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Cognitive I (S1) > Cognitive neuroscience methods > Flashcards

Cognitive neuroscience methods Flashcards

1
Q

What do axons do?

A

Connect brain areas

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2
Q

How are messages passed?

A

Via neurotransmitters

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3
Q

What is an action potential?

A

Electrical signal initiated when the neuron fires

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4
Q

Excitatory?

A

Causes the neuron to fire

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5
Q

What is the visual cortex?

A

The region located at the back of the brain that processes visual information

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6
Q

What is the midbrain?

A

An area that carries out diverse functions in reward, eye movement, hearing, attention and movement

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7
Q

What is cognitive neuroscience?

A

The study of how brain structures and processes mediate cognitive behaviour

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8
Q

What are the objectives of cognitive neuroscience?

A

Understand how the mind is created by the brain and understand the links between cognition and neuroscience
Build models of how the brain works
Establish which brain regions and brain circuits are involved in different tasks and what changes in the brain as a consequence of learnining
Investigate brain imaging and activity produced during cognition

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9
Q

What are some challenges for cognitive neuroscience?

A

Complex systems - around 1 million neurons in 1 cubic mm of brain

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10
Q

Describe techniques to find brain structure

A

Anatomical dissection, structural magnetic resonance imaging

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11
Q

Discuss techniques to look at brain function

A
  • Single electrode stimulation
  • Scalp-located electrodes- EEG, ERP - Functional MRI - Magnetoencephalography MEG
  • Positron emission tomography PET
  • Transcranial Magnetic Stimulation TMS
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12
Q

How do MRIs work?

A
  • Atoms (in this case, hydrogen atoms) are like constantly spinning magnets
  • These atoms align when in a scanner’s magnetic field
  • Then, you send in radiowaves to make them face in a new direction
  • When they relax and return to their previous alignment, they emit energy IE resonance
  • This energy is what the scanner uses to create an image
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13
Q

Discuss MRI scans

A
  • Static structure of the brain
  • Hydrogen atoms in different tissues (such as fat and water) have different relaxation times and can be identified separately
  • The lower the water content of an area, the fewer hydrogen atoms there will be emitting signals
  • The weaker the signal, the darker the area appears on the scan
    The result is shades of grey, fat is light, bone is dark
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14
Q

What are the advantages of MRI scans?

A
  • Excellent spatial resolution
  • Allows you to view the brain from multiple angles
  • Non invasive
    Excellent for looking at soft tissues
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15
Q

What are the disadvantages of MRI scans?

A
  • No temporal information
  • Bad experience as noisy, need to stay still, claustrophobic
  • Expensive
    Older metal implants are not compatible ie pacemaker, brain aneurysm clips
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16
Q

Describe fMRI’s

A

Not just structure, but function too
Based on same MRI technique but looks at blood flow in the brain
Blood contains haemoglobin which contains iron which is magnetic

Deoxygenated blood is affected by a magnetic field differently than oxygenated blood
When neurons are active, they burn energy. This is automatically replenished via oxygen carried by hemoglobin in the blood stream
Active parts of the brain contain more oxygen-rich blood
By measuring the BOLD (blood oxygen level dependent) response in the MRI scanner, we can work out which parts of the brain were active recently

17
Q

How does fMRI work?

A

Oxygen is delivered to neurons by haemoglobin capillary red blood cells
More haemoglobin present in areas of the brain when it needs to replenish the oxygen used by active neurons

18
Q

Describe haemoglobin and oxygen levels

A

Haemoglobin is diamagnetic (weak magnetic field) when oxygenated but paramagnetic (strong magnetic field) when deoxygenated.
BOLD response

19
Q

What are the advantages of fMRI?

A
  • Excellent spatial resolution (get structural data within same session
  • Reasonable temporal resolution
  • Non-invasive
    Tells us which parts of the brain are used in tasks
20
Q

What are the disadvantages of fMRI?

A

Bold isn’t a direct measure of activity
Experience
Expensive
Can’t have any metal based equipment for stimulus presentation

21
Q

Describe positron emission tomography

A
  • Breakthrough brain functional imaging method 1980s
  • Measures blood flow in the brain - more blood flower in active areas
  • Inject, inhale, or swallow a tracer which is absorbed into the blood stream (mildly radioactive)
  • Higher levels of activity show up as bright spots
    Can be used to evaluate certain brain disorders such as alzheimers
22
Q

Advantages of PET

A
  • Reasonable structural resolution
  • Direct reflection of activity
  • No motions artifacts
  • More comfortable experience than MRI Fmri
23
Q

Disadvantages of PET

A

No temporal resolution
Expensive
Injection of very weak radioactive substance so ethical issues
May need to do MR or CT scan as well

24
Q

Describe EEG

A
  • EEG measures electrical signals generated by the brain through electrodes placed at the scalp
  • EEG signals are produced by partial synchronisation of cortical field activity and are measured as changes in voltage, recorded at the scalp, over time
    Analysis of EEG signals may be task dependent or task independent
25
Q

How are EEG signals detected?

A
  • Electrodes are placed on the scalp. Connected with gel or conductive solution
  • EEG signals are transported to an amplifier
  • The amplifier measures the difference in voltage between the active electrode and a reference electrode
    Frequency of measurements - upto 2000HZ
26
Q

Advantages of EEG

A

Very good temporal resolution
Direct reflection of activity
Not claustrophobic - good with infants

27
Q

Disadvantages of EEG

A

Poor spatial resolution, motions artifacts, inverse problems (how can we be sure which brain regions generate the electrical activity

28
Q

Describe the magnetoencephalogram MEG

A
  • The pyramidal cells of the cortex, when active, generate a significant magnetic field
  • MEG records these magnetic fields
  • For both EEG and MEG, the synchronous firing of 10000s neurons is required to produce a field which is large enough to measure
    Magnetic fields are less distorted by the scalp than electrical fields
29
Q

What are the advantages of the MEG

A

Excellent temporal resolution, direct reflection of activity, good spatial resolution

30
Q

Disadvantages of MEG

A

Expensive

31
Q

What is transcranial magnetic stimulation?

A

Uses a changing magnetic field to induce weak electric currents in the cortex

Noninvasive method causing depolarization or hyperpolarisation of neurons in the brain (i.e. decrease/increase activity).

Can produce a simulated temporary ‘lesion’ of a brain region by preventing normal function of that region.

Invented by Tony Barker and colleagues at University of Sheffield in 1985

32
Q

Advantages of the TMS

A

Near portable, can stimulate or lesion

33
Q

Disadvantages of TMS

A

Difficult to specify precise regions, only surface regions

Cognitive I (S1) (9 decks)

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