Auditory temporal coding in dyslexia

Abstract

Developmental dyslexia is generally believed to result from impaired linguistic processing rather than from deficits in low-level sensory function. Challenging this view, we studied the perception of non-verbal acoustic stimuli and low-level auditory evoked potentials in dyslexic adults. Compared with matched controls, dyslexics were selectively impaired in tasks (frequency discrimination and binaural unmasking) which rely on decoding neural discharges phase-locked to the fine structure of the stimulus. Furthermore, this ability to use phase-locking was related to reading ability. In addition, the evoked potential reflecting phase-locked discharges was significantly smaller in dyslexics. These results demonstrate a low-level auditory impairment in dyslexia traceable to the brainstem nuclei.

Patterns of deficit in auditory temporal processing among dyslexic adults

“…Although many studies found poorer performance in dyslexics than in normal readers [4,7,10], others did not [11]. Two inter-study differences may underlie this variance.…”

“…According to this theory, dyslexics should have difficulties in auditory processing whenever stimuli appear in fast succession, but not when presentation rate is slower or stimuli are longer. There is substantial evidence for dyslexics' impaired performance with brief stimuli (see [6,9] for reviews); however deficits with longer stimuli were also reported [5][6][7]9]. For example, in frequency discrimination tasks, using a variety of procedures, significantly higher thresholds were found in disabled compared with agematched normal readers [4,5,7,10].…”

“…There is substantial evidence for dyslexics' impaired performance with brief stimuli (see [6,9] for reviews); however deficits with longer stimuli were also reported [5][6][7]9]. For example, in frequency discrimination tasks, using a variety of procedures, significantly higher thresholds were found in disabled compared with agematched normal readers [4,5,7,10]. Ahissar et al [5] measured two-tone frequency discrimination with both temporal order judgments of brief tones and intervals, and same/different judgments of longer tones and intervals.…”

“…language delay [2]) and the extent of perceptual difficulties [3]. Perceptual deficits in dyslexia have been found on both visual [4] and auditory [5][6][7] tasks. The relationship between perceptual deficits and subtypes of dyslexia is still an open question.…”

Development of structure and function in the infant brain: Implications for cognition, language and social behaviour

“…Across laboratories, research investigating basic auditory processing in individuals with specific language impairment (SLI) or dyslexia suggests that impaired perception and discrimination of auditory stimuli involving two or more rapidly presented transient elements hinders the development of normal language and reading abilities (Tallal and Piercy, 1974;Godfrey et al, 1981;Werker and Tees, 1987;Snowling et al, 1986;Stark and Heinz, 1996;McAnally and Stein, 1997). Further, several studies have suggested that efficient rapid auditory processing (RAP) ability is important for later language skill; performance on RAP tasks in infancy have been shown to relate to later language performance, both in normally developing infants and in those with a family history of language impairment (Benasich and Tallal, 2002;Molfese and Molfese, 1997;Trehub and Henderson, 1996).…”