Beat deafness is a form of congenital amusia characterized by a person's inability to distinguish musical rhythm or move in time to it. [1]
Generally, humans have the ability to hear musical beat and rhythm beginning in infancy. [2] Some people, however, are unable to identify beat and rhythm of music, suffering from what is known as beat deafness. Beat deafness is a newly discovered form of congenital amusia, in which people lack the ability to identify or “hear” the beat in a piece of music. [3] Unlike most hearing impairments in which an individual is unable to hear any sort of sound stimuli, those with beat deafness are generally able to hear normally, but unable to identify beat and rhythm in music. Those with beat deafness are also unable to dance in step to any type of music. Even people who do not dance well can at least coordinate their movements to the song they are listening to, because they can easily keep time to the beat. [3]
The first reported case of beat deafness was of a Canadian graduate student, whom researchers have identified as “Mathieu”. Phillips-Silver et al. (2011) examined the human ability to recognize musical beat in a sample of individuals who had had no previous musical training in their lives. The researchers presented a series of songs from different genres and the participants were instructed to simply bounce up and down to the beat of the music. Results indicated that all participants except for Mathieu were able to move in sync with the beat of the music. The researchers also presented video clips which showed a person dancing to music. Mathieu could not identify when the person was or was not dancing in time to the music. [3] Other participants demonstrated no problem with this task.
When sound waves reach the ears, the energy they contain is converted into electrical signals, which are sent via the auditory nerves to the brain. Sound processing begins when these electrical signals reach the primary auditory receiving area in the core part of the temporal lobe. [4] Signals then travel to the area surrounding the core, known as the belt area, and are then transmitted to the parabelt area, which is located next to the belt. Simple sounds such as pure tones are able to activate the core area of the brain, but both the belt and parabelt areas are activated by only complex sounds, such as those found in speech and music. [4] The auditory cortex in the left hemisphere of the brain is responsible for processing beat and rhythm in music. The right auditory cortex is primarily used in distinguishing between different harmonics, which are simple pure tones that combine to create complex tones. [5]
Phillips-Silver et al. (2011) propose that beat deafness is the result of neurological problems in the areas of the brain that are used for recognizing musical beat, rhythm, and time. The main area responsible for processing musical rhythm is the left auditory cortex, [5] however other areas are most likely involved as well. According to the hypothesis of Phillips-Silver and coworkers, it should therefore be functional abnormalities in the left auditory cortex that cause beat deafness. [6]
Other areas of Mathieu's brain appeared to be functioning normally, including the areas responsible for hearing in general and for motor control, which is used in performing the moves in dancing. [3] Mathieu's deficiencies are therefore not caused by the inability to hear efficiently or control the movement of his body while dancing. Beat deafness has also not been shown to affect other areas of cognitive function such as language, which does not involve any sort of underlying beat or sporadic rhythm changes that are associated with music. [3] Given the normal functioning of Mathieu's brain, the hypothesis about the beat perception deficit occurring in the brain area for rhythm processing in particular is most likely correct.
Beat deafness is however, a very recent discovery and further research is necessary in gaining complete understanding of the phenomenon and its underlying brain processes. [6] In 2016 a study was published that examined the neural correlates of beat perception in two beat-deaf individuals, Mathieu and Marjorie, and a group of control participants. It provided partial support for abnormalities in later cognitive stages of beat processing, reflected in an unreliable P3b component exhibited by Mathieu—but not Marjorie—compared to control participants. [7]
Tone deafness is characterized by the inability to discriminate between different pitches, which are directly related to the frequencies of sound waves. [8] Tone deafness is a related, but distinct disorder from beat deafness. People with tone deafness can recognize beat and can move in time to music, but they cannot perceive pitch. People with beat deafness on the other hand, can recognize and distinguish between different tones as well as the average person and can usually sing in tune, so musical pitch is not the issue. [3] Different areas of the brain in the auditory cortex are involved in the perception of musical pitch and melody. Researchers theorize that tone deafness can potentially be from any of these sections. [8] Both beat deafness and tone deafness are derived from these same areas within the brain.
A research team led by Aniruddh D. Patel of The Neurosciences Institute concluded that sulphur-crested cockatoos have the ability to perceive the beat in music and are able to rhythmically move to the tempo of the music as it changes. Only vocal learning species such as dolphins and parrots are hypothesized to have the ability to perceive beat. This is because beat perception and movement rely on complex vocal learning which require motor and auditory circuits in the brain. Vocal learning and beat perception do some overlapping in the parts of the brain that account auditory and motor areas. There is no significant evidence for beat perception in nonvocal learning species such as dogs and cats. [9] However, California sea lions, a nonvocal learning animal, have demonstrated the ability to perceive beats in music. [10]
Auditory illusions are false perceptions of a real sound or outside stimulus. These false perceptions are the equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or sounds that should not be possible given the circumstance on how they were created.
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to language switching. It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans, curving down and onto the medial surface, on the superior temporal plane, within the lateral sulcus and comprising parts of the transverse temporal gyri, and the superior temporal gyrus, including the planum polare and planum temporale.
Amusia is a musical disorder that appears mainly as a defect in processing pitch but also encompasses musical memory and recognition. Two main classifications of amusia exist: acquired amusia, which occurs as a result of brain damage, and congenital amusia, which results from a music-processing anomaly present since birth.
In acoustics, a beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies.
The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct visual systems. Recently there seems to be evidence of two distinct auditory systems as well. As visual information exits the occipital lobe, and as sound leaves the phonological network, it follows two main pathways, or "streams". The ventral stream leads to the temporal lobe, which is involved with object and visual identification and recognition. The dorsal stream leads to the parietal lobe, which is involved with processing the object's spatial location relative to the viewer and with speech repetition.
Auditory verbal agnosia (AVA), also known as pure word deafness, is the inability to comprehend speech. Individuals with this disorder lose the ability to understand language, repeat words, and write from dictation. Some patients with AVA describe hearing spoken language as meaningless noise, often as though the person speaking was doing so in a foreign language. However, spontaneous speaking, reading, and writing are preserved. The maintenance of the ability to process non-speech auditory information, including music, also remains relatively more intact than spoken language comprehension. Individuals who exhibit pure word deafness are also still able to recognize non-verbal sounds. The ability to interpret language via lip reading, hand gestures, and context clues is preserved as well. Sometimes, this agnosia is preceded by cortical deafness; however, this is not always the case. Researchers have documented that in most patients exhibiting auditory verbal agnosia, the discrimination of consonants is more difficult than that of vowels, but as with most neurological disorders, there is variation among patients.
Music psychology, or the psychology of music, may be regarded as a branch of both psychology and musicology. It aims to explain and understand musical behaviour and experience, including the processes through which music is perceived, created, responded to, and incorporated into everyday life. Modern music psychology is primarily empirical; its knowledge tends to advance on the basis of interpretations of data collected by systematic observation of and interaction with human participants. Music psychology is a field of research with practical relevance for many areas, including music performance, composition, education, criticism, and therapy, as well as investigations of human attitude, skill, performance, intelligence, creativity, and social behavior.
Cortical deafness is a rare form of sensorineural hearing loss caused by damage to the primary auditory cortex. Cortical deafness is an auditory disorder where the patient is unable to hear sounds but has no apparent damage to the structures of the ear. It has been argued to be as the combination of auditory verbal agnosia and auditory agnosia. Patients with cortical deafness cannot hear any sounds, that is, they are not aware of sounds including non-speech, voices, and speech sounds. Although patients appear and feel completely deaf, they can still exhibit some reflex responses such as turning their head towards a loud sound.
