3.6 The Marriage of Function and Structure: Neuroimaging

Question 1

hemodynamic respons

Answer 1

When a brain area is active, increasing the blood flow to that region provides it with more oxygen and glucose at the expense of other parts of the brain

Question 2

blood oxygen level-dependent (BOLD)

Answer 2

the ratio of oxygenerated to deoxygenerated hemoglobin

Question 3

PET

Answer 3

PET activation studies use radioactive-labeled compounds to measure local variations in cerebral blood flow that correlate with mental activity. The radiologist injects a tracer into the bloodstream, which distributes it throughout the brain in step with its metabolic needs. A common tracer isotope used in PET studies is the oxygen-15 (15O), which has a half life of 122 seconds. Although all areas of the body use some of the radioactive oxygen, the fundamental assumption of PET is that there is increased blood flow to the brain regions that have heightened neural activity. Thus, PET activation studies measure relative activity, not absolute metabolic activity. The results are usually reported as a change in regional cerebral blood flow (rCBF) between the control and experimental conditions.

Question 4

magnetic resonance spectroscopy (MRS)

Answer 4

offers a tool to obtain, in vivo, information about the chemical composition of tissues. From the MRS data, researchers can estimate the concentration of different neurochemicals in one brain area or the same neurotransmitter in multiple areas.