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13-03-2013 | Psychology | Article

Verbal short-term memory impaired in children with cochlear implants


Free abstract

medwireNews: Children with cochlear implants have reduced verbal short-term memory (STM) and working memory (WM), which affects some speech and language outcomes, a longitudinal study shows.

The findings, published in Ear and Hearing, remained significant even after accounting for prognostic factors such as age at implantation and maternal education.

"Verbal STM/WM processing skills reflect important underlying core elementary neurocognitive functions and represent potential intervention targets for improving endpoint S/L [speech and language] outcomes in pediatric CI [cochlear implant] users," say Michael Harris (Indiana University School of Medicine, Indianapolis, USA) and colleagues.

The researchers tested verbal STM/WM capacity and speech and language outcomes, at baseline and over time in 54 children who had received cochlear implants at a mean age of 3.81 years. They used the digit span forward (DSF) and digit span backward (DSB) tests, in which participants repeat spoken sequences of digits in forward or reverse order, as a measure of verbal STM/WM.

Among those with cochlear implants, 50.5% were found to be more than 1 standard deviation (SD) below the control group mean across all ages on DSF scores. For DSB scores, this percentage was 44.0%. By contrast, only 16% of the population would be expected to lie more than 1 SD below the mean.

Harris and co-authors also tested the children on four speech and language outcomes: the Phonetically Balanced Kindergarten (PBK) word test; the Peabody Picture Vocabulary Test (PPVT); the HINT-C, which tests the ability to perceive and reproduce sentences; and the Clinical Evaluation of Language Fundamentals (CELF). The PBK and HINT-C test speech perception, whereas the PPVT and CELF test language skills.

The team reports that DSF scores at baseline significantly predicted all four speech and language outcomes, whereas DSB baseline scores significantly predicted scores on the two language measures only. The slope of DSF growth over time was predictive for CELF scores only, and DSB slope was not predictive for any measure.

Overall, children with cochlear implants had parallel but delayed development of verbal STM/WM capacity. The authors suggest: "The relationship between DS [digit span] slope and S/L [speech and language] outcome observed in this study might be changed if children received highly focused interventions to markedly alter the development of STM/WM capacity."

By Afsaneh Gray, medwireNews Reporter

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