A phonological deficit or a broader auditory deficit as a core impairment of dyslexia?

Ahissar, M.

Department of Psychology, Faculty of Social Sciences - The Hebrew University of Jerusalem. Israel

Auditory working memory as un underlying deficit in Dyslexia
A typical characteristic of Dyslexic individuals is their poor working memory. Though mainly studied in the verbal domain (e.g. Digit span), auditory working memory was found to be systematically impaired in Dyslexia across stimulus types. We previously suggested the ?anchoring deficit? which proposes that implicit aspects of working memory, which track regularities in incoming auditory stimuli, are impaired in Dyslexia (Ahissar et al., Nat Neurosci, 2006; Ahissar, TICS, 2007). This hypothesis explains Dyslexics? difficulties in acquiring efficient reading as stemming from difficulties in detecting the repeated underlying phonological patterns that characterize their language. Consequently, they need to actually ?read?, i.e. map the orthography to phonology, rather than retrieve only few reliable cues, as expert readers do. This hypothesis further explains Dyslexics? additional difficulties, e.g. poor performance in auditory discrimination tasks, as revealing a failure to utilize regularities in the sequence of auditory stimuli which typically facilitates perceptual performance (Oganian & Ahissar, 2012). We recently developed a computational model that dissociates between sensory noise and the contribution of recent history (working memory) in discrimination tasks (Raviv, Ahissar & Loewenstein, 2012). We indeed found that Dyslexics differ in their reduced weighting of recent history rather than in their increased sensory noise. The existence of Dyslexic musicians seems to challenge this auditory-general view, since musicians are known as very sensitive to sounds, and as having enhanced auditory working memory. We tested this population and found that even Dyslexic musicians have difficulties in non-verbal auditory memory (e.g. memory for pitch and for rhythm) compared with their peers. Moreover, their non-verbal auditory working memory is mainly impaired in its chunking ability, suggesting reduced ability to utilize regularities. Their working memory was a reliable predictor of their reading accuracy, as previously found for other dyslexic populations.