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.
