How Do We Allocate Our Resources When Listening and Memorizing Speech in Noise? A Pupillometry Study.

OBJECTIVES: Actively following a conversation can be demanding and limited cognitive resources must be allocated to the processing of speech, retaining and encoding the perceived content, and preparing an answer. The aim of the present study was to disentangle the allocation of effort into the effort required for listening (listening effort) and the effort required for retention (memory effort) by means of pupil dilation. DESIGN: Twenty-five normal-hearing German speaking participants underwent a sentence final word identification and recall test, while pupillometry was conducted. The participants' task was to listen to a sentence in four-talker babble background noise and to repeat the final word afterward. At the end of a list of sentences, they were asked to recall as many of the final words as possible. Pupil dilation was recorded during different list lengths (three sentences versus six sentences) and varying memory load (recall versus no recall). Additionally, the effect of a noise reduction algorithm on performance, listening effort, and memory effort was evaluated. RESULTS: We analyzed pupil dilation both before each sentence (sentence baseline) as well as the dilation in response to each sentence relative to the sentence baseline (sentence dilation). The pupillometry data indicated a steeper increase of sentence baseline under recall compared to no recall, suggesting higher memory effort due to memory processing. This increase in sentence baseline was most prominent toward the end of the longer lists, that is, during the second half of six sentences. Without a recall task, sentence baseline declined over the course of the list. Noise reduction appeared to have a significant influence on effort allocation for listening, which was reflected in generally decreased sentence dilation. CONCLUSION: Our results showed that recording pupil dilation in a speech identification and recall task provides valuable insights beyond behavioral performance. It is a suitable tool to disentangle the allocation of effort to listening versus memorizing speech.

Development and validation of the audio processor satisfaction questionnaire (APSQ) for hearing implant users.

Objective: The satisfaction experienced with using an audio processor is very important to hearing implant system users. Currently there are no measures that can be used to assess user satisfaction with an audio processor. This study aims to develop and validate a specific and standardised questionnaire that focuses on user satisfaction with their audio processor.Design: A preliminary version of the questionnaire was initially developed by experts in the field. Following validation of these results, the final version of the Audio Processor Satisfaction Questionnaire (APSQ) was developed consisting of 15 items. Item analyses and questionnaire validation measurements were assessed.Study sample: Sixty-nine subjects were recruited and asked to complete the APSQ twice within 2-4 weeks.Results: Subjects reported a high user satisfaction with the questionnaire and with their audio processor. The questionnaire had good reliability and results for test-retest reliability were high and significant across all items and across subscale analyses.Conclusion: Item analyses and reliability analyses show that the questionnaire is a valid and reliable tool to assess user satisfaction across different audio processors and hearing implant systems. The APSQ is a quick and easy tool to measure user satisfaction with their audio processor.

Auditory Acclimatization to Bilateral Hearing Aids: Effects on Sentence-in-Noise Processing Times and Speech-Evoked Potentials.

OBJECTIVES: Using a longitudinal design, the present study sought to substantiate indications from two previous cross-sectional studies that hearing aid (HA) experience leads to improved speech processing abilities as quantified using eye-gaze measurements. Another aim was to explore potential concomitant changes in event-related potentials (ERPs) to speech stimuli. DESIGN: Groups of elderly novice (novHA) and experienced (expHA) HA users matched in terms of age and working memory capacity participated. The novHA users were acclimatized to bilateral HA fittings for up to 24 weeks. The expHA users continued to use their own HAs during the same period. The participants' speech processing abilities were assessed after 0 weeks (novHA: N = 16; expHA: N = 14), 12 weeks (novHA: N = 16; expHA: N = 14), and 24 weeks (N = 10 each). To that end, an eye-tracking paradigm was used for estimating how quickly the participants could grasp the meaning of sentences presented against background noise together with two similar pictures that either correctly or incorrectly depicted the meaning conveyed by the sentences (the "processing time"). Additionally, ERPs were measured with an active oddball paradigm requiring the participants to categorize word stimuli as living (targets) or nonliving (nontargets) entities. For all measurements, the stimuli were spectrally shaped according to individual real-ear insertion gains and presented via earphones. RESULTS: Concerning the processing times, no changes across time were found for the expHA group. After 0 weeks of HA use, the novHA group had significantly longer (poorer) processing times than the expHA group, consistent with previous findings. After 24 weeks, a significant mean improvement of ~30% was observed for the novHA users, leading to a performance comparable with that of the expHA group. Concerning the ERPs, no changes across time were found. CONCLUSIONS: The results from this exploratory study are consistent with the view that auditory acclimatization to HAs positively impacts speech comprehension in noise. Further research is needed to substantiate them.

