An innovative method for trans-impedance matrix interpretation in hearing pathologies discrimination.

Trans-impedance measurement is a novel methodology for assessing the positioning of a cochlear implant (CI). This study proposes an innovative use of trans-impedance measurements to characterize specific hearing pathologies by means of the trans-impedance matrix (TIM) quantitative analysis. Three indices are used: Shannon Entropy, the Exponential Decay constant and Spatial Correlation. These indices were computed on the TIMs of two groups of patients, clustered in terms of hearing pathology: (i) congenital hearing loss (CONG) and (ii) otosclerosis (OTO). The study aimed to demonstrate the sensitivity of the above synthetic indices in relation to the considered hearing pathologies. Furthermore, the first two indices were employed to explore the influence of the positioning of the electrode, either over (i) the basal or (ii) the apical regions, on the TIMs patterns. The results suggest that the indices were statistically different for the patient groups and the positioning impacted solely on OTO patients. In particular: (i) CONG patients displayed significantly higher Shannon Entropy (p = 0.0002) and (ii) a lower Exponential Decay constant than OTO patients (p = 0.001); (iii) the OTO patients exhibited a lower Shannon Entropy and a higher Exponential Decay constant over the basal regions than the apical regions (p < 0.008); (iv) Spatial Correlation demonstrated that TIMs had specific patterns according to the hearing pathology (p < 0.008).

Frontal brain asymmetries as effective parameters to assess the quality of audiovisual stimuli perception in adult and young cochlear implant users.

How is music perceived by cochlear implant (CI) users? This question arises as "the next step" given the impressive performance obtained by these patients in language perception. Furthermore, how can music perception be evaluated beyond self-report rating, in order to obtain measurable data? To address this question, estimation of the frontal electroencephalographic (EEG) alpha activity imbalance, acquired through a 19-channel EEG cap, appears to be a suitable instrument to measure the approach/withdrawal (AW index) reaction to external stimuli. Specifically, a greater value of AW indicates an increased propensity to stimulus approach, and vice versa a lower one a tendency to withdraw from the stimulus. Additionally, due to prelingually and postlingually deafened pathology acquisition, children and adults, respectively, would probably differ in music perception. The aim of the present study was to investigate children and adult CI users, in unilateral (UCI) and bilateral (BCI) implantation conditions, during three experimental situations of music exposure (normal, distorted and mute). Additionally, a study of functional connectivity patterns within cerebral networks was performed to investigate functioning patterns in different experimental populations. As a general result, congruency among patterns between BCI patients and control (CTRL) subjects was seen, characterised by lowest values for the distorted condition (vs. normal and mute conditions) in the AW index and in the connectivity analysis. Additionally, the normal and distorted conditions were significantly different in CI and CTRL adults, and in CTRL children, but not in CI children. These results suggest a higher capacity of discrimination and approach motivation towards normal music in CTRL and BCI subjects, but not for UCI patients. Therefore, for perception of music CTRL and BCI participants appear more similar than UCI subjects, as estimated by measurable and not self-reported parameters.

Alpha EEG Frontal Asymmetries during Audiovisual Perception in Cochlear Implant Users. A Study with Bilateral and Unilateral Young Users.

OBJECTIVES: The aim of the present study is to investigate the variations of the electroencephalographic (EEG) alpha rhythm in order to measure the appreciation of bilateral and unilateral young cochlear implant users during the observation of a musical cartoon. The cartoon has been modified for the generation of three experimental conditions: one with the original audio, another one with a distorted sound and, finally, a mute version. METHODS: The EEG data have been recorded during the observation of the cartoons in the three experimental conditions. The frontal alpha EEG imbalance has been calculated as a measure of motivation and pleasantness to be compared across experimental populations and conditions. RESULTS: The EEG frontal imbalance of the alpha rhythm showed significant variations during the perception of the different cartoons. In particular, the pattern of activation of normal-hearing children is very similar to the one elicited by the bilateral implanted patients. On the other hand, results related to the unilateral subjects do not present significant variations of the imbalance index across the three cartoons. CONCLUSION: The presented results suggest that the unilateral patients could not appreciate the difference in the audio format as well as bilaterally implanted and normal hearing subjects. The frontal alpha EEG imbalance is a useful tool to detect the differences in the appreciation of audiovisual stimuli in cochlear implant patients.

Differences in the perceived music pleasantness between monolateral cochlear implanted and normal hearing children assessed by EEG.

The perception of the music in cochlear implanted (CI) patients is an important aspect of their quality of life. In fact, the pleasantness of the music perception by such CI patients can be analyzed through a particular analysis of EEG rhythms. Studies on healthy subjects show that exists a particular frontal asymmetry of the EEG alpha rhythm which can be correlated with pleasantness of the perceived stimuli (approach-withdrawal theory). In particular, here we describe differences between EEG activities estimated in the alpha frequency band for a monolateral CI group of children and a normal hearing one during the fruition of a musical cartoon. The results of the present analysis showed that the alpha EEG asymmetry patterns related to the normal hearing group refers to a higher pleasantness perception when compared to the cerebral activity of the monolateral CI patients. In fact, the present results support the statement that a monolateral CI group could perceive the music in a less pleasant way when compared to normal hearing children.

EEG frontal asymmetry related to pleasantness of music perception in healthy children and cochlear implanted users.

Interestingly, the international debate about the quality of music fruition for cochlear implanted users does not take into account the hypothesis that bilateral users could perceive music in a more pleasant way with respect to monolateral users. In this scenario, the aim of the present study was to investigate if cerebral signs of pleasantness during music perception in healthy child are similar to those observed in monolateral and in bilateral cochlear implanted users. In fact, previous observations in literature on healthy subjects have indicated that variations of the frontal EEG alpha activity are correlated with the perceived pleasantness of the sensory stimulation received (approach-withdrawal theory). In particular, here we described differences between cortical activities estimated in the alpha frequency band for a healthy child and in patients having a monolateral or a bilateral cochlear implant during the fruition of a musical cartoon. The results of the present analysis showed that the alpha EEG asymmetry patterns observed in a healthy child and that of a bilateral cochlear implanted patient are congruent with the approach-withdrawal theory. Conversely, the scalp topographic distribution of EEG power spectra in the alpha band resulting from the monolateral cochlear user presents a different EEG pattern from the normal and bilateral implanted patients. Such differences could be explained at the light of the approach-withdrawal theory. In fact, the present findings support the hypothesis that a monolateral cochlear implanted user could perceive the music in a less pleasant way when compared to a healthy subject or to a bilateral cochlear user.

Investigation on the pleasantness of music perception in monolateral and bilateral cochlear implant users by using neuroelectrical source imaging: a pilot study.

There is a debate in the specialized literature about the quality of fruition of music for patients that received a cochlear implant. Interestingly, very few studies have investigated the hypothesis that patients that use a bilateral cochlear implant could perceive the music in a more pleasant way as compared to unilaterally implanted patients. Previous observations in healthy subjects have indicated that variations of particular EEG rhythms correlated with the pleasantness of the perceived music. The aim of the present pilot study is then to apply the state of the art neuroelectrical imaging and the analysis of cortical representation of EEG rhythms to monitor the perceived pleasantness during the observation of a simple videoclip in one patient with a unilateral cochlear implant and in one receiving a bilateral cochlear implant. Results of this pilot study showed that on the base of such previously validated EEG rhythms, the fruition of music and video, in terms of pleasantness, is statistically higher in the bilaterally implanted patient when compared to the monolateral implanted patient.