Publikationsserver der RWTH Aachen University
Wortformen und Konzepte im mentalen Lexikon : eine fMRT-Studie zur Einzelwortverarbeitung bei Sprachgesunden sowie zur Rückbildung nach Aphasie
Abstract
dc:descriptionHomonyms - words with the same phonological word form but two different concepts - were used to study the representation of word forms and concepts in the mental lexicon. The connectionist model of speech production by G. S. Dell assumes that homonyms are represented in different concept- and two different lemma-nodes but share the same lexical entry on the phoneme level. The present study investigates mainly two questions: first, whether the separation of word forms and concepts assumed in the theoretical framework can also be found on the human brain, i.e. whether or not access to word forms and concepts lead to different activations in the brain; secondly, which mechanisms of functional reorganisation of language abilities can be found in a patient with good recovery from aphasia after a left hemisphere lesion. In an event-related fMRI study 15 healthy young men and one patient were scanned during visual language tasks. The first task focussing on word form knowledge required finding a homonym with each meaning related to one of the two given stimuli. In the second task subjects had to find a conceptual association between two stimuli. The interstimulus interval was 12 seconds long and was divided into sequential time windows of one second each. For each window separate hemodynamic response functions were determined. Solved and unsolved items of the homonym task were analyzed separately. In both tasks - the association and the homonym task - and irrespective of whether or not the homonym will be found later, inferior frontal activation is observed, which is assumed to subserve semantic search. Only the solved items of the homonym task lead to bilateral inferior parietal activation including the supramarginal and angular gyrus, mirroring access to word form knowledge. Interpreting these findings in terms of Dell's model this means that not the different levels of processing, instead the mapping of information from one level onto another can be connected with specific activation in the human brain - mapping semantic features onto lexical nodes happens when inferior frontal activation is observed and mapping two lexical nodes onto one phonological word form is connected with activation of the supramarginal and angular gyrus. The patient shows a comparable pattern of activation considering the separation of word form and conceptual knowledge. During the homonym task he shows perilesional activation of residual substrates, which is in accordance with previous findings concerning functional reorganisation. An additional - most likely compensatory - activation is found in the left primary motor hand area.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2004
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Grande, Marion
- Contributors dc:contributor
-
- Huber, Walter
Subjects
dc:subject × 5Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger