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Adaptation to constant or repetitive sensory signals serves to improve detection of novel events in the environment and to encode incoming information more efficiently. Within the auditory modality, contrastive adaptation effects have been observed within a number of categories, including voice and musical instrument type. A recent study found contrastive perceptual shifts between voice and instrument categories following repetitive presentation of adaptors consisting of either vowels or instrument tones. The current study tested the generalizability of adaptation along a voice–instrument continuum, using more ecologically valid adaptors. Participants were presented with an adaptor followed by an ambiguous voice–instrument target, created by generating a 10-step morphed continuum between pairs of vowel and instrument sounds. Listeners’ categorization of the target sounds was shifted contrastively by a spoken sentence or instrumental melody adaptor, regardless of whether the adaptor and the target shared the same speaker gender or similar pitch range (Experiment 1). However, no significant contrastive adaptation was observed when nonspeech vocalizations or nonpitched percussion sounds were used as the adaptors (Experiment 2). The results suggest that adaptation between voice and nonvoice categories does not rely on exact repetition of simple stimuli, nor does it solely reflect the result of a sound being categorized as being human or nonhuman sourced. The outcomes suggest future directions for determining the precise spectro-temporal properties of sounds that induce these voice–instrument contrastive adaptation effects.

We report here the first research into the specificity of the frequency effects of release from stimulus-specific adaptation in the activity of single neurons in the primary fields of the auditory cortex of house mice in the awake state. After adaptation of neuronal responses to sounds using sequences of four identical tones, adult females were presented with a fifth – deviant – tone signal, whose frequency differed from the frequency of the first four tone pulses of the series. This led to complete or partial release of neuronal responses from adaptation in the response to the fifth component of the sequence, i.e., the response to the fifth tone was significantly greater than the responses to the second through fourth tones. The effect of release from stimulus-specific adaptation was enhanced by locating the frequencies of the main tone sequence and the deviant tone in two non-overlapping critical bands of hearing in mice. Thus, these studies confirm the involvement of the critical band mechanism in enhancing the novelty responses of auditory neurons in the midbrain and auditory cortex.

Purpose Single-sided deaf patients following cochlear implantation often compare the sound quality of their implanted ear with normal hearing. The interaural differences can result in dissatisfaction with speech comprehension and reduced time of usage of the speech processor; hence, prolonging auditory adaptation time. The proposed calibration method presented in this study demonstrates how the frequency distribution of the cochlear implant can be set to adequately approximate the pitch perception of the contralateral normal hearing ear towards improving speech intelligibility in a noisy environment. Methods In 12 postlingual single-sided deaf patients, subjective interaural pitch-matching was carried out to determine new central frequencies for the reallocation of the frequency bands of their speech processor (CP910, CP950 or CP1000, Cochlear, Australia). The patients were asked to compare the pitch of the tones presented to their normal hearing ear to the pitch of individual channels of their cochlear implant (CI522 or CI622, Cochlear, Australia). A third-degree polynomial curve was fit to the acquired matching frequencies to create the new frequency allocation table. Audiological measurements (free-field aided thresholds, speech reception thresholds, and monosyllabic word recognition score) in noise, together with a Speech, Spatial and Qualities of Hearing Scale (SSQ12) questionnaire (short version of the original SSQ) results were evaluated prior to the pitch-matching procedure, and again, 2 weeks later. Results The free-field aided thresholds of the patients showed no greater shift than ± 5 dB following the procedure; however, their monosyllabic word recognition score in noise improved significantly (mean − 9.58%, SD 4.98%, matched pairs t test comparison: p <  0.001). The results of the SSQ12 questionnaire also showed significant improvement in speech intelligibility, sound localization, and sound quality (mean 0.96 points, SD 0.45 points, matched pairs t test comparison: p <  0.001). Conclusions Matching the pitch perception of the implanted cochlea with the sensation of the normal hearing contralateral ear, resulted in significant changes in the quality of hearing in patients with single-sided deafness. It is plausible the procedure can usher positive results in bimodal patients or following sequential bilateral cochlear implantation.

Speech sensorimotor adaptation is typically partial, varies across individuals, and often saturates under large auditory perturbations. While sensory and phonological factors have been proposed to explain this variability, the role of motor effort and its influence on the compensatory response remain largely unexplored. Our study examined whether the physical effort involved in producing compensatory gestures influences both the overall magnitude of adaptation and the perturbation level at which this adaptation begins to saturate. Native French speakers produced the minimal pair /ne/–/nø/ while receiving gradually upshifted second-formant (F2) feedback (0–50%) in two conditions using deformable lip tubes: a very flexible tube (FLT) and a more rigid tube (RLT), both allowing lip rounding but increasing the effort required to achieve it. Compensation was quantified acoustically (F2 decrease) and physiologically (increase in EMG activity of the orbicularis oris muscle) in 21 participants. F2 compensation increased with perturbation level but saturated earlier and at a lower magnitude when articulation required greater effort (RLT). Lip-muscle activity showed a similar nonlinear pattern, with saturation in EMG and F2 occurring at comparable perturbation levels. Variations in F1 suggested that most participants initially relied on increased lip rounding, but some shifted at higher perturbation levels toward another articulatory strategy very likely to involve tongue backing. These results show that speech adaptation depends not only on error monitoring and correction but is also constrained by the physical effort required to produce compensatory movements, which both limits the magnitude of adaptation and influences the selection of compensatory strategies.

