Neuroimaging plays a critically important role in neuroscience research and management of neurological and mental disorders. Modern neuroimaging techniques rely on various “source” signals that change across different spatial and temporal scales in accompany with neuronal activity. For instance, neuronal activity intensifies electrophysiological signals, such as action potentials and post-synaptic potentials, which serve as the primary messengers for communication among neurons. It is generally agreed that neural activity is well-characterized by electrophysiological processes which tightly correspond with neuronal dynamics. In addition, neural activity is also coupled with metabolic and hemodynamic processes. As brain function requires sustained blood flow to supply oxygen to compensate for cerebral metabolic energy consumption, changes in neural activity often induce cascaded changes in cerebral metabolic rate of oxygen (CMRO2), cerebral blood flow (CBF), oxygen extraction fraction (OEF), cerebral blood volume (CBV), etc. In contrast to electrophysiological signals, metabolic and hemodynamic responses are much slower and reflect the indirect and secondary effects of neural activity.
