Class 10 - Language and neuroscience Flashcards
Action potential
An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern. Examples of cells that signal via action potentials are neurons and muscle cells.
Post-synaptic potential
chemical reactions released by the transmitters while carrying electrical activity from one axon to another neuron. The PSPs are the potentials recorded by the EEG
Neurotransmitters
chemical messengers that transmit a signal from a neuron across the synapse to a target cell, which can be a different neuron, muscle cell, or gland cell.
Pyramidal cells/neurons
The most common type of neurons in our cortex
EEG
Electroencephalography: it records the electrical activity that is elicited by our brain: the recording happens via electrodes being placed on our scalp.
Direct measurement of neural activity.
ERPs
Measured brain response that is the direct result of a specific sensory, cognitive, or motor event. More formally, it is any stereotyped electrophysiological response to a stimulus.
source: Wikipedia
Steps to convert EEG data into ERPs
ERPs can be reliably measured using electroencephalography (EEG), a procedure that measures electrical activity of the brain over time using electrodes placed on the scalp. The EEG reflects thousands of simultaneously ongoing brain processes. This means that the brain response to a single stimulus or event of interest is not usually visible in the EEG recording of a single trial. To see the brain’s response to a stimulus, the experimenter must conduct many trials and average the results together, causing random brain activity to be averaged out and the relevant waveform to remain, called the ERP.
source: Wikipedia
Time locking
creating a time label, ( trigger, a number in time) that is going to “lock” the stimulus in a specific time-frame.
The scalp is divided into 5 regions…
frontal, central, parietal, occipital, temporal
The brain has 4 lobes…
frontal, occipital parietal, temporal
The brain has 2 hemispheres…
left and right
Usual lateralization of brain responses to language
Left-laterilized
Artifacts that can influence EEG data
- eye movement, very big.
- saccades, looking from one side to the other.
- muscle contractions, even simple leg-crossing.
- swallowing.
ERPs components (can be distinguished by…)
An ERP component can be simply defined as one of the component waves of the more complex ERP waveform. ERP components are defined by their polarity (positive or negative going voltage), timing, scalp distribution, and sensitivity to task manipulations.
source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3816929/#:~:text=An%20ERP%20component%20can%20be,and%20sensitivity%20to%20task%20manipulations.
sourc
What we need to have a successful ERPs based experiment
- present conditions that are almost identical except for what we’re interested in, that should be the only diverging thing (neutral VS deviant condition)
- multiple trials form same conditions: should be between 30-40 trials: for early components even more, for late components, less because they are stronger
- average the trials per condition, per participant. Participants have 2 outputs at the end of the experiment even though they did hundreds of trials, since they were averaged together (in an experiment with 2 conditions).
around 20 participants per experiment, population should be homogeneous.
Grand avarage
A method for comparing variability in event-related single-trial EEG activities across subjects and conditions
source: https://pubmed.ncbi.nlm.nih.gov/25447029/#:~:text=subjects%20and%20conditions-,Grand%20average%20ERP%2Dimage%20plotting%20and%20statistics%3A%20A%20method%20for,J%20Neurosci%20Methods.
N400
component of time-locked EEG signals known as event-related potentials (ERP). It is a negative-going deflection that peaks around 400 milliseconds post-stimulus onset, although it can extend from 250-500 ms, and is typically maximal over centro-parietal electrode sites. The N400 is part of the normal brain response to words and other meaningful (or potentially meaningful) stimuli, including visual and auditory words, sign language signs, pictures, faces, environmental sounds, and smells.
source: Wikipedia
LAN
left anterior negativity, after 300-500 ms. First marker of SYNTACTIC VIOLATION. Also, elicited when there is increase in working memory load.
P600
Elicited during syntactic ambiguity, whenever we commit to something and realize it we should reconsider it: music, language, logical thinking can elicit the P600.
Anytime there is EXPECTATION TOWARDS A STIMULUS PRESENTED AND THE EXPECTATIONS ARE NOT MET.
Mismatch negativity
Component of the event-related potential (ERP) to an odd stimulus in a sequence of stimuli.
fMRI
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.
source: Wikipedia
BOLD measure
blood-oxygen-level dependent contrast used in fMRI scanning
voxels
Single units that make up a 3 dimensional picture in the fMRI scan. Each voxel can represent millions of brain cells.
Is is harder to clean fMRI data or EEG data?
fMRI data
Main adv/dis of EEG
High temporal resolution, really poor spatial resolution. It records where the activity comes out, but not where the activity is generated
Main adv/dis of fMRI
High spatial l resolution, really poor temporal resolution.
Main adv/dis of fMRI
High spatial resolution, really poor temporal resolution.
Area of the brain where processing of phonology and semantics occur
Broca’s area 44/45
Screening tool that can help discern the location of language processes such as phonology and semantics in the brain
TMS
TMS
Noninvasive form of brain stimulation in which a changing magnetic field is used to cause electric current at a specific area of the brain through electromagnetic induction.
source: Wikipedia
MEG
Imaging technique that identifies brain activity and measures small magnetic fields produced in the brain.
source: Wikipedia
