Categorization of common sounds by cochlear implanted and normal hearing adults.

Auditory categorization involves grouping of acoustic events along one or more shared perceptual dimensions which can relate to both semantic and physical attributes. This process involves both high level cognitive processes (categorization) and low-level perceptual encoding of the acoustic signal, both of which are affected by the use of a cochlear implant (CI) device. The goal of this study was twofold: I) compare the categorization strategies of CI users and normal hearing listeners (NHL) II) investigate if any characteristics of the raw acoustic signal could explain the results. 16 experienced CI users and 20 NHL were tested using a Free-Sorting Task of 16 common sounds divided into 3 predefined categories of environmental, musical and vocal sounds. Multiple Correspondence Analysis (MCA) and Hierarchical Clustering based on Principal Components (HCPC) show that CI users followed a similar categorization strategy to that of NHL and were able to discriminate between the three different types of sounds. However results for CI users were more varied and showed less inter-participant agreement. Acoustic analysis also highlighted the average pitch salience and average autocorrelation peak as being important for the perception and categorization of the sounds. The results therefore show that on a broad level of categorization CI users may not have as many difficulties as previously thought in discriminating certain kinds of sound; however the perception of individual sounds remains challenging.

PET-imaging of brain plasticity after cochlear implantation.

In this article, we review the PET neuroimaging literature, which indicates peculiarities of brain networks involved in speech restoration after cochlear implantation. We consider data on implanted patients during stimulation as well as during resting state, which indicates basic long-term reorganisation of brain functional architecture. On the basis of our analysis of neuroimaging literature and considering our own studies, we indicate that auditory recovery in deaf patients after cochlear implantation partly relies on visual cues. The brain develops mechanisms of audio-visual integration as a strategy to achieve high levels of speech recognition. It turns out that this neuroimaging evidence is in line with behavioural findings of better audiovisual integration in these patients. Thus, strong visually and audio-visually based rehabilitation during the first months after cochlear implantation would significantly improve and fasten the functional recovery of speech intelligibility and other auditory functions in these patients. We provide perspectives for further neuroimaging studies in cochlear implanted patients, which would help understand brain organisation to restore auditory cognitive processing in the implanted patients and would potentially suggest novel approaches for their rehabilitation. This article is part of a Special Issue entitled .

Does brain activity at rest reflect adaptive strategies? Evidence from speech processing after cochlear implantation.

In functional neuroimaging studies, task-related activity refers to the signal difference between the stimulation and rest conditions. We asked whether long-term changes in the sensory environment may affect brain activity at rest. To answer this question, we compared regional cerebral blood flow between a group of normally hearing controls and a group of cochlear-implanted (CI) deaf patients. Here we present evidence that long-term alteration of auditory experience, such as profound deafness followed by partial auditory recuperation through cochlear implantation, leads to functional cortical reorganizations at rest. Without any visual or auditory stimulation, CI subjects showed changes of cerebral blood flow in the visual, auditory cortex, Broca area, and in the posterior temporal cortex with an increment of activity in these areas from the time of activation of the implant to less than a year after the implantation.

Improvement in speech-reading ability by auditory training: Evidence from gender differences in normally hearing, deaf and cochlear implanted subjects.

Several neuropsychological and neuroimaging studies on gender differences in speech processing lead to the suggestion that women use the neural network of predictive and integrative analysis of speech to a larger extent than men. During speech-reading there is indeed a lack of reliable clues for word recognition which should emphasize predictive and integrative strategies of the brain. Our study aimed to explore gender differences in deaf and cochlear implanted (CI) patients at different levels during speech-reading, for words or phonemes, that we consider, correspond to increased involvement of predictive and integrative analysis. We collected speech-reading scores in a control group of normally hearing subjects (n=42) and in a group of deaf patients - who are good speech-readers - tested before, early after and late after cochlear implantation (n=97). Patient groups were almost equally distributed between follow-up and new patients. In normally hearing controls, women speech-read words better than men. This difference was also observed in all patients but not in experienced cochlear implant users. We did not observe a gender difference during speech-reading of isolated phonemes neither for controls nor for patients. We conclude that the better speech-reading ability of women for words but not for phonemes is in line with their greater use of predictive and integrative strategies for speech processing. Furthermore, we observed a progressive cross-modal compensation in male CI users after cochlear implantation which suggests a synergetic perceptual facilitation involving the visual and the recovering auditory modalities. This could lead to an improved performance in both auditory and visual modalities, the latter being constantly recruited to complement the crude information provided by the implant. Altogether, our data provide insights into cross-modal compensation in the adult brain following sensory privation.

Functional magnetic resonance imaging may avoid misdiagnosis of cochleovestibular nerve aplasia in congenital deafness.

OBJECTIVE: To investigate a narrow internal auditory canal (IAC) syndrome using functional magnetic resonance imaging (fMRI) of the auditory cortex. STUDY DESIGN: The study design was a case report. The follow-up period lasted 18 months. SETTING: The study was carried out in the audiology clinic of an ear, nose, and throat department and in the department of pediatric neuroradiology at a university hospital. MAIN OUTCOME MEASURES: Age-appropriate observational audiometry, objective audiovestibular tests, computed tomography (CT), magnetic resonance imaging (MRI), and (fMRI) of the auditory cortex were performed to analyze in detail the profound deafness of a young child. RESULTS: Audiovestibular examination demonstrated both measurable hearing and normal vestibulo-ocular reflex, and CT showed narrow IACs combined with normal labyrinths. Axial MR images completed by sagittal sections perpendicular to the IAC delineated a single nerve that was initially supposed to be the facial nerve. No cochleovestibular nerve was identified. However, fMRI performed with the patient under general anesthesia demonstrated activation of the primary auditory cortex during 1-kHz monaural stimulation on the left side. CONCLUSIONS: The absence of cochleovestibular nerve on MR studies cannot exclude connections between the inner ear and the central auditory pathways. This might be caused by a lack of spatial resolution of anatomical MR studies. The single nerve delineated within the IAC might also carry both facial and cochleovestibular fibers. Functional MRI can assess the cortical response to acoustic stimuli when aplasia of the cochleovestibular nerve is suspected. This case study illustrates a novel and atypical presentation of cochlear nerve dysplasia.