Auditory and audio-visual processing in patients with cochlear, auditory brainstem, and auditory midbrain implants: An EEG study.

There is substantial variability in speech recognition ability across patients with cochlear implants (CIs), auditory brainstem implants (ABIs), and auditory midbrain implants (AMIs). To better understand how this variability is related to central processing differences, the current electroencephalography (EEG) study compared hearing abilities and auditory-cortex activation in patients with electrical stimulation at different sites of the auditory pathway. Three different groups of patients with auditory implants (Hannover Medical School; ABI: n = 6, CI: n = 6; AMI: n = 2) performed a speeded response task and a speech recognition test with auditory, visual, and audio-visual stimuli. Behavioral performance and cortical processing of auditory and audio-visual stimuli were compared between groups. ABI and AMI patients showed prolonged response times on auditory and audio-visual stimuli compared with NH listeners and CI patients. This was confirmed by prolonged N1 latencies and reduced N1 amplitudes in ABI and AMI patients. However, patients with central auditory implants showed a remarkable gain in performance when visual and auditory input was combined, in both speech and non-speech conditions, which was reflected by a strong visual modulation of auditory-cortex activation in these individuals. In sum, the results suggest that the behavioral improvement for audio-visual conditions in central auditory implant patients is based on enhanced audio-visual interactions in the auditory cortex. Their findings may provide important implications for the optimization of electrical stimulation and rehabilitation strategies in patients with central auditory prostheses. Hum Brain Mapp 38:2206-2225, 2017. © 2017 Wiley Periodicals, Inc.

Toward Automated Cochlear Implant Fitting Procedures Based on Event-Related Potentials.

OBJECTIVES: Cochlear implants (CIs) restore hearing to the profoundly deaf by direct electrical stimulation of the auditory nerve. To provide an optimal electrical stimulation pattern the CI must be individually fitted to each CI user. To date, CI fitting is primarily based on subjective feedback from the user. However, not all CI users are able to provide such feedback, for example, small children. This study explores the possibility of using the electroencephalogram (EEG) to objectively determine if CI users are able to hear differences in tones presented to them, which has potential applications in CI fitting or closed loop systems. DESIGN: Deviant and standard stimuli were presented to 12 CI users in an active auditory oddball paradigm. The EEG was recorded in two sessions and classification of the EEG data was performed with shrinkage linear discriminant analysis. Also, the impact of CI artifact removal on classification performance and the possibility to reuse a trained classifier in future sessions were evaluated. RESULTS: Overall, classification performance was above chance level for all participants although performance varied considerably between participants. Also, artifacts were successfully removed from the EEG without impairing classification performance. Finally, reuse of the classifier causes only a small loss in classification performance. CONCLUSIONS: Our data provide first evidence that EEG can be automatically classified on single-trial basis in CI users. Despite the slightly poorer classification performance over sessions, classifier and CI artifact correction appear stable over successive sessions. Thus, classifier and artifact correction weights can be reused without repeating the set-up procedure in every session, which makes the technique easier applicable. With our present data, we can show successful classification of event-related cortical potential patterns in CI users. In the future, this has the potential to objectify and automate parts of CI fitting procedures.

Cochlear implant effectiveness in postlingual single-sided deaf individuals: what's the point?

OBJECTIVES: By extending the indication criteria for cochlear implants (CI), the population of CI candidates increased in age, as well as range and type of hearing loss. This qualitative study identified factors that contributed to seek CI treatment in single-sided deaf individuals and gained insights how single-sided deafness (SSD) and hearing with a CI affect their lives. DESIGN: An open-ended questionnaire and a standardised inventory (IOI-HA) were used. Qualitative data reflecting the reasons to seek CI treatment and the individual experiences after CI switch-on were collected. STUDY SAMPLE: A total of 19 postlingually deafened single-sided deaf CI users. RESULTS: Participants use their CI daily and stated that their life satisfaction increased since CI activation. The analysis of the qualitative data revealed four core categories: sound localisation, tinnitus and noise sensitivity, fear to lose the second ear and quality of life. CONCLUSIONS: Our results show how strongly and diversely quality of hearing and quality of life is affected by acquired SSD and improved after CI activation. Our data suggest that the fear of hearing loss (HL) on the normal hearing (NH) ear is an important but so far neglected reason to seek treatment with a CI in individuals with postlingual SSD.

