Are there critical periods for musical development?

Musician-Advantage on Listening Effort for Speech in Noise Perception: A Dual-Task Paradigm Measure

BACKGROUND AND OBJECTIVES

Speech in noise (SIN) perception is essential for effective day-to-day communication, as everyday conversations seldom transpire in silent environments. Numerous studies have documented how musical training can aid in SIN discrimination through various neural-pathways, such as experience-dependent plasticity and overlapping processes between music and speech perception. However, empirical evidence regarding the impact of musical training on SIN perception remains inconclusive. This study aimed to investigate whether musicians trained in South Indian classical "Carnatic" style of music exhibited a distinct advantage over their non-musician counterparts in SIN perception. The study also attempted to explore whether the listening effort (LE) associated in this process was different across musicians and non-musicians, an area that has received limited attention.

SUBJECTS AND METHODS

A quasi-experimental design was employed, involving two groups comprising 25 musicians and 35 non-musicians, aged 18-35 years, with normal hearing. In phase 1, participants' musical abilities were assessed using the Mini-Profile of Music Perception Skills (Mini-PROMS). In phase 2, SIN abilities were tested using the Tamil phonemically balanced words and Tamil Matrix Sentence Test at -5 dB, 0 dB, and +5 dB SNR. Phase 3 tested LE using a dual-task paradigm including auditory and visual stimuli as primary and secondary tasks.

RESULTS

Fractional logit and linear regression models demonstrated that musicians outperformed non-musicians in the Mini-PROMS assessment. Musicians also fared better than non-musicians in SIN and LE at 0 dB SNR for words and +5 dB SNR for sentences.

CONCLUSIONS

The findings of this study provided limited evidence to support the claim that musical training improves speech perception in noisy environments or reduces the associated listening effort.

The impact of early musical training on striatal functional connectivity

Evidence from language, visual and sensorimotor learning suggests that training early in life is more effective. The present work explores the hypothesis that learning during sensitive periods involves distinct brain networks in addition to those involved when learning later in life. Expert pianists were tested who started their musical training early (<7 years of age; n = 21) or late (n = 15), but were matched for total lifetime practice. Motor timing expertise was assessed using a musical scale playing task. Brain activity at rest was measured using fMRI and compared with a control group of nonmusicians (n = 17). Functional connectivity from seeds in the striatum revealed a striatal-cortical-sensorimotor network that was observed only in the early-onset group. In this network, higher connectivity correlated with greater motor timing expertise, which resulted from early/late group differences in motor timing expertise. By contrast, networks that differentiated musicians and nonmusicians, namely a striatal-occipital-frontal-cerebellar network in which connectivity was higher in musicians, tended to not show differences between early and late musicians and not be correlated with motor timing expertise. These results parcel musical sensorimotor neuroplasticity into a set of musicianship-related networks and a distinct set of predominantly early-onset networks. The findings lend support to the possibility that we can learn skills more easily early in development because during sensitive periods we recruit distinct brain networks that are no longer implicated in learning later in life.

The Role of Canalization and Plasticity in the Evolution of Musical Creativity

Creativity is defined as the ability to generate something new and valuable. From a biological point of view this can be seen as an adaptation in response to environmental challenges. Although music is such a diverse phenomenon, all people possess a set of abilities that are claimed to be the products of biological evolution, which allow us to produce and listen to music according to both universal and culture-specific rules. On the one hand, musical creativity is restricted by the tacit rules that reflect the developmental interplay between genetic, epigenetic and cultural information. On the other hand, musical innovations seem to be desirable elements present in every musical culture which suggests some biological importance. If our musical activity is driven by biological needs, then it is important for us to understand the function of musical creativity in satisfying those needs, and also how human beings have become so creative in the domain of music. The aim of this paper is to propose that musical creativity has become an indispensable part of the gene-culture coevolution of our musicality. It is suggested that the two main forces of canalization and plasticity have been crucial in this process. Canalization is an evolutionary process in which phenotypes take relatively constant forms regardless of environmental and genetic perturbations. Plasticity is defined as the ability of a phenotype to generate an adaptive response to environmental challenges. It is proposed that human musicality is composed of evolutionary innovations generated by the gradual canalization of developmental pathways leading to musical behavior. Within this process, the unstable cultural environment serves as the selective pressure for musical creativity. It is hypothesized that the connections between cortical and subcortical areas, which constitute cortico-subcortical circuits involved in music processing, are the products of canalization, whereas plasticity is achieved by the means of neurological variability. This variability is present both at the level of an individual structure’s enlargement in response to practicing (e.g., the planum temporale) and within the involvement of neurological structures that are not music-specific (e.g., the default mode network) in music processing.

The Musical Ear Test: Norms and correlates from a large sample of Canadian undergraduates

We sought to establish norms and correlates for the Musical Ear Test (MET), an objective test of musical ability. A large sample of undergraduates at a Canadian university (N > 500) took the 20-min test, which provided a Total score as well as separate scores for its Melody and Rhythm subtests. On each trial, listeners judged whether standard and comparison auditory sequences were the same or different. Norms were derived as percentiles, Z-scores, and T-scores. The distribution of scores was approximately normal without floor or ceiling effects. There were no gender differences on either subtest or the total score. As expected, scores on both subtests were correlated with performance on a test of immediate recall for nonmusical auditory stimuli (Digit Span Forward). Moreover, as duration of music training increased, so did performance on both subtests, but starting lessons at a younger age was not predictive of better musical abilities. Listeners who spoke a tone language exhibited enhanced performance on the Melody subtest but not on the Rhythm subtest. The MET appears to have adequate psychometric characteristics that make it suitable for researchers who seek to measure musical abilities objectively.

Characterization of EGR-1 Expression in the Auditory Cortex Following Kanamycin-Induced Hearing Loss in Mice

Deprivation of acoustic input during a critical period leads to abnormal auditory development in humans. The molecular basis underlying the susceptibility of auditory cortex to loss of afferent input remains largely unknown. The transcription factor early growth response-1 (EGR-1) expression in the visual cortex has been shown to be crucial in the formation of vision, but the role of EGR-1 during the process of auditory function formation is still unclear. In this study, we presented data showing that EGR-1 was expressed in the neurons of the primary auditory cortex (A1) in mice. We observed that the auditory deprivation induced by kanamycin during the auditory critical period leads to laminar-specific alteration of neuronal distribution and EGR-1 expression in A1. In addition, MK-801 administration inhibited the expression of EGR-1 in A1 and aggravated the abnormal cortical electric response caused by kanamycin injection. Finally, we showed that the expression of PI3K, the phosphorylation of Akt, as well as the phosphorylation of cAMP-responsive element-binding protein (CREB) were decreased in A1 after kanamycin-induced hearing loss. These results characterized the expression of EGR-1 in A1 in response to the acoustic input and suggested the involvement of EGR-1 in auditory function formation.

Is it impossible to acquire absolute pitch in adulthood?

Absolute pitch (AP) refers to the rare ability to name the pitch of a tone without external reference. It is widely believed to be only for the selected few with rare genetic makeup and early musical training during the critical period, and therefore acquiring AP in adulthood is impossible. Previous studies have not offered a strong test of the effect of training because of issues like small sample size and insufficient training. In three experiments, adults learned to name pitches in a computerized, gamified and personalized training protocol for 12 to 40 hours, with the number of pitches gradually increased from three to twelve. Across the three experiments, the training covered different octaves, timbre, and training environment (inside or outside laboratory). AP learning showed classic characteristics of perceptual learning, including generalization of learning dependent on the training stimuli, and sustained improvement for at least one to three months. 14% of the participants (6 out of 43) were able to name twelve pitches at 90% or above accuracy, comparable to that of 'AP possessors' as defined in the literature. Overall, AP continues to be learnable in adulthood, which challenges the view that AP development requires both rare genetic predisposition and learning within the critical period. The finding calls for reconsideration of the role of learning in the occurrence of AP, and pushes the field to pinpoint and explain the differences, if any, between the aspects of AP more trainable in adulthood and the aspects of AP that are potentially exclusive for the few exceptional AP possessors observed in the real world.

An Investigation Into the Relationship Between Onset Age of Musical Lessons and Levels of Sociability in Childhood

Previous studies have suggested that musical training in childhood is beneficial for sociability. However, it remains unclear how age of onset of group music lessons is associated with the late sociability of children from a long-term perspective. This study investigated associations between group music lessons conducted at a music school and children's levels of sociability by focusing on the age of onset of the lessons. We conducted a survey of 276 children aged 4-5 years (M = 58.5 months) and 6-7 years (M = 82.7 months) who commenced music lessons at ages 1, 2, 4, and 6 years. We found that (1) the empathy scores of children aged 6-7 years who began lessons when 1-year-old were greater than those who began lessons when 4-years-old, (2) the communication scores of children aged 4-5 years who began lessons when 1-year-old were greater than those who began lessons when older than 1 year, and (3) the empathy and extraversion scores were high in those aged 6-7 years who began lessons in that age range. The results suggest that early onset of music lessons could positively influence children's sociability; in contrast, after about age 7 years, children who already had high sociability may be more inclined to select group music lessons. By focusing on the impact of regular group music lessons from a very young age on later levels of sociability, these results further elucidate the effects of musical lessons. In sum, participation in group music lessons 2-4 times per month can be effective social training for very young children and foster their later sociability.

Early Influence of Musical Abilities and Working Memory on Speech Imitation Abilities: Study with Pre-School Children

Musical aptitude and language talent are highly intertwined when it comes to phonetic language ability. Research on pre-school children’s musical abilities and foreign language abilities are rare but give further insights into the relationship between language and musical aptitude. We tested pre-school children’s abilities to imitate unknown languages, to remember strings of digits, to sing, to discriminate musical statements and their intrinsic (spontaneous) singing behavior (“singing-lovers versus singing nerds”). The findings revealed that having an ear for music is linked to phonetic language abilities. The results of this investigation show that a working memory capacity and phonetic aptitude are linked to high musical perception and production ability already at around the age of 5. This suggests that music and (foreign) language learning capacity may be linked from childhood on. Furthermore, the findings put emphasis on the possibility that early developed abilities may be responsible for individual differences in both linguistic and musical performances.

Effects of transient auditory deprivation during critical periods on the development of auditory temporal processing

OBJECTIVES

The central auditory pathway matures through sensory experiences and it is known that sensory experiences during periods called critical periods exert an important influence on brain development. The present study aimed to investigate whether temporary auditory deprivation during critical periods (CPs) could have a detrimental effect on the development of auditory temporal processing.

MATERIALS AND METHODS

Twelve neonatal rats were randomly assigned to control and study groups; Study group experienced temporary (18-20 days) auditory deprivation during CPs (Early deprivation study group). Outcome measures included changes in auditory brainstem response (ABR), gap prepulse inhibition of the acoustic startle reflex (GPIAS), and gap detection threshold (GDT). To further delineate the specific role of CPs in the outcome measures above, the same paradigm was applied in adult rats (Late deprivation group) and the findings were compared with those of the neonatal rats.

RESULTS

Soon after the restoration of hearing, early deprivation study animals showed a significantly lower GPIAS at intermediate gap durations and a larger GDT than early deprivation controls, but these differences became insignificant after subsequent auditory inputs. Additionally, the ABR results showed significantly delayed latencies of waves IV, V, and interpeak latencies of wave I-III and wave I-V in study group. Late deprivation group didn't exhibit any deterioration in temporal processing following sensory deprivation.

CONCLUSION

Taken together, the present results suggest that transient auditory deprivation during CPs might cause reversible disruptions in the development of temporal processing.

Cortical hemispheric asymmetries are present at young ages and further develop into adolescence

Specialization of the auditory cortices for pure tone listening may develop with age. In adults, the right hemisphere dominates when listening to pure tones and music; we thus hypothesized that (a) asymmetric function between auditory cortices increases with age and (b) this development is specific to tonal rather than broadband/non-tonal stimuli. Cortical responses to tone-bursts and broadband click-trains were recorded by multichannel electroencephalography in young children (5.1 ± 0.8 years old) and adolescents (15.2 ± 1.7 years old) with normal hearing. Peak dipole moments indicating activity strength in right and left auditory cortices were calculated using the Time Restricted, Artefact and Coherence source Suppression (TRACS) beamformer. Monaural click-trains and tone-bursts in young children evoked a dominant response in the contralateral right cortex by left ear stimulation and, similarly, a contralateral left cortex response to click-trains in the right ear. Responses to tone-bursts in the right ear were more bilateral. In adolescents, peak activity dominated in the right cortex in most conditions (tone-bursts from either ear and to clicks from the left ear). Bilateral activity was evoked by right ear click stimulation. Thus, right hemispheric specialization for monaural tonal stimuli begins in children as young as 5 years of age and becomes more prominent by adolescence. These changes were marked by consistent dipole moments in the right auditory cortex with age in contrast to decreases in dipole activity in all other stimulus conditions. Together, the findings reveal increasingly asymmetric function for the two auditory cortices, potentially to support greater cortical specialization with development into adolescence.

Musical Sophistication and the Effect of Complexity on Auditory Discrimination in Finnish Speakers

Musical experiences and native language are both known to affect auditory processing. The present work aims to disentangle the influences of native language phonology and musicality on behavioral and subcortical sound feature processing in a population of musically diverse Finnish speakers as well as to investigate the specificity of enhancement from musical training. Finnish speakers are highly sensitive to duration cues since in Finnish, vowel and consonant duration determine word meaning. Using a correlational approach with a set of behavioral sound feature discrimination tasks, brainstem recordings, and a musical sophistication questionnaire, we find no evidence for an association between musical sophistication and more precise duration processing in Finnish speakers either in the auditory brainstem response or in behavioral tasks, but they do show an enhanced pitch discrimination compared to Finnish speakers with less musical experience and show greater duration modulation in a complex task. These results are consistent with a ceiling effect set for certain sound features which corresponds to the phonology of the native language, leaving an opportunity for music experience-based enhancement of sound features not explicitly encoded in the language (such as pitch, which is not explicitly encoded in Finnish). Finally, the pattern of duration modulation in more musically sophisticated Finnish speakers suggests integrated feature processing for greater efficiency in a real world musical situation. These results have implications for research into the specificity of plasticity in the auditory system as well as to the effects of interaction of specific language features with musical experiences.

Connectivity patterns during music listening: Evidence for action-based processing in musicians

Musical expertise is visible both in the morphology and functionality of the brain. Recent research indicates that functional integration between multi-sensory, somato-motor, default-mode (DMN), and salience (SN) networks of the brain differentiates musicians from non-musicians during resting state. Here, we aimed at determining whether brain networks differentially exchange information in musicians as opposed to non-musicians during naturalistic music listening. Whole-brain graph-theory analyses were performed on participants' fMRI responses. Group-level differences revealed that musicians' primary hubs comprised cerebral and cerebellar sensorimotor regions whereas non-musicians' dominant hubs encompassed DMN-related regions. Community structure analyses of the key hubs revealed greater integration of motor and somatosensory homunculi representing the upper limbs and torso in musicians. Furthermore, musicians who started training at an earlier age exhibited greater centrality in the auditory cortex, and areas related to top-down processes, attention, emotion, somatosensory processing, and non-verbal processing of speech. We here reveal how brain networks organize themselves in a naturalistic music listening situation wherein musicians automatically engage neural networks that are action-based while non-musicians use those that are perception-based to process an incoming auditory stream. Hum Brain Mapp 38:2955-2970, 2017. © 2017 Wiley Periodicals, Inc.

Stability and Variability in Aesthetic Experience: A Review

Based on psychophysics’ pragmatic dualism, we trace the cognitive neuroscience of stability and variability in aesthetic experience. With regard to different domains of aesthetic processing, we touch upon the relevance of cognitive schemata for aesthetic preference. Attitudes and preferences are explored in detail. Evolutionary constraints on attitude formation or schema generation are elucidated, just as the often seemingly arbitrary influences of social, societal, and cultural nature are. A particular focus is put on the concept of critical periods during an individual’s ontogenesis. The latter contrasting with changes of high frequency, such as fashion influences. Taken together, these analyses document the state of the art in the field and, potentially, highlight avenues for future research.

Commentary on the special issue on the adolescent brain: Adolescence, trajectories, and the importance of prevention

Adolescence as highlighted in this special issue is a period of tremendous growth, synaptic exuberance, and plasticity, but also a period for the emergence of mental illness and addiction. This commentary aims to stimulate research on prevention science to reduce the impact of early life events that often manifest during adolescence. By promoting a better understanding of what creates a normal and abnormal trajectory, the reviews by van Duijvenvoorde et al., Kilford et al., Lichenstein et al., and Tottenham and Galvan in this special issue comprehensively describe how the adolescent brain develops under typical conditions and how this process can go awry in humans. Preclinical reviews also within this issue describe how adolescents have prolonged extinction periods to maximize learning about their environment (Baker et al.), whereas Schulz and Sisk focus on the importance of puberty and how it interacts with stress (Romeo). Caballero and Tseng then set the stage of describing the neural circuitry that is often central to these changes and psychopathology. Factors that affect the mis-wiring of the brain for illness, including prenatal exposure to anti-mitotic agents (Gomes et al.) and early life stress and inflammation (Schwarz and Brenhouse), are included as examples of how exposure to early adversity manifests. These reviews are synthesized and show how information from the maturational stages that precede or occur during adolescence is likely to hold the key towards optimizing development to produce an adolescent and adult that is resilient and well adapted to their environment.

A developmental study of latent absolute pitch memory

The ability to recall the absolute pitch level of familiar music (latent absolute pitch memory) is widespread in adults, in contrast to the rare ability to label single pitches without a reference tone (overt absolute pitch memory). The present research investigated the developmental profile of latent absolute pitch (AP) memory and explored individual differences related to this ability. In two experiments, 288 children from 4 to12 years of age performed significantly above chance at recognizing the absolute pitch level of familiar melodies. No age-related improvement or decline, nor effects of musical training, gender, or familiarity with the stimuli were found in regard to latent AP task performance. These findings suggest that latent AP memory is a stable ability that is developed from as early as age 4 and persists into adulthood.

How age of acquisition influences brain architecture in bilinguals

In the present study, we explored how Age of Acquisition (AoA) of L2 affected brain structures in bilingual individuals. Thirty-six native English speakers who were bilingual were scanned with high resolution MRI. After MRI signal intensity inhomogeneity correction, we applied both voxel-based morphometry (VBM) and surface-based morphometry (SBM) approaches to the data. VBM analysis was performed using FSL's standard VBM processing pipeline. For the SBM analysis, we utilized a semi-automated sulci delineation procedure, registered the brains to an atlas, and extracted measures of twenty four pre-selected regions of interest. We addressed three questions: (1) Which areas are more susceptible to differences in AoA? (2) How do AoA, proficiency and current level of exposure work together in predicting structural differences in the brain? And (3) What is the direction of the effect of AoA on regional volumetric and surface measures? Both VBM and SBM results suggested that earlier second language exposure was associated with larger volumes in the right parietal cortex. Consistently, SBM showed that the cortical area of the right superior parietal lobule increased as AoA decreased. In contrast, in the right pars orbitalis of the inferior frontal gyrus, AoA, proficiency, and current level of exposure are equally important in accounting for the structural differences. We interpret our results in terms of current theory and research on the effects of L2 learning on brain structures and functions.

Layman versus Professional Musician: Who Makes the Better Judge?

The increasing number of casting shows and talent contests in the media over the past years suggests a public interest in rating the quality of vocal performances. In many of these formats, laymen alongside music experts act as judges. Whereas experts' judgments are considered objective and reliable when it comes to evaluating singing voice, little is known about laymen’s ability to evaluate peers. On the one hand, layman listeners–who by definition did not have any formal training or regular musical practice–are known to have internalized the musical rules on which singing accuracy is based. On the other hand, layman listeners’ judgment of their own vocal skills is highly inaccurate. Also, when compared with that of music experts, their level of competence in pitch perception has proven limited. The present study investigates laypersons' ability to objectively evaluate melodies performed by untrained singers. For this purpose, laymen listeners were asked to judge sung melodies. The results were compared with those of music experts who had performed the same task in a previous study. Interestingly, the findings show a high objectivity and reliability in layman listeners. Whereas both the laymen's and experts' definition of pitch accuracy overlap, differences regarding the musical criteria employed in the rating task were evident. The findings suggest that the effect of expertise is circumscribed and limited and supports the view that laypersons make trustworthy judges when evaluating the pitch accuracy of untrained singers.

Four principles of bio-musicology

As a species-typical trait of Homo sapiens, musicality represents a cognitively complex and biologically grounded capacity worthy of intensive empirical investigation. Four principles are suggested here as prerequisites for a successful future discipline of bio-musicology. These involve adopting: (i) a multicomponent approach which recognizes that musicality is built upon a suite of interconnected capacities, of which none is primary; (ii) a pluralistic Tinbergian perspective that addresses and places equal weight on questions of mechanism, ontogeny, phylogeny and function; (iii) a comparative approach, which seeks and investigates animal homologues or analogues of specific components of musicality, wherever they can be found; and (iv) an ecologically motivated perspective, which recognizes the need to study widespread musical behaviours across a range of human cultures (and not focus solely on Western art music or skilled musicians). Given their pervasiveness, dance and music created for dancing should be considered central subcomponents of music, as should folk tunes, work songs, lullabies and children's songs. Although the precise breakdown of capacities required by the multicomponent approach remains open to debate, and different breakdowns may be appropriate to different purposes, I highlight four core components of human musicality--song, drumming, social synchronization and dance--as widespread and pervasive human abilities spanning across cultures, ages and levels of expertise. Each of these has interesting parallels in the animal kingdom (often analogies but in some cases apparent homologies also). Finally, I suggest that the search for universal capacities underlying human musicality, neglected for many years, should be renewed. The broad framework presented here illustrates the potential for a future discipline of bio-musicology as a rich field for interdisciplinary and comparative research.

Song recognition by young children with cochlear implants: comparison between unilateral, bilateral, and bimodal users

PURPOSE

To examine song identification by preschoolers with normal hearing (NH) versus preschoolers with cochlear implants (CIs).

METHOD

Participants included 45 children ages 3;8-7;3 (years;months): 12 with NH and 33 with CIs, including 10 with unilateral CI, 14 with bilateral CIs, and 9 bimodal users (CI-HA) with unilateral CI and contralateral hearing aid. Preschoolers were asked to identify children's songs presented via 5 versions: (a) full (lyrics sung with piano accompaniment); (b) a cappella (only lyrics); (c) melodic (matching main melodic contour); (d) tonal (only pitch information); and (e) rhythmic (only song's rhythm).

RESULTS

The NH group surpassed all CI groups at identifying songs via melodic and tonal versions, but no significant differences emerged between the NH group and any CI group via full, a cappella, or rhythmic versions. Among the CI groups, no significant differences emerged via melodic or rhythmic versions, but bimodal users performed significantly better than bilateral users via the tonal version. Chronological age and duration of CI use correlated significantly with identification via the rhythmic version.

CONCLUSION

Bimodal users showed an advantage in identifying songs in the tonal version through use of complementary information.

A longitudinal study on children's music training experience and academic development

This study examined the relation between long-term music training and child development based on 250 Chinese elementary school students' academic development of first language (L1), second language (L2), and mathematics. We found that musician children outperformed non-musician children only on musical achievement and second language development. Additionally, although music training appeared to be correlated with children's final academic development of L1, L2, and mathematics, it did not independently contribute to the development of L1 or mathematical skills. Our findings suggest caution in interpreting the positive findings on the non-musical cognitive benefits of music learning.

Vocal motor changes beyond the sensitive period for song plasticity

Behavior is critically shaped during sensitive periods in development. Birdsong is a learned vocal behavior that undergoes dramatic plasticity during a sensitive period of sensorimotor learning. During this period, juvenile songbirds engage in vocal practice to shape their vocalizations into relatively stereotyped songs. By the time songbirds reach adulthood, their songs are relatively stable and thought to be "crystallized." Recent studies, however, highlight the potential for adult song plasticity and suggest that adult song could naturally change over time. As such, we investigated the degree to which temporal and spectral features of song changed over time in adult Bengalese finches. We observed that the sequencing and timing of song syllables became more stereotyped over time. Increases in the stereotypy of syllable sequencing were due to the pruning of infrequently produced transitions and, to a lesser extent, increases in the prevalence of frequently produced transitions. Changes in song tempo were driven by decreases in the duration and variability of intersyllable gaps. In contrast to significant changes to temporal song features, we found little evidence that the spectral structure of adult song syllables changed over time. These data highlight differences in the degree to which temporal and spectral features of adult song change over time and support evidence for distinct mechanisms underlying the control of syllable sequencing, timing, and structure. Furthermore, the observed changes to temporal song features are consistent with a Hebbian framework of behavioral plasticity and support the notion that adult song should be considered a form of vocal practice.

Promoting our understanding of neural plasticity by exploring developmental plasticity in early and adult life

Developmental plasticity (DP) is widely considered to be a property of early life stages, but evidence suggests it can be reactivated in mature brains. For example, recent developments on animal models suggest that experience in enriched environments (EE) can induce DP and enable adult recovery from amblyopia; even when the typical critical period for that recovery has closed. An interesting body of evidence suggests that extrapolation of the rejuvenatory power of that paradigm in mature human brains is feasible. These studies show that exposure to EE throughout life is associated with a delay, or even prevention, of age-related cognitive deficits. Consequently, it can be concluded that DP might underlie the neuroprotective effects against a neurocognitive breakdown that have been observed, and that EE exposure later in life might induce DP in a similar way to early EE exposure. Thus, the DP might exert its influence beyond the typical developing age ranges: childhood and adolescence. Although further research is still required, the observation of EE related neuroprotective effects are a breakthrough in the study of DP in humans and new advances in our understanding of neural plasticity have thus been reached.

Early development of polyphonic sound encoding and the high voice superiority effect

Previous research suggests that when two streams of pitched tones are presented simultaneously, adults process each stream in a separate memory trace, as reflected by mismatch negativity (MMN), a component of the event-related potential (ERP). Furthermore, a superior encoding of the higher tone or voice in polyphonic sounds has been found for 7-month-old infants and both musician and non-musician adults in terms of a larger amplitude MMN in response to pitch deviant stimuli in the higher than the lower voice. These results, in conjunction with modeling work, suggest that the high voice superiority effect might originate in characteristics of the peripheral auditory system. If this is the case, the high voice superiority effect should be present in infants younger than 7 months. In the present study we tested 3-month-old infants as there is no evidence at this age of perceptual narrowing or specialization of musical processing according to the pitch or rhythmic structure of music experienced in the infant׳s environment. We presented two simultaneous streams of tones (high and low) with 50% of trials modified by 1 semitone (up or down), either on the higher or the lower tone, leaving 50% standard trials. Results indicate that like the 7-month-olds, 3-month-old infants process each tone in a separate memory trace and show greater saliency for the higher tone. Although MMN was smaller and later in both voices for the group of sixteen 3-month-olds compared to the group of sixteen 7-month-olds, the size of the difference in MMN for the high compared to low voice was similar across ages. These results support the hypothesis of an innate peripheral origin of the high voice superiority effect.

Learning, neural plasticity and sensitive periods: implications for language acquisition, music training and transfer across the lifespan

Sensitive periods in human development have often been proposed to explain age-related differences in the attainment of a number of skills, such as a second language (L2) and musical expertise. It is difficult to reconcile the negative consequence this traditional view entails for learning after a sensitive period with our current understanding of the brain's ability for experience-dependent plasticity across the lifespan. What is needed is a better understanding of the mechanisms underlying auditory learning and plasticity at different points in development. Drawing on research in language development and music training, this review examines not only what we learn and when we learn it, but also how learning occurs at different ages. First, we discuss differences in the mechanism of learning and plasticity during and after a sensitive period by examining how language exposure versus training forms language-specific phonetic representations in infants and adult L2 learners, respectively. Second, we examine the impact of musical training that begins at different ages on behavioral and neural indices of auditory and motor processing as well as sensorimotor integration. Third, we examine the extent to which childhood training in one auditory domain can enhance processing in another domain via the transfer of learning between shared neuro-cognitive systems. Specifically, we review evidence for a potential bi-directional transfer of skills between music and language by examining how speaking a tonal language may enhance music processing and, conversely, how early music training can enhance language processing. We conclude with a discussion of the role of attention in auditory learning for learning during and after sensitive periods and outline avenues of future research.

Early musical training is linked to gray matter structure in the ventral premotor cortex and auditory-motor rhythm synchronization performance

Evidence in animals and humans indicates that there are sensitive periods during development, times when experience or stimulation has a greater influence on behavior and brain structure. Sensitive periods are the result of an interaction between maturational processes and experience-dependent plasticity mechanisms. Previous work from our laboratory has shown that adult musicians who begin training before the age of 7 show enhancements in behavior and white matter structure compared with those who begin later. Plastic changes in white matter and gray matter are hypothesized to co-occur; therefore, the current study investigated possible differences in gray matter structure between early-trained (ET; <7) and late-trained (LT; >7) musicians, matched for years of experience. Gray matter structure was assessed using voxel-wise analysis techniques (optimized voxel-based morphometry, traditional voxel-based morphometry, and deformation-based morphometry) and surface-based measures (cortical thickness, surface area and mean curvature). Deformation-based morphometry analyses identified group differences between ET and LT musicians in right ventral premotor cortex (vPMC), which correlated with performance on an auditory motor synchronization task and with age of onset of musical training. In addition, cortical surface area in vPMC was greater for ET musicians. These results are consistent with evidence that premotor cortex shows greatest maturational change between the ages of 6-9 years and that this region is important for integrating auditory and motor information. We propose that the auditory and motor interactions required by musical practice drive plasticity in vPMC and that this plasticity is greatest when maturation is near its peak.

Plasticity after perceptual narrowing for voice perception: reinstating the ability to discriminate monkeys by their voices at 12 months of age

Differentiating individuals by their voice is an important social skill for infants to acquire. In a previous study, we demonstrated that the ability to discriminate individuals by voice follows a pattern of perceptual narrowing (Friendly et al., 2013). Specifically, we found that the ability to discriminate between two foreign-species (rhesus monkey) voices decreased significantly between 6 and 12 months of age. Also during this period, there was a trend for the ability to discriminate human voices to increase. Here we investigate the extent to which plasticity remains at 12 months, after perceptual narrowing has occurred. We found that 12-month-olds who received 2 weeks of monkey-voice training were significantly better at discriminating between rhesus monkey voices than untrained 12-month-olds. Furthermore, discrimination was reinstated to a level slightly better than that of untrained 6-month-olds, suggesting that voice-processing abilities remain considerably plastic at the end of the first year.

Musical training heightens auditory brainstem function during sensitive periods in development

Experience has a profound influence on how sound is processed in the brain. Yet little is known about how enriched experiences interact with developmental processes to shape neural processing of sound. We examine this question as part of a large cross-sectional study of auditory brainstem development involving more than 700 participants, 213 of whom were classified as musicians. We hypothesized that experience-dependent processes piggyback on developmental processes, resulting in a waxing-and-waning effect of experience that tracks with the undulating developmental baseline. This hypothesis led to the prediction that experience-dependent plasticity would be amplified during periods when developmental changes are underway (i.e., early and later in life) and that the peak in experience-dependent plasticity would coincide with the developmental apex for each subcomponent of the auditory brainstem response (ABR). Consistent with our predictions, we reveal that musicians have heightened response features at distinctive times in the life span that coincide with periods of developmental change. The effect of musicianship is also quite specific: we find that only select components of auditory brainstem activity are affected, with musicians having heightened function for onset latency, high-frequency phase-locking, and response consistency, and with little effect observed for other measures, including lower-frequency phase-locking and non-stimulus-related activity. By showing that musicianship imparts a neural signature that is especially evident during childhood and old age, our findings reinforce the idea that the nervous system's response to sound is “chiseled” by how a person interacts with his specific auditory environment, with the effect of the environment wielding its greatest influence during certain privileged windows of development.

Informal musical activities are linked to auditory discrimination and attention in 2-3-year-old children: an event-related potential study

The relation between informal musical activities at home and electrophysiological indices of neural auditory change detection was investigated in 2-3-year-old children. Auditory event-related potentials were recorded in a multi-feature paradigm that included frequency, duration, intensity, direction, gap deviants and attention-catching novel sounds. Correlations were calculated between these responses and the amount of musical activity at home (i.e. musical play by the child and parental singing) reported by the parents. A higher overall amount of informal musical activity was associated with larger P3as elicited by the gap and duration deviants, and smaller late discriminative negativity responses elicited by all deviant types. Furthermore, more musical activities were linked to smaller P3as elicited by the novel sounds, whereas more paternal singing was associated with smaller reorienting negativity responses to these sounds. These results imply heightened sensitivity to temporal acoustic changes, more mature auditory change detection, and less distractibility in children with more informal musical activities in their home environment. Our results highlight the significance of informal musical experiences in enhancing the development of highly important auditory abilities in early childhood.

A little goes a long way: how the adult brain is shaped by musical training in childhood

Playing a musical instrument changes the anatomy and function of the brain. But do these changes persist after music training stops? We probed this question by measuring auditory brainstem responses in a cohort of healthy young human adults with varying amounts of past musical training. We show that adults who received formal music instruction as children have more robust brainstem responses to sound than peers who never participated in music lessons and that the magnitude of the response correlates with how recently training ceased. Our results suggest that neural changes accompanying musical training during childhood are retained in adulthood. These findings advance our understanding of long-term neuroplasticity and have general implications for the development of effective auditory training programs.

Critical period for acoustic preference in mice

Preference behaviors are often established during early life, but the underlying neural circuit mechanisms remain unknown. Adapting a unique nesting behavior assay, we confirmed a "critical period" for developing music preference in C57BL/6 mice. Early music exposure between postnatal days 15 and 24 reversed their innate bias for silent shelter, which typically could not be altered in adulthood. Instead, exposing adult mice treated acutely with valproic acid or carrying a targeted deletion of the Nogo receptor (NgR(-/-)) unmasked a strong plasticity of preference consistent with a reopening of the critical period as seen in other systems. Imaging of cFos expression revealed a prominent neuronal activation in response to the exposed music in the prelimbic and infralimbic medial prefrontal cortex only under conditions of open plasticity. Neither behavioral changes nor selective medial prefrontal cortex activation was observed in response to pure tone exposure, indicating a music-specific effect. Open-field center crossings were increased concomitant with shifts in music preference, suggesting a potential anxiolytic effect. Thus, music may offer both a unique window into the emotional state of mice and a potentially efficient assay for molecular "brakes" on critical period plasticity common to sensory and higher order brain areas.

Musical training facilitates the neural discrimination of major versus minor chords in 13-year-old children

Music practice since childhood affects the development of hearing skills. An important classification in Western music is the chords' major-minor dichotomy. Its preattentive auditory discrimination was studied here using a mismatch negativity (MMN) paradigm in 13-year-olds with active hobbies, music-related (music group) or other (control group). In a context of root major chords, root minor chords and inverted major chords were presented infrequently. The interval structure of inverted majors differs more from root majors than the interval structure of root minors. However, the identity of the chords is the same in inverted and root majors (major), but different in root minors. The deviant chords introduced no new frequencies to the paradigm. Hence, an MMN caused by physical deviance was prevented. An MMN was elicited by the minor chords but not by the inverted majors. The MMN amplitude in the music group was larger than in the control group. Thus, the conceptual discrimination skills are present already in the preattentive processing level of the auditory cortex, and musical training can advance these skills.

Development of simultaneous pitch encoding: infants show a high voice superiority effect

Infants must learn to make sense of real-world auditory environments containing simultaneous and overlapping sounds. In adults, event-related potential studies have demonstrated the existence of separate preattentive memory traces for concurrent note sequences and revealed perceptual dominance for encoding of the voice with higher fundamental frequency of 2 simultaneous tones or melodies. Here, we presented 2 simultaneous streams of notes (15 semitones apart) to 7-month-old infants. On 50% of trials, either the higher or the lower note was modified by one semitone, up or down, leaving 50% standard trials. Infants showed mismatch negativity (MMN) to changes in both voices, indicating separate memory traces for each voice. Furthermore, MMN was earlier and larger for the higher voice as in adults. When in the context of a second voice, representation of the lower voice was decreased and that of the higher voice increased compared with when each voice was presented alone. Additionally, correlations between MMN amplitude and amount of weekly music listening suggest that experience affects the development of auditory memory. In sum, the ability to process simultaneous pitches and the dominance of the highest voice emerge early during infancy and are likely important for the perceptual organization of sound in realistic environments.

Active music classes in infancy enhance musical, communicative and social development

Previous studies suggest that musical training in children can positively affect various aspects of development. However, it remains unknown as to how early in development musical experience can have an effect, the nature of any such effects, and whether different types of music experience affect development differently. We found that random assignment to 6 months of active participatory musical experience beginning at 6 months of age accelerates acquisition of culture-specific knowledge of Western tonality in comparison to a similar amount of passive exposure to music. Furthermore, infants assigned to the active musical experience showed superior development of prelinguistic communicative gestures and social behaviour compared to infants assigned to the passive musical experience. These results indicate that (1) infants can engage in meaningful musical training when appropriate pedagogical approaches are used, (2) active musical participation in infancy enhances culture-specific musical acquisition, and (3) active musical participation in infancy impacts social and communication development.

Subcortical processing of speech regularities underlies reading and music aptitude in children

Background

Neural sensitivity to acoustic regularities supports fundamental human behaviors such as hearing in noise and reading. Although the failure to encode acoustic regularities in ongoing speech has been associated with language and literacy deficits, how auditory expertise, such as the expertise that is associated with musical skill, relates to the brainstem processing of speech regularities is unknown. An association between musical skill and neural sensitivity to acoustic regularities would not be surprising given the importance of repetition and regularity in music. Here, we aimed to define relationships between the subcortical processing of speech regularities, music aptitude, and reading abilities in children with and without reading impairment. We hypothesized that, in combination with auditory cognitive abilities, neural sensitivity to regularities in ongoing speech provides a common biological mechanism underlying the development of music and reading abilities.

Methods

We assessed auditory working memory and attention, music aptitude, reading ability, and neural sensitivity to acoustic regularities in 42 school-aged children with a wide range of reading ability. Neural sensitivity to acoustic regularities was assessed by recording brainstem responses to the same speech sound presented in predictable and variable speech streams.

