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Cochlear implants partially restore auditory sensation in individuals affected by severe to profound hearing loss. We investigated vowel detection, identification, and discrimination in a group of congenitally-deafened, unilaterally-implanted, Italian children and in a group of age-matched controls, by combining behavioral and neurophysiologic measures. Comparable vowel identification and discrimination performance emerged for cochlear-implant and normal- hearing ch ildren at the behavioral level. At the neurophysiologic level, on the other hand, cochlear-implant children appeared to lag behind their age-matched normal- hearing peers for vowel detection and identification, but not for vowel discrimination. Length of cochlear implant use sign ificantly affected vowel processing at the neurophysiologic level, although not systematically.

We assessed sound localisation abilities of late-implanted adults fitted with a single cochlear implant (CI) and examined whether these abilities are affected by the duration of implant use. Ten prelingually and four postlingually deafened adults who received a unilateral CI were tested in a sound-source identification task. Above chance performance was observed in those prelingual CI recipients who had worn their implant for longer time (9 years on average), revealing some monaural sound localisation abilities in this population but only after extensive CI use. On the contrary, the four postlingual recipients performed equal or better with respect to the best prelingual participants despite shorter experience with the monaural implant (11 months on average). Our findings reveal that some sound localisation ability can emerge in prelingually deafened adults fitted with a single implant, at least in a controlled laboratory setting. This ability, however, appears to emerge only after several years of CI use. Furthermore, the results of four postlingually deafened adults suggest that early experience with auditory cues may result in more rapid acquisition of spatial hearing with a single CI. © 2009 Elsevier B.V. All rights reserved.

We investigated temporal processing in profoundly deaf individuals by testing their ability to make temporal order judgments (TOJs) for pairs of visual stimuli presented at central or peripheral visual eccentricities. Ten profoundly deaf participants judged which of the two visual stimuli appearing on opposite sides of central fixation was delivered first. Stimuli were presented either symmetrically, at central or peripheral locations, or asymmetrically (i.e. one central and the other peripheral) at varying stimulus onset asynchronies (SOAs) using the method of constant stimuli. Two groups of hearing controls were also tested in this task: 10 hearing controls auditory-deprived during testing and 12 hearing controls who were not subjected to any deprivation procedure. Temporal order thresholds (i.e. just noticeable differences) and points of subjective simultaneity for the two visual stimuli did not differ between groups. However, faster discrimination responses were systematically observed in the deaf than in either group of hearing controls, especially when the first of the two stimuli appeared at peripheral locations. Contrary to some previous findings, our results show that a life-long auditory deprivation does not alter temporal processing abilities in the millisecond range. In fact, we show that deaf participants obtain similar temporal thresholds to hearing controls, while also responding much faster. This enhanced reactivity is documented here for the first time in the context of a temporal processing task, and we suggest it may constitute a critical aspect of the functional changes occurring as a consequence of profound deafness. © 2008 Springer-Verlag.

Several studies conducted in mammals and humans have shown that multisensory processing may be impaired following congenital sensory loss and in particular if no experience is achieved within specific early developmental time windows known as sensitive periods. In this study we investigated whether basic multisensory abilities are impaired in hearing-restored individuals with deafness acquired at different stages of development. To this aim, we tested congenitally and late deaf cochlear implant (CI) recipients, age-matched with two groups of hearing controls, on an audio-tactile redundancy paradigm, in which reaction times to unimodal and crossmodal redundant signals were measured. Our results showed that both congenitally and late deaf CI recipients were able to integrate audio-tactile stimuli, suggesting that congenital and acquired deafness does not prevent the development and recovery of basic multisensory processing. However, we found that congenitally deaf CI recipients had a lower multisensory gain compared to their matched controls, which may be explained by their faster responses to tactile stimuli. We discuss this finding in the context of reorganisation of the sensory systems following sensory loss and the possibility that these changes cannot be "rewired" through auditory reafferentation. © 2014 Nava et al.

Profound deafness affects orienting of visual attention. Until now, research focused exclusively on covert attentional orienting, neglecting whether overt oculomotor behavior may also change in deaf people. Here we used the pro- and anti-saccade task to examine the relative contribution of reflexive and voluntary eye-movement control in profoundly deaf and hearing individuals. We observed a behavioral facilitation in reflexive compared to voluntary eye movements, indexed by faster saccade latencies and smaller error rates in pro- than anti-saccade trials, which was substantially larger in deaf than hearing participants. This provides the first evidence of plastic changes related to deafness in overt oculomotor behavior, and constitutes an ecologically relevant parallel to the modulations attributed to deafness in covert attention orienting. Our findings also have implications for designers of real and virtual environments for deaf people and reveal that experiments on deaf visual abilities must not ignore the prominent reflexive eye-movement orienting in this sensory-deprived population. © 2012 Copyright 2012 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business.

Purpose: Several studies have reported faster response time to visual stimuli in profoundly deaf individuals. This result is often linked to the processing of peripheral targets, and it is assumed to occur in relation to attention orienting. We evaluated whether enhanced reactivity to visual events in profoundly deaf individuals can be explained by faster orienting of visual attention alone. Methods: We examined 11 deaf individuals and 11 hearing controls, in a simple detection task and in a shape discrimination task. While simple detection can be performed under distributed attention, shape discrimination requires orienting of spatial attention to the target. The same visual targets served for both tasks, presented at central or peripheral locations and corrected for cortical magnification. Results: The simple detection task revealed faster RTs in deaf than hearing controls, regardless of target location. Moreover, while hearing controls paid a cost in responding to peripheral than central targets, deaf participants performed equally well regardless of target eccentricity. In the shape discrimination task deaf never outperformed hearing controls. Conclusions: These findings reveal that enhanced reactivity to visual stimuli in the deaf cannot be explained only by faster orienting of visual attention and can emerge for centr l as well as peripheral targets. Moreover, the persisting advantage for peripheral locations in the deaf, observed here under distributed attention, suggests that this spatially-selective effect could result from reorganised sensory processing rather than different attentional gradients. © 2010 - IOS Press and the authors. All rights reserved.

Bilateral cochlear implants (CI) offer a unique opportunity for the study of spatial hearing plasticity in humans. Here we studied the recovery of spatial hearing in two sequential bilateral CI recipients, adopting a longitudinal approach. Each recipient was tested in a sound-source identification task shortly after bilateral activation and at 1, 6, and 12 months follow-up. The results show fast recovery (1 month from CI activation) in the recipient who had substantial experience with auditory cues in adulthood. By contrast, the bilateral CI recipient who developed profound deafness in childhood, regained spatial hearing abilities only 12 months after CI activation. These findings provide the first direct evidence that recovery of auditory spatial abilities in bilateral CI recipients can occur shortly after activation of the two devices. In addition, they suggest that previous auditory experience can constrain the time course of this recovery. © 2008 Elsevier Ltd. All rights reserved.