Consequences of Stimulus Type on Higher-Order Processing in Single-Sided Deaf Cochlear Implant Users.

Single-sided deaf subjects with a cochlear implant (CI) provide the unique opportunity to compare central auditory processing of the electrical input (CI ear) and the acoustic input (normal-hearing, NH, ear) within the same individual. In these individuals, sensory processing differs between their two ears, while cognitive abilities are the same irrespectively of the sensory input. To better understand perceptual-cognitive factors modulating speech intelligibility with a CI, this electroencephalography study examined the central-auditory processing of words, the cognitive abilities, and the speech intelligibility in 10 postlingually single-sided deaf CI users. We found lower hit rates and prolonged response times for word classification during an oddball task for the CI ear when compared with the NH ear. Also, event-related potentials reflecting sensory (N1) and higher-order processing (N2/N4) were prolonged for word classification (targets versus nontargets) with the CI ear compared with the NH ear. Our results suggest that speech processing via the CI ear and the NH ear differs both at sensory (N1) and cognitive (N2/N4) processing stages, thereby affecting the behavioral performance for speech discrimination. These results provide objective evidence for cognition to be a key factor for speech perception under adverse listening conditions, such as the degraded speech signal provided from the CI.

Psychometric properties of the English version of the Audio Processor Satisfaction Questionnaire (APSQ).

OBJECTIVE: The Audio Processor Satisfaction Questionnaire (APSQ) is a standardized tool to measure a user's satisfaction with their audio processor(s). It was first developed and validated in the German language. The purpose of the current study was to validate the English version of the APSQ. DESIGN: The 15 items of the APSQ were translated into English. Item and scale analyses assessed the quality of individual items and of the questionnaire in its entirety. STUDY SAMPLE: Sixty-seven adults with hearing implants participated. Forty-six of them completed the questionnaire twice within 2-4 weeks. RESULTS: High mean values were obtained with total scores and with scores of the comfort, social life, and usability domains, indicating that users are generally satisfied with their audio processors. The questionnaire achieved good test-retest reliability with high internal consistency. A significant positive correlation between time since implantation and user satisfaction was found. CONCLUSION: Results of the item and reliability analyses suggest that the English version of the APSQ is a valid and reliable tool to assess user satisfaction with their audio processor(s).

ARTFit-A Quick and Reliable Tool for Performing Initial Fittings in Users of MED-EL Cochlear Implants.

This study assessed the safety and performance of ARTFit, a new tool embedded in MAESTRO, the cochlear implant (CI) system software by MED-EL GmbH (Innsbruck, Austria). ARTFit automatically measures thresholds of the electrically evoked compound action potential (ECAP) to produce initial 'maps' (ECAPMAPs), i.e., configuration settings of the audio processor that the audiologist switches to live mode and adjusts for comfortable loudness (LiveECAPMAPs). Twenty-three adult and ten pediatric users of MED-EL CIs participated. The LiveECAPMAPs were compared to behavioral maps (LiveBurstMAPs) and to the participants' everyday clinical maps (ClinMAPs). Four evaluation measures were considered: average deviations of the maximum comfortable loudness (MCL) levels of the LiveECAPMAPs and the LiveBurstMAPs from the MCLs of the ClinMAPs; correlations between the MCLs of the LiveECAPMAPs (MCLecap) and the LiveBurstMAPs (MCLburst) with the MCLs of the ClinMAPs (MCLclin); fitting durations; and speech reception thresholds (SRTs). All evaluation measures were analyzed separately in the adult and pediatric subgroups. For all evaluation measures, the deviations of the LiveECAPMAPs from the ClinMAPs were not larger than those of the LiveBurstMAPs from the ClinMAPs. The Pearson correlation between the MCLecap and the MCLclin across all channels was r2 = 0.732 (p < 0.001) in the adult and r2 = 0.616 (p < 0.001) in the pediatric subgroups. The mean fitting duration in minutes for the LiveECAPMAPs was significantly shorter than for that of the LiveBurstMAPs in both subgroups: adults took 5.70 (range 1.90-11.98) vs. 9.27 (6.83-14.72) min; children took 3.03 (1.97-4.22) vs. 7.35 (3.95-12.77). SRTs measured with the LiveECAPMAPs were non-inferior to those measured with the ClinMAPs and not statistically different to the SRTs measured with the LiveBurstMAPs. ARTFit is a safe, quick, and reliable tool for audiologists to produce ECAP-based initial fitting maps in adults and young children who are not able to provide subjective feedback.

