LINGUIST List 18.2068
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Mon Jul 09 2007
Diss: Neuroling/Psycholing/Cog Sci: Roehm: 'Waves and Words: Oscill...'
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1. Dietmar
Roehm,
Waves and Words: Oscillatory activity and language processing
Message 1: Waves and Words: Oscillatory activity and language processing
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Date: 06-Jul-2007
From: Dietmar Roehm <roehmcbs.mpg.de>
Subject: Waves and Words: Oscillatory activity and language processing
Institution: Philipps University Marburg
Program: Department of Germanic Linguistics
Dissertation Status: Completed
Degree Date: 2004
Author: Dietmar Roehm
Dissertation Title: Waves and Words: Oscillatory activity and language processing
Dissertation URL: http://archiv.ub.uni-marburg.de/diss/z2005/0110/pdf/ddr.pdf
Linguistic Field(s):
Cognitive Science
Neurolinguistics
Psycholinguistics
Dissertation Director:
Hubert Haider
Matthias Schlesewsky
Dissertation Abstract:
Successful language comprehension depends not only on the involvement of
different domain-specific linguistic processes, but also on their
respective time-courses. Both aspects of the comprehension process can be
examined by means of event-related brain potentials (ERPs), which not only
provide a direct reflection of human brain activity within the millisecond
range, but also allow for a qualitative dissociation between different
language-related processing domains. However, recent ERP findings indicate
that the desired one-to-one mapping between ERP components and linguistic
processes cannot be upheld, thus leading to an interpretative uncertainty.
This thesis presents a fundamentally new analysis technique for
language-based ERP components, which aims to address the ambiguity
associated with traditional language-related ERP effects. It is argued that
this new method, which supplements ERP measures with corresponding
frequency-based analyses, not only allows for a differentiation of ERP
components on the basis of activity in distinct frequency bands and
underlying dynamic behaviour (in terms of power changes and/or phase
locking), but also provides further insights into the functional
organisation of the language comprehension system and its inherent
complexity. On the basis of 5 EEG experiments, I show (1) that it is
possible to dissociate two superficially indistinguishable language-related
ERP components on the basis of their respective underlying frequency
characteristics (Experiment 1), thereby resolving the vagueness of
interpretation inherent to the ERP components themselves; (2) that the
processing nature of the 'classical' semantic N400 effect can be
unambiguously specified in terms of its underlying frequency
characteristics, i.e. in terms of (evoked and whole) power and
phase-locking differences in specific frequency bands, thereby allowing for
a first interpretative categorisation of the N400 effect with respect to
its underlying neuronal processing dynamics; and (3) that frequency-based
analyses may be employed to distinguish the semantic N400 effect from
N400-like effects that appear in contexts which cannot readily be
characterised as semantic-interpretative processes. Depending on the
respective task and stimulus manipulations, the N400 effect appears as a
result of the superposition of functionally different activities, which can
be clearly distinguished in terms of their underlying frequency
characteristics. In this way, the proposed frequency-based methods directly
bear upon the interpretation of language-related ERP effects and thus have
straightforward consequences for psycholinguistic theory. In view of the
phenomenon that language-related processes have, in a number of cases, been
directly attributed to the lexical-semantic processing domain on account of
the observation of an N400, these results not only call for a
reinterpretation of previous findings but also for a reinterpretation of
their theoretical consequences.
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