1. What are the kinds of direct brain activity that we are able to measure?
Electrical activity and blood flow (BOLD signal).
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2. What do we mean when we say that a methodology allows us to observe brain activity “time-locked to a particular cognitive event”?
It allows us to investigate changes in brain activity that occur as the stimulus is presented.
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3. Dependent variable refers to the actual measurement that one makes through a methodology. What is the dependent variable for EEG?
The sum of postsynaptic electrical activity.
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4. What is the dependent variable for ERP?
The average the postsynaptic electrical activity timed to a specific event (stimulus of interest).
a) What is an N400 effect? What kind of linguistic process is it normally associated with?
A centro-parietal negativity with a latency of 400 ms after stimulus presentation that correlates with the expectancy of a word.
b) What is a P600 effect? What kind of linguistic process is it normally associated with?
A centro-parietal positivity with a latency of 600 ms after stimulus presentation that correlates with processing of linguistic structure.
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5. What is the dependent variable for fMRI?
Changes in blood oxygen levels (BOLD signal).
b) What is “hemodynamic response”?
Increase of brain activity in one region as a result of increased blood flow.
c) What is a ROI?
A subset of regions selected to extract data.
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6) What is the dependent variable for PET?
The density of O15 as measured by its radioactive decay.
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7) What is the dependent variable for TMS?
Measures of cortical excitability, such as TMS intensity.
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8) Why are fMRI, PET and TMS said to be high in spatial resolution and low in temporal resolution? What is the reason for their low temporal resolution?
The are high in spatial resolution because they provide precise information about the source localization of the signal. They are low in temporal resolution because the hemodynamic response to a particular stimulus is registered with some delayed.
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9) Regarding ERP, what is the “inverse problem”? How does it affect our interpretation of ERP effects?
The ‘inverse problem’ arises because the location of the source of the summed postsynaptic activity in response to an event cannot be uniquely reconstructed from the EEG signal. As a result, there are always multiple potential regions that may be attributed to processing the specific linguistic stimuli and we cannot attribute activity to one of them.
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10) What are “behavioral” methods?
These are methods that measure a participant’s conscious response to a particular stimulus.
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11) What are “online” methods?
These are methods that measure a participant’s response that is timed to the stimulus (i.e., occurs as the same time as the stimulus is encountered).
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12) What advantages does each set of methods offer? Disadvantages?
Offline methods - provide a composite measure of processing (i.e., a response to the stimulus once it has been processed). It is the result of a conscious process and thus it is subjected to participant’s strategies and thus to more variation.
Online methods - provide a measure of processing as the sentence unfolds over time. No methodology at this point offers both good temporal and spatial information.