Before neuroimaging, scientists had to employ invasive techniques to examine a person’s brain. Starting at about 1850, scientists realized a more in-depth view of brains would provide more valuable data in order to reach a diagnosis. Before the nineteenth century, doctors began cutting open living patient’s skulls in order to activate or inactivate specific brain anatomy by introducing electrical stimuli, chemicals, heat or coldness, lesions, or ablation, to watch for telling certain reactions. Needless this was ethically questionable at best.
The advantage to any of the neuroimaging techniques is that they allow scientists a noninvasive view of the brain’s anatomy and physiology while the patient remains conscious. There are five types of neuroimaging techniques which are CTs, EEGs, PETs, most popularly MRIs and the newest type fMRIs.
One type of neuroimaging technique is known as a CT, or computerized axial tomography, scan. In a CT scan, an axis of X rays moving in a small circular arc penetrate a patient’s head where the strength of the rays are gauged by an identically moving detector on the other side. The different intensities of the X rays measure the location of and variant density of brain tissue and is used by a computer to construct a composite picture of the brain. This type of neuroimaging can be used in a number of ways including an identification of blockage, clot, or bleeding in the brain because such instances would constitute variant density than the surrounding normal tissue and could be represented visually by a computer composite. The limitation with CTs as an effective neuroimaging device is that while they effectively display brain anatomy, they can not discern whether it is functioning properly. In addition being called CT scans, computerized axial tomography is sometimes called a “CAT” scan.
A second type of neuroimaging is the EEG, or electroencephalograph, and is the product of medical scientists’ first try at making a neuroimaging device which could also gauge physiology. By taping tiny metal electrodes on the top and sides of a patient’s head, an EEG can measure neuron generated electrical currents on the surface of the brain. Event-related potentials, or sometimes known as evoked potentials, may be computed by measuring averages of an EEG’s reaction to repeated stimulus. These EEG generated potentials are valuable in that they measure the functionality of sensory and neuromuscular pathways. Thus, this type of neuroimaging is most commonly used to diagnose epilepsy and sleep disorders.
PET, or positron emission tomography, scans are a third type of neuroimaging and were revolutionary because they were the first neuroimaging device to create 3D localization of brain function. In order for this variation of neuroimaging to work, a patient must ingest or be injected with radioactive sugar. This presents the limitation of session duration, as a large enough dose will be damaging. This sugar emits positrons which will be more readily used by parts of the brain more active or stimulated. A computer composite is generated in similar ways as with CT scans and the medical personnel are thus notified if certain neuroimaging suggest tumors, lesions, or psychological abnormalities. In the case of psychological abnormalities, this type of neuroimaging can identify the brain’s metabolic levels, a low level suggesting an illness such as depression and a high level suggesting an illness such as schizophrenia.
The fourth type of neuroimaging is the magnetic resonance imaging scan or the MRI, which is also the most popular sort of neuroimaging. Because this type of neuroimaging uses nuclear magnetic resonance rather than X rays, MRIs are safer than CTs, though they are very similar neuroimaging techniques. By placing electromagnets around a patient’s head, MRIs function by disturbing the nuclei at the center of atoms in the brain which in turn creates variant frequencies depending on the atom’s specific location. This technique allows an MRI to use the frequency information to create a visual representation of someone’s brain. MRIs can be used to identify tumors, tissue degeneration, and blood clots. However, like CTs, MRIs are a limited form of neuroimaging because they can only provide anatomical information, not physiological.
The fifth form an neuroimaging system may take is the functional MRI scan, also known as an fMRI. This neuroimaging method is a re-vamped version of standard MRIs in that it may measure rapidly changing physiology and may generate 3D virtual reality displays of a brain, demonstrating the blood and oxygen flow as a cognitive task is being solved.
Though modern science has provided the medical community with five very effective, noninvasive types of neuroimaging, it is safe to predict more will soon be developed as we move towards the singularity.