Cochlear implant (CI) users show limited sensitivity to the temporal pitch conveyed by electric stimulation, contributing to impaired perception of music and of speech in noise. Neurophysiological studies in cats suggest that this limitation is due, in part, to poor transmission of the temporal fine structure (TFS) by the brainstem pathways that are activated by electrical cochlear stimulation. It remains unknown, however, how that neural limit might influence perception in the same animal model. For that reason, we developed non-invasive psychophysical and electrophysiological measures of temporal (i.e., non-spectral) pitch processing in the cat. Normal-hearing (NH) cats were presented with acoustic pulse trains consisting of band-limited harmonic complexes that simulated CI stimulation of the basal cochlea while removing cochlear place-of-excitation cues. In the psychophysical procedure, trained cats detected changes from a base pulse rate to a higher pulse rate. In the scalp-recording procedure, the cortical-evoked acoustic change complex (ACC) and brainstem-generated frequency following response (FFR) were recorded simultaneously in sedated cats for pulse trains that alternated between the base and higher rates. The range of perceptual sensitivity to temporal pitch broadly resembled that of humans but was shifted to somewhat higher rates. The ACC largely paralleled these perceptual patterns, validating its use as an objective measure of temporal pitch sensitivity. The phase-locked FFR, in contrast, showed strong brainstem encoding for all tested pulse rates. These measures demonstrate the cat's perceptual sensitivity to pitch in the absence of cochlear-place cues and may be valuable for evaluating neural mechanisms of temporal pitch perception in the feline animal model of stimulation by a CI or novel auditory prostheses.

Pitch and timbre perception are both based on the frequency content of sound, but previous perceptual experiments have disagreed about whether these two dimensions are processed independently from each other. We tested the interaction of pitch and timbre variations using sequential comparisons of sound pairs. Listeners judged whether two sequential sounds were identical along the dimension of either pitch or timbre, while the perceptual distances along both dimensions were parametrically manipulated. Pitch and timbre variations perceptually interfered with each other and the degree of interference was modulated by the magnitude of changes along the un-attended dimension. These results show that pitch and timbre are not orthogonal to each other when both are assessed with parametrically controlled variations.

Congenital amusia is currently thought to be a life-long neurogenetic disorder in music perception, impervious to training in pitch or melody discrimination. This study provides an explicit test of whether amusic deficits can be reduced with training. Twenty amusics and 20 matched controls participated in four sessions of psychophysical training involving either pure-tone (500 Hz) pitch discrimination or a control task of lateralization (interaural level differences for bandpass white noise). Pure-tone pitch discrimination at low, medium, and high frequencies (500, 2000, and 8000 Hz) was measured before and after training (pretest and posttest) to determine the specificity of learning. Melody discrimination was also assessed before and after training using the full Montreal Battery of Evaluation of Amusia, the most widely used standardized test to diagnose amusia. Amusics performed more poorly than controls in pitch but not localization discrimination, but both groups improved with practice on the trained stimuli. Learning was broad, occurring across all three frequencies and melody discrimination for all groups, including those who trained on the non-pitch control task. Following training, 11 of 20 amusics no longer met the global diagnostic criteria for amusia. A separate group of untrained controls (n = 20), who also completed melody discrimination and pretest, improved by an equal amount as trained controls on all measures, suggesting that the bulk of learning for the control group occurred very rapidly from the pretest. Thirty-one trained participants (13 amusics) returned one year later to assess long-term maintenance of pitch and melody discrimination. On average, there was no change in performance between posttest and one-year follow-up, demonstrating that improvements on pitch- and melody-related tasks in amusics and controls can be maintained. The findings indicate that amusia is not always a life-long deficit when using the current standard diagnostic criteria.

