Functional near-infrared spectroscopy (fNIRS) offers researchers a powerful noninvasive tool for studying brain activity by measuring changes in blood oxygen levels. These changes reflect how various brain regions respond to stimuli such as tasks that involve thinking, emotion, movement, and social interaction. These are often in natural, real-world settings that are not possible with other brain imaging methods. However, fNIRS is not without its own limitations. Systemic fluctuations in the body, such as breathing patterns, cardiovascular changes, and autonomic responses, can result in signal noise that is misinterpreted as brain activity by traditional fNIRS. The solution: a visit to the SPA.
Systemic Physiology Augmented fNIRS (SPA-fNIRS) is an advanced approach to fNIRS that goes beyond measuring local changes in cerebral oxygenation. While standard fNIRS measures cortical hemodynamics by tracking oxygenated (HbO) and deoxygenated (HbR) hemoglobin, noise originating from systemic physiological changes can corrupt those signals. Combining data from both neural and systemic physiological signals, SPA-fNIRS provides researchers with a more diverse and accurate view of how the brain and body interact in real time.
The method is being applied across various fields, including psychophysiology, cognitive neuroscience, exercise physiology, mental health, and human performance research. Studies have utilized SPA-fNIRS to investigate a range of topics, including meditation and emotional regulation, movement control, and social interaction. The broader goal is to move beyond studying the brain in isolation and to understand it as part of an integrated mind-body system. This holistic view is transforming how scientists interpret brain-function data, opening new paths for applied research in education, rehabilitation, and human-machine interface design.
Researchers in India investigated the impact of a traditional sound-based meditation technique, known as the Mind-Sound Resonance Technique (MSRT), on both brain and heart activity. Using fNIRS to track changes in oxygen levels in the prefrontal cortex, and a BIOPAC data acquisition and analysis system with AcqKnowledge software to record and analyze heart rate variability (HRV), the study employed a SPA-fNIRS design, integrating neural and physiological data in a single, synchronized dataset. HRV analysis allowed the researchers to quantify shifts in autonomic balance during and after meditation. The results showed increased oxygenation in the right prefrontal cortex and enhanced low-frequency HRV components, reflecting greater parasympathetic regulation. Together, these findings suggest that sound-based meditation not only improves brain oxygenation but also promotes calmer, more balanced heart-brain dynamics, illustrating how SPA-fNIRS methods can reveal the comprehensive physiological impact of mindfulness practices.
In her doctoral research at the Université de Lille in France, neuroscientist Aurore Guérin examined how the brain controls movement speed using a multimodal combination of fNIRS and physiological data recording systems. Participants performed repetitive arm movements at fast, natural, and slow tempos. At the same time, the study captured oxygenation in the prefrontal and motor cortices using fNIRS, alongside heart rate and respiration signals collected with a BIOPAC data acquisition system. A respiratory effort transducer measured breathing patterns, while a BioNomadix ECG module recorded cardiac activity for HRV analysis. All physiological signals were synchronized and analyzed in AcqKnowledge software, allowing the team to identify and remove systemic influences (e.g., heartbeat and breathing rhythms) from the fNIRS signals, following a SPA-fNIRS approach. The results revealed that faster movements primarily engaged motor regions, while slower, more deliberate pacing resulted in higher prefrontal activation, reflecting greater cognitive control. By integrating physiological monitoring with fNIRS, the study provided a clearer picture of how the brain and body coordinate timing and control during movement.
These studies illustrate how SPA-fNIRS is reshaping the way scientists investigate the interaction between brain and body. By combining neural and physiological data in a single synchronized system, researchers can separate brain activity from systemic noise and uncover the interplay between cognition, emotion, and autonomic regulation. For more information on this topic, watch our webinar on Multimodal SPA-fNIRS and check our our latest multimoldal fNIRS research products.
Are you planning a study that blends fNIRS with other physiological signals? Contact your local BIOPAC customer service representative to learn more about how SPA-fNIRS can benefit your research.
Recent Comments