Evoked Potentials and Neuroimaging

Question 1

What are the 2 broad classes for studying the nervous system?

Answer 1

1.) Electrical potentials
2.) Imaging

Question 2

What is spatial resolution?

Answer 2

How small of a unique location in the brain you can identify

Question 3

What is temporal resolution

Answer 3

How small of a unique unit of time you can identify

Question 4

What are the 2 ways to record electrical activity?

Answer 4

1.) Near field
2.) Far field

Question 5

What is near field?

Answer 5

Inserting recording electrode into the region of the brain under study

Question 6

What is far field?

Answer 6

Placing electrodes on or under the skin

Question 7

What is volume conduction?

Answer 7

Electrical response must be conducted from the neurons to the electrodes through fluids, brain tissues, bone, skin, etc

Question 8

What are the 2 variables we can control with volume conduction?

Answer 8

1.) Impedance of the electrode to the skin
2.) Generate as big of a response as possible

Question 9

What is Electroencephalogram (EEG)?

Answer 9

Measurement of synaptic and action potentials in the cortex (proximal to the skull surface)

Question 10

What is a seizure?

Answer 10

A sudden increase in electrical activity in a discrete region of the cortex

Question 11

What is Magnetoencephalography (MEG)?

Answer 11

A device that detects the tiny magnetic fields created by electrical currents in the brain

Question 12

What is a disadvantage of EEG?

Answer 12

It does not allow localization of deep brain structures

Question 13

What is an advantage of MEG?

Answer 13

It improves on spatial resolution compared to an EEG and ABR

Question 14

What are evoked potentials?

Answer 14

Measurements of synchronous nervous system electrical activity

Question 15

How to evoked potentials work?

Answer 15

When neurons undergo excitation, they produce small electrical activities. When a group of neurons located together all fire at the same time, the electrical activity is large enough to be measured

Question 16

How do you evoke a stimulus in the sensory system?

Answer 16

By using the appropriate sensory stimulus

Question 17

How do you evoke a stimulus in the motor system?

Answer 17

Typically by using an electrical stimulus

Question 18

What is the problem with ABR?

Answer 18

The recording electrode is on the surface of the skull and you are recording from the brainstem; volume conduction is crucial

Question 19

Why is ABR good for the auditory nervous system?

Answer 19

Auditory neurons are very good at phase-locking to a stimulus. It creates synchronized firing and increases the amplitude of the response you are recording

Question 20

What are 3 advantages of EVPs?

Answer 20

1.) Tells you if tissue is working/sensitive to invisible lesions
2.) Typically non-invasive
3.) Portable

Question 21

What is a disadvantage to EVPs?

Answer 21

Poor spatial resolution for deep brain structures

Question 22

What does a CT scan do?

Answer 22

Provides static detailed images of hard bone structures along with images of soft tissue and blood vessels

Question 23

What does a PET scan do?

Answer 23

It gives a dynamic view of the brain over time and can provide insights into areas of activation or damage that may not be visible in static CT or MRI images

Question 24

What are 2 advantages of using an MRI?

Answer 24

1.) Better spatial resolution than a PET scan
2.) Can distinguish between different types of body tissue

Question 25

How is an fMRI similar to a PET scan?

Answer 25

It takes a dynamic picture over time

Question 26

How does an fMRI work?

Answer 26

1.) Hemoglobin in red blood cells change response to the MRI magnet when oxygenated or de-oxygenated 2.) Initial burst of brain activity induces de-oxygenation 3.) Blood flow is quickly increased to supply more oxygen 4.) This increase in oxygen is demonstrated on the fMRI

Question 27

What do blue zones show on an fMRI?

Answer 27

De-oxygenation relative to baseline

Question 28

What do red/yellow zones show on an fMRI?

Answer 28

Heavy oxygenation

Question 29

What are 3 disadvantages of fMRI and PET?

Answer 29

1.) Changes lag behind neuron activity 2.) Use blood flow or metabolic activity to detect neural activation 3.) EEG and MEG directly test neuronal electrical activity