Lecture One: Neuroscience Methods Flashcards by Olivia Simpkin

What are 5 tools/methods used for studying Neuroscience

Electroencephalography (EEG)
Magnetoencephalography (MEG)
Magnetic Resonance Imaging (MRI)
Transcranial Electrical Stimulation (TES)
fMRI neurofeedback

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What Neuroscience tools/methods that look at Event-Related Potentials (ERPs) and Frequency Analyses?

Electroencephalography (EEG) and magnetoencephalography (MEG)

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What are the two ways MRI can be used in Neuroscience?

To look at:

Structure (T1 weighted, diffusion, flair)
Function (task-based, resting-state)

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What are the two techniques used for a manipulating activity?

Transcranial Electrical Stimulation (TES) and fMRI neurofeedback

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What tools/methods would we use to take a casual inference approach?

Those used for manipulating activities; Transcranial Electrical Stimulation (TES), Transcranial Magnetic Stimulation (TMS) and fMRI neurofeedback

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What are the downsides of post-mortem analysis?

No experimental control

- You have to wait until patients are deceased

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What does in-vivo mean?

Experimentation involving completely living organisms

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What does an EEG measure?

measures aggregate neuronal activity form the scalp using electrodes

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What are the 4 stages of brainwaves from most alert to least? (include Hz if needed)

Beta - Awake + mental activity (14-30 Hz)
Alpha - Awake + resting (8-13 Hz)
Theta - Sleeping (4-7 Hz)
Delta - Deep Sleep (<3.5 Hz)

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What does an EEG Time-Frequency Analysis look at?

Looks at / plots 3 factors onto a graph

Brain wave Hz (wave frequency between 0-20 {e.g. Beta waves at >14 Hz}) [Y axis ^]
Wave decibel (dB) (The strength/height of the electrical impulse wave) [Colour on graph regions]
Time (ms) [X axis ->]

Ultimately shows which brain waves (e.g. delta) were most strongly used/present over a period of time

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What are the segments in an Event related potential (ERP) analysis?

Records brain activity in response to a stimulus being presented:

Waves I-VI = Brainstem activity
N0-P1 = Early cortical activity
P1-N1 = Late cortical activity

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What do dotted and dashed lines on an Event Related Potential (ERP) Analysis represent? How are they different from what solid lines represent?

Cognitive activity that occurs to decode and understand the stimulus presented (e.g. recognising that an image you see shows a tree). Solid lines show cognitive activity that occurs to perceive the stimulus presentation (e.g. to see an image but not decode or understand what the image is showing)

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How does Source Reconstruction work for Electroencephalpgram (EEG) data?

electrical impulses from brain waves are recorded by the EEG at different locations around the brain. A brain model is then formes and colour coded according to the intensity of waves in areas of the brain. Only looks at levels of brain activity at ONE point in time.

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What is MEG (name and what it measures) and how is it similar to EEG?

MEG = Magnetoencephalogram; measures the magnetic fields produced by neuronal firing.
Similar because it can be used to obtain the same 3 types of data:
1. Event-related potentials (ERP)
2. Time-frequency analysis
3. Source reconstruction

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What is the biggest differences between what an MEG and EEG can measure?

EEG is sensetive to parallel electric currents (observes activity in the vertical length of brain tissue)
MEG is sensetive to perpendicular magnetic fields (observes activity in the horizontal length of brain tissue)

They measure fields that the other is blind to

See slides 14&15 Lecture One

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What are the different Pros for MEG and EEG?

EEG Pros:

Much cheaper than MEG (MEG = millions, EEG = thousands)
Portable and can be used in conjunction with other imaging methods
Small and doesn’t take lots of space like the MEG

MEG Pros:
- Much better reconstruction capabilities (not as good as fMRI though)

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How does an MRI work?

MRI produces an RF pulse that changes the direction that hydrogen atoms spin (dephase), and monitors how they return to their original position/direction

What are voxels?

Voxels are a 3-D pixel in the shape of a cube. So a cube filled with 3-D imaging data. A voxel set is like a Rubix cube, made of many stacked voxels into a larger cube shape.

What is a structural MRI used for? (T1 weighted, flair)

It is used to obtain a highly detailed (static) image of the brain to see its structure. Can detect Tumors and Bleeds.