Absolute pitch (AP) has been shown to be associated with morphological changes and neurophysiological adaptations in the planum temporale, a cortical area involved in higher-order auditory and speech perception processes. The direct link between speech processing and AP has hitherto not been addressed. We provide first evidence that AP compared with relative pitch (RP) ability is associated with significantly different hemodynamic responses to complex speech sounds. By systematically varying the lexical and/or prosodic information of speech stimuli, we demonstrated consistent activation differences in AP musicians compared with RP musicians and nonmusicians. These differences relate to stronger activations in the posterior part of the middle temporal gyrus and weaker activations in the anterior mid-part of the superior temporal gyrus. Furthermore, this pattern is considerably modulated by the auditory acuity of AP. Our results suggest that the neural underpinnings of pitch processing expertise exercise a strong influence on propositional speech perception (sentence meaning).

Congenital amusia (amusia, hereafter) is a developmental disorder that impacts negatively on the perception of music. Psychophysical testing suggests that individuals with amusia have above average thresholds for detection of pitch change and pitch direction discrimination; however, a low-level auditory perceptual problem cannot completely explain the disorder, since discrimination of melodies is also impaired when the constituent intervals are suprathreshold for perception. The aim of the present study was to test pitch memory as a function of (a) time and (b) tonal interference, in order to determine whether pitch traces are inherently weaker in amusic individuals. Memory for the pitch of single tones was compared using two versions of a paradigm developed by Deutsch (1970a). In both tasks, participants compared the pitch of a standard (S) versus a comparison (C) tone. In the time task, the S and C tones were presented, separated in time by 0, 1, 5, 10, and 15 s (blocked presentation). In the interference task, the S and C tones were presented with a fixed time interval (5 s) but with a variable number of irrelevant tones in between 0, 2, 4, 6, and 8 tones (blocked presentation). In the time task, control performance remained high for all time intervals, but amusics showed a performance decrement over time. In the interference task, controls and amusics showed a similar performance decrement with increasing number of irrelevant tones. Overall, the results suggest that the pitch representations of amusic individuals are less stable and more prone to decay than those of matched non-amusic individuals.

Attentional blink (AB) is a phenomenon in which the perception of a second target is impaired when it appears within 200-500 ms after the first target. Sound affects an AB and is accompanied by the appearance of an asymmetry during audiovisual integration, but it is not known whether this is related to the tonal representation of sound. The aim of the present study was to investigate the effect of audiovisual asymmetry on attentional blink and whether the presentation of pitch improves the ability to detect a target during an AB that is accompanied by audiovisual asymmetry. The results showed that as the lag increased, the subject's target recognition improved and the pitch produced further improvements. These improvements exhibited a significant asymmetry across the audiovisual channel. Our findings could contribute to better utilizations of audiovisual integration resources to improve attentional transients and auditory recognition decline, which could be useful in areas such as driving and education.

As we listen to everyday sounds, auditory perception is heavily shaped by interactions between acoustic attributes such as pitch, timbre and intensity; though it is not clear how such interactions affect judgments of acoustic salience in dynamic soundscapes. Salience perception is believed to rely on an internal brain model that tracks the evolution of acoustic characteristics of a scene and flags events that do not fit this model as salient. The current study explores how the interdependency between attributes of dynamic scenes affects the neural representation of this internal model and shapes encoding of salient events. Specifically, the study examines how deviations along combinations of acoustic attributes interact to modulate brain responses, and subsequently guide perception of certain sound events as salient given their context. Human volunteers have their attention focused on a visual task and ignore acoustic melodies playing in the background while their brain activity using electroencephalography is recorded. Ambient sounds consist of musical melodies with probabilistically-varying acoustic attributes. Salient notes embedded in these scenes deviate from the melody's statistical distribution along pitch, timbre and/or intensity. Recordings of brain responses to salient notes reveal that neural power in response to the melodic rhythm as well as cross-trial phase alignment in the theta band are modulated by degree of salience of the notes, estimated across all acoustic attributes given their probabilistic context. These neural nonlinear effects across attributes strongly parallel behavioral nonlinear interactions observed in perceptual judgments of auditory salience using similar dynamic melodies; suggesting a neural underpinning of nonlinear interactions that underlie salience perception.

