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Neural Basis > Lecture 3-Neuroimaging > Flashcards

Lecture 3-Neuroimaging Flashcards

1
Q

What are two types of structural imaging?

A
  1. MRI
  2. CT
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2
Q

What are three types of functional imaging?

A
  1. PET
  2. fMRI
  3. TMS (Neurostimulation method)
  4. ERP
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3
Q

What are the advantages of TMS?

A
  1. High spatial resolution
  2. High temporal resolution
  3. Can be used repeatedly without causing harm
  4. Provides information about the role of different brain areas in particular perceptual/cognitive/motor function
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4
Q

Disadvantages of TMS:

A
  1. Restricted to brain regions close to the skull
  2. Holding the coil in place not easy, can lead to imprecise targeting, inconsistent stimulation
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5
Q

What are the advantages and disadvantages of CT scans?

A

Advantages include being inexpensive, provide quickly imaging, detailed images while disadvantages are poor spatial resolution and exposure to ionizing radiation.

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6
Q

What are advantages and disadvantages of MRI?

A

Advantages include good spatial resolution; disadvantages are that it can’t be used with people who have metal implants or pacemakers.

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7
Q

How does the static magnetic field contribute to MRI?

A

The static magnetic field in MRI machines helps align hydrogen atoms in the body, which are abundant in water and fat.

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8
Q

What is the purpose of the pulse sequence in MRI?

A

The pulse sequence disrupts the alignment of hydrogen atoms in the body temporarily during the MRI scan.

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9
Q

Define relaxation time in the context of MRI.

A

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.

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10
Q

How is a brain volume collected in structural brain imaging?

A

By collecting multiple slices that represent different sections of the brain, compiling them into one complete brain volume, which typically takes 6-10 minutes.

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11
Q

What does PET imaging involve and what are its characteristics?

A

involves injecting radioactive tracers into the bloodstream to measure brain activity. It provides good spatial resolution but has poor temporal resolution.

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12
Q

What have PET scans revealed in cognitive studies comparing younger and older adults?

A

PET scans show more frontal brain activity in older adults compared to younger ones, suggesting age-related changes in brain function.

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13
Q

How is PET used in neurotransmitter studies?

A

PET is used to study neurotransmitters by showing that higher dopamine receptor binding is associated with stronger functional connectivity between brain regions.

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14
Q

What does fMRI measure and how does it work?

A

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.

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15
Q

What is the difference between the basal and activated states of the brain as detected by fMRI?

A

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.

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16
Q

What does the Hemodynamic Response Function (HRF) describe in the context of fMRI and the BOLD effect?

A

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

17
Q

What is the trade-off when increasing the temporal resolution of fMRI scans?

A

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.

18
Q

How are differences in brain activity located using Whole Brain Analysis in fMRI studies?

A
  1. 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.
19
Q

What does Region of Interest (ROI) Analysis in fMRI studies allow researchers to do?

A

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.

20
Q

What is the structure of a block design in fMRI studies?

A
  • 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.
21
Q

What does the block design measure in fMRI?

A

Allows researchers to measure the brain’s response to prolonged stimuli.

22
Q

What are the advantages of blocked fMRI?

A
  1. Allows researchers to compare brain activity between conditions presented in distinct blocks, making it easier to detect differences
  2. Most widely used in fMRI studies due to its efficacy in capturing brain responses to various tasks/stimuli
23
Q

Disadvantages of blocked fMRI? (3)

A
  1. Subjects may mentally prepare for each block, making their responses less spontaneous
  2. The design’s predictability can limit its ability to capture natural brain responses
  3. Difficult to examine how the brain responds to individual events within the experimental task such as correct vs incorrect responses
24
Q

What is the characteristic feature of an Event-Related fMRI design?

A

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.

25
Q

What distinguishes a Rapid Event-Related fMRI design from a standard Event-Related design?

A

A Rapid Event-Related fMRI design presents stimuli in a quick and randomized sequence, preventing anticipation and allowing for the analysis of brain responses to rapidly occurring, varied events.

26
Q

Advantages of Event Related MRI

A
  1. Complex design enables studying complex cognitive processes by designing experiments with intricate sequences of tasks.
  2. Random task presentations: With event-related fMRI, allows random task presentations, reducing predictability and isolating specific brain responses.
  3. Post-hoc conditions based on behavior: researchers can analyze brain activity based on participants’ behavior after scanning, offering insights into specific trial outcomes or behaviors.
27
Q

Disadvantages of Event Related fMRI

A
  1. Event-related fMRI, compared to block designs, may have a harder time detecting brain activity because the signal produced by each specific event might not be as strong, making it more challenging to distinguish from background noise or other brain activity.
  2. The need for accurate modeling of the HRF, which varies across brain regions, aking accurate modeling challenging.
28
Q

What does Resting-State Functional Connectivity (RSFC) focus on in fMRI studies?

A

Focuses on the spontaneous or intrinsic activity of the brain when a subject is not performing a specific task, revealing correlated activity within large-scale functional brain networks.

29
Q

What are Large-Scale Brain Networks as seen in fMRI studies?

A

Large-Scale Brain Networks are various intrinsic networks within the brain, each responsible for specialized functions, as revealed by fMRI studies. These include networks such as the default, control, dorsal attention, and visual networks.

30
Q

How do Resting-State Networks differ from Task-Based Networks in fMRI studies?

A

Resting-State Networks are active when no specific task is being performed and reflect the brain’s intrinsic activity, whereas Task-Based Networks are engaged during the performance of specific tasks, as identified by fMRI studies.

31
Q

What networks are active during both resting-state and task-based conditions?

A

Default mode network
Dorsal attention network
Control network

32
Q

What is TMS (transcranial magnetic stimulation)

A

A non-invasive procedure that uses magnetic fields to stimulate nerve cells in the brain

33
Q

What are Event Related Potentials

A

Electrical patterns in the brain recorded through electrodes on the scalp in response to specific events or stimuli

34
Q

What are advantages of fMRI?

A
  1. Good spatial resolution
  2. Non-invasive technique
    3.Adaptable to many experimental designs – e.g., block and event- related​
  3. Can conduct whole brain imaging which can help measure connectivity between different regions
35
Q

Disadvantages of fMRI (2)

A
  1. fMRI measures changes in blood flow rather than direct neuronal activity, which may inaccurately reflect brain function.
  2. Signal dropouts in certain regions lead to unclear or incomplete images.

Neural Basis (9 decks)

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