The examples of Functional Neuroimaging include fMRI, PET, and SPECT.

Functional Magnetic Resonance Imaging (fMRI)

An fMRI assesses the metabolic activity in an area of the nervous system with associated neural activity. It is one of the least expensive methods and one of the more commonly used methods in neuropsychological research.

Example of functional magnetic resonance imaging (fMRI)
An fMRI portraying elationship between dopamine (DA) D2 receptors in the brains of cocaine abusers and methamphetamine abusers, and metabolic activity in orbitofrontal cortex (Volkow & Wise, 2005). Source: Researchgate

Positron Emission Topography (PET)

PET scan produces a realtime image of an area of the brain after a radionuclide is injected into the bloodstream. PET scan measures the emissions from the radionuclide after an area of the brain is activated.

Example of positron emission topography (PET)
A PET scan can compare brain activity during periods of depression (left) with normal brain activity (right). An increase of blue and green colors, along with decreased white and yellow areas, shows decreased brain activity due to depression. Source: Mayo Clinic

Single-Photon Emission Computerized Tomography (SPECT)

SPECT scans utilize  a gamma camera that rotates around the individual and takes scans from different angles. These images are then used to create a cross-sectional (tomographic) image.

 

Example of single-photon emission computerized tomography (SPECT)
A SPECT scan of healthy brain on the left and a brain with schizophrenia on the right. Source: Thompson/UCLA

Volkow, Nora & Wise, Roy. (2005). How can drug addiction help us understand obesity? Nat Neurosci 8: 555-560.