Lecture 10: Language processing and neuroscience

Question 1

What is MMN?

Answer 1

Mismatch negativity (MMN) is an auditory event-related potential that occurs when a sequence of repetitive sounds is interrupted by an occasional “oddball” sound that differs in frequency or duration.

• The older the infant exposed to non-native language, the smaller the MMN
• Pre-attentive response (no need for conscious attention, tested with people in comma, infants)

Note: this only works if there is 80% of ‘good’ stimuli, and only 20% of ‘bad’ stimuli. If there are more, the MMN effect doesn’t show.

Question 2

What is the N400?

Answer 2

ERP peak also called “The semantic marker”.
Negative polarity, peaks aournd 400 ms.
Peaks when the brain detects a SEMANTICAL violation.
N400 is present for both visual and auditory stimuli.
N400 is a MMN (mismatch negativity) component

Question 3

What is LAN?

Answer 3

ERP peak called “Left Anterior Negativity”.
Peaks around 300-500ms
Negative polarity
LAN is elicited when someone is presented with a grammatical violation (like: she sleep at home)

Question 4

Why are the N400 and the LAN peaking at 400 ms not the same?

Answer 4

There is a third component that gives us the possibility to distinguish peaks, which is the scalp distribution. So even though both the LAN and the N 400 hhave a negative polarity and both peak/ can peak at 400ms, their position in the brain tells us that they aren’t the same.

Question 5

What is P600?

Answer 5

ERP peak, concerned with syntactic violation.
Peaks around 500-800ms
Positive polarity
Whenever you have to re-evaluate something that’s perceived as syntactically wrong, P600 is elicited. P600 can be found with structure violations in language, but also music and math.

Question 6

What’s the difference between LAN and P600?

Answer 6

LAN
○ Responds to the first identification of morpho-syntactic violation
○ Automatic

P600
○ Re-analysis of the morpho-syntactic violation
○ Controlled

Question 7

What is action potential? Why can’t we measure it? What do we measure instead?

Answer 7

An action potential is the changing of electrical activity in the neuron. So it’s basically the ‘firing’ of the neuron. As they are extremely fast, we are not able to measure them.

We measure postsynaptic potentials instead (surge of neurotransmitters between one neuron and the next. This process takes 200 ms, which is long enough to measure in an EEG.

So: in an EEG we don’t measure the firing of the neuron, but the short period after it.

Question 8

What exactly does an EEG measurement record?

Answer 8

Potential differences over time (positive or negative electrical charge) of a group of pyramidal cells (most common neurons in the cortex).

Question 9

What are some artifacts in EEG measurement?

Answer 9

Blinking, Saccades, grinding teeth, swallowing, …

Question 10

How does fMRI record brain activity?

Answer 10

fMRI registers different levels of oxygen and blood flow that is recruited by a specific task, with the use of magnets.

In fMRI, the brain images are recorded voxel by voxel (voxel = 3D pixel), so it has a high spacial
resolution. Changes between 0.5% and 5% can be captured.

Question 11

Advantages and disadvantages of fMRI

Answer 11

Advantages of fMRI:

• Excellent spatial resolution
• Non-invasive, no harmful radiation

Disadvantages of fMRI:

• Indirect measurement of activity (measuring blood flow instead of electrical activity)
• Distortion due to breathing, body movements, drugs and stimulants
• Low temporal solution (It takes 1-3 seconds for the blood flow to increase after the brain activity)
• Expensive

Question 12

Can data distortion in fMRI be corrected? How?

Answer 12

fMRI data distortion can be corrected by means of algorithms such as independent component analysis; however, it is difficult and it results in compromising the data.

Question 13

What do you know about MEG (Magnetoencephalography)?

Answer 13

Magnetoencephalography (MEG) is a method of brain recording that has high spatial and temporal resolution but is extremely expensive.

Question 14

Problem: we know that BA44, 45 and 46 are related to phonology and semantics. However, fMRI cannot tell us whether they are all concerned with semantics, or only one/two areas, because the spatial resolution is not that good. What can help here?

Answer 14

This is where TMS (Transcranial Magnetic Stimulation) can help. TMS can disrupt one specific area, which can help determine what areas are/aren’t involved in certain cognitive tasks.

Question 15

Which brain activity measurement tool can be used to disrupt a specific brain area?

Answer 15

TMS (Transcranial Magnetic Stimulation)

Question 16

What are the linguistic consequences of disrupting Broca’s area?

Answer 16

People with a disrupted Broca’s area have a harder time with semantic tasks.

Question 17

What is ELAN?

Answer 17

It was first thought to be an early version of LAN, but it was found to be an artifact.