Neuroimaging

Neuroimaging involves the different techniques used to image parts of the brain in order to identify either structure, function or both

  • Magnetic Resonance Imaging (MRI)
  • Positron Emission Tomography (PET)
  • Diffusion Tensor Imaging (DTI)
  • Electroencephalography (EEG)

 

MRI

MRI images (two or three dimensional) are created by the use of magnetic fields and radio pulses. These images are very detailed but appear as gray and white. The white areas of the brain are known as white matter and the gray regions are called gray matter. Interestingly, if you ever look at an MRI image, you will notice that a normal brain has a much higher percentage of white matter in comparison to gray matter. On the other hand, gray matter which is composed of glial cells (support cells for neurons) is lower in amount.

PET

In contrast to MRI images, PET images are not gray and white but instead show a range of colors. However, these images can also be two or three dimensional. PET uses radioactivity within the bloodstream to map distribution of chemicals within the brain. Each color on the PET image corresponds to a different level of activtity. Key advantages of PET include viewing oxygen levels and glucose metabolism within the functioning brain.

DTI

As the name suggests, DTI measures the diffusion of water in different regions of the brain. Therefore, one advantage of DTI is displaying the small neural tracts with detail.

 

EEG

One of the most popular  form of neuroimaging is the EEG which does not show a three dimensional image, but it does display activity within the brain in the form of waves. When impulses are transmitted along axons, this triggers the recording of the activity as oscillations. Specifically, activity in certain regions of the brain can be understood by noting the frequency of the waves. A higher frequency is indication of a high level of activity and vice versa.

Other forms of Neuroimaging:

SPECT --> less detailed image created (simgle photon used)

MRS --> measures neurotransmitter concentration

MEG --> indicates where certain areas are active

Event related optical signal --> shows neural activity lasting milliseconds

TMS --> powerful magnetics pulse sent against scalp