Wednesday, June 01, 2005

Per Alm "blames" the basal ganglia

The good thing about my blog is that I start receiving lots of interesting research news and articles. Please do send me interesting research. I will try to include them in my post, describe the research and discuss it. You have the benefit that others know about your work and they can give you feedback through comments.

Some days ago, Per Alm has sent me his PhD thesis. He is based at the Dep of Clinical Neuroscience at Lund University in Sweden. He believes in a dysfunction of the basal ganglia as the major cause of PDS: see this article . I didn't have time to read much of his work yet, but the papers look like good science. I like his introduction to history and theories of PDS. Short, clear, and pretty pictures. You can ask him for a copy of his PhD thesis and articles by sending him an email to "Per.Alm AT psychology.lu.se".

In his abstract, he writes: "The theoretical work focused [on] the basal ganglia, leading to a model based on the dual premotor systems hypothesis (G. Goldberg, 1985, 1991), which defines two parallel premotor systems: the medial (basal ganglia + SMA), and the lateral (lateral premotor cortex + cerebellum). Stuttering is suggested to be caused by a disturbance of the medial system, in most cases in the basal ganglia. The core dysfunction is proposed to be impaired "go-signals" from the medial system, supposed to trigger the next motor segment in speech.

Under some conditions speech control is shifted from the medial to the lateral system, thereby bypassing the dysfunction and resulting in fluent speech. The lateral system is suggested to be active when speech is combined with sensory input, like chorus speech or metronome. Also the effect of altered auditory feedback in reducing stuttering is proposed to be based on this mechanism. The lateral system is able control speech timing without sensory input, but this demands increased attention to some particular aspect of speech, as occurs in imitation of dialects, exaggerated rhythm, reduced speech rate, or role play. Also singing is suggested to be based on the lateral system." (Source: Per Alm, PhD thesis 2005, Lund University in Sweden)

It is an interesting theory as it seems to explain the fluency-inducing effects quite naturally. Others also support this theory or at least work on it. Katrin Neuman talks about the basal ganglia in Oxford at the end of this month. And someone else which I don't know called Bijleveld, will talk about the basal ganglia and the limbic system there.

Others are more sceptical, see less evidence and how it should fit the big picture. I will talk about their position in my next post.

3 comments:

Roland Pauli said...

Hier kommt eine laienhafte Übersetzung zu diesem Abstract:

Per Alm ist ein schwedischer Neuropsychologe. Er unterrichtet zur Zeit in den USA an der Universität von Alberta.
Seine theoretischen Abhandlungen beziehen sich insbesondere auf die Beteiligung der Basalganglien an der Genese des Stotterns.

Die Basalganglien sind ein subkortikales Gebiet von neuronalen Kernen, dessen grösste Struktur das Corpus Striatum ist.
Man geht davon aus, dass die Basalganglien insbesondere für die Modulation von motorischer Aktivität von Bedeutung sind.
Einige wissenschaftliche Modelle zum Stottern konstatieren, dass es zumindest zwei verschiedene Verschaltungsschleifen (Loops) im Gehirn gibt, auf welchen das Sprechen generiert wird. Man unterscheidet hierbei einen lateralen (äusseren) Loop, dem das induzierte Sprechen, also beispielsweise Chorsprechen, zugeordnet wird und einen medialen (inneren) Loop als Signalkreis für spontanes Sprechen. Mit letzterem haben Stotterer ja insbesondere Probleme. In diesen Signalkreis scheinen die Basalganglien bedeutsam involviert zu sein.

Per Alm beschäftigt sich im Kern seiner Arbeit mit diesem Gehirnbereich und führt an, dass ein Teil der Störung dort im premotorischen Bereich durch ein Ausbleiben oder ein falsches Timing des "go-signals" verursacht werden könnte. Wenn ich das richtig verstanden habe ist das "go-signal" die Startsequenz zur Initiierung von Muskelkontraktionen, welche für die Artikulation und Phonation von Sprache notwendig sind.

Das Sprechen und auch seine Störungen sind ja primär an eine physikalische Kausalkette gekoppelt.
Die wissenschaftliche Forschung hat insbesondere in den letzten Jahren zahlreiche mit dem Stottern in Zusammenhang stehende Besonderheiten in Fragmenten dieser Kausalkette entdeckt. Per Alm versucht die Fragmente zusammenzufügen.


Herzlichst

Roland Pauli
www.ropana.de

Anonymous said...

hi all

I just thought it would be good to introduce myself to everyone!

Can't wait to get to know you all better!

-Marshall

Thanks again!

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