alberto Dalla Mora,Antonio Pifferi,Alessandro Torricelli,Alberto Tosi,Davide Contini,Mauro Buttafava,Bruno Cozzi,Lorenzo Spinelli,Franco Zappa

doi:10.1117/1.nph.8.1.015006

Abstract

.Significance: This study is a preliminary step toward the identification of a noninvasive and reliable tool for monitoring the presence and progress of gaiting dysfunctions.Aim: We present the results of a pilot study for monitoring the motor cortex hemodynamic response function (HRF) in freely walking subjects, with time-domain functional near-infrared spectroscopy (TD fNIRS).Approach: A compact and wearable single-channel TD fNIRS oximeter was employed. The lower limb motor cortex area of three healthy subjects was monitored while performing two different freely moving gaiting tasks: forward and backward walking.Results: The time course of oxygenated and deoxygenated hemoglobin was measured during the different walking tasks. Brain motor cortex hemodynamic activations have been analyzed throughout an adaptive HRF fitting procedure, showing a greater involvement of motor area in the backward walking task. By comparison with the HRF obtained in a finger-tapping task performed in a still condition, we excluded any effect of motion artifacts in the gaiting tasks.Conclusions: For the first time to our knowledge, the hemodynamic motor cortex response was measured by TD fNIRS during natural, freely walking exercises. The cortical response during forward and backward walking shows differences, possibly related to the diverse involvement of the motor cortex in the two types of gaiting.

Highlights

Gaiting is a natural skill, making humans able to move around in free space in upright position
For the first time to our knowledge, the hemodynamic motor cortex response was measured by TD Functional near-infrared spectroscopy (fNIRS) during natural, freely walking exercises
Studies have been performed by functional magnetic resonance imaging and positron emission tomography (PET) on brain activations during imaginary walking tasks, the only way to simulate gaiting due to the severe movement limitations of these techniques

Summary

Introduction

Gaiting is a natural skill, making humans able to move around in free space in upright position. Lacerenza et al.: Monitoring the motor cortex hemodynamic response function. Studies have been performed by functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) on brain activations during imaginary walking tasks, the only way to simulate gaiting due to the severe movement limitations of these techniques. Less can be found on brain hemodynamic monitoring during real gaiting in ecological experimental conditions. Different fNIRS and fMRI studies have shown how goal-directed locomotion, such as walking on assigned steps, given pathlengths, or walking on a straight line (real or imagined), significantly affects prefrontal cortex hemodynamics, reason why many experiments have monitored these areas. The involvement of motor cortex areas and the comparison of goal-directed locomotion with the more natural forward walking is not clear yet

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