Dokument: Neurophysiological investigations on action word processing

Titel:Neurophysiological investigations on action word processing
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URN (NBN):urn:nbn:de:hbz:061-20150713-113641-8
Dokumententyp:Wissenschaftliche Abschlussarbeiten » Dissertation
Autor: Klepp, Anne [Autor]
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Dateien vom 13.07.2015 / geändert 13.07.2015
Dewey Dezimal-Klassifikation:600 Technik, Medizin, angewandte Wissenschaften » 610 Medizin und Gesundheit
Beschreibung:The present thesis investigated the neurophysiological processing of action verbs and the contributions of the motor system. Embodied cognition or grounded cognition theories claim that
distributed modal networks in the sensorimotor system form the basis of cognitive functions, of concept acquisition and semantic memory activation as well as language processing. Concepts are not merely associated with their sensory and motor features. Rather, neuronal circuits in the sensory and motor areas actually create the formation of conceptual knowledge through their activation during learning in body-environment interactions. These same circuits are activated by the principle of Hebbian learning when concepts are accessed.
This thesis investigated neural activation reflecting motor system involvement in verb processing regarding its spatial localisation, its time course, and its functional mechanisms in interaction with motor behaviour using magnetoencephalography (MEG).
In a first study, participants silently read verbs describing actions performed with the hands, with the feet, and abstract verbs that did not contain an action. Despite the absence of any movement in this task, individual neuromagnetic sources that had been derived from a separate movement execution task were somatotopically active during action verb reading. Activity peaked around 200 ms after word onset, indicating that it is part of the access to meaning in semantic memory and not a post-lexical effect.
Complementary to these findings in evoked brain responses, a second study investigated oscillatory brain dynamics in the same paradigm. Neuronal oscillations are thought to be an important mechanism in neuronal communication. For the sensorimotor system, oscillations in the alpha (8-12 Hz) and beta (13-30 Hz) frequency bands are most characteristic and show typical patterns of modulation before, during, and after movement execution. Here, a suppression of oscillatory power is associated with neuronal activation. Silent reading of action verbs led to power suppression in the alpha and beta frequency range, stronger in body-part specific channel selections.
A third study directly investigated the interaction of verb processing with a simultaneous motor task. This was operationalised using a semantic decision paradigm that required a button press in response to both hand and foot action verbs. Only for hand verbs the match between verb and response effector was expected to produce interference while foot verbs served as the control condition. Neuronal beta oscillations in the time window of concurrent verb processing and response preparation were analysed. Language-motor interactions were only found for action verbs with high imageability. Here, reaction times were slower for hand verbs. This was accompanied by weaker motor preparatory power suppression in the beta frequency band.
Taken together, this thesis tested the embodied cognition hypothesis of motor cortex involvement in language in a series of MEG experiments on single action verb processing. This is important because despite mounting evidence supporting this claim, comparability between studies is hampered by differences in methods and design. A comprehensive investigation of the spatial and temporal characteristics of motor system contributions using MEG and simple language stimuli had as of yet been lacking. The three studies show that motor cortex contributions to verb processing are individually specific and somatotopic, that they recruit neuronal oscillations in the beta and alpha frequencies, and that interactions with motor execution occur behaviourally and
Fachbereich / Einrichtung:Medizinische Fakultät » Institute » Institut für Medizinische Psychologie
Dokument erstellt am:13.07.2015
Dateien geändert am:13.07.2015
Promotionsantrag am:17.03.2015
Datum der Promotion:09.06.2015
Status: Gast