Event-related potentials

Time-locked neural response measured with EEG. General class of potentials that display stable time relationships to a definable reference event (Vaughan 1969).

ERP Components

Negative and positive deflections cannot be clearly interpreted as being associated with excitation or inhibition of neural activity. Rather, we can make a claim about accumulation of charge associated with mobilization of neural resources — we care more about the amplitude when it comes to this. The polarity of charge allows us to distinguish between different ERPs through relation to each other (if we took the square of the signal, it’d be more difficult to differentiate between ERPs as we’d lose that dimension of the data).

Exogenous v. endogenous

Exogenous ERPs tap into early sensory processing (bottom-up) while endogenous refer more to “higher order” cognitive processing.

Exogenous:

• Depend on physical features of sensory stimulus
• Does not depend on subjects’ level of consciousness
• Not influenced by cognitive processes

Endogenous:

• Doesn’t depend on physical features of sensory stimulus. Can be evoked with stimulus expectancy in absence of stimulus.
• Can change depending on level of attention, its relevancy during task, and resources required for stimulus processing.
• Related to cognitive processing