Near Infrared Spectroscopy (NIRS)
Near Infrared Spectroscopy (NIRS) is a fascinating technique that allows us to see how infants’ brains work. In a NIRS study, we measure infants’ brain activity while they are listening to language stimuli. We record the brain activity using special sensors worn by the infant. The sensors are made of silicone, and are held in place on the infant’s head with soft, stretchy material. The optical sensors monitor the level of oxygenation in different areas of the brain, providing an indirect measure of how active each area is. When a given brain area processes some input, such as speech sounds, it uses more oxygen than when it is in a state of rest. Thus, the level of oxygenation in the brain tells us which areas contribute to the understanding of speech.
Studies currently take place at our Centre on UBC campus as well as at BC Children’s and Women’s Hospital. During the study visit, a researcher from our Centre puts the cap on the child while the child is lying quietly in a bed or sitting on a parent’s lap. Once the cap is on, the baby sits quietly or sleeps while speech sounds are being played to them. As in all of our studies, Mom and/or Dad are also present throughout the entire study.
One major advantage of using this technique is that it does not require infants to make any particular behavioural response to the stimuli. In fact, babies can sleep throughout the study; it’s only their brains that are at work! This allows us to use the technique even with newborns that are only a few days old.
Event-Related Potential (ERP)
This exciting new technology allows us to see how the brain functions, and complements and extends our behavioural studies. In an ERP study, we measure infants’ brain activity while they are listening to language stimuli. We record the brain activity from a special cap worn by the infant, which fits like a shower or swimmer’s cap. The cap itself is made of soft, stretchy material and has electrodes sewn into it. The electrodes in the cap function like a microphone in picking up the activity from the brain. In this manner we are able to monitor any changes in the electrical brain activity while the infant is listening to language stimuli.
During the study visit, one of the researchers from our Centre puts the cap on the child, while an assistant entertains and distracts the child with a variety of toys. As in all of our studies, Mom and/or Dad are also present throughout the entire study. Once the cap is on, the electrodes on the cap are filled with a gel (similar to ultrasound gel) that helps us pick up the brain activity. After the cap has been properly arranged, we head to the study room where the infant, sitting on Mom or Dad’s lap will watch a silent movie while they are listening to speech sounds.
One major advantage of using this technique is that ERP does not require the participant (the infants in our case) to make any particular behavioural response to the stimuli. This means that we do not need to use an indirect measure of processing (such as looking time), but rather can measure the brain response directly.