Sprachliche Vagheit : sprachtheoretische Überlegungen und neurolinguistische Untersuchungen zur Bedeutungsflexibilität der Sprache

摘要

In the present study, I was interested in the neurofunctional representation of ambiguity processing by using functional magnetic resonance imaging (fMRI). The aim of this study was to combine linguistic, neurolinguistic and neuroscientific points of view to develop a consistent model regarding the neural processing of ambiguity. Connectionist models of speech production and perception (Dell, 1986) provide a useful basis for this attempt. Linguistic features such as ambiguity processing are breaking points in regular communication. Therefore, disturbed communication might open new perspectives on understanding the regularities of daily communication. As pointed out by Jäger (2004, p. 35), language confusion and disturbances are essential for language performance in general. Communication in total seems to be „risky“ (Luhmann, 1997). The fragility of language perception including high order language functions such as ambiguity processing has been neglected by many traditional linguists. But there are philosophers such as Jacques Derrida („dissemination of meaning“, see: Derrida, 1995) or Donald Davidson („radical interpretation of meaning“, see: Davidson, 1986) who published on this controversial topic. Reading these philosophers one might assume that language in total is vague. This hypothesis is emphasized by connectionist models processing a target item step by step through a neural network. Connectionist models might link theoretical positions to empirical data collected by functional imaging. Twelve right-handed, healthy adults aged between 21 and 29 years (6 male, 6 female) underwent an ambiguity resolution task with 4 different conditions (dominant vs. non-dominant; dominant vs. distractor; non-dominant vs. distractor; distractor vs. distractor). After subtraction of the corresponding control task (distractor vs. distractor) there was significant activation especially in the thalamus and some parts of the basal ganglia (caudate nucleus, putamen). The findings implicate a participation of the thalamus and other basal ganglia circuits in high level linguistic functions and match with theoretical considerations on this highly controversial topic. Subcortical neural circuits probably become activated when the language processing system cannot rely entirely on automatic mechanisms but has to recruit controlled processes as well. Furthermore, there was broad activation in the inferior parietal lobule, the prefrontal gyrus, pre-SMA and SMA and the cingulate cortex. This might reflect a strategic semantic search mechanism which probably can be illustrated with connectionist models of language processing. According to this, one might hypothesize a neuroregulatory role for the thalamus and basal ganglia in regulating and monitoring the release of preformulated language segments for motor programming and semantic verification. There is strong evidence, that especially the thalamus, the caudate nucleus, the cingulate cortex, the inferior parietal lobule and the prefrontal cortex are responsible for an accurate ambiguity resolution in the human brain. In opposition to traditional linguistic statements, this study shows that high order language features such as ambiguities are processed by a widespread network which is on one hand easy to irritate but on the other hand is able to react very quickly and flexible on disturbances (e.g. vague meanings).