What are Morphometrics?

Analysis of size and shape. When in reference to the brain it involves looking at tissue segmentation and spatial normalization.

What can be found within a single 3x3x3 mm voxel of the brain?

20-30 thousand neurons
1 billion synapses
4 km of axons
0.4 km of dendrites

What do Diffusion Weighted Images (DWI) measure?

Measure the diffusion of water throughout the brain

How does water diffuse in the brain?

In free space (without constraint) water diffuses in all directions = Isotropic
When there are barriers or structures in the space (e.g. white matter fibres) diffusion of water is directional (parallel) to the constraining barriers = Anisotropic

What is tractography?

a 3D modelling technique used to visually represent nerve tracts using data collected by diffusion MRI

What two resources can be derived from a Tractography?

- Pathway Integrity | - Structural connectome

What are 3 important points to remember about tractography?

- Tracts are NOT axons, they are a whole pathway of nerve fibres. - Tractography is only an approximation of underlying white matter - Crossing fibres can confuse this estimate (one voxel may contain multiple white matter tracts)

What is an fMRI? What imaging technique does it often use?

an fMRI looks at the brains state of functioning over a period of time. It often uses Echo-Planar Imaging (EPI)

What is the BOLD signal? and what imaging technique measures this signal?

BOLD = Blood-Oxygenation-Level-Dependent signal. Looks at the ratio between oxygen-rich and oxygen-poor blood. an MRI looks at this ratio difference in each voxel. oxygen is needed for brain activity, so higher the BOLD (% of oxygen rich blood), = higher the level of brain activity.

An fMRI is modelled using what?

``` The General Linear Model (GLM) Y = XB + E Y: Activity in voxel X: Predictor B: Weight E: Error ```

A good match between the predicted response and the actual response for an fMRI shows what?

Good match implies that the activity in a voxel is related to the stimulus provided (not just random).

What is the downside of using BOLD?

Bold does not directly correlate to neuronal activity, and does not show if the brain activity is related to the stimulus or something else. It also has bad temporal resolution

Fill in the gaps The brain represents ___% of body weight, but accounts for ___% of oxygen consumption

The brain represents 2% of body weight, but accounts for 20% of oxygen consumption

Fill in the gaps | Task-evoked activity accounts for

Task-evoked activity accounts for <5% of the brain’s energy consumption; possibly as low as 1%

How is resting-state activity quantified in an fMRI?

Often quantified using: – seed-based connectivity (a-priori regions of interest) – Independent component analysis (ICA; data driven)

What is seed-based connectivity?

Seed-based functional connectivity, also called ROI-based functional connectivity, finds regions correlated with the activity in a seed region. In seed-based analysis, the cross-correlation is computed between the time-series of the seed and the rest of the brain (telling us where the traffic is communicating between selected cities)

What is: Spatial resolution Temporal resolution

Spatial Resolution = capacity a technique has to tell you exactly which area of the brain is active Temporal Resolution = describes its ability to tell you exactly when the activation happened.

Which imaging technique has the best Spatial resolution for brain activity?

fMRI

What is the general Temporal Resolution time for fMRI, MEG and EEG?

fMRI = Seconds | MEG & EEG = Milliseconds

Which methods are the most flexible (which ones can do multiple data collection types)?

MRI = Diffusion, T1, Resting-State, & Flair | MEG & EEG = Time freq analyses & ERP

How can techniques for manipulating activity (casual inference approaches) help cognitive/psychiatric/neurological deficits?

- TMS: Generates small magnetic field, which induces electric current in nearby neuronal populations - TES (e.g., direct current stimulation), increases neuronal excitability in the areas under the scalp to increase likelihood of action potentials firing - fMRI neurofeedback: allows individuals to gain control over the BOLD response to ‘train’ specific regions or networks (like a muscle)

Best Pro for each imaging technique (MRI, fMRI, EEG/MEG, EEG, TMS/TES, fMRI NFB [x2 pros for nfb])

``` • MRI: multi-modal • fMRI: good spatial resolution • EEG/MEG: good temporal resolution • EEG: good portability • TMS/TES: good inference (though anatomically imprecise) • fMRI NFB: good inference & spatial resolution ```