The human brain, being the most intricate organ in the body, poses a significant challenge for scientists seeking to understand its complex functions and interactions. The study of neuronal activity is crucial for unraveling the roles of different brain regions, particularly when subjects are awake and engaged in controlled tasks.
However, the most accurate measurement devices for this purpose are often invasive, limiting their use on healthy individuals in real-life settings.Â
In response to this challenge, scientists have developed ingenious techniques for noninvasive measurement of brain activity. One prominent example is functional magnetic resonance imaging (fMRI), which uses magnetic fields and radio waves to map changes in blood flow in the brain. However, the size and cost of the equipment required for fMRI restrict its widespread adoption in laboratory and clinical settings.Â
A promising alternative is functional near-infrared spectroscopy (fNIRS), a noninvasive method involving the placement of a light source and detector on the scalp to measure localized changes in hemoglobin concentration, correlating with brain activity. Despite its advantages, including simplicity and portability, the full potential of fNIRS remains largely unexplored in many brain regions.Â
A recent study published in Neurophotonics, led by Professor Minghao Dong from China’s Xidian University and Professor Chaozhe Zhu from Beijing Normal University, aimed to investigate the capabilities of fNIRS for measuring brain activity in the lateral occipital complex (LOC) and the fusiform face area (FFA). These regions are crucial components of the ventral visual pathway, with the LOC involved in object recognition and the FFA specialized in processing and recognizing faces.Â
To test their hypothesis that fNIRS measurements might be more successful in the LOC due to its proximity to the scalp, the researchers recruited 63 adult subjects. During the study, participants engaged in object- and face-recognition tasks while fNIRS measurements were performed using a portable instrument. The researchers used a tool called the “transcranial brain atlas” to optimize the placement of the instrument’s sensors for each individual subject.Â
The study provided valuable insights by demonstrating that placing the target channel corresponding to the target coordinates was sufficient for measuring LOC activity, eliminating the need for additional supplementary channels around the target coordinates. The results aligned with the researchers’ expectations, showing that the LOC target channel selectively activated in response to objects, while the FFA target channel did not.Â
One potential explanation for this observation is that the depth at which the FFA is located exceeds the detection threshold of fNIRS. Despite this limitation, the researchers concluded that the LOC region appears to be a suitable target for fNIRS-based detection.Â
The findings represent a step forward in refining techniques for studying the brain and assessing the feasibility of fNIRS for practical applications. The study is notable for being the first to examine the viability of fNIRS in monitoring cortical activity within the ventral visual pathway.
The researchers believe that further advancements in fNIRS technology could lead to practical, low-cost diagnostics for certain brain disorders and potential neuroenhancement devices, offering new possibilities for augmenting cognitive functions or treating neurological conditions. The future of neuroscience holds promise, with ongoing research shedding light on the capabilities of innovative techniques like fNIRS.Â
Journal Reference Â
Weilu Chai et al, Feasibility study of functional near-infrared spectroscopy in the ventral visual pathway for real-life applications, Neurophotonics (2024). DOI: 10.1117/1.NPh.11.1.015002. Â
