Poor Frequency Discrimination Probes Dyslexics with Particularly Impaired Working Memory

Abstract

Substantial difficulties in performing simple auditory discriminations were previously found in some individuals with a specific reading disability but not in others. This high variability in psychoacoustic performance raises the question of whether this difficulty is related to the reading deficit. Addressing this question, we compared adult dyslexics with and without difficulty in simple auditory discriminations, using 2-tone frequency discrimination as our probe. The distribution of their frequency discrimination scores was bimodal. On this basis, we divided our participants into subgroups having either poor or adequate psychoacoustic performance. Only dyslexics with poor psychoacoustic scores had significantly impaired verbal working memory compared to their matched controls. Furthermore, and only in this subgroup, working memory scores were correlated with both cognitive abilities and reading-related tasks. Consistent with the hypothesis that in this subgroup poor working memory impedes performance in a broad range of academically related tasks, we found that the majority of dyslexics in this subgroup had more extensive academic difficulties and consequently needed special support in schools. We propose that dyslexics with poor psychoacoustic abilities form a distinct subtype of dyslexia in which the core deficit is not specific to phonological components. For these individuals, poor verbal working memory may be the main impediment to success in academic environments.

Auditory Temporal Processing as a Specific Deficit Among Dyslexic Readers

“…Consequently, the findings of the current study confirm our second hypothesis that dyslexic readers will perform poorly on tasks that require auditory temporal processing, independently from any deficit in working memory. Based on these findings, we conclude that the present study supports the hypothesis that dyslexic readers' deficit in auditory temporal processing is specific to temporal perception, and is not a product of a deficit in working memory, as it had been previously suggested (Ahissar, 2007;Banai & Ahissar, 2004).…”

Auditory Temporal Processing and Working Memory: Two Independent Deficits for Dyslexia

“…However, the authors also found that working memory and auditory temporal resolution were not only poorer among dyslexic readers, but also were independently associated with their reading ability. Thus, it appears that both working memory and auditory temporal resolution are basic abilities that are involved in reading among dyslexic readers (Banai & Ahissar, 2004;Ben-Artzi et al, 2005;Reed, 1989;Tallal, 1980;Wright, Bowen, & Zecker, 2000). The complementary finding, which among the normal readers' performances on a digit span task and on a dichotic TOJ task did not predict reading ability, leads to the suggestion that working memory and auditory temporal resolution are utilized by the dyslexic in the processing associated with reading in a manner that is not used by the normal readers.…”

“…Moreover, some researchers suggested that working memory underlies the difficulties that dyslexic readers exhibit in auditory temporal resolution tasks, since it reduces the access to stored information (Banai & Ahissar, 2004). Several questions remain to be addressed regarding the reported deficits of dyslexic readers in working memory and auditory temporal resolution.…”

Perceptual learning as a tool for boosting working memory among individuals with reading and learning disability

“…However, in a series of subsequent studies (Ben-Yehudah et al, 2001;Amitay et al, 2002a;Amitay et al, 2002b;Banai and Ahissar, 2004;Ahissar et al, 2006;Banai and Ahissar, 2006) we found that their difficulties depend on task protocol more than on the complexity of stimulus or the perceptual resolution required. Specifically, while the general population performs substantially better when a limited set of stimuli is used repeatedly, individuals with D-LD display impaired 'anchoring' ability, and their thresholds remain high even with stimulus specific repetitions .…”