March 2, 2024

Using Spectroscopy to Measure Visual Recognition: Advancements in Noninvasive Brain Monitoring

A team of researchers from Xidian University and Beijing Normal University in China recently conducted a study to investigate the potential of functional near-infrared spectroscopy (fNIRS) in measuring brain activity in two key regions of the ventral visual pathway—the lateral occipital complex (LOC) and the fusiform face area (FFA). The study aimed to evaluate the feasibility and ecological validity of fNIRS in detecting brain activity in these regions, which play important roles in object recognition and face processing, respectively.

The brain, being one of the most complex organs, poses challenges for researchers studying its functions and interactions. Traditionally, invasive measurement devices have been used to study neuronal activity in awake subjects performing controlled tasks. However, the invasiveness of these devices limits their use on healthy humans in real-life settings. To overcome this obstacle, scientists have developed noninvasive techniques, such as fNIRS, which measures changes in hemoglobin concentration to infer brain activity.

Unlike functional magnetic resonance imaging (fMRI), which requires large and expensive equipment, fNIRS offers simplicity and portability. It involves placing a light source and detector on the scalp to measure localized changes in hemoglobin concentration, which correlate with brain activity. However, the full potential of fNIRS remains largely unexplored in many brain regions.

Previous studies have demonstrated the effectiveness of fNIRS in detecting brain activity in the ventral visual pathway. However, the researchers in this study aimed to investigate the feasibility and ecological validity of fNIRS in measuring brain activity in the LOC and FFA. To test their hypothesis, the team recruited 63 adult subjects and conducted object and face recognition tasks while measuring brain activity using a portable fNIRS instrument.

The study revealed that the LOC target channel selectively activates in response to objects, while the FFA target channel does not. The researchers speculated that the depth at which the FFA is located may exceed the detection threshold of fNIRS, making it more challenging to collect FFA activity using this technique. Nevertheless, the study highlights the potential of fNIRS in detecting LOC activity and provides valuable insights into sensor placement optimization.

The research team utilized a transcranial brain atlas tool, which they had developed in a previous study, to determine the optimal placement of the fNIRS sensors for each subject. The study also demonstrated that placing the target channel corresponding to the target coordinates is sufficient for measuring LOC activity, eliminating the need for additional supplementary channels around the target coordinates.

These findings contribute to our understanding of the feasibility of fNIRS for practical applications and represent a significant step in the development of better techniques for studying the brain. Further advancements in fNIRS technology could lead to low-cost diagnostics for brain disorders and potential neuroenhancement devices, offering opportunities to augment cognitive functions and treat neurological conditions in the future.

While the study focused on the ventral visual pathway, fNIRS holds promise for exploring other brain regions and understanding complex cognitive processes. As researchers continue to refine and innovate fNIRS technology, its potential impact on neuroscience research and clinical applications remains to be seen.

1. Source: Coherent Market Insights, Public sources, Desk research
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