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Functional activation studies in adults with fNIRS
The past couple of decades have seen a rapid increase in the use of functional near-infrared spectroscopy (fNIRS) for the monitoring of functional brain activity, especially for neuroscience applications. fNIRS is based on neurovascular coupling and derives information on the functional state of the brain by measuring the concentration changes of oxygenated (DHbO2) and deoxygenated (DHHb) hemoglobin that follow neuronal activity. Thanks to the recent technological advancements, more portable and wearable fNIRS devices have been developed and have paved the way to new neuroscientific investigations in more ecologically-valid scenarios, with people free to walk and interact with the environment as they would normally do in everyday life.
Since 2014, our group in collaboration with neuroscientists form the Institute of Cognitive Neuroscience at UCL have been exploring the feasibility of this new generation of wearable and miniaturized fNIRS instruments for the monitoring of brain activity in naturalistic situations. We have demonstrated that fNIRS is suitable to detect hemodynamic changes within the prefrontal cortex in response to an ecological prospective memory (PM) task conducted in streets of London on freely-moving people using the Wearable Optical Topography (WOT) system developed by Hitachi (Figure 1). The video of the whole experimental procedure can be found in [1].
Figure 1. Representative participant carrying out the PM task in the streets of London (A) and example of DHbO2 (red line) and DHHb (blue line) changes in response to the PM task (B, adapted from [1]).
However, the identification of functional events necessary for any analysis of fNIRS data can be extremely challenging in case of ecological and unstructured functional protocols. To overcome this issue, our group have developed a new algorithm called AIDE (Automatic IDentification of Functional Events) that takes a ‘brain-first’ approach and recovers the onsets of functional events directly from fNIRS data with no assumption on the stimuli timeline. AIDE is a Matlab-based software and can be downloaded here: https://github.com/multimodalspectroscopy/AIDE.git.
Recently, we are working on the assessment of typical and atypical functional activation patterns in Autism Spectrum Disorder (ASD) with fNIRS in more ecological scenarios. Preliminary results from this study have been recently presented at the fNIRS UK Meeting.
References
[1] Pinti, P., Aichelburg, C., Lind, F., Power, S., Swingler, E., Merla, A., ... & Tachtsidis, I. (2015). Using fiberless, wearable fNIRS to monitor brain activity in real-world cognitive tasks. Journal of visualized experiments: JoVE, (106).
[2] Pinti, P., Merla, A., Aichelburg, C., Lind, F., Power, S., Swingler, E., ... & Tachtsidis, I. (2017). A novel GLM-based method for the Automatic IDentification of functional Events (AIDE) in fNIRS data recorded in naturalistic environments. NeuroImage, 155, 291-304.