Do Not Go Gentle into That Deaf Night: A Holistic Perspective on Cochlear Implant Use as Part of Healthy Aging.

Research suggests that cochlear implant (CI) use in elderly people improves speech perception and health-related quality of life (HRQOL). CI provision could also prevent dementia and other comorbidities and support healthy aging. The aim of this study was (1) to prospectively investigate potential changes in HRQOL and speech perception and (2) to identify clinical action points to improve CI treatment. Participants (n = 45) were CI recipients aged 60-90 with postlingual deafness. They were divided into groups, according to age: Group 1 (n = 20) received a CI between the age of 60-70 years; group 2 (n = 25) between the age of 71-90 years. HRQOL and speech perception were assessed preoperatively, and three and twelve months postoperatively. HRQOL and speech perception increased significantly within one year postoperatively in both groups. No difference between groups was found. We conclude that CI treatment improves speech perception and HRQOL in elderly users. Improvement of the referral process for CI treatment and a holistic approach when discussing CI treatment in the elderly population could prevent auditory deprivation and the deterioration of cognitive abilities.

Spatio-temporal brain dynamics in a combined stimulus-stimulus and stimulus-response conflict task.

It is yet not well known whether different types of conflicts share common or rely on distinct brain mechanisms of conflict processing. We used a combined Flanker (stimulus-stimulus; S-S) and Simon (stimulus-response; S-R) conflict paradigm both in an fMRI and an EEG study. S-S conflicts induced stronger behavioral interference effects compared to S-R conflicts and the latter decayed with increasing response latencies. Besides some similar medial frontal activity across all conflict trials, which was, however, not statically consistent across trials, we especially found distinct activations depending on the type of conflict. S-S conflicts activated the anterior cingulate cortex and modulated the N2 and early P3 component with underlying source activity in inferior frontal cortex. S-R conflicts produced distinct activations in the posterior cingulate cortex and modulated the late P3b component with underlying source activity in superior parietal cortex. Double conflict trials containing both S-S and S-R conflicts revealed, first, distinct anterior frontal activity representing a meta-processing unit and, second, a sequential modulation of the N2 and the P3b component. The N2 modulation during double conflict trials was accompanied by increased source activity in the medial frontal gyrus (MeFG). In summary, S-S and S-R conflict processing mostly rely on distinct mechanisms of conflict processing and these conflicts differentially modulate the temporal stages of stimulus processing.

Which Questions Do Children With Cochlear Implants Understand? An Eye-Tracking Study.

Purpose The purpose of this study was to investigate the processing of morphosyntactic cues (case and verb agreement) by children with cochlear implants (CIs) in German which-questions, where interpretation depends on these morphosyntactic cues. The aim was to examine whether children with CIs who perceive the different cues also make use of them in speech comprehension and processing in the same way as children with normal hearing (NH). Method Thirty-three children with CIs (age 7;01-12;04 years;months, M = 9;07, bilaterally implanted before age 3;3) and 36 children with NH (age 7;05-10;09 years, M = 9;01) received a picture selection task with eye tracking to test their comprehension of subject, object, and passive which-questions. Two screening tasks tested their auditory discrimination of case morphology and their perception and comprehension of subject-verb agreement. Results Children with CIs who performed well on the screening tests still showed more difficulty on the comprehension of object questions than children with NH, whereas they comprehended subject questions and passive questions equally well as children with NH. There was large interindividual variability within the CI group. The gaze patterns of children with NH showed reanalysis effects for object questions disambiguated later in the sentence by verb agreement, but not for object questions disambiguated by case at the first noun phrase. The gaze patterns of children with CIs showed reanalysis effects even for object questions disambiguated at the first noun phrase. Conclusions Even when children with CIs perceive case and subject-verb agreement, their ability to use these cues for offline comprehension and online processing still lags behind normal development, which is reflected in lower performance rates and longer processing times. Individual variability within the CI group can partly be explained by working memory and hearing age. Supplemental Material https://doi.org/10.23641/asha.7728731.

