Document Type : Research Paper
Authors
1 Speech therapist, PhD student in cognitive linguistics, Dr. Ali Shariati Faculty of Literature and Humanities, Ferdowsi University of Mashhad, Mashhad, Iran.
2 Department of Linguistics, Faculty of Literature and Humanities, Dr. Ali Sharyati, Ferdowsi University of Mashhad, Mashhad, Iran.
3 Department of Linguistics, University of Sistan and Baluchestan, Zahedan, Iran
Abstract
Abstract
Employing a Cognitive Linguistics framework—specifically Langacker's Cognitive Grammar, Rosch's Prototype Theory, and Hickok and Poeppel's dual-streams model—this research explores Inconsistent Phonological Disorder (IPD) in Persian-speaking children aged 5-7 years. Speech data from seven children with IPD (Inconsistent Phonological Disorder ) were analyzed using both quantitative and qualitative methods, revealing the following results:
First, 73% of phoneme production errors showed a relationship between instability ( e.g., /k/ to /t/ substitutions) and a deficit in phonological encoding at the formulation stage of the Levelt model.
Second, syllabic simplification in the form of CVC to CV structures was the dominant strategy for reducing cognitive load in children with IPD ( Inconsistent Phonological Disorder ) (mean of CV syllables = 0.68). Third, dysfunction in the dorsal stream, especially in the parietal-premotor connections, was identified as a neural factor in the instability of phoneme production. Cross-linguistic comparisons showed that in Persian, IPD errors mainly involve phoneme substitution, while in languages with complex phoneme clusters, such as English, the reduction of these clusters predominates. This study suggests that efficient IPD treatment should focus on strengthening phoneme cues and improving the function of dorsal stream neural circuits. In addition to enriching the neurocognitive literature on IPD, the findings of this study provide guidelines for the developing integrated treatment protocols. Therefore, IPD is considered a multifaceted deficit resulting from the dysfunctional interaction of cognitive, linguistic, and neural systems. Its treatment requires a comprehensive approach targeting both mental representations of phonemes and the associated neural circuits. It is suggested that therapeutic exercises be designed based on Rosch's theory, focusing on strengthening the representation of exemplars through frequent words. Also, neuromodulation methods such as transcranial direct current stimulation (tDCS) may prove useful and effective in improving premotor cortex function and the transfer of phonological schemas in these children .
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