The role of verbal short term memory, speech perception and duration of implantation in language and academic outcomes of a group of children with cochlear implant

In order to analyse the trend of language and academical learning in case of hearing loss, our Unit has assessed 44 preverbally deaf children fitted with Cochlear Implant (CI) through a neuropsychological protocol. Patients in the sample have normal intelligence, no developmental disorder, chronological age of 7÷13 years, mean age at implantation of 5.0 (sd=3) and mean duration of implantation (dCI) of 4.3 years (sd=2.7). For Language acquisition, data analysis highlights significant correlations between i) Digit span (DS) and verbal fluency, receptive and expressive vocabulary, and receptive grammar (r ranges -.47÷.75, p<.01); ii) speech perception skills and receptive and expressive vocabulary, and receptive grammar (r ranges -.47 ÷ .53, p<.01). As regards Literacy acquisition, correlations prove significant between DS and all measures of reading, both decoding and comprehension (r ranges .42 ÷ .60, p<.01). Multiple regressions reveal the role of other factors: Words reading speed is explained by age, dCI, speech perception skill and backward DS [ R2adj= .67; F(6, 30) =11.11, p=.000]: this last proved to be the only one affecting accuracy as well [ R2adj= .32; F(6, 30) =3.35, p<.05] . As regards Nonwords reading speed, age is the only variable which explains variance [R2adj= .39; F(6, 26) =3.69, p<.05]. Accuracy in nonword reading is explained by age, dCI and backward DS [ R2adj= .46; F(6, 26) =4.63, p<.01]; age proves to affect Reading comprehension as does forward DS [R2adj= .57; F(6, 25) =6.45, p=.001]. It is clear that verbal short term memory has an important effect on the development of receptive and expressive vocabulary, as well as on reading acquisition. Also dCI and speech perception explain individual differences in CI children’s reading skills. However, reading comprehension does not exhibit associations with speech perception.