Physiological basis and image processing in functional magnetic resonance imaging: Neuronal and motor activity in brain

Recent investigations focused on specific brain regional and functional specificity to delineate the specific distribution of neural activities at a given moment in the brain as a whole. Functional magnetic resonance imaging (fMRI) was introduced to map the changes in brain local blood flow and oxygenation or hemodynamics that correspond to regional neuronal activity of brain accompanying metabolic events. It extended brain anatomical imaging to map structures and specific function of human brain. High resolution, noninvasive neural activity by a blood oxygen level dependent signal has tremendous potentials for assessing the neurological status and neurosurgical risk [1-4]. Later fMRI applications extended the understanding of neuronal and motor activities associated with different brain regional functions. Presently, fMRI serves as non-invasive imaging of neurophysiological activities of brain that depend more on physiological characteristics of brain.The paper reviews the physiological basis of fMRI signal origin and contrast mechanisms with state-of-art fMRI segmentation and registration algorithms to identify cortical visual response and event related cortical areas associated with neurophysiological measurements and potential image post-processing directions in future.Neurovascular and neurometabolic coupling establishes the critical link between a focal change in neuronal activity and MRI-detectable observations. In fact, all task performances such as arousal, attention, alertness, adaptation, sleep, or consciousness that affect the vascular hemodynamics do interfere with oxygenation-sensitive mapping by fMRI techniques.Historically, these observations initially were supported by reports on local reduction in deoxyhemoglobin due to increased blood flow without change in oxygen extraction [5]. Deoxyhemoglobin acts as paramagnetic endogenous contrast agent and alters the T2* weighted magnetic resonance image signal [6-9] and serves as the source of the signal fo