Temporal hierarchy of cortical responses reflects core-belt-parabelt organization of auditory cortex in musicians

Should absolute pitch be considered as a unique kind of absolute sensory judgment in humans? A systematic and theoretical review of the literature

Absolute pitch is the name given to the rare ability to identify a musical note in an automatic and effortless manner without the need for a reference tone. Those individuals with absolute pitch can, for example, name the note they hear, identify all of the tones of a given chord, and/or name the pitches of everyday sounds, such as car horns or sirens. Hence, absolute pitch can be seen as providing a rare example of absolute sensory judgment in audition. Surprisingly, however, the intriguing question of whether such an ability presents unique features in the domain of sensory perception, or whether instead similar perceptual skills also exist in other sensory domains, has not been explicitly addressed previously. In this paper, this question is addressed by systematically reviewing research on absolute pitch using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) method. Thereafter, we compare absolute pitch with two rare types of sensory experience, namely synaesthesia and eidetic memory, to understand if and how these phenomena exhibit similar features to absolute pitch. Furthermore, a common absolute perceptual ability that has been often compared to absolute pitch, namely colour perception, is also discussed. Arguments are provided supporting the notion that none of the examined abilities can be considered like absolute pitch. Therefore, we conclude by suggesting that absolute pitch does indeed appear to constitute a unique kind of absolute sensory judgment in humans, and we discuss some open issues and novel directions for future research in absolute pitch.

Effects of absolute pitch on brain activation and functional connectivity during hearing-in-noise perception

Hearing-in-noise (HIN) ability is crucial in speech and music communication. Recent evidence suggests that absolute pitch (AP), the ability to identify isolated musical notes, is associated with HIN benefits. A theoretical account postulates a link between AP ability and neural network indices of segregation. However, how AP ability modulates the brain activation and functional connectivity underlying HIN perception remains unclear. Here we used functional magnetic resonance imaging to contrast brain responses among a sample (n = 45) comprising 15 AP musicians, 15 non-AP musicians, and 15 non-musicians in perceiving Mandarin speech and melody targets under varying signal-to-noise ratios (SNRs: No-Noise, 0, -9 dB). Results reveal that AP musicians exhibited increased activation in auditory and superior frontal regions across both HIN domains (music and speech), irrespective of noise levels. Notably, substantially higher sensorimotor activation was found in AP musicians when the target was music compared to speech. Furthermore, we examined AP effects on neural connectivity using psychophysiological interaction analysis with the auditory cortex as the seed region. AP musicians showed decreased functional connectivity with the sensorimotor and middle frontal gyrus compared to non-AP musicians. Crucially, AP differentially affected connectivity with parietal and frontal brain regions depending on the HIN domain being music or speech. These findings suggest that AP plays a critical role in HIN perception, manifested by increased activation and functional independence between auditory and sensorimotor regions for perceiving music and speech streams.

Individual variability in functional connectivity of human auditory cortex

Individual variability in functional connectivity underlies individual differences in cognition and behaviors, yet its association with functional specialization in the auditory cortex remains elusive. Using resting-state functional magnetic resonance imaging data from the Human Connectome Project, this study was designed to investigate the spatial distribution of auditory cortex individual variability in its whole-brain functional network architecture. An inherent hierarchical axis of the variability was discerned, which radiates from the medial to lateral orientation, with the left auditory cortex demonstrating more pronounced variations than the right. This variability exhibited a significant correlation with the variations in structural and functional metrics in the auditory cortex. Four auditory cortex subregions, which were identified from a clustering analysis based on this variability, exhibited unique connectional fingerprints and cognitive maps, with certain subregions showing specificity to speech perception functional activation. Moreover, the lateralization of the connectional fingerprint exhibited a U-shaped trajectory across the subregions. These findings emphasize the role of individual variability in functional connectivity in understanding cortical functional organization, as well as in revealing its association with functional specialization from the activation, connectome, and cognition perspectives.

Neuroanatomical Disposition, Natural Development, and Training-Induced Plasticity of the Human Auditory System from Childhood to Adulthood: A 12-Year Study in Musicians and Nonmusicians

Auditory perception is fundamental to human development and communication. However, no long-term studies have been performed on the plasticity of the auditory system as a function of musical training from childhood to adulthood. The long-term interplay between developmental and training-induced neuroplasticity of auditory processing is still unknown. We present results from AMseL (Audio and Neuroplasticity of Musical Learning), the first longitudinal study on the development of the human auditory system from primary school age until late adolescence. This 12-year project combined neurologic and behavioral methods including structural magnetic resonance imaging (MRI), magnetoencephalography (MEG), and auditory tests. A cohort of 112 typically developing participants (51 male, 61 female), classified as "musicians" (n = 66) and "nonmusicians" (n = 46), was tested at five measurement timepoints. We found substantial, stable differences in the morphology of auditory cortex (AC) between musicians and nonmusicians even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. Maturational plasticity led to a continuous increase in white matter myelination and systematic changes of the auditory evoked P1-N1-P2 complex (decreasing latencies, synchronization effects between hemispheres, and amplitude changes) regardless of musical expertise. Musicians showed substantial training-related changes at the neurofunctional level, in particular more synchronized P1 responses and bilaterally larger P2 amplitudes. Musical training had a positive influence on elementary auditory perception (frequency, tone duration, onset ramp) and pattern recognition (rhythm, subjective pitch). The observed interplay between "nature" (stable biological dispositions and natural maturation) and "nurture" (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.Significance Statement We present results from AMseL (Audio and Neuroplasticity of Musical Learning), a 12-year longitudinal study on the development of the human auditory system from childhood to adulthood that combined structural magnetic resonance imaging (MRI), magnetoencephalography (MEG), and auditory discrimination and pattern recognition tests. A total of 66 musicians and 46 nonmusicians were tested at five timepoints. Substantial, stable differences in the morphology of auditory cortex (AC) were found between the two groups even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. We also observed neuroplastic and perceptual changes with age and musical practice. This interplay between "nature" (stable biological dispositions and natural maturation) and "nurture" (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.