Krista L. Hyde

Musical Training Shapes Structural Brain Development

The human brain has the remarkable capacity to alter in response to environmental demands. Training-induced structural brain changes have been demonstrated in the healthy adult human brain. However, no study has yet directly related structural brain changes to behavioral changes in the developing brain, addressing the question of whether structural brain differences seen in adults (comparing experts with matched controls) are a product of “nature” (via biological brain predispositions) or “nurture” (via early training). Long-term instrumental music training is an intense, multisensory, and motor experience and offers an ideal opportunity to study structural brain plasticity in the developing brain in correlation with behavioral changes induced by training. Here we demonstrate structural brain changes after only 15 months of musical training in early childhood, which were correlated with improvements in musically relevant motor and auditory skills. These findings shed light on brain plasticity and suggest that structural brain differences in adult experts (whether musicians or experts in other areas) are likely due to training-induced brain plasticity.

Varieties of Musical Disorders

Abstract: Multiple disorders of musical abilities can occur after brain damage. Conversely, early brain anomalies or vast brain injuries may sometimes spare ordinary musical skills in individuals who experience severe cognitive losses. To document these incidences, comprehensive behavioral testing is required. We propose to use the Montreal Battery of Evaluation of Amusia (MBEA) because it is arguably the best tool currently available. Over the last decade, this battery was developed and validated in populations with brain damage of various etiologies. Furthermore, the MBEA is theoretically motivated and satisfies important psychometric properties. It is sensitive, normally distributed, reliable on test‐retest, and correlates with Gordons Musical Aptitude Profile, another more widely used battery of tests. To promote its wide usage, the MBEA is now available upon request. In addition, individual MBEA data of 160 normal participants of variable age and education have been made available to all via the internet.

Brains That Are out of Tune but in Time

It is estimated that about 4% of the general population may have amusia (or tone deafness). Congenital amusia is a lifelong disability for processing music despite normal intellectual, memory, and language skills. Here we present evidence that the disorder stems from a deficit in fine-grained pitch perception. Amusic and control adults were presented with monotonic and isochronous sequences of five tones (i.e., constant pitch and intertone interval). They were required to detect when the fourth tone was displaced in pitch or time. All amusic participants were impaired in detecting the pitch changes, and showed no sign of improvement with practice. In contrast, they detected time changes as well as control adults and exhibited similar improvements with practice. Thus, the degraded pitch perception seen in the amusic individuals cannot be ascribed to nonspecific problems with the task or to poor hearing in general. Rather, the data point to the presence of a congenital neural anomaly that selectively impairs pitch processing.

Cortical Thickness in Congenital Amusia: When Less Is Better Than More

Congenital amusia (or tone deafness) is a lifelong disorder characterized by impairments in the perception and production of music. A previous voxel-based morphometry (VBM) study revealed that amusic individuals had reduced white matter in the right inferior frontal gyrus (IFG) relative to musically intact controls (Hyde et al., 2006). However, this VBM study also revealed associated increases in gray matter in the same right IFG region of amusics. The objective of the present study was to better understand this morphological brain anomaly by way of cortical thickness measures that provide a more specific measure of cortical morphology relative to VBM. We found that amusic subjects (n = 21) have thicker cortex in the right IFG and the right auditory cortex relative to musically intact controls (n = 26). These cortical thickness differences suggest the presence of cortical malformations in the amusic brain, such as abnormal neuronal migration, that may have compromised the normal development of a right frontotemporal pathway.

Neuroanatomical differences in brain areas implicated in perceptual and other core features of autism revealed by cortical thickness analysis and voxel-based morphometry

Autism spectrum disorder is a complex neurodevelopmental variant thought to affect 1 in 166 [Fombonne ( 2003 ): J Autism Dev Disord 33:365–382]. Individuals with autism demonstrate atypical social interaction, communication, and repetitive behaviors, but can also present enhanced abilities, particularly in auditory and visual perception and nonverbal reasoning. Structural brain differences have been reported in autism, in terms of increased total brain volume (particularly in young children with autism), and regional gray/white matter differences in both adults and children with autism, but the reports are inconsistent [Amaral et al. (2008): Trends Neurosci 31:137–145]. These inconsistencies may be due to differences in diagnostic/inclusion criteria, and age and Intelligence Quotient of participants. Here, for the first time, we used two complementary magnetic resonance imaging techniques, cortical thickness analyses, and voxel‐based morphometry (VBM), to investigate the neuroanatomical differences between a homogenous group of young adults with autism of average intelligence but delayed or atypical language development (often referred to as “high‐functioning autism”), relative to a closely matched group of typically developing controls. The cortical thickness and VBM techniques both revealed regional structural brain differences (mostly in terms of gray matter increases) in brain areas implicated in social cognition, communication, and repetitive behaviors, and thus in each of the core atypical features of autism. Gray matter increases were also found in auditory and visual primary and associative perceptual areas. We interpret these results as the first structural brain correlates of atypical auditory and visual perception in autism, in support of the enhanced perceptual functioning model [Mottron et al. (2006): J Autism Dev Disord 36:27–43]. Hum Brain Mapp, 2010.

