L11 Global Brain Activity

Question 1

What is the mechanism of EEG? What are the 2 requirements for one?

Answer 1

Measures voltage in the small fields generated by pyramidal cells.

Requirements:

• active & synchronous activity
• neurons must be parallel so they summate

Question 2

What is the role of the brainstem nuclei

Answer 2

modulate the rhythm of interactions between the thalamus and the cortex

Question 3

What are the 3 functional states of sleep?

Answer 3

Awake
Non-REM
REM

Question 4

What the functions of sleep

Answer 4

Conservation of metabolic energy
Cognition
Thermoregulation

Neural maturation and mental health

Question 5

How does structural imaging differ from functional imaging?

Give examples of each

Answer 5

functional is dynamic whereas structural is static
Structural=MRI, CT
Functional=PET, fMRI

Question 6

Alpha rhythm

Answer 6

Indicates being awake but with eyes closed

low amplitude

8-13 Hz

Question 7

Beta rhythm

Answer 7

Indicates being awake with eyes open, conscious

14-60Hz

Question 8

Theta waves

Answer 8

Indicates drowsiness/sleep, or pathological condition

very low frequency

4-7 Hz

Question 9

Delta waves

Answer 9

Indicates deep sleep

very low frequency

<4Hz

Question 10

Stages of sleep

Answer 10

Awake [alpha or beta rhythm]

Non-REM sleep

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

REM: beta and alpa waves, desynchronised. Similar to being awake

Question 11

How does the thalamus generate synchronous activity?

Answer 11

Thalamic pacemaker neurons have voltage gated channels that generate discharge patterns
-synchronises other thalamic neurones by setting a pace

Cells also become synchronised without [external]pacemaker activity
-Each neuron is set at a frequency to fire, which lines up eventually

Question 12

Sleep cycle

Answer 12

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

Repeats

Question 13

Behavioural criteria for sleep [4]

Answer 13

Reduced motor activity

Decreased response to stimulation

Stereotypic postures

Relatively easy reversibility

Question 14

CT vs MRI

• Spatial resolution
• Contrast resolution
• Radiation
• Time
• Expense

Answer 14

Spatial resolution
-Higher in CT

Contrast resolution
-Higher in MRI

Radiation

• CT has high radiation
• MRI has no radiation

Time
-MRI takes longer to take image

Expense
-MRI much more expensive

Question 15

Outline the physiology of PET

Answer 15

measures change of blood flow to a region

Can use pharmacological tracers.

Question 16

Outline the physiology of fMRI

Answer 16

sensitive to the concentration of oxygen in the blood.

BOLD- blood oxygen level dependant

Question 17

PET vs fMRI

• Radioactivity
• Temporal resolution
• Spatial resolution
• Sensitivity
• Tracers
• Patient comfort

Answer 17

Radioactivity
PET dependant on radioactive tracer, fMRI-no

Temporal resolution
PET-30”, fMRI-1-2”

Spatial resolution
PET better- 10mm, fMRI- 1mm

Sensitivity
PET sensitive to whole brain, some areas in fMRI are hard to image

Tracers
PET can use pharmacological tracers

Patient comfort
-PET pt scanned once or few times only