Global brain activity Flashcards

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1
Q

EEG

  • Function
  • Where it is used
A

Electroencephalogram
- Measures electrical rhythm in from the brain through electrodes placed on the scalp.

Use:

  • Sleep studies
  • Diagnosing + monitoring epilepsy
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2
Q

Mechanism of EEG

A

Measures voltage in the small fields generated by pyramidal cells.

Requirements for signal:

  • Neurones must be active and synchronised
  • Neurones must be parallel so that they summate.
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3
Q

Alpha rhythm

A

8-13 Hz
- Low amplitude

Indicates being awake but with eyes closed.

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4
Q

Beta rhythm

A

14-60 Hz
- Higher amplitude, high frequency.

Indicates being awake with eyes open
- Mental activity and attention is happening

Rhythm in REM sleep

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5
Q

Theta rhythm

A

4-7 Hz
- High amplitude, very low frequency.

Indicates drowsiness/ sleep

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6
Q

Delta rhythm

A

< 4 Hz
- Very low frequency and high amplitude

  • Indicates deep sleep [stage 3 NREM]
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7
Q

Stages of sleep

A

Awake [alpha or beta rhythm]

Non REM {NREM]

  • Stage 1: Theta waves
  • Stage 2: Spindle waves + K complex
  • Stage 3: Delta waves

REM: beta + alpha waves, desynchronised. Similar to being awake.

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8
Q

Thalamus in generating synchronous brain rhythms

A

Thalamic pacemaker neurones generate discharge patterns [voltage gated channels]
- Synchronises other thalamic neurones by setting a pace

Cells also become synchronised without pacemaker activity
- Each neurone is set at a frequency to fire, which lines up eventually.

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9
Q

Sleep cycle

A

Awake—> Stage 1 NREM—> 2—> 3—> 4—> 3—>2—> REM

Repeats

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10
Q

Behavioural criteria for sleep

A

Reduced motor activity

Decreased response to stimulation

Relatively easy to reverse

Stereotypical posture.

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11
Q

Possible functions of sleep

A

Conservation of energy

Thermoregulation

Neural maturation

Mental health

Cognition

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12
Q

Structural imaging of the brain

A

Static map of the brain
- Spatial configuration of tissue types.

Examples:

  • MRI
  • CT
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13
Q

Functional imaging of the brain

A

Dynamic map of the brain
- Indirectly measures neuronal activity.

Examples:

  • PET
  • fMRI
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14
Q

CT and imaging the brain

A

Used to diagnose:

  • Tumours
  • Bleeds
  • Gross brain anomalies
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15
Q

MRI and brain imaging

A

Used to diagnose:

  • Tumours
  • Bleeds
  • Brain anomalies

Better contrast resolution than CT:

  • Better white-grey discrimination.
  • Less radiation
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16
Q

CT vs MRI

  • Spatial resolution
  • Radiation
  • Time
  • Expense
A

Spatial resolution:
- Higher in CT

Radiation:

  • CT has high radiation
  • MRI uses no radiation [magnet]

Time:
- MRI takes longer to take image

Expense:
- MRI much more expensive than CT

17
Q

Physiology of MRI

A

Produces an magnetic resonance signal by orientating the protons inside the body

Helps to produce static maps or dynamic maps [fMRI]

18
Q

fMRI

  • Type of imaging
  • Mechanism
  • BOLD
  • HRF
A

Functional MRI
- Type of functional imaging

Mechanism:
- Measures metabolic activity of tissues by detecting BOLD signal

BOLD [blood oxygen level-dependant] contrast
- Ratio of oxy/deoxyhaemoglobin in the blood

HRF= haemodynamic response function
- Changes in BOLD signal over tie

19
Q

PET

A

Functional imaging technique that measures blood flow to brain regions.

20
Q

PET vs fMRI

  • Radioactivity
  • Temporal resolution
  • Spatial resolution
  • Sensitivity
  • Tracers
A

Radioactivity

  • PET is radioactive because of tracers
  • fMRI is not

Temporal resolution

  • fMRI is quicker [1-4]
  • PET = 30

Spatial resolution:
- fMRI has higher spatial resolution [1mm, PET= 10mm]

Sensitivity
- PET sensitive to whole brain, fMRI only to certain regions