Towards a functional neural systems model of developmental stuttering

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Abstract

This paper overviews recent developments in an ongoing program of brain imaging research on developmental stuttering that is being conducted at the University of Texas Health Science Center, San Antonio. This program has primarily used H215O PET imaging of different speaking tasks by right-handed adult male and female persistent stutterers, recovered stutterers and controls in order to isolate the neural regions that are functionally associated with stuttered speech. The principal findings have emerged from studies using condition contrasts and performance correlation techniques. The emerging findings from these studies are reviewed and referenced to a neural model of normal speech production recently proposed by Jürgens [Neurosci. Biobehav. Rev. 26 (2002) 235]. This paper will report (1) the reconfiguration of previous findings within the Jürgens Model; (2) preliminary findings of an investigation with late recovered stutterers; (3) an investigation of neural activations during a treatment procedure designed to produce a sustained improvement in fluency; and (4) an across-studies comparison that seeks to isolate neural regions within the Jürgens Model that are consistently associated with stuttering. Two regions appear to meet this criterion: right anterior insula (activated) and anterior middle and superior temporal gyri (deactivated) mainly in right hemisphere. The implications of these findings and the direction of future imaging investigations are discussed.

Educational objectives: The reader will learn about (1) recent uses of H215O PET imaging in stuttering research; (2) the use of a new neurological model of speech production in imaging research on stuttering; and (3) initial findings from PET imaging investigations of treated and recovered stutterers.

Section snippets

The Jürgens Model of speech production

A recent model of the neural basis of speech production proposed by Jürgens (2002) has attempted to synthesize current knowledge about the neurologic foundations of speech production. This elaborate “box and arrow” model of neural regions and structures participating in speech production is derived from a careful integration of findings from lesion, invasive brain stimulation, single-unit recording and brain imaging studies. The model builds on currently known structural connections between and

The San Antonio studies: an overview

Over the course of a series of H215O PET studies conducted in the Research Imaging Center at the University of Texas Health Science Center, San Antonio, the authors and colleagues have sought to systematically isolate the neural regions that are functionally associated with developmental stuttering. These studies have been confined to right-handed participants and include adult stutterers of both genders, plus controls matched for age and sex. The findings of these studies have been reported in

Study 1: neural region activations by stutterers and controls during oral reading

This section uses the framework of the Jürgens Model to reanalyze the findings of the Fox et al. (1996) study. Fox et al. used PET to investigate the neural region effects of chorus reading on stuttering.

Discussion

The San Antonio studies constitute a program of brain imaging research that is designed to isolate the neural regions that are consistently associated with stuttering and its frequency during connected speech. Beginning with the Fox et al. (1996) study it was observed that stuttering was associated with unusual overactivation in the right hemisphere with abnormal activations in motor cortex, subcortical regions, and cerebellum. There was an absence of activation—even strong deactivation—in the

Acknowledgements

This work was supported by grants from the National Institutes of Health (1RO1MH60246-01; 1RO1DC036801-A1; PO1MH/DA52176) and from the National Library of Medicine (LM06858).

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