by Researchers from Tokyo Metropolitan University have utilized near-infrared spectroscopy (NIRS) to measure changes in oxygenated hemoglobin levels in the brains of infants in response to touch. By placing external sensors on the scalps of sleeping infants, the researchers discovered that while the peak time of oxygenated hemoglobin levels remains constant regardless of the age of the infant, the amplitude, or range, of the signal varies over time. These findings provide valuable insights into the physiological development of infants.
The early stages of an infant’s life are marked by rapid and profound developmental changes. Neuroscience has leveraged advanced measurement techniques to gain unprecedented understanding of these processes, with functional magnetic resonance imaging (fMRI) and NIRS of the brain serving as critical tools in this journey.
NIRS allows scientists to track the flow of different compounds in the brain over time. Hemoglobin, a crucial component for carrying oxygen in the blood, is of particular interest. As the brain responds to external stimuli such as light, heat, and touch, oxygen is transported to the brain. NIRS facilitates the measurement of hemoglobin levels, enabling the identification of oxygenated hemoglobin and deoxygenated hemoglobin.
The team led by Assistant Professor Yutaka Fuchino from Tokyo Metropolitan University employed NIRS to study how infant brains respond to touch. Their study, published in the journal NeuroImage, focused on infants ranging from newborns to one year old. The researchers placed sensors on the infants’ scalps while they were asleep and monitored the changes in oxygenated hemoglobin levels as their limbs were gently shaken. Interestingly, infants of different ages displayed similar response times, with a small peak in hemoglobin levels occurring a few minutes after the stimulus was administered.
The consistent response time across infants in their first month and those over six months suggests that the factors influencing the speed of the response are already present at birth.
However, the researchers also observed significant differences in the amplitude of the signal, or the range of variation, among infants of different age groups. This amplitude did not follow a linear pattern; it decreased for infants aged one to two months and then increased as the infants grew older.
This intriguing behavior can be attributed to several aspects of an infant’s first few months of life. When infants are born, there is a rapid increase in oxygen levels as they begin breathing normally. This elevation in oxygen inhibits the production of erythropoietin, a small protein responsible for stimulating red blood cell production. As a result, temporary anemia occurs during the initial months. However, erythropoietin production gradually recovers, leading to the restoration of normal oxygen levels. Other factors, such as the development of nerves, veins, and blood flow, also contribute to these variations.
Significantly, this study highlights how NIRS measurements of hemoglobin levels in the brain can reflect developmental changes. Further research is anticipated to explore other physiological responses related to changes in blood flow dynamics, providing additional insights into the development of the brain and its interactions with the body.
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1. Source: Coherent Market Insights, Public sources, Desk research
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