Isabelle Peretz

Modularity of music processing

The music faculty is not a monolithic entity that a person either has or does not. Rather, it comprises a set of neurally isolable processing components, each having the potential to be specialized for music. Here we propose a functional architecture for music processing that captures the typical properties of modular organization. The model rests essentially on the analysis of music-related deficits in neurologically impaired individuals, but provides useful guidelines for exploring the music faculty in normal people, using methods such as neuroimaging.

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.

Universal Recognition of Three Basic Emotions in Music

It has long been debated which aspects of music perception are universal and which are developed only after exposure to a specific musical culture. Here, we report a crosscultural study with participants from a native African population (Mafa) and Western participants, with both groups being naive to the music of the other respective culture. Experiment 1 investigated the ability to recognize three basic emotions (happy, sad, scared/fearful) expressed in Western music. Results show that the Mafas recognized happy, sad, and scared/fearful Western music excerpts above chance, indicating that the expression of these basic emotions in Western music can be recognized universally. Experiment 2 examined how a spectral manipulation of original, naturalistic music affects the perceived pleasantness of music in Western as well as in Mafa listeners. The spectral manipulation modified, among other factors, the sensory dissonance of the music. The data show that both groups preferred original Western music and also original Mafa music over their spectrally manipulated versions. It is likely that the sensory dissonance produced by the spectral manipulation was at least partly responsible for this effect, suggesting that consonance and permanent sensory dissonance universally influence the perceived pleasantness of music.

Congenital Amusia: A Disorder of Fine-Grained Pitch Discrimination

We report the first documented case of congenital amusia. This disorder refers to a musical disability that cannot be explained by prior brain lesion, hearing loss, cognitive deficits, socioaffective disturbance, or lack of environmental stimulation. This musical impairment is diagnosed in a middle-aged woman, hereafter referred to as Monica, who lacks most basic musical abilities, including melodic discrimination and recognition, despite normal audiometry and above-average intellectual, memory, and language skills. The results of psychophysical tests show that Monica has severe difficulties with detecting pitch changes. The data suggest that music-processing difficulties may result from problems in fine-grained discrimination of pitch, much in the same way as many language-processing difficulties arise from deficiencies in auditory temporal resolution.

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.

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.

Individual differences in rhythmic cortical entrainment correlate with predictive behavior in sensorimotor synchronization

The current study aims at characterizing the mechanisms that allow humans to entrain the mind and body to incoming rhythmic sensory inputs in real time. We addressed this unresolved issue by examining the relationship between covert neural processes and overt behavior in the context of musical rhythm. We measured temporal prediction abilities, sensorimotor synchronization accuracy and neural entrainment to auditory rhythms as captured using an EEG frequency-tagging approach. Importantly, movement synchronization accuracy with a rhythmic beat could be explained by the amplitude of neural activity selectively locked with the beat period when listening to the rhythmic inputs. Furthermore, stronger endogenous neural entrainment at the beat frequency was associated with superior temporal prediction abilities. Together, these results reveal a direct link between cortical and behavioral measures of rhythmic entrainment, thus providing evidence that frequency-tagged brain activity has functional relevance for beat perception and synchronization.

The amusic brain: in tune, out of key, and unaware

Like language, music engagement is universal, complex and present early in life. However, approximately 4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.

Singing in the Brain: Independence of Lyrics and Tunes

Why is vocal music the oldest and still the most popular form of music? Very possibly because vocal music involves an intimate combination of speech and music, two of the most specific, high-level skills of human beings. The issue we address is whether people listening to a song treat the linguistic and musical components separately or integrate them within a single percept. Event-related potentials were recorded while musicians listened to excerpts from operas sung a capella. Excerpts were ended by semantically congruous or incongruous words sung either in or out of key. Results clearly demonstrated the independence of lyrics and tunes, so that an additive model of semantic- and harmonic-violations processing predicted the data extremely well. These results are consistent with a modular organization of the human cognitive system and open new perspectives in the search for the similarities and differences between language and music processing.