Global Brain Activity

Question 1

What does EEG stand for, what does it record, and what can it be used for?

Answer 1

Electroencephalography

Records brain waves

Used for brain rhythms and the sleep cycle

Question 2

What methods can be used to image the brain, and what are the two types of imaging that can be done?

Answer 2

Structural Imaging (CT and MRI)

Functional Imaging (fMRI and PET)

Question 3

What are examples of events that have brain cycles?

Answer 3

• Sleeping / Waking
• Stages of night sleep
• Breathing cycles
• Steps of walking

Question 4

What are the requirements for a signal to be detected by EEG?

Answer 4

Whole population of neurons must be active in synchrony in order to generate an electrical field large enough to be detected at the scalp

The population of neurons must be aligned in a parallel orientation so that they summate and not cancel out (the more synchronous they are, the larger the amplitude of the signal)

Question 5

What are the 4 basic EEG phenomena, what are their frequencies, and when are they present?

Answer 5

Beta rhythm (14-60Hz) and eyes are open + there is mental activity and attention

Alpha rhythm (8-13Hz) and subjects are awake with their eyes closed

Theta waves (4-7Hz) and occur during drowsiness/sleep or a pathological condition

Delta waves (< 3Hz) and also occur during drowsiness/sleep or a pathological condition

Question 6

What is the behavioural criteria for sleep?

Answer 6

• Reduced motor activity
• Decreased response to stimulation
• Stereotypical postures
• Relatively easy to be reversed

Question 7

Why is the sleep of animals that are preyed on different to the sleep of predatory animals?

Answer 7

Because animals that are preyed on need to be alert, they only sleep for a short periods of time.

Oppositely, predatory animals can undergo long, uninterrupted periods of sleep.

Question 8

What part of the brain is able to produce rhythmic, self-sustaining discharge patterns, and what other part of the brain modulates the rhythm of its interaction with the cortex?

Answer 8

Thalamic cells create them via voltage-gated ion channels

Brainstem nuclei modulate the rhythm of interactions between the thalamus and cortex

Question 9

What are the 3 functional stages of sleep, and the neurons of which system controls sleeping and waking?

Answer 9

Awake
REM
Non-REM

Neurons of the diffuse modulatory system control sleeping and waking

Question 10

Why do CT scans appear the way they do, and what are they used for?

Answer 10

Because bone is able to absorb the most amount of x-rays, it appears white.

Brain matter absorbs an intermediate amount of x-rays so appears grey.

CSF absorbs the smallest amount of x-rays so appears black.

CT scans are used clinically to spot any brain abnormalities

Question 11

What are some pros of using MRI over CT scans?

Answer 11

MRI is safe to use

MRI has a better spatial resolution, so is better at discriminating between white and gray matter

Question 12

In what normal circumstance would there be an increased blood flow to the brain?

Answer 12

Increased metabolic activity of neurons in the brain

Question 13

What do PET scans measure?

Answer 13

Changes in blood flow to the brain, meaning they are based on blood volume

Question 14

What do fMRI scans measure?

Answer 14

Changes in oxygen concentration of the blood

Question 15

What does BOLD stand for and what is it used in?

Answer 15

Blood Oxygen Level Dependent

Used for fMRI and relates to the concentration of oxyhemoglobin in the blood.

Question 16

What does HRF stand for and what does it describe?

Answer 16

Haemodynamic Response Function

Describes changes in the BOLD signal over time

Question 17

What is the difference between structural and functional imaging?

Answer 17

Structural imaging is for the physical characteristics of the brain

Functional imaging is for physiological changes in the brain