Zusammenfassung
Bildgebende Verfahren leisten einen wichtigen Beitrag zum Verständnis der zerebralen
Mechanismen sprechmotorischer Kontroll- und Steuerungsvorgänge, die sich aus phonetischen
Planungs- und Ausführungsprozessen zusammensetzen. Eine Reihe von Studien konnte ein
minimales neuronales Netzwerk für die Gesamtheit der sprechmotorischen Prozesse definieren,
das verschiedene Hirnstrukturen umfasst. Bis heute ist jedoch noch nicht eindeutig
geklärt, wie viele bzw. welche Netzwerkkomponenten für den Planungsprozess entscheidend
sind. Funktionell bildgebende Studien sowie Untersuchungen, in denen die Läsionen
von Patienten mit und ohne sprechmotorischen Planungsstörungen (Sprechapraxie) untersucht
wurden, lassen darauf schließen, dass Sprechplanungsprozesse in der linken, sprachdominanten
Hemisphäre lokalisiert sind. Hier scheint insbesondere die perisylvische Region, einschließlich
des Broca-Areals, eine wichtige Rolle einzunehmen. Die Hypothese, die Insel sei das
für die phonetische Enkodierung kritische Areal, steht aufgrund der widersprüchlichen
Ergebnisse nach wie vor zur Diskussion.
Abstract
Neuroimaging data contribute in a substantial way to a better understanding of the
cerebral mechanisms underlying speech motor control, which can be subdivided into
at least a phonetic planning and a motor execution stage. A series of functional imaging
studies delineated a widely accepted minimal network of speech motor control encompassing
various brain structures. However, there is still an ongoing discussion about the
possible neuroanatomical correlates subserving speech motor programming. Functional
imaging investigations and clinical studies analysing lesion locations in patients
with and without a speech programming deficit (apraxia of speech) point to a left
lateralised representation of phonetic encoding processes. Within this hemisphere
the perisylvian cortex, i. e. the ventral part of premotor cortex and Broca's area
seem to be of special relevance for speech motor programming. Results of imaging studies
investigating the hypothesised role of the anterior insula in this context are still
conflicting and inconsistent. Whereas the insula is considered in some studies as
a crucial area for speech motor programming, i. e. for establishing new motor plans,
others suggest a contribution of the insula to articulatory processes. Another controversial
issue addressed recently by various imaging studies is related to the influence of
sublexical frequencies on phonetic encoding mechanisms or associated hemodynamic activation
patterns, respectively. So far, data showed a rather weak support for a possible impact
of syllable frequencies but nonetheless it can not be excluded that (other) sublexical
frequency variables may affect the process of speech motor programming.
Schlüsselwörter
bildgebende Verfahren - neuronales sprechmotorisches Netzwerk - sprechmotorische Planungsprozesse
- Broca-Areal - linke vordere Insel
Key words
neuroimaging - minimal cerebral network for speech motor control - phonetic encoding
processes - Broca's area - left anterior insula
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Korrespondenzadresse
Dr. phil. B. Brendel
Zentrum für Neurologie
Hertie Institut für klinische
Hirnforschung
Universität Tübingen
Hoppe-Seyler-Straße 3
72076 Tübingen
eMail: bettina.brendel@uni-tuebingen.de