Lecture 6 - Methods of studying the brain Flashcards

1
Q

How do CT scans work?

A

CT scans use X-rays passed through the brain at different angles
–> CT measures the amount of radiation not absorbed by the brain as X-rays are passed through

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2
Q

How does a CT scan image appear?

A

Bone absorbs the most and so appears white

Cerebrospinal fluid appears black

The brain appears grey

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3
Q

Advantages of CT scans

A
  • Can be used in healthy and clinical samples
  • Non-invasive
  • indicates areas of structural brain abnormality
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4
Q

Disadvantages of CT scans

A
  • Poor spatial resolution
  • provides only measure of structure, not activity
  • involves radiation
  • expensive
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5
Q

How do MRI scans work?

A

Create high-resolution images of the brain based on changed in the magnetic properties of hydrogen atoms.

Radio waves tased though head whilst a strong magnetic field is used to align protons of the hydrogen nuclei

Reverberations of wobbling protons detected and recorded

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6
Q

Advantages of MRI scans

A
  • Non-invasive and non-toxic
  • allows structural imaging in vivo
  • high spatial resolution
  • no known biological risk
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7
Q

Disadvantages of MRI scans

A
  • Claustrophobic
  • noisy
  • images near to large cavities difficult to obtain
  • expensive
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8
Q

How do PET scans work?

A

Uses a radioactive tracer injected into the bloodstream to track blood flow

The greater the blood flow = greater signal emitted by tracer

Map produced superimposed onto brain scan image

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9
Q

Advantages of PET scans

A
  • Can be used to measure brain activity during a task

- Suitable for most clinical and healthy subjects

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10
Q

Disadvantages of PET scans

A
  • Invasive
  • Poor spatial and temporal resolution
  • unsuitable for certain subjects
  • expensive
  • indirect measure of neural activity
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11
Q

How do fMRI scans work?

A

Uses standard MRI equipment to produce images of brain activity

produces images representing oxygen flow in the blood to active areas of the brain

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12
Q

What is the name of the signal recorded by fMRI?

A

Blood-Oxygen-Level-Dependent (BOLD signal)

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13
Q

Advantages of fMRI

A
  • Non-invasive and non-toxic
  • Allows functional imaging
  • No known risks
  • Widely available and cheaper than PET
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14
Q

Disadvantages of fMRI

A
  • Claustrophobic
  • Noisy
  • Poor temporal resolution (better than PET)
  • Susceptible to movement artefacts
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15
Q

Advantages of Neuropsychology

A
  • Utilises naturally occurring lesions
  • May highlight role/function of damaged region
  • can provide insight
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16
Q

Disadvantages of Neuropsychology

A
  • Locus of damage can be variable and not always described accurately
  • Other damaged brain regions could be having an effect
  • May be other confounding factors
17
Q

Describe the process of Transcranial Magnetic Stimulation (TMS)

A

Uses a highly focused magnetic field to disrupt the function of neurons

Magnetic stimulation temporarily turns off part of the brain

18
Q

Advantages of TMS

A
  • non-invasive
  • lesion is focal
  • temporary
  • can study human brain directly
  • can determine causation
19
Q

Disadvantages of TMS

A
  • questions regarding safety
  • Deep structures cannot be reached
  • effects often smaller/less noticeable
20
Q

Advantages of animal lesion methods

A
  • Each animals behaviour can be compared before and after the lesion
  • highly selective lesions
  • not possible in humans
21
Q

Disadvantages of animal lesion methods

A
  • Ethics

- Hard to determine functions due to structures being interconnected

22
Q

What happens during single-cell recording?

A

Action potential directly measured

Single-cell recordings obtained by implanting a very small electrode into the axon or outside the membrane

23
Q

Penfield and Jasper (1954) Electrical stimulation

A

Simulating certain parts of the brain of patients undergoing surgery for epilepsy produced reports of sensations

24
Q

How does an EEG work?

A

Electrical activity of the brain is recorded by electrodes placed on the scalp

25
Q

Advantages of EEG’s

A
  • Non-invasive
  • high temporal resolution
  • cheap and easy
  • applicable to healthy and clinical populations
  • brain activity recorded in real time
26
Q

Disadvantages of EEG’s

A
  • Poor spatial resolution
  • Activity reflects millions of neurons
  • brain activity may be unpredictable and chaotic
  • susceptible to movement artefacts
27
Q

What does the Wada Technique involve?

A

Sodium amytal is injected into the carotid artery in order to temporarily anaesthetise the ipsilateral hemisphere

28
Q

Advantage of the Wada technique

A

Provides means of examining functions of an entire hemisphere

29
Q

Disadvantages of Wada technique

A
  • Invasive

- cannot be used on healthy subjects