engleski

Optical topography and ERP study of speech perception changes following cochlear implantation: a case study

Restoration of hearing in deaf people after cochlear implantation depends on intrinsic properties of the cerebral cortex to process new auditory sensory inputs. Of particular importance in the restoration of hearing is an ability to process speech and to establish a competent social communication. The exploration of the mechanisms underlying auditory learning in altered auditory systems can contribute to the understanding of the brain organization. The first part of the talk will be devoted to the short description of the rehabilitation process following the cochlear implantation in a 29-year old adult. In addition, some personal notes on the process of the rehabilitation will be presented and discussed. The second part of the talk will present novel findings obtained from the modern neuroimaging techniques during the rehabilitation period showing remarkable changes in the brain processing of different auditory stimuli over the period of 5 months in a 29-year old adult whose case was presented in the first part of the talk. This study explores the brain activity following a cochlear implantation (CI) in a profoundly deaf adult using two neuroimaging techniques. We explored phonological discrimination using event related potential (ERP) and language discrimination using optical topography (OT). The participant was tested in both linguistic tasks once a month in the period of 4 months. During this period, the participant underwent a speech rehabilitation program based on the verbotonal method. A first evaluation was done 7 weeks after the implantation surgery and 2 weeks after the first set-up of the implant. In order to avoid data artifacts caused by the cochlear implant which was located on his right side of the head, we restricted the recordings of both ERP and OT to the left side of the head. ERP recorded the brain electrical responses during vowel and consonant-vowel (CV) syllable discrimination in a mismatch paradigm. OT reflects the brain hemodynamic responses, through the estimation of changes of the concentration of totalhemoglobin (total-Hb). OT was recorded over the left hemisphere (LH) during a language discrimination task in which participant had to classify a set of sentences to three possible categories: 1) Croatian language, which corresponded to his native language (L1) ; 2) English language (L2) or 3) non-language (NONL), which corresponded to Croatian sentences played reversed in time. Significant differences in phonological and language discrimination were observed over time in both behavioral and imaging results. Brain activity changes during early adaptation to the new sensory inputs are discussed. In the extension, this study demonstrate the possibility to use optical topography to study brain organization in the CI users, which has some advantages over other imaging techniques such as fMRI (magnetic and noise interference), MEG (data artifacts due to magnetic interference) or PET (invasiveness).

optical topography; cochlear implantation

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