Lecture 3-Neuroimaging Flashcards
What are two types of structural imaging?
- MRI
- CT
What are three types of functional imaging?
- PET
- fMRI
- TMS (Neurostimulation method)
- ERP
What are the advantages of TMS?
- High spatial resolution
- High temporal resolution
- Can be used repeatedly without causing harm
- Provides information about the role of different brain areas in particular perceptual/cognitive/motor function
Disadvantages of TMS:
- Restricted to brain regions close to the skull
- Holding the coil in place not easy, can lead to imprecise targeting, inconsistent stimulation
What are the advantages and disadvantages of CT scans?
Advantages include being inexpensive, provide quickly imaging, detailed images while disadvantages are poor spatial resolution and exposure to ionizing radiation.
What are advantages and disadvantages of MRI?
Advantages include good spatial resolution; disadvantages are that it can’t be used with people who have metal implants or pacemakers.
How does the static magnetic field contribute to MRI?
The static magnetic field in MRI machines helps align hydrogen atoms in the body, which are abundant in water and fat.
What is the purpose of the pulse sequence in MRI?
The pulse sequence disrupts the alignment of hydrogen atoms in the body temporarily during the MRI scan.
Define relaxation time in the context of MRI.
Refers to the time it takes for hydrogen atoms to return to their original alignment within the magnetic field after being disrupted by radio waves. This time varies depending on the type of tissue.
How is a brain volume collected in structural brain imaging?
By collecting multiple slices that represent different sections of the brain, compiling them into one complete brain volume, which typically takes 6-10 minutes.
What does PET imaging involve and what are its characteristics?
involves injecting radioactive tracers into the bloodstream to measure brain activity. It provides good spatial resolution but has poor temporal resolution.
What have PET scans revealed in cognitive studies comparing younger and older adults?
PET scans show more frontal brain activity in older adults compared to younger ones, suggesting age-related changes in brain function.
How is PET used in neurotransmitter studies?
PET is used to study neurotransmitters by showing that higher dopamine receptor binding is associated with stronger functional connectivity between brain regions.
What does fMRI measure and how does it work?
fMRI measures brain activity by detecting changes in blood oxygenation and flow, relies on
the Blood Oxygen Level Dependent (BOLD) effect that contrasts the magnetic properties of oxygenated and deoxygenated blood.
What is the difference between the basal and activated states of the brain as detected by fMRI?
In the basal state, the brain has a normal level of blood flow and oxygenation. In the activated state, there is increased blood flow and oxygenation in response to heightened neuronal activity, leading to an increase in the MR signal detected by fMRI.
What does the Hemodynamic Response Function (HRF) describe in the context of fMRI and the BOLD effect?
characterizes the time course of the BOLD signal in the brain following a stimulus. It includes a rapid rise to a peak, followed by a decrease below baseline (undershoot), and a return to baseline,which can be used to map brain activity
What is the trade-off when increasing the temporal resolution of fMRI scans?
Increasing the temporal resolution of fMRI scans results in a trade-off with spatial resolution; as the temporal resolution becomes faster, the spatial resolution becomes poorer, meaning that details in the images are less clear.
How are differences in brain activity located using Whole Brain Analysis in fMRI studies?
- Functional images taken under different conditions are compared using a subtraction method to highlight differences.
2.These differences are then superimposed on a structural MRI to precisely locate the areas of brain activity.
What does Region of Interest (ROI) Analysis in fMRI studies allow researchers to do?
Allows researchers to focus on specific brain regions and track the percentage change in fMRI signal over time and under different conditions, providing detailed analysis of those particular areas.
What is the structure of a block design in fMRI studies?
- In a block design for fMRI studies, stimuli and rest periods are alternated in blocks
- The fMRI images are taken during these blocks, and the BOLD response is recorded, showing a pattern that fluctuates with these blocks.
What does the block design measure in fMRI?
Allows researchers to measure the brain’s response to prolonged stimuli.
What are the advantages of blocked fMRI?
- Allows researchers to compare brain activity between conditions presented in distinct blocks, making it easier to detect differences
- Most widely used in fMRI studies due to its efficacy in capturing brain responses to various tasks/stimuli
Disadvantages of blocked fMRI? (3)
- Subjects may mentally prepare for each block, making their responses less spontaneous
- The design’s predictability can limit its ability to capture natural brain responses
- Difficult to examine how the brain responds to individual events within the experimental task such as correct vs incorrect responses
What is the characteristic feature of an Event-Related fMRI design?
Characterized by its ability to measure brain responses to individual events or stimuli as they occur, allowing for the examination of the BOLD response to specific, isolated events.
