Monday, August 22, 2016

Watch Area 44 and not Area 51!

Looks like a very interesting piece of brain imaging work by the Martin Sommer team with the main author Nicole Neef here:
Area 44 is a cytoarchitectonically distinct portion of Broca's region. Parallel and overlapping large-scale networks couple with this region thereby orchestrating heterogeneous language, cognitive and motor functions. In the context of stuttering, area 44 frequently comes into focus because structural and physiological irregularities affect developmental trajectories, stuttering severity, persistency, and etiology. A remarkable phenomenon accompanying stuttering is the preserved ability to sing. Speaking and singing are connatural behaviours recruiting largely overlapping brain networks including left and right area 44. Analysing which potential subregions of area 44 are malfunctioning in adults who stutter, and what effectively suppresses stuttering during singing, may provide a better understanding of the coordination and reorganization of large-scale brain networks dedicated to speaking and singing in general. We used fMRI to investigate functionally distinct subregions of area 44 during imagery of speaking and imaginary of humming a melody in 15 dextral males who stutter and 17 matched control participants. Our results are fourfold. First, stuttering was specifically linked to a reduced activation of left posterior-dorsal area 44, a subregion that is involved in speech production, including phonological word processing, pitch processing, working memory processes, sequencing, motor planning, pseudoword learning, and action inhibition. Second, left posterior-area-44-to-parietal functional coupling was deficient in stuttering. Third, despite the preserved ability to sing, males who stutter showed bilaterally a reduced activation of area 44 when imagine humming a melody, suggesting that this fluency-enhancing condition seems to bypass posterior-dorsal area 44 to achieve fluency. Fourth, time courses of the posterior subregions in area 44 showed delayed peak activations in the right hemisphere in both groups, possibly signaling the offset response. Because these offset response-related activations in the right hemisphere were comparably large in males who stutter, our data suggest a hyperactive mechanism to stop speech motor responses and thus possibly reflect a pathomechanism, which, until now, has been neglected. Overall, the current results confirmed a recently described co-activation based parcellation supporting the idea of functionally distinct subregions of left area 44.
Area 44 seems to be a kind of orchestra conductor, which goes somewhat into recent suggestions (and my belief) that stuttering is a system failure, i.e. that it's not necessarily a single function (in one area) breaking down but the system of different interacting areas as a whole but in this case it's one area that is needed to orchestrate the system. But I have to say that I do not know enough about this topic to make more informed comments.


Torsten Hesse said...

Thank you for pointing to this study, Tom. I overlooked it in PubMed because the word 'stuttering' is not contained in the title.

Myself was a participant of the study. The tasks were counting from one upwards and humming Mozart's Serenade No. 13., both as imagery (internal speech). That was in 2013 – it's astonishing how much time things need.

Robert van de Vorst said...

Interesting. Coincidentally, I was planning for designing a similar kind of experiment: investigating planning stages in speech and singing in PWS; but others were clearly ahead of me!
I didn't read the whole thing yet, but they seemed to have looked only at imaginary speech and humming. This has the obvious advantage that it reduces motion and other physiological artefacts that may likely be present when singing or speaking aloud in a scanner. The downside, nonetheless, is that these results still don't tell us very much. When comparing singing with speech (in stuttering), it may be especially important to control for confounding factors such as rate, linguistic complexity, propositional communication and to compare with other fluency-inducing conditions (choral speech, metronome speech, etc.). Another aspect that they couldn't delve into is real-time auditory-motor coupling and sensorimotor adaptation, which I assume (and has appeared) to be one of the core malfunctioning elements in stuttering. I am also a bit skeptical about their statement of right-hemisphere abnormalities as part of the pathophysiology of stuttering, but I have to read the article more in depth to look at their arguments.

Pascal said...

But even if the activity in area 44 is the culprit: how to influence this specific brain area?

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