Neuroimaging
In this lesson, we'll learn how neuroimaging techniques let us study the living brain by measuring its structure and activity.
1) Start with these videos:
2) Read this article for some additional perspective on interpreting neuroimaging studies:
What are we getting wrong in neuroscience?
3) Finally, answer these questions to test your understanding:
1. Which of the following neuroimaging techniques provides information about what parts of the brain were most active while the image was acquired?
- A. functional magnetic resonance imaging (fMRI)
- B. magnetic resonance imaging (MRI)
- C. computed tomography (CT)
- D. diffusion tensor imaging (DTI)
Show Answer
Correct answer: A
fMRI provides information about brain activity. It detects changes in blood flow in the brain, which is an indirect measure of brain activity because parts of the brain that are more active require more blood flow. MRI and CT scans provide information about the structure of the brain, while DTI provides information about white matter tracts, or pathways, within the brain.
2. Which of the following types of neuroimaging typically provides information on brain structure only (not function)?
- A. functional magnetic resonance imaging (fMRI)
- B. computed tomography (CT)
- C. positron emission tomography (PET)
- D. electroencephalography (EEG)
Show Answer
Correct answer: B
Computed tomography, also known as computed axial tomography, is a type of structural neuroimaging. It is usually called a CAT or CT scan. It involves taking a series of x-ray images from various locations around the head. These images can then be combined to construct an image of the brain. The other answer choices all are used to obtain information about brain function.
3. What does an electroencephalogram (EEG) primarily measure?
- A. the electrical activity of single neurons
- B. the electrical activity of populations of neurons active at the same time
- C. changes in cerebral blood flow
- D. action potentials in subcortical structures
Show Answer
Correct answer: B
An EEG records voltage fluctuations from large groups of neurons, particularly when their activity is synchronized, mainly in the cerebral cortex. It does not have the spatial resolution to detect activity from single neurons; it reflects the summed electrical activity of many neurons.
4. The most commonly used method in functional MRI (fMRI) for detecting brain activity is based on which signal?
- A. EEG (electroencephalographic) signal
- B. BOLD (blood-oxygen-level–dependent) signal
- C. DTI (diffusion tensor imaging) signal
- D. MEG (magnetoencephalographic) signal
Show Answer
Correct answer: B
Functional MRI (fMRI) typically uses the BOLD signal, which detects small changes in blood oxygenation associated with neural activity. Increased neural activity leads to increased local blood flow, changing the ratio of oxygenated to deoxygenated hemoglobin (and thus the fMRI signal intensity).
5. Which type of neuroimaging involves the injection of a radioactive tracer and the measurement of gamma rays to assess brain activity by tracking the distribution of the tracer (e.g., reflecting metabolic activity or blood flow)?
- A. positron emission tomography (PET)
- B. computerized tomography (CT)
- C. functional magnetic resonance imaging (fMRI)
- D. magnetic resonance imaging (MRI)
Show Answer
Correct answer: A
To do a PET scan, a patient is injected with a radioactive substance that emits positrons, which then emit gamma rays when they collide with electrons in brain tissue. These gamma rays are detected by the PET scanner. Detection of these rays can be used to determine blood flow to more active parts of the brain as well as the distribution of specific molecules, depending on the tracer that is used.
