Thursday, September 8, 2011

Limbic Stuttering

We have previously discussed the possibility that stuttering may have two components: one generated by brain disfunctions and the other generated by the “mind.”  The mind is a manifestation of the brain and involves, in particular, emotions.  Hence, we now refer to stuttering generated by the mind as limbic stuttering, since the limbic system is instrumental in determining emotions. 
  
Limbic stuttering may be engendered, for example, by a specific social context (e.g., speaking before an audience) or by an anticipatory emotional reaction when coming upon a word having a sound over which one has previously blocked (e.g., any words starting with “f” such as “favorite”).

As discussed previously, some theories of stuttering posit that the disruption of timing signals between the basal ganglia and speech motor areas in the left cortical hemisphere contributes to or causes stuttering.  The dorsal striatum in the basal ganglia is involved in the timing of speech and excessive dopaminergic activity in the dorsal striatum disrupts timing signals for a subgroup of stutterers. 

The ventral striatum, in physical proximity to the dorsal striatum, is part of the limbic circuitry governing emotions.  Emotional activation of the ventral striatum (e.g., coming upon a feared word) further contributes to the dopaminergic activity that disrupts timing. 

Is there any way that we could empirically determine if a blocking incident is limbic stuttering?  To answer this question, consider a technique for preempting a block.  Namely, when you come to a block, don’t try to plow through it.  Rather, stop, go back several words and continue with your sentence.  So you might be trying to say, “Let me tell you about my favorite restaurant in New York,” and you perceive a block on the word “favorite.” 

Then the approach might be to say, “Let me tell you about my (block) tell you about my favorite restaurant in New York.”  Chances are that if the block was not limbic-based, you will be able to complete your sentence without a block.  I say “chances are,” since there is a probability that a brain-based block (as opposed to mind) may again repeat itself on the word “favorite.”

Note that this approach of repeating several words is related to voluntary stuttering on a syllable such as “f-f-f-favorite,” and might be characterized as voluntary phrase stuttering.  If block occurrences in one’s speech are not excessively frequent, then this approach may not be viewed as disfluency from the listener’s point of view.  

However, it is unlikely that the technique will be effective for limbic stuttering since anticipatory fear will repeatedly activate the dopaminergic system.  Thus, the technique’s lack of efficacy might be regarded as an indicator of limbic stuttering.

1 comment:

sachin said...

A very clear description of mind's and brain's contribution to stuttering. Very clear. Thank you.