A Review of Functional Near-Infrared Spectroscopy Studies of Attention Deficit/Hyperactivity Disorder Neurological Activation Patterns.
In September 2014 a literature review was published investigating the current state of research using functional near-infrared spectroscopy (fNIRS) imaging methods in evaluating neurological activation patterns of attention deficit/hyperactivity disorder (ADHD) populations.
The primary application of NIRS to the human body uses the fact that the transmission and absorption of NIR light in human body tissues contains information about hemoglobin concentration changes. When a specific area of the brain is activated, the localized blood volume in that area changes quickly. Optical imaging can measure the location and activity of specific regions of the brain by continuously monitoring blood hemoglobin levels through the determination of optical absorption coefficients.
NIRS can be used for non-invasive assessment of brain function through the intact skull in human subjects by detecting changes in blood hemoglobin concentrations associated with neural activity, e.g., in branches of Cognitive psychology as a partial replacement for fMRI techniques. NIRS can be used on infants, and NIRS is much more portable than fMRI machines, even wireless instrumentation is available, which enables investigations in freely moving subjects. However, NIRS cannot fully replace fMRI because it can only be used to scan cortical tissue, where fMRI can be used to measure activation throughout the brain.
It was found that ADHD patients displayed a consistent trend of altered activation patterns. Specifically, ADHD patients exhibited decreased levels of oxygenated hemoglobin levels during tasks. A similar pattern emerged for deoxygenated hemoglobin levels, but group differences were smaller. Results from studies investigating the effects of methylphenidate stimulant medications indicated that these altered activation patterns showed a normalization trend when participants began taking methylphenidate medications.Although fNIRS has been identified as a viable imaging technique with both temporal and spatial resolution, few studies have been conducted using fNIRS to evaluate neurological activation patterns in participants with ADHD. Studies that have utilized fNIRS technology indicate that ADHD participants consistently demonstrate altered activation patterns when compared to controls. Ths has potential implications in the assessment and treatment of ADHD.