Event-related neuronal responses to acoustic novelty in single-sided deaf cochlear implant users: Initial findings.

OBJECTIVE: A cochlear implant (CI) is an auditory prosthesis restoring profound hearing loss. However, CI-transmitted sounds are degraded compared to normal acoustic hearing. We investigated cortical responses related to CI-degraded against acoustic listening. METHODS: Event-related potentials (ERPs) were recorded from eight single-sided deaf CI users who performed a three-stimulus oddball task, separately with their normal hearing ear and CI ear. The oddball tones were occasionally intermitted by novel sounds. ERP responses were compared between electric and acoustic listening for the auditory (N1) and auditory-cognitive (Novelty P3, Target-P3) ERP components. RESULTS: CI-degraded listening was associated with attenuated sensory processing (N1) and with attenuated early cortical responses to acoustic novelty whereas the late cortical responses to acoustic novelty and the target-P3 did not differ between NH and CI ears. CONCLUSION: The present study replicates the CI-attenuation of Novelty-P3 amplitudes in a within-subject comparison. Further, we show that the CI-attenuation of Novelty-P3 amplitudes extends to early cortical responses to acoustic novelty, but not to late novelty responses. SIGNIFICANCE: The dissociation into CI-attenuated P3 early Novelty-P3 amplitudes and CI-unaffected late Novelty-P3 amplitudes represents a cortical fingerprint of CI-degraded listening. It further contributes to general claims of distinct auditory Novelty-P3 sub-components.

Feasibility of 15O-water PET studies of auditory system activation during general anesthesia in children.

BACKGROUND: 15O-Water positron emission tomography (PET) enables functional imaging of the auditory system during stimulation via a promontory electrode or cochlear implant, which is not possible using functional magnetic resonance imaging (fMRI). Although PET has been introduced in this context decades ago, its feasibility when performed during general anesthesia has not yet been explored. However, due to a shift to earlier (and bilateral) auditory implantation, the need to study children during general anesthesia appeared, since they are not able to cooperate during scanning. Therefore, we evaluated retrospectively results of individual SPM (statistical parametric mapping) analysis of 15O-water PET in 17 children studied during general anesthesia and compared them to those in 9 adults studied while awake. Specifically, the influence of scan duration, smoothing filter kernel employed during preprocessing, and cut-off value used for statistical inferences were evaluated. Frequencies, peak heights, and extents of activations in auditory and extra-auditory brain regions (AR and eAR) were registered. RESULTS: It was possible to demonstrate activations in auditory brain regions during general anesthesia; however, the frequency and markedness of positive findings were dependent on some of the abovementioned influence factors. Scan duration (60 vs. 90 s) had no significant influence on peak height of auditory cortex activations. To achieve a similar frequency and extent of AR activations during general anesthesia compared to waking state, a lower cut-off for statistical inferences (p < 0.05 or p < 0.01 vs. p < 0.001) had to be applied. However, this lower cut-off was frequently associated with unexpected, "artificial" activations in eAR. These activations in eAR could be slightly reduced by the use of a stronger smoothing filter kernel during preprocessing of the data (e.g., [30 mm]3). CONCLUSIONS: Our data indicate that it is feasible to detect auditory cortex activations in 15O-water PET during general anesthesia. Combined with the improved signal to noise ratios of modern PET scanners, this suggests reasonable prospects for further evaluation of the method for clinical use in auditory implant users. Adapted parameters for data analysis seem to be helpful to improve the proportion of signals in AR versus eAR.

Speech intelligibility and subjective benefit in single-sided deaf adults after cochlear implantation.

