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A ‘Basin of Attraction’ Theory of Stuttering
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
Frank Guenther1, Soo-Eun Chang2, Jonathan Cannon3; 1Boston University, 2University of Michigan, 3McMaster University
Recent advances in motor neuroscience suggest that well-learned actions are implemented as stereotyped neural trajectories in population state space. Here we build on this research to propose a neurocomputational theory of stuttering. We first extend the neural trajectory framework to speech production by hypothesizing that motor programs for words correspond to attractor-like trajectories embedded in cortical dynamics. Each word’s attractor trajectory has an associated basin of attraction in the neural state space; once this basin has been entered the word’s attractor trajectory will be followed in an automated way since it is robustly encoded in the synapses within cortex. To successfully produce a word the distributed speech network must be driven into the basin of attraction to initiate production of the word. We hypothesize that the cortico–basal ganglia–thalamo–cortical (BGTC) circuit plays a central role in this process by coordinating preparatory activity across speech-relevant cortical regions, including motor, premotor, and auditory areas. Rather than acting as a simple trigger, this circuit is proposed to generate a temporally structured pattern of inputs that steers neural population activity into the appropriate basin the upcoming word. Once this state is reached, the ensuing motor trajectory unfolds autonomously through cortico-cortical dynamics, minimizing the need for continued basal ganglia involvement. We then propose that stuttering arises from impaired or unreliable initialization of the cortical speech network. Specifically, the BGTC circuit fails to consistently coordinate the preparatory states of distributed effectors—respiratory, laryngeal, and articulatory—preventing the system from entering the basin of attraction for the intended word. This failure leads to repeated or prolonged attempts to achieve the necessary preparatory configuration, manifesting behaviorally as repetitions, blocks, or prolongations. Because the basin must be entered prior to trajectory execution, the theory naturally explains the predominance of stuttering at word onsets. The model provides a unifying account of diverse empirical findings regarding stuttering. Elevated inter-articulator variability in people who stutter is interpreted as a consequence of impaired cross-effector coordination. Neural oscillatory abnormalities, e.g. in the beta band, are interpreted as reflecting impaired temporal coordination across the cortical regions involved in speech. The framework also accounts for well-known fluency-enhancing conditions. Rhythmic cues, such as metronome pacing, are proposed to provide external timing signals that facilitate coordinated entry into the basin of attraction. Non-rhythmic auditory manipulations, including altered auditory feedback and masking noise, are hypothesized to reduce the precision required for auditory cortical preparation, effectively enlarging the basin of attraction and increasing the likelihood of successful initiation. Finally, the theory generates specific, testable predictions. Neural recordings should reveal incomplete, inconsistent, or unstable preparatory states preceding stutters. Fluency-enhancing manipulations should increase inter-regional coherence and reduce variability in preparatory state dynamics. High-resolution electrophysiological methods may allow direct observation of basin-entry dynamics in speech-related cortical populations. By integrating dynamical systems principles with established models of speech motor control, this basin-of-attraction framework provides a mechanistic account of speech initiation and a principled explanation for stuttering, linking neural dynamics, circuit-level function, and observable behavior.
Topic Areas: Speech Motor Control, Disorders: Developmental