Neuroimaging is the use of quantitative techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the human brain in a non-invasive manner.
There are many brain imaging tools available to cognitive neuroscientists, including positron emission tomography(PET), near infrared spectroscopy (NIRS), magnetoencephalogram (MEG), electroencephalography (EEG), and functional magnetic resonance imaging (fMRI).
We will cover the most common neuroimaging techniques used for Mental Fatigue & Brain Endurance Training (BET) research.
EEG
Electroencephalogram (EEG) is a test that measures electrical activity in the brain using small, metal discs (electrodes) attached to the scalp.
Brain cells communicate via electrical impulses and are active all the time, even during asleep. This activity shows up as wavy lines on an EEG recording.
EEG neuroimaging has shown that mental fatigue generally increases whole brain activation. It increases theta activity in frontal, central and posterior sites and alpha activity in central and posterior sites (Tran et al., 2020). These frequency bands can be linked to inhibition control and decreased alertness, which indicates that mental fatigue makes it more difficult to maintain focus on the task at hand, which contributes to less efficient performance (Habay et al., 2021).
In their conclusion, Tran et al. (2020) suggested that mainly the increase in theta activity can be seen as a valid and definite neurophysiological marker for mental fatigue.
fMRI
Functional magnetic resonance imaging, or FMRI, works by detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area.
fMRI has shown an association of increased mental fatigue with the following brain areas: somatosensory association cortex, supramarginal gyrus, the insula, dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC).
These regions monitor the potential task-related benefits and individuals' internal states, as well as regulating the extent of effort, taking the costs and benefits of task performance into account.
NIRS
Near-infrared spectroscopy (NIRS) is a brain imaging method that measures light absorbance to calculate oxy-hemoglobin (oxy-HB) and deoxy-hemoglobin (deoxy-HB), which provides an indirect measure of brain activity, particularly in the frontal cortex.
Research with NIRS neuroimaging has shown that engaging in Brain Endurance Training (BET) can lead to improvements in performance, due to an increased ability to maintain Pre Frontal Cortex (PFC) oxygenation.
Tissue Oxygenation
