Definition:
Brain mapping is nothing but study of anatomy and physiology of the central nervous system (that is the brain and spinal cord) using various techniques. Brain mapping gives us a detailed knowledge of the structure of the brain. Brain mapping helps us to associate the anatomical area of the brain to the function it performs. The central nervous system forms a very important part of the body. It is responsible for complete functioning of the body. In other words, it is the control unit of your body. Hence, it becomes extremely necessary to know about the brain more intimately. We should know the location of the area of a brain corresponding to a certain function, the changes that take place in the brain as we grow – development of brain and result of ageing and the changes in the brain during some mental illness.
Methods and technology
Study of this system consists of various techniques. Few of them are:
CAT : Computed Axial Tomography
EEG : Electroencephalography
MEG : Magnetic encephalography
MRI : Magnetic resonance imaging
fMRI : functional magnetic resonance imaging
phMRI : pharmacological Magnetic resonance imaging
PET : positron emission tomography
DTI : Diffusion tensor MRI
NIRS : near infra-red spectroscopy and imaging
CAT scan: Also referred as computer assisted tomography or X-ray computed tomography. It X-rays the brain from many angles in order to show structural abnormalities. The x-rays are processed by the computer so that it produces tomographic image (also known as virtual slices) of the scanned areas of a specific object. A three dimensional image of the inside of the object is generated using digital geometry processing. For that a large series of two dimensional images are taken around a single axis of rotation. Thus this procedure permits the user to see the inside area without cutting it. CAT scan is used for diagnostic and therapeutic purposes.
EEG: It is a method to measure the electric activity of the brain. Electrodes are placed on the scalp and results in encephalogram which is the representation of electrical signals generated as a result of ionic current flow in the neurons.
It is a non-invasive method hence widely used in research purposes. It is also useful in the diagnosis of epilepsy, coma, encepholopathies, brain death, tumors, stroke etc.MEG: Individual neurons have electrochemical property. This results in flow of electrically charged ions in a cell. That means electric currents occur naturally in the brain which produce magnetic fields. The magnitude of magnetic field of a single neuron is negligible but when a group of neurons in certain area is activated they generate a measureable magnetic field at the scalp. MEG is a functional neuroimaging method which marks the brain activity by using very sensitive magnetometers to record the magnetic fields produced by the electrical current in brain. SQUIDs – Superconducting quantum interference devices are widely used as magnetometers.
MRI: It is used for imaging the anatomical structure of the brain. Strong magnetic fields and radio waves are used by MRI scanners in order to form images. It is used extensively for diagnostic and research purposes. It is used in hospitals for medical diagnosis, staging of disease and for follow-up. It helps to determine the structural alterations and behavioral correlations. An MRI studies the hydrogen nuclei of the water molecule.
fMRI: It is used to view the metabolic function of the brain. It is one of the highlights of MRI technology. It shows the brain activity when a person performs certain tasks. It gets the functional image of the brain by measuring the blood flow or the blood oxygen level. The main use of fMRI is gathering the data relevant to the consumption of oxygen by the tissues. When the area of the brain is used, the blood flow to that region increases. People are not required to undergo shots, invasions or to ingest materials or exposure to radiation; hence it has become a very important technique for brain mapping.
phMRI: Neuronal activity can be elicited using drugs as well. Use of pharmacological ligands can cause a hemodynamic change. This technique can generate maps of the consequences of receptor stimulation which can thereby be used as a diagnostic tool for a large number of cerebral disorders.
PET: It is used to measure the activity in the brain using radioactive markers. It produces a three dimensional image of the functional processes in the brain. The marker or the tracer is a positron emitting radio nuclide which emits gamma rays. A tracer is ingested, injected or inhaled. A diseased area generally has a higher level of chemical activity. The tracer accumulates in that area and appears as bright spots in PET scan.
DTI: Diffusion tensor MRI is a noninvasive method. It follows water movement in the brain. It maps the diffusion process of molecules in biological tissues in vivo. It is mainly used in diagnostic purposes especially in patients with acute stroke. It exposes the abnormalities in the structure of the white matter fiber hence it is common used to the white matter abnormalities.
NIRS: Electromagnetic spectrum is a range of frequencies of electromagnetic radiation. As the name suggests it uses near infra-red region of electromagnetic spectrum- 800 nm to 2500 nm. It is not a very sensitive technique. But it can be used for the examination of a bulk material.
Trans cranial magnetic stimulation: It is a noninvasive method. It triggers certain behaviors by stimulating specific parts of brain. The magnetic field is changed rapidly using electromagnetic induction. This rapidly changing magnetic field induces weak electric currents which cause activities in specific or general parts of brain which can then be recorded.
Uses:
Brain is a very complex structure and brain mapping helps us to understand the brain better. The practical use of brain mapping is in for diagnostic purposes. It helps in diagnosis and treatment of neurological conditions like epilepsy, tumors, structural abnormalities, neurodegenerative disorders like Alzheimer's and Parkinson's, developmental abnormalities like autism, mental illness like schizophrenia , panic disorder, bipolar disorder, depression, anxiety etc.