Electrophysiological Evidence for Sentence Comprehension - Wings

ERP waveform. Components are conventions in ERP research. Their names usually
consist of polarity and peak latency (N and P for negative and positive with a number
attached to it; for example, N400 for a negative peak at approximately 400 milliseconds
from the onset of the stimuli). Sometimes they have an ordinal number after the polarity
sign. The ordinal number represents the position of the peak after the stimulus (e.g. P1 is
the first positive wave after the stimulus, P2 second, etc.). Functional names are
sometimes given; for example, Syntax Positive Shift (SPS) for a positive wave obtained
with stimuli that contain syntactic error. Finally, sometimes the names are based on the
scalp distribution, for example, ‘left anterior negativity’ (LAN) for the negative wave that
can be recorded on the left frontal electrodes.
There is no complete agreement to what the components really mean (Coles & Rugg,
1995, Otten & Rugg, 2005). There are two general approaches to component
identification: physiological and psychological. The first (physiological) approach is
characterized by the claim that the neuronal population that carries out the activity that
generates the recorded deflection in the ERP waveform should be specific (Näätänen &
Picton, 1987). In other words, the defining characteristic of a component is its anatomical
source (Coles & Rugg, 1995:8). The researchers who adopt the psychological approach
claim that the component is, in fact, the information process that is manipulated in the
experiment. The effect of this manipulation is visible as a deflection in the ERP
waveform. So, components are the cognitive functions that are performed by brain (and
are manipulated in experiments). In practice, the definition of the component comprises
both physiological and psychological criteria (Otten & Rugg, 2005): while polarity and
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