Our auditory environment is constantly changing and evolving over time, requiring us to rapidly adapt to a complex dynamic sensory input. This adaptive ability of our auditory system can be observed at different levels, from individual cell responses to complex neural mechanisms and behavior, and is essential to achieve successful speech communication, correct orientation in our full environment, and eventually survival. These adaptive processes may differ in individuals with hearing loss, whose auditory system may cope via “readapting” itself over a longer time scale to the changes in sensory input induced by hearing impairment and the compensation provided by hearing devices. These devices themselves are now able to adapt to the listener’s individual environment, attentional state, and behavior. These topics related to auditory adaptation, in the broad sense of the term, were central to the 6th International Symposium on Auditory and Audiological Research held in Nyborg, Denmark, in August 2017. The symposium addressed adaptive processes in hearing from different angles, together with a wide variety of other auditory and audiological topics. The papers in this special issue result from some of the contributions presented at the symposium.

The intersensory effects of auditory adaptation to motion have thus far been studied only in relation to visual perception, though auditory adaptation can also influence other sensory systems. We report here the first attempts to demonstrate the reaction of the postural regulatory system during and after 45-sec adaptation to an approaching and receding sound source, which was modeled in conditions of a free field using sequences of rhythmic tonal bursts of changing amplitude and frequency. A stabilometric method identified oscillations of the center of pressure in the sagittal plane during the stimulation rhythm, more marked for approach than recession. These oscillations led to increases in the length of the trajectory of the center of pressure and the mean linear speed of motion. While listening to approaching sound sources, the center of pressure was displaced in the direction of motion; during the 20 sec following the end of the stimulus, displacement in the opposite direction was seen – a typical “negative” aftereffect. These data are consistent with results from studies of postural reactions to moving visual stimuli, where “negative” effects are also observed.

The aftereffects of continuously and discontinuously approaching sound images were studied. Moving images were formed using sequences of wideband noise pulses with linear amplitude modulation delivered via two loudspeakers located in an anechoic chamber at distances of 1.1 and 4.5 m from the subject. Adaptation to continuous approach evoked a change in the perception of continuously moving sound sources, while adaptation to discontinuous approach altered the perception of discontinuously moving sources. Aftereffects did not arise when the adaptation and test stimuli had different movement qualities. Regardless of movement quality (discontinuous or continuous), when the rhythmic structure of the adaptation and test stimuli were the same, aftereffects were stronger than when their rhythmic structures were different. These results suggest that the pathways processing information on continuously and discontinuously moving sound sources are different.

Adaptation to a sound source motion can cause noticeable changes in the spatial perception of subsequent sound stimuli. This phenomenon, called the auditory motion aftereffect, is believed to be underlain by the neural mechanisms of selective motion sensitivity. Auditory motion aftereffects were demonstrated under different stimulation conditions, i.e. both after the presentation of different motion models and in the real sound source motion. The auditory aftereffect is specifically characterized by its spatial and frequency selectivity as well as by the optimal motion velocity at which the effect is maximal. These features and the presence of the intersensory motion adaptation effects indicate a common nature of the auditory and visual motion aftereffects and suggest the existence of the common system of motion adaptation for different modalities underlying spatial orientation.

In addition to sensory processing, recent neurobiological models of speech perception postulate the existence of a left auditory dorsal processing stream, linking auditory speech representations in the auditory cortex with articulatory representations in the motor system, through sensorimotor interaction interfaced in the supramarginal gyrus and/or the posterior part of the superior temporal gyrus. The present state-dependent transcranial magnetic stimulation study is aimed at determining whether speech recognition is indeed mediated by the auditory dorsal pathway, by examining the causal contribution of the left ventral premotor cortex, supramarginal gyrus and posterior part of the superior temporal gyrus during an auditory syllable identification/categorization task. To this aim, participants listened to a sequence of /ba/ syllables before undergoing a two forced-choice auditory syllable decision task on ambiguous syllables (ranging in the categorical boundary between /ba/ and /da/). Consistent with previous studies on selective adaptation to speech, following adaptation to /ba/, participants responses were biased towards /da/. In contrast, in a control condition without prior auditory adaptation no such bias was observed. Crucially, compared to the results observed without stimulation, single-pulse transcranial magnetic stimulation delivered at the onset of each target stimulus interacted with the initial state of each of the stimulated brain area by enhancing the adaptation effect. These results demonstrate that the auditory dorsal pathway contribute to auditory speech adaptation.