Results

Through correlation analyses and structural equation modeling, we reveal that music aptitude and literacy both relate to the extent of subcortical adaptation to regularities in ongoing speech as well as with auditory working memory and attention. Relationships between music and speech processing are specifically driven by performance on a musical rhythm task, underscoring the importance of rhythmic regularity for both language and music.

Conclusions

These data indicate common brain mechanisms underlying reading and music abilities that relate to how the nervous system responds to regularities in auditory input. Definition of common biological underpinnings for music and reading supports the usefulness of music for promoting child literacy, with the potential to improve reading remediation.

Sing that tune: infants' perception of melody and lyrics and the facilitation of phonetic recognition in songs

To better understand how infants process complex auditory input, this study investigated whether 11-month-old infants perceive the pitch (melodic) or the phonetic (lyric) components within songs as more salient, and whether melody facilitates phonetic recognition. Using a preferential looking paradigm, uni-dimensional and multi-dimensional songs were tested; either the pitch or syllable order of the stimuli varied. As a group, infants detected a change in pitch order in a 4-note sequence when the syllables were redundant (experiment 1), but did not detect the identical pitch change with variegated syllables (experiment 2). Infants were better able to detect a change in syllable order in a sung sequence (experiment 2) than the identical syllable change in a spoken sequence (experiment 1). These results suggest that by 11 months, infants cannot "ignore" phonetic information in the context of perceptually salient pitch variation. Moreover, the increased phonetic recognition in song contexts mirrors findings that demonstrate advantages of infant-directed speech. Findings are discussed in terms of how stimulus complexity interacts with the perception of sung speech in infancy.

Absolute pitch: effects of timbre on note-naming ability

Background

Absolute pitch (AP) is the ability to identify or produce isolated musical tones. It is evident primarily among individuals who started music lessons in early childhood. Because AP requires memory for specific pitches as well as learned associations with verbal labels (i.e., note names), it represents a unique opportunity to study interactions in memory between linguistic and nonlinguistic information. One untested hypothesis is that the pitch of voices may be difficult for AP possessors to identify. A musician's first instrument may also affect performance and extend the sensitive period for acquiring accurate AP.

Methods/Principal Findings

A large sample of AP possessors was recruited on-line. Participants were required to identity test tones presented in four different timbres: piano, pure tone, natural (sung) voice, and synthesized voice. Note-naming accuracy was better for non-vocal (piano and pure tones) than for vocal (natural and synthesized voices) test tones. This difference could not be attributed solely to vibrato (pitch variation), which was more pronounced in the natural voice than in the synthesized voice. Although starting music lessons by age 7 was associated with enhanced note-naming accuracy, equivalent abilities were evident among listeners who started music lessons on piano at a later age.

Conclusions/Significance

Because the human voice is inextricably linked to language and meaning, it may be processed automatically by voice-specific mechanisms that interfere with note naming among AP possessors. Lessons on piano or other fixed-pitch instruments appear to enhance AP abilities and to extend the sensitive period for exposure to music in order to develop accurate AP.

Development of auditory phase-locked activity for music sounds

The auditory cortex undergoes functional and anatomical development that reflects specialization for learned sounds. In humans, auditory maturation is evident in transient auditory-evoked potentials (AEPs) elicited by speech or music. However, neural oscillations at specific frequencies are also known to play an important role in perceptual processing. We hypothesized that, if oscillatory activity in different frequency bands reflects different aspects of sound processing, the development of phase-locking to stimulus attributes at these frequencies may have different trajectories. We examined the development of phase-locking of oscillatory responses to music sounds and to pure tones matched to the fundamental frequency of the music sounds. Phase-locking for theta (4-8 Hz), alpha (8-14 Hz), lower-to-mid beta (14-25 Hz), and upper-beta and gamma (25-70 Hz) bands strengthened with age. Phase-locking in the upper-beta and gamma range matured later than in lower frequencies and was stronger for music sounds than for pure tones, likely reflecting the maturation of neural networks that code spectral complexity. Phase-locking for theta, alpha, and lower-to-mid beta was sensitive to temporal onset (rise time) sound characteristics. The data were also consistent with phase-locked oscillatory effects of acoustic (spectrotemporal) complexity and timbre familiarity. Future studies are called for to evaluate developmental trajectories for oscillatory activity, using stimuli selected to address hypotheses related to familiarity and spectral and temporal encoding suggested by the current findings.

Neural representation of transposed melody in infants at 6 months of age

We examined adults' and 6-month-old infants' event-related potentials in response to occasional changes (deviants) in a 4-note melody presented at different pitch levels from trial to trial. In both groups, responses to standard and deviant stimuli differed significantly; however, adults produced a typical mismatch negativity (MMN), whereas 6-month-old infants exhibited a slow positive wave. We conclude that 6-month-old infants, like adults, encode melodic information in terms of relative pitch distances, but that the underlying cortical activity differs significantly from that of adults.

A protocol for cross-cultural research on the acquisition of singing

As part of a major collaborative research initiative, Advancing Interdisciplinary Research in Singing (AIRS), we developed a protocol for obtaining audiovisual information reflecting aspects of the ability to sing. We also developed a digital library prototype, the Children's International Media Exchange for Singing (CHIMES), to index and store the data for access through the Internet by researchers worldwide. The protocol was piloted at five monthly intervals with 20 individuals (children 3, 5, and 7 years of age and adults differing in vocal training level), validating its feasibility in Western culture and producing rich data amenable to numerous levels and kinds of analysis.