Treatment with cochlear implants (CIs) in single-sided deaf individuals started less than a decade ago. CIs can successfully reduce incapacitating tinnitus on the deaf ear and allow, so some extent, the restoration of binaural hearing. Until now, systematic evaluations of subjective CI benefit in post-lingually single-sided deaf individuals and analyses of speech intelligibility outcome for the CI in isolation have been lacking. For the prospective part of this study, the Bern Benefit in Single-Sided Deafness Questionnaire (BBSS) was administered to 48 single-sided deaf CI users to evaluate the subjectively perceived CI benefit across different listening situations. In the retrospective part, speech intelligibility outcome with the CI up to 12 month post-activation was compared between 100 single-sided deaf CI users and 125 bilaterally implanted CI users (2nd implant). The positive median ratings in the BBSS differed significantly from zero for all items suggesting that most individuals with single-sided deafness rate their CI as beneficial across listening situations. The speech perception scores in quiet and noise improved significantly over time in both groups of CI users. Speech intelligibility with the CI in isolation was significantly better in bilaterally implanted CI users (2nd implant) compared to the scores obtained from single-sided deaf CI users. Our results indicate that CI users with single-sided deafness can reach open set speech understanding with their CI in isolation, encouraging the extension of the CI indication to individuals with normal hearing on the contralateral ear. Compared to the performance reached with bilateral CI users' second implant, speech reception threshold are lower, indicating an aural preference and dominance of the normal hearing ear. The results from the BBSS propose good satisfaction with the CI across several listening situations.

On the relationship between auditory cognition and speech intelligibility in cochlear implant users: An ERP study.

There is a high degree of variability in speech intelligibility outcomes across cochlear-implant (CI) users. To better understand how auditory cognition affects speech intelligibility with the CI, we performed an electroencephalography study in which we examined the relationship between central auditory processing, cognitive abilities, and speech intelligibility. Postlingually deafened CI users (N=13) and matched normal-hearing (NH) listeners (N=13) performed an oddball task with words presented in different background conditions (quiet, stationary noise, modulated noise). Participants had to categorize words as living (targets) or non-living entities (standards). We also assessed participants' working memory (WM) capacity and verbal abilities. For the oddball task, we found lower hit rates and prolonged response times in CI users when compared with NH listeners. Noise-related prolongation of the N1 amplitude was found for all participants. Further, we observed group-specific modulation effects of event-related potentials (ERPs) as a function of background noise. While NH listeners showed stronger noise-related modulation of the N1 latency, CI users revealed enhanced modulation effects of the N2/N4 latency. In general, higher-order processing (N2/N4, P3) was prolonged in CI users in all background conditions when compared with NH listeners. Longer N2/N4 latency in CI users suggests that these individuals have difficulties to map acoustic-phonetic features to lexical representations. These difficulties seem to be increased for speech-in-noise conditions when compared with speech in quiet background. Correlation analyses showed that shorter ERP latencies were related to enhanced speech intelligibility (N1, N2/N4), better lexical fluency (N1), and lower ratings of listening effort (N2/N4) in CI users. In sum, our findings suggest that CI users and NH listeners differ with regards to both the sensory and the higher-order processing of speech in quiet as well as in noisy background conditions. Our results also revealed that verbal abilities are related to speech processing and speech intelligibility in CI users, confirming the view that auditory cognition plays an important role for CI outcome. We conclude that differences in auditory-cognitive processing contribute to the variability in speech performance outcomes observed in CI users.

Dual routes to cortical orienting responses: novelty detection and uncertainty reduction.

Sokolov distinguished between reactive and proactive variants of the orienting response (OR). The Novelty P3 is considered as an electrophysiological signature of the reactive OR. Recent work suggests that the proactive OR is reflected in frontally distributed P3 activity elicited by uncertainty-reducing stimuli in task-switching paradigms. Here, we directly compare the electrophysiological signatures of reactive and proactive ORs. Participants completed a novelty oddball task and a task-switching procedure while the electroencephalogram was measured. Novel and uncertainty-reducing stimuli evoked prominent fronto-centrally distributed Novelty P3 and Uncertainty P3 waves, respectively. We found a substantial negative correlation between Novelty P3 and Uncertainty P3 across participants, suggesting that reactive and proactive ORs converge on a common neural pathway, but also that distinguishable routes to orienting exist. Moreover, response accuracy was associated with reduced Novelty-P3 and enhanced Uncertainty-P3 amplitudes. The relation between Novelty P3 and Uncertainty P3 might serve as an index of individual differences in distractibility and cognitive control.