The most studied form of congenital amusia is characterized by a difficulty with detecting pitch anomalies in melodies, also referred to as pitch deafness. Here, we tested for the presence of associated deficits in rhythm processing, beat in particular, in pitch deafness. In Experiment 1, participants performed beat perception and production tasks with musical excerpts of various genres. The results show a beat finding disorder in six of the ten assessed pitch-deaf participants. In order to remove a putative interference of pitch variations with beat extraction, the same participants were tested with percussive rhythms in Experiment 2 and showed a similar impairment. Furthermore, musical pitch and beat processing abilities were correlated. These new results highlight the tight connection between melody and rhythm in music processing that can nevertheless dissociate in some individuals.

Pitch perception and pitch matching may link to individual reading skills.

Language and music epitomize the complex representational and computational capacities of the human mind. Strikingly similar in their structural and expressive features, a longstanding question is whether the perceptual and cognitive mechanisms underlying these abilities are shared or distinct--either from each other or from other mental processes. One prominent feature shared between language and music is signal encoding using pitch, conveying pragmatics and semantics in language and melody in music. We investigated how pitch processing is shared between language and music by measuring consistency in individual differences in pitch perception across language, music, and three control conditions intended to assess basic sensory and domain-general cognitive processes. Individuals' pitch perception abilities in language and music were most strongly related, even after accounting for performance in all control conditions. These results provide behavioral evidence, based on patterns of individual differences, that is consistent with the hypothesis that cognitive mechanisms for pitch processing may be shared between language and music.

This work sought correlates of pitch perception, defined by neural activity above the lower limit of pitch (LLP), in auditory cortical neural ensembles, and examined their topographical distribution. Local field potentials (LFPs) were recorded in eight patients undergoing invasive recordings for pharmaco-resistant epilepsy. Stimuli consisted of bursts of broadband noise followed by regular interval noise (RIN). RIN was presented at rates below and above the LLP to distinguish responses related to the regularity of the stimulus and the presence of pitch itself. LFPs were recorded from human cortical homologues of auditory core, belt, and parabelt regions using multicontact depth electrodes implanted in Heschl's gyrus (HG) and Planum Temporale (PT), and subdural grid electrodes implanted over lateral superior temporal gyrus (STG). Evoked responses corresponding to the temporal regularity of the stimulus were assessed using autocorrelation of the evoked responses, and occurred for stimuli below and above the LLP. Induced responses throughout the high gamma range (60-200 Hz) were present for pitch values above the LLP, with onset latencies of approximately 70 ms. Mapping of the induced responses onto a common brain space demonstrated variability in the topographical distribution of high gamma responses across subjects. Induced responses were present throughout the length of HG and on PT, which is consistent with previous functional neuroimaging studies. Moreover, in each subject, a region within lateral STG showed robust induced responses at pitch-evoking stimulus rates. This work suggests a distributed representation of pitch processing in neural ensembles in human homologues of core and non-core auditory cortex.

We have previously used direct electrode recordings in two human subjects to identify neural correlates of the perception of pitch (Griffiths, Kumar, Sedley et al., Direct recordings of pitch responses from human auditory cortex, Curr. Biol. 22 (2010), pp. 1128-1132). The present study was carried out to assess virtual-electrode measures of pitch perception based on non-invasive magnetoencephalography (MEG). We recorded pitch responses in 13 healthy volunteers using a passive listening paradigm and the same pitch-evoking stimuli (regular interval noise; RIN) as in the previous study. Source activity was reconstructed using a beamformer approach, which was used to place virtual electrodes in auditory cortex. Time-frequency decomposition of these data revealed oscillatory responses to pitch in the gamma frequency band to occur, in Heschl's gyrus, from 60 Hz upwards. Direct comparison of these pitch responses to the previous depth electrode recordings shows a striking congruence in terms of spectrotemporal profile and anatomical distribution. These findings provide further support that auditory high gamma oscillations occur in association with RIN pitch stimuli, and validate the use of MEG to assess neural correlates of normal and abnormal pitch perception.

