Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 69

What parts of the brain are active when children solve problems or feel emotions? How does the brain change with development? Until recently, the brain was a mystery. Over the past hundred years, researchers have devised several ways of studying brain activity that have increased our understanding of how the brain functions and how it develops.

The earliest instrument created to measure brain activity was the electroencephalogram, first used with humans in the 1920s (Collura, 1993). Electroencephalography (EEG) measures electrical activity patterns produced by the brain via electrodes placed on the scalp. Researchers study fluctuations in activity that occur when participants are presented with stimuli or when they sleep. EEG recordings measure electrical activity in the brain, but they do not provide information about the location of activity.

Not until the invention of positron emission tomography (PET) in the early 1950s did researchers obtain the first glimpse of the inner workings of the brain (Portnow, Vaillancourt, & Okun, 2013). Researchers inject a small dose of radioactive material into the participant’s bloodstream and the PET scan measures its flow throughout the brain. The resulting images can illustrate what parts of the brain are active as participants view stimuli and solve problems. Developed in 1971, computerized tomography, known as the CT scan, produces X-ray images of brain structures that are combined to make a three-dimensional picture of the person’s brain, providing images of bone, brain vasculature, and tissue (Cierniak, 2011). Because both PET and CT scans rely on the use of radioactive material, these methods are generally only used for diagnosis rather than research.

Commonly used for research, functional magnetic resonance imaging (fMRI) measures brain activity by monitoring changes in blood flow in the brain (Bandettini, 2012). Developed in the 1990s, MRI machines house a powerful magnet that uses radio waves to measure the blood oxygen level. Active areas of the brain require more oxygen-rich blood. Like PET scans, fMRI enables researchers to determine what parts of the brain are active as individuals complete cognitive tasks.

Near-infrared spectroscopy (NIRS) involves directing infrared light into brain tissue and detecting its differential absorption in response to neural activity. Unlike fMRI, NIRS does not require the child to remain motionless (Yücel, Selb, Huppert, Franceschini, & Boas, 2017). The infant wears a cap with sensors and can move and interact with others during testing (McDonald & Perdue, 2018). NIRS, however, measures activity only on the outer part of the brain, the cortex, limiting its use somewhat.