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

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.

How much do time-domain functional near-infrared spectroscopy (fNIRS) moments improve estimation of brain activity over traditional fNIRS?

“…Even then, the Kernel flow consumes a considerable amount of power and the helmet alone weights more than four pounds, limiting its mobility, especially compared to the recent CW systems, which are trending toward wearability, 35 , 36 affordability, and open source. 37 Despite this, it is expected that TD fNIRS technology will continue progressing in usability and cost, and there are efforts toward developing more portable implementations of the technology, 38 which might result in innovative clinical and practical applications (such as identification of intoxication biomarkers 39 ).…”

Opening the dialogue: A preliminary exploration of hair color, hair cleanliness, light, and motion effects on fNIRS signal quality

“…To test the independent variables (i.e., hair color, hair cleanliness, environmental light) in E1, E2, and E3, participants completed a finger-tapping task (i.e., repeatedly touching each finger to the thumb one by one). Finger tapping was selected for its extensive documentation and frequent utilization in both fMRI [ 38 ] and fNIRS research [ 4 , 30 – 32 , 35 , 39 – 41 ], presenting a straightforward motor task that is easily executed and standardized across participants. In E4, participants completed a series of gross motor movements (i.e., walking, turning the head, nodding the head) to test their effects on signal quality (see Lacerenza et al [ 32 ] for a similar design used to monitor the hemodynamic response function during forward and backward walking).…”

“…Finger tapping was selected for its extensive documentation and frequent utilization in both fMRI [ 38 ] and fNIRS research [ 4 , 30 – 32 , 35 , 39 – 41 ], presenting a straightforward motor task that is easily executed and standardized across participants. In E4, participants completed a series of gross motor movements (i.e., walking, turning the head, nodding the head) to test their effects on signal quality (see Lacerenza et al [ 32 ] for a similar design used to monitor the hemodynamic response function during forward and backward walking). All experiments used a block-design, similar to those found in the fNIRS literature [ 30 – 32 , 35 , 39 , 40 ].…”

“…In E4, participants completed a series of gross motor movements (i.e., walking, turning the head, nodding the head) to test their effects on signal quality (see Lacerenza et al [ 32 ] for a similar design used to monitor the hemodynamic response function during forward and backward walking). All experiments used a block-design, similar to those found in the fNIRS literature [ 30 – 32 , 35 , 39 , 40 ]. Details specific to each experimental procedure can be found below.…”

“…This flexibility can enhance the ecological validity of the research; 6) Ease of Implementation : SCEDs are often relatively simple to implement, requiring fewer participants and resources compared to group designs. This can make SCEDs more feasible, particularly in settings with limited resources or when studying hard-to-reach populations; 7) Ethical Considerations : SCEDs involve fewer participants, which reduced ethical concerns related to participant burden given the systematic nature of Experiments 2, 3 and 4, in particular (see also [ 30 – 32 ] for similar designs using fNIRS).…”