The cochlear implant (CI) is the most widely used neuroprosthesis, recovering hearing for more than half a million severely-to-profoundly hearing-impaired people. However, CIs still have significant limitations, with users having severely impaired pitch perception. Pitch is critical to speech understanding (particularly in noise), to separating different sounds in complex acoustic environments, and to music enjoyment. In recent decades, researchers have attempted to overcome shortcomings in CIs by improving implant technology and surgical techniques, but with limited success. In the current study, we take a new approach of providing missing pitch information through haptic stimulation on the forearm, using our new mosaicOne_B device. The mosaicOne_B extracts pitch information in real-time and presents it via 12 motors that are arranged in ascending pitch along the forearm, with each motor representing a different pitch. In normal-hearing subjects listening to CI simulated audio, we showed that participants were able to discriminate pitch differences at a similar performance level to that achieved by normal-hearing listeners. Furthermore, the device was shown to be highly robust to background noise. This enhanced pitch discrimination has the potential to significantly improve music perception, speech recognition, and speech prosody perception in CI users.

The perception of pitch is a fundamental percept, which is mediated by the auditory system, requiring the abstraction of stimulus properties related to the spectro-temporal structure of sound. Despite its importance, there is still debate as to the precise areas responsible for its encoding, which may be due to species differences or differences in the recording measures and choices of stimuli used in previous studies. Moreover, it was unknown whether the human brain contains pitch neurons and how distributed such neurons might be. Here, we present the first study to measure multiunit neural activity in response to pitch stimuli in the auditory cortex of intracranially implanted humans. The stimulus sets were regular-interval noise with a pitch strength that is related to the temporal regularity and a pitch value determined by the repetition rate and harmonic complexes. Specifically, we demonstrate reliable responses to these different pitch-inducing paradigms that are distributed throughout Heschl's gyrus, rather than being localized to a particular region, and this finding was evident regardless of the stimulus presented. These data provide a bridge across animal and human studies and aid our understanding of the processing of a critical percept associated with acoustic stimuli.

Pitch discrimination is important for language or music processing. Previous studies indicate that auditory perception depends on pre-target neural activity. However, so far the pre-target electrophysiological conditions which enable the detection of small pitch changes are not well studied, but might yield important insights into pitch-processing. We used magnetoencephalography (MEG) source imaging to reveal the pre-target effects of successful auditory detection of small pitch deviations from a sequence of standard tones. Participants heard a sequence of four pure tones and had to determine whether the last target tone was different or identical to the first three standard sounds. We found that successful pitch change detection could be predicted from the amplitude of theta (4-8 Hz) oscillatory activity in the right inferior frontal gyrus (IFG) as well as beta (12-30 Hz) oscillatory activity in the right auditory cortex. These findings confirm and extend evidence for the involvement of theta as well as beta-band activity in auditory perception.

Languages can use a common repertoire of vocal sounds to signify distinct meanings. In tonal languages, such as Mandarin Chinese, pitch contours of syllables distinguish one word from another, whereas in non-tonal languages, such as English, pitch is used to convey intonation. The neural computations underlying language specialization in speech perception are unknown. Here, we use a cross-linguistic approach to address this. Native Mandarin- and English- speaking participants each listened to both Mandarin and English speech, while neural activity was directly recorded from the non-primary auditory cortex. Both groups show language-general coding of speaker-invariant pitch at the single electrode level. At the electrode population level, we find language-specific distribution of cortical tuning parameters in Mandarin speakers only, with enhanced sensitivity to Mandarin tone categories. Our results show that speech perception relies upon a shared cortical auditory feature processing mechanism, which may be tuned to the statistics of a given language.

