Abstract
Developmental stuttering is a disorder of speech fluency with an unknown pathogenesis. The similarity of its phenotype and natural history with other childhood neuropsychiatric disorders of frontostriatal pathology suggests that stuttering may have a closely related pathogenesis. We investigated in this study the potential involvement of frontostriatal circuits in developmental stuttering. We collected functional magnetic resonance imaging data from 46 persons with stuttering and 52 fluent controls during performance of the Simon Spatial Incompatibility Task. We examined differences between the two groups of blood-oxygen-level-dependent activation associated with two neural processes, the resolution of cognitive conflict and the context-dependent adaptation to changes in conflict. Stuttering speakers and controls did not differ on behavioral performance on the task. In the presence of conflict-laden stimuli, however, stuttering speakers activated more strongly the cingulate cortex, left anterior prefrontal cortex, right medial frontal cortex, left supplementary motor area, right caudate nucleus, and left parietal cortex. The magnitude of activation in the anterior cingulate cortex correlated inversely in stuttering speakers with symptom severity. Stuttering speakers also showed blunted activation during context-dependent adaptation in the left dorsolateral prefrontal cortex, a brain region that mediates cross-temporal contingencies. Frontostriatal hyper-responsivity to conflict resembles prior findings in other disorders of frontostriatal pathology, and therefore likely represents a general mechanism supporting functional compensation for an underlying inefficiency of neural processing in these circuits. The reduced activation of dorsolateral prefrontal cortex likely represents the inadequate readiness of stuttering speakers to execute a sequence of motor responses.
Highlights
Developmental stuttering is a disorder of speech fluency that disrupts the rhythm and timing of speech, producing frequent repetitions, and prolongations and blocks of syllables and words
Studies using language-related tasks in persons who stutter, have been unable to distinguish the abnormalities in brain activation that contribute to generating speech dysfluencies in stuttering speakers from the activations that derive from the attempts to control those dysfluencies
Both groups maintained a high level of accuracy throughout the task (.70% across three runs); groups did not differ in accuracy during incongruent (t96 = 20.56, p = 0.57) or congruent trials (t96 = 20.91, p = 0.36)
Summary
Developmental stuttering is a disorder of speech fluency that disrupts the rhythm and timing of speech, producing frequent repetitions, and prolongations and blocks of syllables and words. Stuttering symptoms follow a distinctive developmental trajectory, with speech dysfluency typically beginning in early childhood, gradually attenuating with the development of language skills, and remitting by adolescence in approximately 75% of persons who stutter [1]. Recent stuttering research has revealed impairments in capacities that can broadly be described as self-regulation, including regulation of attention, emotion, and motor activity [15,16,17,18] These capacities may contribute to the maintenance and exacerbation of speech dysfluencies [16,18,19], prior neuroimaging studies have not yet assessed the functional integrity of self-regulatory systems. Findings from studies in children have suggested that a compromised capacity of self-regulation may predispose to the development of stuttering [15,19]
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