At the dawn of the 19th century, pioneering astronomer Sir William Herschel discovered the existence of infrared radiation, which is electromagnetic radiation invisible to the human eye but identifiable via its ability to heat objects. Infrared radiation is commonly divided into three categories, near, mid, or far infrared waves. In ensuing years, infrared radiation was found to be useful for industrial, scientific, military, and law enforcement applications, such as heat signature tracking and night vision goggles. Over two decades ago, a new technology called near infrared spectroscopy (NIRS) was developed for non-invasively measuring specific aspects of human physiology using near infra-red waves. While far infrared waves lie closest to the microwave region, near infrared waves are closest in length to the visible light part of the electromagnetic spectrum, and are microscopic in size. Unlike far infrared waves, near infrared waves do not produce any heat. In fact, we can’t feel them at all. They are the small waves used by common devices such as a
Today, near infrared waves are commonly used for studying many application areas of human physiology, notably by the fNIRS Imaging Systems to gather precise, high-density brain function and muscle oxygenation data.
How does fNIRS work with regard to human physiology? It’s an optical technology which sends light into the tissue and records the light that scatters back via a photo-diode and sensor attached to the subject. The fNIRS continuous wave technology uses an optical window in the near infrared spectrum that enables light to pass through. For example, when you hold your hand in front of a strong white light, the tissue can appear red and almost translucent. fNIRS shines light into the skull or muscle tissue, and using special detectors, records the resulting light scatter that returns to the surface. The light penetrates skin, bone, and alights on the brain before its return trip to the surface detectors, and accomplishes this painlessly without heat. In fact, the subject does not even feel the near infrared energy and the light is harmless. The result is startling images and functional data of the brain at work. The fNIRS Systems (ranging from Educational to High-Density versions) include fNIRsoft software for processing, analyzing and visualizing functional near infrared (fNIR) spectroscopy signals through a graphical user interface. Additionally, the fNIRS Systems work with the BIOPAC MP160 Research System and AcqKnowledge software in conjunction with other physiological signals such as ECG, respiration, cardiac output, blood pressure, electrodermal activity, and stimulus response markers. AcqKnowledge software also provides automated analysis tools for event related potentials and ensemble averaging.
fNIRS brain function application areas include workload assignment, VR, stress, attention, geriatrics, economics, ergonomics, learning and performance, sports science, HCI, pain perception, and cognitive workload – low or high.
fNIRS Systems can also be used to measure muscle oxygenation data, including oxidative capacity, muscle load, lateral imbalances (left vs. right muscle group) oxygenated hemoglobin and de-oxygenated hemoglobin in muscle activity.
BIOPAC offers a wide array of wired and wireless equipment that can be used in your research. To find more information on solutions for recording and analyzing signals such as ECG, heart rate, respiration and more using any platforms mentioned in this blog post, you can visit the individual application pages on the BIOPAC website.