A Stochastic View of Comorbidity in Speech Disorders

Author(s): Moura TRS

We used discrete random walks for the analysis of two chronic conditions that may be present simultaneously in a patient. We analyzed the comorbidity between two symptoms referring to the pathological repetition of speech: palilalia and echolalia. We used memory walks with coupled memory with probability f. The probability f quantifies the mutual interaction between pairs of random walkers. We perform measures that quantify two characteristics of the walks; one of the local nature, the fractal dimension (D) and another of a global nature, the exponent of Hust (H). We found that typical measures of D are related to less severe degrees of palilalia and echolalia, followed by variations smaller than H. The H measures show that the regime is superdiffusive and there is no transition between diffusion regimes. In the region of comorbidity, the diffusive regimes do not exhibit quantitative values of H of ERW. We find curves for which the symptoms of palilalia and echolalia do not vary. That is, certain changes in the environment, quantified by the feedback parameter (p) and the probability of interaction (f); do not cause variations in the degree of severity of the two types of pathological speech repetition that were studied.