Comparison of LED- and LASER-based fNIRS technologies to record the human peri‑spinal cord neurovascular response

Highlights•The human peri‑spinal neurovascular response elicited by a non-noxious electrical stimulus can be recorded non-invasively with Functional Near-Infrared Spectroscopy (fNIRS), using either a LED or LASER-based system.•The peri‑spinal NVR obtained by different fNIRS technologies is highly reproducible with LED or LASER-based fNIRS system.•Most of the parameters of the peri‑spinal NVR were similar, the main difference between both techniques was the amplitude of the signal, probably due to the power of the systems which should be considered when assessing the human peri‑spinal vascular network. Recently, functional Near-Infrared Spectroscopy (fNIRS) was applied to obtain, non-invasively, the human peri‑spinal Neuro-Vascular Response (NVR) under a non-noxious electrical stimulation of a peripheral nerve. This method allowed the measurements of changes in the concentration of oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) from the peri‑spinal vascular network. However, there is a lack of clarity about the potential differences in perispinal NVR recorded by the different fNIRS technologies currently available. In this work, the two main noninvasive fNIRS technologies were compared, i.e., LED and LASER-based. The recording of the human peri‑spinal NVR induced by non-noxious electrical stimulation of a peripheral nerve was recorded simultaneously at C7 and T10 vertebral levels. The amplitude, rise time, and full width at half maximum duration of the perispinal NVRs were characterized in healthy volunteers and compared between both systems. The main difference was that the LED-based system shows about one order of magnitude higher values of amplitude than the LASER-based system. No statistical differences were found for rise time and for duration parameters (at thoracic level). The comparison of point-to-point wave patterns did not show significant differences between both systems. In conclusion, the peri‑spinal NRV response obtained by different fNIRS technologies was reproducible, and only the amplitude showed differences, probably due to the power of the system which should be considered when assessing the human peri‑spinal vascular network.