Regional Homogeneity

Regional homogeneity (ReHo) is a measure of brain activity and organization commonly used in neuroimaging studies. It quantifies the degree of similarity between the regional time-series data of different regions of the brain. It is typically measured using the Kendall’s coefficient of concordance and calculated by correlating the time-series of each brain region with every other brain region. ReHo is believed to reflect the level of brain connectivity, the functioning of neuronal networks, and the degree of communications between different brain regions. Recent studies have found that altered ReHo is associated with various diseases and psychiatric disorders, such as Alzheimer’s, major depressive disorder, schizophrenia, and autism spectrum disorder. In Alzheimer’s, for instance, a decrease in ReHo has been observed in various brain regions, such as the default-mode network, temporal lobe, and hippocampus. ReHo is also thought to reflect the integrity of the neural networks involved in memory and executive functions, as well as sensory processing. In addition to the disease-related findings, ReHo could be a useful measure for exploring the effects of various interventions, such as cognitive training, drug therapies, and electrical stimulation. For instance, studies have found that a cognitive training program increases ReHo in brain regions related to visual and motor processing in healthy elderly adults. However, the size of these effects can vary according to the training program that is used. ReHo may also provide a valuable tool for characterizing the neurophysiological features of neurological and psychiatric diseases. For instance, a study used ReHo to successfully differentiate between Alzheimer’s patients and healthy controls, as well as schizophrenia patients and healthy controls. Furthermore, it could be used to track pre- to post-treatment changes in the regional organization of the brain. In conclusion, ReHo is a valuable measure of the regional organization of the brain and is useful for distinguishing between different diseases, tracking changes in brain function, and exploring the effects of various interventions.