fNIRS reveals new insights into brain activity
summary: Researchers are exploring the potential of functional near-infrared spectroscopy (fNIRS) as a non-invasive tool to measure brain activity. In contrast to invasive methods, fNIRS offers simplicity and portability, making it a promising option for real-world applications.
The study focuses on the ventral visual pathway, especially the lateral occipital complex (LOC) and the fusiform facial area (FFA). The results indicate that fNIRS is more effective in detecting LOC activity compared to FFA, opening doors to practical brain monitoring and potential applications in diagnostic and neuroenhancement devices.
- Functional near-infrared spectroscopy (fNIRS) provides a non-invasive measurement of brain activity.
- fNIRS shows promising results in monitoring the ventral visual pathway, especially LOC.
- Future developments in fNIRS technology could revolutionize neuroscience and brain-related diagnostics.
The brain is not only the most complex organ in the human body, but it is also one of the most difficult to study. To understand the roles of different regions of the human brain and how they interact, it is necessary to measure neuronal activity with awake people while they perform controlled tasks. However, the most accurate measuring devices are invasive, which greatly limits their use in healthy humans in real-life settings.
To overcome this major hurdle, scientists have come up with ingenious techniques to measure brain activity in safe, non-invasive ways. One prominent example is functional magnetic resonance imaging (fMRI), which uses strong magnetic fields and radio waves to map changes in blood flow in the brain. The main drawback of fMRI is the size and cost of the equipment needed, which limits its wider adoption in laboratories and clinical settings.
Fortunately, a different technique called functional near-infrared spectroscopy (fNIRS) is starting to gain more interest. This method involves placing a light source and detector on the scalp to measure local changes in hemoglobin concentration, which correlate with brain activity. Despite its advantages, which include simplicity and portability, the true potential of fNIRS remains unexplored in many brain regions.
Previous studies have used fNIRS to detect brain activity in the ventral visual pathway, but none have evaluated its feasibility and ecological validity, or whether the detected signal is desirable.
Against this background, a research team including Professor Minghao Dong from Xidian University, China, together with Professor Zhaoze Zhu from Beijing Normal University, set out to test the capabilities of fNIRS to measure brain activity in the lateral occipital complex (LOC) and fusiform. Facial area (FFA), two main areas in what is known as the ventral visual pathway.
Their study was published in the journal Gold Open Access Neurophotonics.
To understand experiments, it is useful to know the functions of LOC and FFA. LOC plays a crucial role in object recognition; Its neurons are involved in processing information about the shapes and shapes of objects. On the other hand, FFA specializes in face processing and recognition.
Compared to FFA, LOC is much closer to the scalp. Hence, the team hypothesized that fNIRS measurements were more likely to be successful in this region than in the LOC.
To test this hypothesis, the researchers recruited 63 adults, 35 of whom were included in the current study, while another 28 were included in a follow-up study, whose results matched those in the current study but were not reported in the publication.
The team performed several object and face recognition tasks while performing fNIRS measurements using a portable instrument. The idea was to check whether the corresponding brain area would display activity in response to images of objects or faces that the person had seen previously during the experiment.
It is worth noting that the team used a tool called the Transcranial Brain Atlas, which they developed in a previous study, to determine the optimal placement of the tool’s sensors for each individual subject.
Furthermore, the present study provides valuable insights by showing that placing the target channel corresponding to target coordinates is sufficient to measure LOC activity, eliminating the need for additional supplementary channels around target coordinates.
The results matched the researchers’ expectations, says Dong: “According to our findings, the LOC target channel activates selectively in response to objects, while the FFA target channel does not.”
The most likely explanation is that the depth at which the FFA is located exceeds the fNIRS detection threshold.
“The LOC region seems to be a suitable target for fNIRS-based detection, despite the fact that fNIRS detection has limitations in collecting FFA activity,” Dong adds.
Overall, the research team’s efforts represent a step toward better techniques for studying the brain.
“Our results help understand the feasibility of fNIRS for practical applications. To our knowledge, this work is the first to examine the feasibility of this technique in monitoring cortical activity within the ventral visual pathway.”
Further advances in fNIRS technology could lead to practical, low-cost diagnoses of some brain disorders, as well as potential avenues for neuroenhancing devices. This equipment would enable us to enhance specific cognitive functions or help treat neurological conditions.
Only time will tell what fNIRS may hold for the future of neuroscience!
About neuroimaging research news
author: Danette Stevens
communication: Danette Stevens – SPIE
picture: Image credited to Neuroscience News
Original search: Open access.
“Feasibility study of functional near-infrared spectroscopy in the ventral visual pathway for real-life applications” by Minghao Dong et al. Neurophotonics
Studying the feasibility of functional near-infrared spectroscopy in the ventral visual pathway for real-life applications
fNIRS-based neuroenhancement relies on the possible detection of hemodynamic responses in targeted brain regions. Using the lateral occipital complex (LOC) and the fusiform face area (FFA) in the ventral visual pathway as neurofeedback targets enhances performance in visual recognition. However, the feasibility of using fNIRS to detect LOC and FFA activity in adults still needs to be validated because the depth of these regions may exceed the detection limit of fNIRS.
This study aimed to examine the feasibility of using fNIRS to measure hemodynamic responses in the ventral visual pathway, specifically in the LOC and FFA, in adults.
We recorded hemodynamic activities of the LOC and FFA regions in 35 subjects using an eight-channel portable fNIRS instrument. A standard face and single-back object recognition task was used to elicit selective brain responses in the LOC and FFA regions. The placement of fNIRS optodes for LOC and FFA detection was guided by the transcranial brain atlas (TBA) of our group.
Our findings revealed selective activation of the LOC target channel (CH2) in response to objects, whereas the FFA target channel (CH7) did not show selective activation in response to faces.
Our findings indicate that although fNIRS detection has limitations in capturing FFA activity, the LOC region emerges as a viable target for fNIRS-based detection. Moreover, our results call for the adoption of the TBA-based method to determine the LOC target channel, providing a promising solution for optrode placement. This feasibility study serves as the inaugural validation of fNIRS for detecting cortical activity in the ventral visual pathway, confirming its ecological validity. We propose that our findings establish a pivotal technical foundation for potential real-life applications of fNIRS-based research.