Former studies have shown that a pitch change in utterances in speech was detected accurately in both native (French) and unfamiliar (Portuguese) language and produced an early negativity and a late positivity in the event-related brain potentials (ERPs), more clearly marked in the native language (Schön et al., 2004; Marques et al., 2007). The present study used the same design to further investigate the influence of the familiarity of the language context on pitch perception with Italian participants. The aim was to examine the effects of pitch change in the native (Italian) and foreign (French) languages, and in meaningless sentences preserving the intonational contour of the mother tongue (jabberwocky).

In single-sided deafness patients fitted with a cochlear implant (CI) in the affected ear and preserved normal hearing in the other ear, acoustic and electric hearing can be directly compared without the need for an external control group. Although poor pitch perception is a crucial limitation when listening through CIs, it remains unclear how exactly the cortical processing of pitch information differs between acoustic and electric hearing. Hence, we separately presented both ears of 20 of these patients with vowel sequences in which the pitch contours were either repetitive or variable, while simultaneously recording functional near-infrared spectroscopy (fNIRS) and EEG data. Overall, the results showed smaller and delayed auditory cortex activity in electric hearing, particularly for the P2 event-related potential component, which appears to reflect the processing of voice pitch information. Both the fNIRS data and EEG source reconstructions furthermore showed that vowel sequences with variable pitch contours evoked additional activity in posterior right auditory cortex in electric but not acoustic hearing. This surprising discrepancy demonstrates, firstly, that the acoustic detail transmitted by CIs is sufficient to distinguish between speech sounds that only vary regarding their pitch information. Secondly, the absence of a condition difference when stimulating the normal-hearing ears suggests a saturation of cortical activity levels following unilateral deafness. Taken together, these results provide strong evidence in favour of using CIs in this patient group.

In music, the perception of pitch is governed largely by its tonal function given the preceding harmonic structure of the music. While behavioral research has advanced our understanding of the perceptual representation of musical pitch, relatively little is known about its representational structure in the brain. Using Magnetoencephalography (MEG), we recorded evoked neural responses to different tones presented within a tonal context. Multivariate Pattern Analysis (MVPA) was applied to "decode" the stimulus that listeners heard based on the underlying neural activity. We then characterized the structure of the brain's representation using decoding accuracy as a proxy for representational distance, and compared this structure to several well established perceptual and acoustic models. The observed neural representation was best accounted for by a model based on the Standard Tonal Hierarchy, whereby differences in the neural encoding of musical pitches correspond to their differences in perceived stability. By confirming that perceptual differences honor those in the underlying neuronal population coding, our results provide a crucial link in understanding the cognitive foundations of musical pitch across psychological and neural domains.

Previous studies indicate that temporal predictability can enhance timing and intensity perception, but it is not known whether it also enhances pitch perception, despite pitch being a fundamental perceptual attribute of sound. Here we investigate this in the context of rhythmic regularity, a form of predictable temporal structure common in sound streams, including music and speech. It is known that neural oscillations in low (delta: 1-3 Hz) and high (beta: 15-25 Hz) frequency bands entrain to rhythms in phase and power, respectively, but it is not clear why both low and high frequency bands entrain to external rhythms, and whether they and their coupling serve different perceptual functions. Participants discriminated near-threshold pitch deviations (targets) embedded in either rhythmic (regular/isochronous) or arrhythmic (irregular/non-isochronous) tone sequences. Psychophysically, we found superior pitch discrimination performance for target tones in rhythmic compared to arrhythmic sequences. Electroencephalography recordings from auditory cortex showed that delta phase, beta power modulation, and delta-beta coupling were all modulated by rhythmic regularity. Importantly, trial-by-trial neural-behavioural correlational analyses showed that, prior to a target, the depth of U-shaped beta power modulation predicted pitch discrimination sensitivity whereas cross-frequency coupling strength predicted reaction time. These novel findings suggest that delta phase might reflect rhythmic temporal expectation, beta power temporal attention, and delta-beta coupling auditory-motor communication. Together, low and high frequency auditory neural oscillations reflect different perceptual functions that work in concert for tracking rhythmic regularity and proactively facilitate pitch perception.