Comments on neurolinguistic study

Gopee Krishnan, Shivani Tiwari, Bellur Rajashekar 
 Department of Speech and Hearing, Manipal College of Allied Health Sciences, Manipal University, Manipal, Karnataka, India

Correspondence Address:
Gopee Krishnan
Department of Speech and Hearing, Manipal College of Allied Health Sciences, Manipal University, Manipal, Karnataka
India

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Sir,

It was a great experience to read "Dysarthric Bengali speech: A neurolinguistic study" and the authors deserve to be complimented for carrying out this study in the Indian context. [1] Dysarthria has been one of the major (47% of all) neurogenic communication disorders subsequent to neurological impairment [2] and the most understudied conditions in India. In this context, we feel that the study evokes added attention to this clinical condition.

However, it is felt that the authors have not clearly delineated the distinction between speech and language. 'Neurolinguistic' studies deal with evaluating models of language using measures from brain structures and function, and/or in investigating brain structure and function with respect to language representation using proposed models of language. [3] That is, it deals with issues pertaining to the representation and processing of both normal and disordered language within the brain. It is apparently different from the execution of speech, impairment to which results in dysarthria. That is, speech is purely a motor act whereas language is an abstract and non-motoric act. [2]

Language is processed by various neuro-anatomical structures majorly in the left hemisphere in majority of the right-handed subjects. [4] Dysarthria, unlike aphasia, could result from damage to the motor pathways extending from the cerebral cortex to the speech musculature. In this context, the term "Neurolinguistic" to study the speech characteristics of dysarthria seems misleading. This lack of delineation between speech and language is observed in the manuscript as well. The authors state that 'with respect to the five linguistic domains namely, respiration, phonation, articulation, resonance and prosody...'. [1] We think that these domains clearly belong to motor speech production and not to linguistic processing.

The authors describe 'speech motor programming abnormalities as aphasia', [1] which we feel is incorrect as abnormalities in speech motor programming lead to another motor speech disorder known as apraxia of speech. [2] Aphasia refers to the disturbance of any or all of the skills, associations, and habits of spoken and written language, produced by injury to certain brain areas that are specialized for these functions. Disturbances in communication that are due to paralysis or incoordination of the musculature of speech or writing are not, themselves aphasic. [5]

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