Task 3 - EEG & ERP

Question 1

What is one aspect that might make multiunit recording more useful than single cell paradigms?

Answer 1

As the activity and interplay of larger groups of neurons is often more informative than simply recording each neuron individually.

Question 2

What has better spatial resolution? EEG or MEG?

Answer 2

MEG

Question 3

Why does MEG only detect currents that are parallel to the skull?

Answer 3

Since the induced magnetic field is perpendicular to the direction of the current, only currents that are parallel to the skull produce magnetic fields, that go outside the skull.

Question 4

What are two physical disadvantages of MEG?

Answer 4

1. The room has to be isolated against the earth’s magnetic field.
2. The SQUIDS have to be kept at ~4 Kelvin, which requires a lot of energy.

Question 5

Explain the two types of conduction that are relevant for EEG.

Answer 5

Volume Conduction: Through a medium which allows electrons to move in wave-form (within the brain)

Capacitive Conduction: Chain of attraction and repulsions in separate layers (skull, etc.)

Question 6

What does the input impedance determine?

Answer 6

how well the amplifier can tolerate a poor connection to the scalp

Question 7

What distinguishes active and passive ways to reduce noise in EEG research?

Answer 7

Active involves somehow filtering out signal from noise. Passive involves improving the external circumstances.

Question 8

What are the three categories of ERPs?

Answer 8

Exogenous - Automatically triggered by a stimulus
Endogenous - Neural activity accompanying the task
Motor - Accompanying the preparation and execution of behavior

Question 9

What does the N170 ERP typically react more strongly to?

Answer 9

Faces

Question 10

What is the amplitude of the P3(00) wave correlated with?

Answer 10

The relative novelty of a stimulus

Question 11

Explain what the two subcomponents of the P3 wave P3a and P3b refer entail.

Answer 11

P3a - Reacts to novelty independent of the task

P3b - Larger when a stimulus is part of a more improbably group in a given task.

Question 12

Why can’t we pinpoint the location of a dipole in the brain?

Answer 12

Because for this, only one dipole would have to be active at a time. There is a large amount of noise.

Question 13

When naming EEG electrodes, which numbers stand for the left hemisphere?

Answer 13

Odd

Question 14

How many reference electrodes are required for an EEG experiment?

Answer 14

1

Question 15

What are the most common physiological sources of artifacts?

Answer 15

Blinking
Eye Movements
Jaw Muscles

Question 16

Why does the P3 ERP require less trials to obtain through averaging than P1?

Answer 16

Because P1 is smaller.

Question 17

Why is it better to report amplitude over a certain time window rather than the peaks?

Answer 17

Because peak measurements are unreliable.

Question 18

What is the cocktail party effect?

Answer 18

You can focus on a single conversation even when there are many things happening around, that could attract your attention.

Question 19

Describe the Biased Competition Model

Answer 19

When different stimuli fall within the receptive field of a visual neuron, the bottom-up signals compete to control the neuron’s firing. Attention can resolve this competition in favor of the attended stimulus. The sizes of neuronal receptive fields increase as you go higher in the visual hierarchy, thus there is a greater chance for competition between different stimuli within a neuron’s receptive field, and therefore, a greater need for attention to help resolve the competition.

Question 20

For smaller stimuli, attention acts at ____ processing stages.

Answer 20

Earlier

Question 21

What is “Inhibition of Return”?

Answer 21

After about 0.3s, the spotlight of attention moves back from a cued location, after which this location receives a lack of attention for a short time window.

Question 22

In what way can EEG be used clinically?

Answer 22

It can be used to investigate whether the brain reacts normally to stimuli or at baseline.

Question 23

What is the name of the paradigm, that shows a certain stimulus only rarely and thus elicits a P3 response?

Answer 23

Oddball Paradigm

Question 24

What basic cognitive process is P1 associated with?

Answer 24

Perception

Question 25

Due to what fact is it that attention affects P1 amplitude?

Answer 25

That modulations in the visual ERPs due to attention begin as early as 70 – 90ms after stimulus onset.

Question 26

Excitatory PSPs create more ___ extracellular voltage.

Answer 26

Negative

Question 27

Why can an electrode not detect a dipole if the positive and negative charges are at equal distance from it?

Answer 27

Because then, the charges would cancel itself out.

Question 28

Which types of dipoles can be measured with EEG?

Answer 28

Radial and Tangential