Auditory distraction transmitted by a cochlear implant alters allocation of attentional resources.

Cochlear implants (CIs) are auditory prostheses which restore hearing via electrical stimulation of the auditory nerve. The successful adaptation of auditory cognition to the CI input depends to a substantial degree on individual factors. We pursued an electrophysiological approach toward an analysis of cortical responses that reflect perceptual processing stages and higher-level responses to CI input. Performance and event-related potentials on two cross-modal discrimination-following-distraction (DFD) tasks from CI users and normal-hearing (NH) individuals were compared. The visual-auditory distraction task combined visual distraction with following auditory discrimination performance. Here, we observed similar cortical responses to visual distractors (Novelty-N2) and slowed, less accurate auditory discrimination performance in CI users when compared to NH individuals. Conversely, the auditory-visual distraction task was used to combine auditory distraction with visual discrimination performance. In this task we found attenuated cortical responses to auditory distractors (Novelty-P3), slowed visual discrimination performance, and attenuated cortical P3-responses to visual targets in CI users compared to NH individuals. These results suggest that CI users process auditory distractors differently than NH individuals and that the presence of auditory CI input has an adverse effect on the processing of visual targets and the visual discrimination ability in implanted individuals. We propose that this attenuation of the visual modality occurs through the allocation of neural resources to the CI input.

Enhanced audio-visual interactions in the auditory cortex of elderly cochlear-implant users.

Auditory deprivation and the restoration of hearing via a cochlear implant (CI) can induce functional plasticity in auditory cortical areas. How these plastic changes affect the ability to integrate combined auditory (A) and visual (V) information is not yet well understood. In the present study, we used electroencephalography (EEG) to examine whether age, temporary deafness and altered sensory experience with a CI can affect audio-visual (AV) interactions in post-lingually deafened CI users. Young and elderly CI users and age-matched NH listeners performed a speeded response task on basic auditory, visual and audio-visual stimuli. Regarding the behavioral results, a redundant signals effect, that is, faster response times to cross-modal (AV) than to both of the two modality-specific stimuli (A, V), was revealed for all groups of participants. Moreover, in all four groups, we found evidence for audio-visual integration. Regarding event-related responses (ERPs), we observed a more pronounced visual modulation of the cortical auditory response at N1 latency (approximately 100 ms after stimulus onset) in the elderly CI users when compared with young CI users and elderly NH listeners. Thus, elderly CI users showed enhanced audio-visual binding which may be a consequence of compensatory strategies developed due to temporary deafness and/or degraded sensory input after implantation. These results indicate that the combination of aging, sensory deprivation and CI facilitates the coupling between the auditory and the visual modality. We suggest that this enhancement in multisensory interactions could be used to optimize auditory rehabilitation, especially in elderly CI users, by the application of strong audio-visually based rehabilitation strategies after implant switch-on.

The effects of foreknowledge and task-set shifting as mirrored in cue- and target-locked event-related potentials.

The present study examined the use of foreknowledge in a task-cueing protocol while manipulating sensory updating and executive control in both, informatively and non-informatively pre-cued trials. Foreknowledge, sensory updating (cue switch effects) and task-switching were orthogonally manipulated in order to address the question of whether, and to which extent, the sensory processing of cue changes can partly or totally explain the final task switch costs. Participants responded faster when they could prepare for the upcoming task and if no task-set updating was necessary. Sensory cue switches influenced cue-locked ERPs only when they contained conceptual information about the upcoming task: frontal P2 amplitudes were modulated by task-relevant cue changes, mid-parietal P3 amplitudes by the anticipatory updating of stimulus-response mappings, and P3 peak latencies were modulated by task switching. Task preparation was advantageous for efficient stimulus-response re-mapping at target-onset as mirrored in target N2 amplitudes. However, N2 peak latencies indicate that this process is faster for all repeat trials. The results provide evidence to support a very fast detection of task-relevance in sensory (cue) changes and argue against the view of task repetition benefits as secondary to purely perceptual repetition priming. Advanced preparation may have a stronger influence on behavioral performance and target-locked brain activity than the local effect of repeating or switching the task-set in the current trial.