The Electrophysiological Brain
This chapter considers the basic principles behind the electrophysiological methods of single-cell recordings and electroencephalography (EEG). Single-cell recording is an invasive method in which the number of action potentials generated by a neuron is recorded. The rate and timing of this measure can be used to infer the functional properties of a neuron (e.g., what it is specialized for). By contrast, EEG measures the summed electrical activity of many (millions of) neurons detected at the scalp. The most common use of EEG in cognitive neuroscience is the method known as ERP, event-related potentials. The EEG waveform reflects neural activity from all parts of the brain. Changes in the timing or amplitude of this waveform can be linked to differences in cognitive function. Magnetoencephalography can be regarded as a parallel method to EEG, based on measuring magnetic fields generated by neural activity, that is similar in many regards.
Multiple Choice Questions
Flashcards
Properties of the world that are manifested in cognitive systems (mental representation) and neural systems (neural representation)
These measure the responsiveness of a neuron to a given stimulus (in terms of action potentials per second)
Single-cell recordings (or single-unit recordings)
The time taken between the onset of a stimulus/event and the production of a behavioral response (e.g. a button press).
Reaction time (or response time)
Measurements of electrical signals generated by the brain through electrodes placed on different points on the scalp
Electroencephalography (EEG)
The average amount of change in voltage at the scalp that is linked to the timing of particular cognitive events (e.g. stimulus, response)
Event-related potential (ERP)
The electrical activity (in terms of action potentials per second) of many individually recorded neurons recorded at one or more electrodes
Multi-cell recordings (or multi-unit recordings)
A hypothetical neuron that just responds to one particular stimulus (e.g. the sight of a person)
The informational content of a neuron as related to the number of action potentials per second
The synchrony of firing by a population of neurons to code the same stimulus or event
The study of the time course of information processing in the human nervous system
A pair of positive and negative electrical charges separated by a small distance
A general method for dividing reaction times into different stages
An ERP component (negative potential at 170 ms) linked to perceiving facial structure
Reaction times are faster to stimulus X after being presented to stimulus Y if X and Y have previously been associated together (e.g. if they tend to co-occur)
EEG component related to properties of the stimulus
EEG component related to properties of the task
The difficulty of locating the sources of electrical activity from measurements taken at the scalp (in ERP research)
An attempt to solve the inverse problem in ERP research that involves assuming how many dipoles (regions of electrical activity) contribute to the signal recorded at the scalp
Useful Links
Professor Steve Luck has made available slides, videos, and other educational material relating to ERP analysis (for researchers who will gain hands-on experience):
www.erpinfo.org/educational-materials
