Electrophysiological Evidence for Sentence Comprehension - Wings

filtered out in averaging process. Therefore, multiple presentations of the same stimulus
(or the same category of stimuli) have to be presented to the participant. With multiple
presentations of the same stimuli (multiple trials) the contribution of the background EEG
subsides and favorable signal-to-noise ratio is achieved.
Just like eye-tracking, ERP provides multidimensional data: it provides data on latency of
a process, scalp distribution and spectrum. It can also provide data on the neural
generators of the brain activity, although it is not the best choice for that. With the
millisecond resolution it can be used to find out when a process is going on in the brain.
However, it can give limited information where it takes place (Hopfinger et al., 2005).
The distribution of current recorded on the scalp can be consistent with infinitely many
reconstructions of the neural generators (the problem known as the ‘inverse problem’
which is mathematically ill-posed) so the reconstructed sources of the activity as recorded
on the scalp are in fact models. Nevertheless, different scalp distribution across
experimental conditions tells us that the neuronal generators are different. ERPs reflect
processing of sensory characteristics of the stimuli as well as cognitive processes elicited
by the stimuli. ERP components sensitive to the physical characteristics of the stimuli
(e.g. loudness or brightness) are referred to as the exogenous or obligatory components.
On the other hand, the endogenous (or cognitive) components of the ERP are thought to
be influenced by internal events, i.e. by the type of cognitive processing of the stimuli.
The waveform obtained in the averaging process is usually divided in ERP components.
Generally, components are just positive or negative deflections that can be observed in an
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