Auditory-Verbal Processing Disorder and Dyslexia in Adulthood

Abstract

28 Università degli Studi di Salerno Introduction According to the Diagnostic and Statistic Manual of Mental Disorders (DSM-V), the neurodevelopment disorders are characterised by an atypical development of some cognitive domains, with a dysfunctional behavioural correlation supported by phenotypes with a genetic connection. Among these are the specific learning disabilities, which are united by a single condition characterised by difficulty in learning and using academic skills in the presence of an adequate IQ; these include dyslexia, dyscalculia and dysorthography. The clinical features are an inaccurate or slow and laborious reading of the words, difficulty in understanding the meaning of what is read, difficulty in spelling, in written expression, in mastering the concept of number, numerical data ora calculation, and in arithmetic reasoning. Recently, thanks to the better understanding of the neurobiological mechanisms underlying these disorders and thanks to the improvement of neuroimaging and genetic analysis, we better understood the evolution of these pathologies and consequently we have refined the diagnosis and treatment. Studies focused particularly more on dyslexia, both due to its high frequency in general population and to the better understanding of its pathogenesis. Various cognitive models are developed to explain the nature of the processes underlying the recognition of written words; the models explained partially the cause of dyslexia, tracing it back to a phonological deficit of consciousness. Today none of these models seems to prevail, but we believe that, in the context of a general reading disorder, there are several difficulties that can be either phonological or about phonological, motor or visual consciousness, due to the failure of magnocellular/auditory neurons development, because of an altered central processing. Already in the 80s, Tallal et al. recognised the phonological deficit as a symptom of a deficit of sound processing presented in rapid sequence (proper of verbal oral language) and therefore a deficit of elaboration at the auditory temporal cortex. This difficulty in the sounds analysis could lead to a wrong categorization and to a failure to recognise the phoneme as the acoustic characteristics change. From studies carried out on children with dyslexia, deficient performances emerged in conditions of short auditory stimuli presented in rapid sequence, while the performance improved with a longer stimulus interval. These difficulties lead to a need for longer times to discriminate short sounds in rapid sequence. Tallal deduced that children with dyslexia presented not a linguistic deficit but a deficit of temporal elaboration of the variation of the auditory patterns, which then translated into a difficulty in the perception of isolated language. In auditory perception of sounds, both when proposed in rapid sequences and with a longer time intervals, a primary role is played by auditory attention, expecially by focused auditory attention. The aim of this work is to present the features of adult patients wit a specific learning disability in reading and to evaluate the possible correlation with phonological awareness deficits (therefore the ability to analyse and manipulate the linguistic structure of words), and with auditory-verbal processing disorders.