Development of auditory memory in cochlear implanted children over time

Abstract

Short term auditory memory is extremely important for speech development in hearing or hearing impaired children. Objective of this study was to assess development of auditory memory in a group of cochlear implanted children and to discover the factors that affect it. A group of 30 CI children aged 3 to 12 has been tested using a Test of immediate verbal memory developed by Spasenija Vladisavljević (Subtests I-IV).The test consists of four subtests of increasing complexity. Children were divided in three subgroups according to hearing age: A. With less than 1 year, B. 1- 2 years and C. More than 2 years. Two subgroups were compared regarding age at implantation: those implanted before the age of 3 and those implanted later than 3 years of age. Duration of rehabilitation was analyzed in this study as well and the children were divided in two groups, those with less than 3 years of speech and hearing rehabilitation and those with more than 3 years. Results have shown that short-term auditory memory is constantly improving over time in all of the cochlear implantees. Scores are increasing after three years of rehabilitation, especially for the most complex subtest of short sentences. Children that were implanted before the age of 3, have show considerably better scores in all four subtests, which implies that development of auditory memory is dependent on central nervous system plasticity. Improvement of short-term auditory memory is consistently seen over time in postoperative rehabilitation of cochlear implanted children. Early implantation, before the age of 3, enables maximal achievement in hearing, speech and auditory memory.

Neposredno verbalno pamćenje je izuzetno važno za razvoj govora i jezika kod dece bilo da ona sasvim normalno čuju ili imaju oštećen sluh. Cilj ovog rada je da proceni uticaj kohlearne implantacije na razvoj auditivne memorije u grupi kohlearno implantirane dece i da utvrdi faktore koji na to utiču. Grupa od 30 dece sa kohlearnim implantom, uzrasta od 3 do 12 godina ispitana je Testom neposrednog verbalnog pamćenja no Spaseniji Vladisavljević (prva 4 subtesta). Složenost subtestova raste od subtesta I do IV. Deca su podeljena u tri podgrupe prema slušnom uzrastu, t.j. vremenu od priključenja kohlearnog implanta: Podgrupa A: Slušni uzrast ispod godinu dana; Podgrupa B: Slušni uzrast između jedne i dve godine; Podgrupa C: Slušni uzrast iznad dve godine. Prema vremenu operacije deca su podeljena u dve podgrupe: implantirane pre treće godine života i one implantirane kasnije. Prema trajanju rehabilitacije deca su podeljena u dve grupe, na rehabilitaciji manje od 3 i više od 3 godine. Rezultati testiranja neposrednog verbalnog pamćenja pokazuju da se ono konstantno razvija tokom vremena kod sve kohlearno implantirane dece. Skorovi značajno rastu posle više od 3 godine rehabilitacije, posebno za složenije subtestove. Deca implantirana pre 3 godine života imaju bolje rezultate na testovima neposrednog verbalnog pamćenja, što ukazuje na uticaj plastičnosti centralnog nervnog sistema na razvoj auditivne memorije. Uočava se konstantan razvoj neposrednog verbalnog pamćenja tokom rehabilitacije kod sve dece sa kohlearnim implantom. Rana implantacija, pre treće godine, omogućava maksimalan razvoj funkcije slušanja, govora i auditivne memorije.