Auditory agnosia is a form of agnosia that manifests itself primarily in the inability to recognize or differentiate between sounds. It is not a defect of the ear or "hearing", but rather a neurological inability of the brain to process sound meaning. While auditory agnosia impairs the understanding of sounds, other abilities such as reading, writing, and speaking are not hindered. It is caused by bilateral damage to the anterior superior temporal gyrus, which is part of the auditory pathway responsible for sound recognition, the auditory "what" pathway.
Musical memory refers to the ability to remember music-related information, such as melodic content and other progressions of tones or pitches. The differences found between linguistic memory and musical memory have led researchers to theorize that musical memory is encoded differently from language and may constitute an independent part of the phonological loop. The use of this term is problematic, however, since it implies input from a verbal system, whereas music is in principle nonverbal.
The neuroscience of music is the scientific study of brain-based mechanisms involved in the cognitive processes underlying music. These behaviours include music listening, performing, composing, reading, writing, and ancillary activities. It also is increasingly concerned with the brain basis for musical aesthetics and musical emotion. Scientists working in this field may have training in cognitive neuroscience, neurology, neuroanatomy, psychology, music theory, computer science, and other relevant fields.
Cognitive musicology is a branch of cognitive science concerned with computationally modeling musical knowledge with the goal of understanding both music and cognition.
Neuroscientists have learned much about the role of the brain in numerous cognitive mechanisms by understanding corresponding disorders. Similarly, neuroscientists have come to learn much about music cognition by studying music-specific disorders. Even though music is most often viewed from a "historical perspective rather than a biological one" music has significantly gained the attention of neuroscientists all around the world. For many centuries music has been strongly associated with art and culture. The reason for this increased interest in music is because it "provides a tool to study numerous aspects of neuroscience, from motor skill learning to emotion".
Cross modal plasticity is the adaptive reorganization of neurons to integrate the function of two or more sensory systems. Cross modal plasticity is a type of neuroplasticity and often occurs after sensory deprivation due to disease or brain damage. The reorganization of the neural network is greatest following long-term sensory deprivation, such as congenital blindness or pre-lingual deafness. In these instances, cross modal plasticity can strengthen other sensory systems to compensate for the lack of vision or hearing. This strengthening is due to new connections that are formed to brain cortices that no longer receive sensory input.
Change deafness is a perceptual phenomenon that occurs when, under certain circumstances, a physical change in an auditory stimulus goes unnoticed by the listener. There is uncertainty regarding the mechanisms by which changes to auditory stimuli go undetected, though scientific research has been done to determine the levels of processing at which these consciously undetected auditory changes are actually encoded. An understanding of the mechanisms underlying change deafness could offer insight on issues such as the completeness of our representation of the auditory environment, the limitations of the auditory perceptual system, and the relationship between the auditory system and memory. The phenomenon of change deafness is thought to be related to the interactions between high and low level processes that produce conscious experiences of auditory soundscapes.
The Levitin effect is a phenomenon whereby people, even those without musical training, tend to remember songs in the correct key. The finding stands in contrast to the large body of laboratory literature suggesting that such details of perceptual experience are lost during the process of memory encoding, so that people would remember melodies with relative pitch rather than absolute pitch.
Culture in music cognition refers to the impact that a person's culture has on their music cognition, including their preferences, emotion recognition, and musical memory. Musical preferences are biased toward culturally familiar musical traditions beginning in infancy, and adults' classification of the emotion of a musical piece depends on both culturally specific and universal structural features. Additionally, individuals' musical memory abilities are greater for culturally familiar music than for culturally unfamiliar music. The sum of these effects makes culture a powerful influence in music cognition.
The temporal dynamics of music and language describes how the brain coordinates its different regions to process musical and vocal sounds. Both music and language feature rhythmic and melodic structure. Both employ a finite set of basic elements that are combined in ordered ways to create complete musical or lingual ideas.
Auditory arrhythmia is the inability to rhythmically perform music, to keep time, and to replicate musical or rhythmic patterns. It has been caused by damage to the cerebrum or rewiring of the brain.