What is specific to music processing? Insights from congenital amusia

Musical abilities are generally regarded as an evolutionary by-product of more important functions, such as those involved in language. However, there is increasing evidence that humans are born with musical predispositions that develop spontaneously into sophisticated knowledge bases and procedures that are unique to music. Recent findings also suggest that the brain is equipped with music-specific neural networks and that these can be selectively compromised by a congenital anomaly. This results in a disorder, congenital amusia, that appears to be limited to the processing of music. Recent evidence points to fine-grained perception of pitch as the root of musical handicap. Hence, musical abilities appear to depend crucially on the fine-tuning of pitch, in much the same way that language abilities rely on fine time resolution.

Evidence for the role of the right auditory cortex in fine pitch resolution

The neural basis of human pitch perception is not fully understood. It has been argued that the auditory cortices in the two hemispheres are specialized, such that certain right auditory cortical regions have a relatively finer resolution in the frequency domain than homologous regions in the left auditory cortex, but this concept has not been tested directly. Here, we used functional magnetic resonance imaging (fMRI) to test this specific prediction. Healthy volunteers were scanned while passively listening to pure-tone melodic-like sequences in which the pitch distance between consecutive tones was varied in a parametric fashion. As predicted, brain activation in a region of right lateral auditory cortex, corresponding to the planum temporale, was linearly responsive to increasing pitch distance, even across the fine changes in pitch. In contrast, the BOLD signal at the homologous left cortical region was relatively constant as a function of pitch distance, except at the largest pitch change. The results support the model of relative hemispheric specialization and indicate that the right secondary auditory cortex has a finer pitch resolution than the left.

The effects of musical training on structural brain development: a longitudinal study.

Long‐term instrumental music training is an intense, multisensory and motor experience that offers an ideal opportunity to study structural brain plasticity in the developing brain in correlation with behavioral changes induced by training. Here, for the first time, we demonstrate structural brain changes after only 15 months of musical training in early childhood, which were correlated with improvements in musically relevant motor and auditory skills. These findings shed light on brain plasticity, and suggest that structural brain differences in adult experts (whether musicians or experts in other areas) are likely due to training‐induced brain plasticity.

Structural brain changes linked to delayed first language acquisition in congenitally deaf individuals.

Early language experience is essential for the development of a high level of linguistic proficiency in adulthood and in a recent functional Magnetic Resonance Imaging (fMRI) experiment, we showed that a delayed acquisition of a first language results in changes in the functional organization of the adult brain (Mayberry et al., 2011). The present study extends the question to explore if delayed acquisition of a first language also modulates the structural development of the brain. To this end, we carried out anatomical MRI in the same group of congenitally deaf individuals who varied in the age of acquisition of a first language, American Sign Language -ASL (Mayberry et al., 2011) and used a neuroanatomical technique, Voxel-Based Morphometry (VBM), to explore changes in gray and white matter concentrations across the brain related to the age of first language acquisition. The results show that delayed acquisition of a first language is associated with changes in tissue concentration in the occipital cortex close to the area that has been found to show functional recruitment during language processing in these deaf individuals with a late age of acquisition. These findings suggest that a lack of early language experience affects not only the functional but also the anatomical organization of the brain.

Auditory-musical processing in autism spectrum disorders: a review of behavioral and brain imaging studies

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by atypical social and communication skills, repetitive behaviors, and atypical visual and auditory perception. Studies in vision have reported enhanced detailed (“local”) processing but diminished holistic (“global”) processing of visual features in ASD. Individuals with ASD also show enhanced processing of simple visual stimuli but diminished processing of complex visual stimuli. Relative to the visual domain, auditory global–local distinctions, and the effects of stimulus complexity on auditory processing in ASD, are less clear. However, one remarkable finding is that many individuals with ASD have enhanced musical abilities, such as superior pitch processing. This review provides a critical evaluation of behavioral and brain imaging studies of auditory processing with respect to current theories in ASD. We have focused on auditory‐musical processing in terms of global versus local processing and simple versus complex sound processing. This review contributes to a better understanding of auditory processing differences in ASD. A deeper comprehension of sensory perception in ASD is key to better defining ASD phenotypes and, in turn, may lead to better interventions.