Neuroimaging Techniques

Question 1

The basis for neuroimaging is that the brain is ———– and ————–

Answer 1

bloody and electric

Question 2

What is the logic behind hemodynamic neuroimaging techniques?

Answer 2

An increase in neuronal activity increases metabolic demand for glucose and oxygen increase the cerebral blood flow (CBF) to the active region.

Question 3

What is the logic behind electro-magnetic techniques?

Answer 3

The brain works because neurons communicate with each other and they do this by sending out tiny electrical impulses. Neurons ‘fire’ and if we see an increase in an electrical activity, it means neurons in a certain area are more active.

Question 4

Measuring lood flow is ———– and ———— while electriciy is a ————— and ———— measure of neural activity.

Answer 4

Measuring lood flow is slow and indirect while electriciy is a direct and fast measure of neural activity.

Question 5

What is the general divide between hemodynamic and electro-magnetic techniques?

Answer 5

For hemodynamic techniques, we have the positron emission tomography (PET) and the functional magnetic resonance imaging (fMRI). It has excellent spatial resolution (<1mm) poor temporal resolution (-1s). For electro-magnetic techniques, we know electroencephalography (EEG) and magneto-encephalography (MEG). They have reasonable spatial resolution (<1cm) and excellent temporal resolution (<1msec). MEG is better.

Question 6

We read results of an ERP according to the ——————– electrode, which is placed in the middle of the head.

Answer 6

reference

Question 7

When reading an ERP signal, early activation signals ————— processing while later activation signals ———— processes.

Answer 7

When reading an ERP signal, early activation signals automatic processing while later activation signals cognitive processes.

Question 8

You are conducting research with an EEG. The person is read the following sentence:
“ I baked a cake in my tablet”
What kind of electrical activity (what kind of peak) would you expect to see? What does it signify?

Answer 8

I would expect the N400 signal as this sentence has a semantically inappropriate word. N400 is a language specific peak that signifies semantic mistakes.

Question 9

You are conducting research with an EEG. The person is read the following sentence:
‘‘A mammoth is a chair”
What kind of electrical activity (what kind of peak) would you expect to see? What does it signify?

Answer 9

The N400, which signifies false statements of category membership (or information inconsistent with previous knowledge)

Question 10

In which direction does the N400 point?

Answer 10

Up! (N = negative = up)

Question 11

You are conducting research with an EEG. The person is read the following sentence:
“The sheep followed borrow shepherd”
What kind of electrical activity (what kind of peak) would you expect to see? What does it signify?

Answer 11

The P600, which is evoked by syntactic anomalies. Sometimes, if a sentence is both semantically and syntactically incongrous, it can evoke both the N400 and the P600.

Question 12

What do garden path sentences tell us about P600 (in regards to what it reflects). [ideally, you would see a graph in which you have “The broker persuaded to sell the stock was sent to jail” and the P600 is around the ‘to’ while the normal sentence doesn’t have this peak/dip).

Answer 12

The biggest difference between the control sentence and the garden path sentence at ‘to’ which is the point in which we re-analyse our structure. As such, we assume that P600 reflects grammatical re-analysis (and not just syntactic ungrammaticality/integration difficulty)

Question 13

You’re conducting research on binding violations (how pronouns are grammatically associated to the thing they’re referred to) using an EEG. Which peak would you expect to see?
Example:
The hungry guests helped themselves/himself to me.

Answer 13

The p600 (stronger than n400).

Question 14

You want to research how fast infants acquire the ability to make grammaticality judgements, specifically if something is syntactically anomalous or not. For this research, what type of neuroimaging technique would you use and why?

Answer 14

I would probably use an EEG because it is a non-invasive technique that can be used auditorily and does not require any vocal feedback from the participants (so, babies r fine). Also, there are documented language specific peaks, which we can use to observe whether or not an infant reacts to a syntactically anomalous

This is completely made up, I don’t know if it’s actually possible…

Question 15

You would like to find which lobe is activated when a participant is singing opera in a non-native language. Which neuroimaging technique would you use? What are some advantages or disadvantages of this technique?

Answer 15

I could use an fMRI but considering the movements during opera singing, it might be hard to get a clear picture. That is why I would opt to use PET, which offers better spatial resolution than an EEG though it is quite invasive and you are unlikely to get only areas involved in the task.

Question 16

The results of a study using MEG compared neural activation between generating past tense forms for regular and irregular verbs. They found that at 250ms, there was activation for both regular and irregular verbs while at 350ms there as activation only for regular forms. How would you interpret this result? What are some advantages of using MEG? Disadvantages?

Answer 16

It shows that regular and irregular verbs are in fact different. It seems that at 250ms, we have stem recognition but suffixation only occurs for regular forms and this happens at 350ms. (this study also showed they occur in different locations).

Advantages: great temporal resolution, great spatial resolution, non invasive, direct measure of brain activity but very expensive

Question 17

Pylkannen; Marantz did many different experiments and concluded that there are language specific activations in the MEG. the M170 occurs after 170ms and it reflects …………….. processing. Then, at M250, there is the ……………………… processing. Later, there is activation of th word representations in the mental lexicon in M350.

Answer 17

M170 - letter string processing
M250 - pre-lexical processing

Question 18

Which neuroimaging technique would you use when comparing touching a thumb with the fingers of the same hand vs. of the opposite hand?

Answer 18

An fMRI because it has excellent spatial resolution and it can very specifically show the location (MEG too expensive, PET not specific enough).

Question 19

Why do we use blocked design in fMRI studies?

Answer 19

It is easirer to detect significant differences in brain activation between conditions and it enhances the SNR (signal-to-noise-ratio). Researchers can average brain responses over a longer period and thus reduce variability caused by neural fluctuations. They are useful for detecting large and consistent effects (like, reading vs. naming colors for example)

Question 20

Compare blocked vs. event related randomised design?

Answer 20

In an event-related design, the task and the control task are interspersed. Data from two tasks collated separately. This design prevents the subject from habituating to performance on a given task.
Blocked: 35 stimuli of the same duration in a row
Event-related: stimuli of different durations presented randomly → stimuli from one condition, from another one
Additionally, the chunk of time is randomized (in both cases!) you manipulate the time of examination. The blood flow, the peak, is 7s. But you don’t know when you’re going to coincide with the peak, the picture so to be on the safe side, you randomize it.
Instead of tasks, think of conditions. Let’s say you have to process irregular verb tenses. When you have a block design, your participant sees just irregulars. Then, for 5min just regulars. Then, for 5 minutes just neutral. Problem: they get used to the word, they habituate. This is why the best design mixes conditions but the problem is that in the fMRI you are after BOLD, so there is no way to know whether the timepoint of you showing the point of interest will coincide with the peaks of bloodflow but you will never see this if the stimulus is always at the beginning.

Question 21

You would like to compare brain activation in adults with dyslexia in comparison with neurotypical adults. What neuroimaging technique would you use?

Answer 21

fMRI probably

Question 22

Discuss the statement “fMRI is a technique which, because of its excellent spatial resolution, gives good answers as to where specific activation occurs. However, this is nothing more than an advanced form of phrenology.”

Answer 22

Knowing ‘’where’’ a cognitive function is located is vitally important. Neuropsychology, invasive manipulation of brain function and functional imaging each give us different windows of understanding into what each brain region does.

Question 23

You want to analyse how we understand non-specific sentences (like, John began the book). Specifically, you want to know if this is due to pragmatics (Which activate the RH region) or due to coercion (an entity goes from an object to an event; would activate Broca’s area).

Answer 23

For this type of research, an fMRI would be best.