Home > Conscious > Chapter 1 > 1.3. Neuroimaging

 

Neuroimaging can show not only brain lesions, but also allows researchers to observe normal brain activity while the subject is performing tasks. The main imaging techniques include computed tomography (CT scan), positron emission tomography (PET) and magnetic resonance imaging (MRI).

  • CT scan uses X-ray to irradiate the brain from different angles, producing cross-sectional images, and then reconstruct the three-dimensional image.
  • PET constructs images from the positrons emitted during radioactive decay by the radionuclide (tracer) that was injected into the blood vessel (Figure 1-4).
  • MRI utilize nuclear resonance between applied magnetic fields and atomic nuclei in the brain.

Functional MRI (fMRI) is a further application of MRI on the basis of BOLD (blood oxygen-level dependent). Neural activity will consume oxygen, which requires transport by blood vessels. Thus, the brain's activity is accompanied by changes in blood oxygen concentration. Generally, a stronger BOLD signal in a brain area indicates stronger neural activity in that area (Figure 1-4).

Both PET and fMRI can be used to show active brain areas during a variety of feelings and cognitions. The study found, while we feel pain, a group of regions called "pain matrix" will increase activities. In contrast, during orgasm, some regions will greatly reduce activities. Depression has also been demonstrated to arise from overactive resting state networks. Further details will be discussed in later chapters of this book.

Images

Figure 1-4. Images obtained by PET and fMRI. [Source: Wikipedia]