Persistent Stutterers Research Articles

Report of the GNPTAB c.3598G>A, p.Glu1200Lys founder mutation associated with persistent stuttering in South Indian population

Stuttering is a disorder that affects the fluency of speech resulting in interruptions that are highly heritable. The present study aimed to evaluate the occurrence of the founder mutation GNPTAB c.3598G>A, p.Glu1200Lys (rs137853825) which is associated with stuttering. A total of 96 unrelated persistent stutterers from south India were included in this study. Genotyping the exon 19 of the GNPTAB gene by Sanger sequencing identified the pathogenic mutation in 5/96 (5.2 %) participants. A noncoding mutation GNPTAB c.3602+62A>G (rs1952847841) was also detected in 16/96 (16.6 %) cases. Further studies are warranted to identify the pathogenic loci of other genes of the lysosomal pathway, which would provide further insights into the genetic constitution of stuttering.

64. Differences in intracortical inhibition of tongue motor representations between persistent adult developmental stutterers and normal speakers

The causes of developmental stuttering are not known, but increasing evidence shows differences in the motor system of persistent adult developmental stutterers (PADS) in comparison to normal speakers (NS). Right handed males PADS and matched NS (considering age, sex, handedness, smoking habits and musical expertise) were evaluated by using transcranial magnetic stimulation on their tongue primary motor cortex. We assessed resting and active motor thresholds, silent period threshold (SPT), and silent period duration (SPD, stimulating at 130% of SPT) in both hemispheres. Preliminary results suggest the presence of higher SPT for the PADS group with respect to NS. Moreover, SPD were increased in the left hemisphere of PADS with respect to NS. This result suggests a particular intracortical balance in the tongue motor cortex of PADS compared to NS. More specifically, while the higher SPT in PADS could suggest a lower intracortical inhibition, the longer SPD in the left hemisphere of PADS points up to a greater inhibition in these brain regions, thus compensated by the presence of lower inhibition in the right hemisphere of the same group. This data, in line with previous evidence in stuttering research, could be useful for rehabilitative purposes.

How the brain repairs stuttering

Stuttering is a neurodevelopmental disorder associated with left inferior frontal structural anomalies. While children often recover, stuttering may also spontaneously disappear much later after years of dysfluency. These rare cases of unassisted recovery in adulthood provide a model of optimal brain repair outside the classical windows of developmental plasticity. Here we explore what distinguishes this type of recovery from less optimal repair modes, i.e. therapy-induced assisted recovery and attempted compensation in subjects who are still affected. We show that persistent stuttering is associated with mobilization of brain regions contralateral to the structural anomalies for compensation attempt. In contrast, the only neural landmark of optimal repair is activation of the left BA 47/12 in the orbitofrontal cortex, adjacent to a region where a white matter anomaly is observed in persistent stutterers, but normalized in recovered subjects. These findings show that late repair of neurodevelopmental stuttering follows the principles of contralateral and perianomalous reorganization.

A study of familial stuttering

Here we study 13 families with stuttering. Of the 13 families, 9 were persistent stutterers and 4 were recovered stutterers. In the 9 families with persistent stuttering, 24 were male and 10 were females. Of the 4 families with recovered stutterers, 17 were male and 3 were female. Of the 17 males, 12 were persistent stutterers and 5 recovered after adolescence. All females were recovered stutterers. We conclude with a short discussion of recent molecular studies.

Towards a functional neural systems model of developmental stuttering

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 H 2 15 O 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 H 2 15 O 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.

Speech-Motor Control and Interhemispheric Relations in Recovered and Persistent Stuttering

The neurological basis of stuttering is associated with anomalies of interhemispheric relations and of the neural mechanisms of speech-motor control, specifically those involving the supplementary motor area (SMA). Stuttering typically develops through childhood and adolescence but many children will recover without formal treatment or intervention. The hypothesis that such spontaneous recovery is related to a maturation of the SMA is explored. Four experimental tasks were performed by adults whose stuttering has persisted, adults who reported having stuttered as children, and a control group of adults who reported never having stuttered. A Sequence Reproduction Finger Tapping task (Webster, 1986) and a Bimanual Crank Turning task (Preilowski, 1972) examined the functioning of the SMA, and 2 Divided Visual Field tasks examined asymmetries of hemispheric activation. The overall pattern of results for persistent stutterers compared to nonstutterers was consistent with motor-perceptual anomalies previously reported in the literature. The Bimanual Crank Turning task revealed additionally that the bimanual coordination deficits reported in adults who stutter are kinesthetically based and mediated through anterior callosal systems, including the SMA. Ex-stutterers were similar to nonstutterers in their performance of the motor control tasks, but similar to persistent stutterers in perceptual asymmetries associated with Divided Visual Field tasks. Taken together, the results from the four experimental tasks support the general hypothesis that an anomaly in interhemispheric relations and a deficit in the mechanisms of speech-motor control are each a necessary but not sufficient condition for stuttering and that recovery from childhood stuttering reflects a maturation of the mechanisms of speech-motor control.

Persistence and remission of incipient stuttering among high-risk children

This investigation concerns the persistence of stuttering and recovery from it among high-risk children. At the end of the second year of a 6-year prospective study, 26 of 93 preschool children with a parental history of stuttering were classified as stutterers. Four years later, seven of these children were classified as persistent stutterers, and 16 children were classified as recovered stutterers. The articulatory and linguistic skills of these two groups of children and the communicative and speaking behaviors of their mothers, were measured before and after the onset of stuttering. The analysis of these measures revealed that the articulatory skills of the children and the communicative style and language complexity of the mothers differentiated the incipient stutters whose stuttering subsequently became chronic from those who recovered.

Recovery and persistence of stuttering among relatives of stutterers.

Recovery and persistence of stuttering were examined in the first-degree relatives of a large group of adult persistent stutters. The percentage of recovered individuals reported in these families supports the hypothesis that recovered and persistent stuttering are not independent disorders. Sex and type of relative were significant variables in the distributions of recovery and persistence of stuttering. Handedness in male subjects and birth order did not distinguish between recovered and persistent stutterers. Female recovered stutterers had significantly earlier ages of stuttering onset than the other groups (male recovered stutterers and male and female persistent stutterers). Female recovered stutterers also tended to recover earlier than male recovered stutterers, and the durations of stuttering symptoms were similar in both sexes.