Music And The Brain Flashcards
What is music?
- not one definition
- varies with culture
- can involve instruments and vocals
- in research often Western view –> there is much more to music
Animal music
- animals respond to music
- question remains whether animals produce music –> possible
Auditory processing - Ear
Eardrum - starts vibrating when soundwaves hit
Ossicles (tiny bones) - amplify vibrations
Cochlea - filled with cochlear fluid
- sound waves generate waves
- basilar membrane vibrates and hair cells transduce vibrations into electrical signals
- tonotopy codes different frequencies (pitches) –> are preserved throughout the auditory network
Auditory processing - Brain
- electrical signal from hair cells (cochlea) travel along auditory nerve
- to the brain stem: helps process sound localisation by comparing input from both ears
- to the thalamus
- and to the auditory cortex
- music engages in a variety of networks
Predictive coding of music (PCM) model
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Synesthesia
- syn = together/joining
- aesthesia = perception/sensation
= a rare condition/trait at its most fundamental level, involves the uniting of two qualities that the average person does not experience together
Inducer = stimulation in one sense
Concurrent = an unstimulated second sense
Chromesthesia
= coloured-hearing, a phenomenon in which colour images are evoked by auditory stimuli
–> sound to colour
- sound evokes colour
- BUT colours do not evoke sound perception
Key features of synesthesia
Involuntary and automatic
- occurs passivley, without consciousness effort or control
- is triggered by specific stimuli
consistency over time
- associations remain stable
- over 90% consistency for stimuli like grapheme-colour synesthesia
Idiosyncratic nature
- highly personal
- the same stimulus elicits unique associations for each individual
Unidirectionality (mostly)
- stimuli often only elicit response in one direction (sound to colour BUT not colour to sound)
- cases of bi-directional synesthesia exist
Additive perception
- enhances perception by adding sensations without replacing or masking normal sensory inputs
emotional significance
- perceptions feel real and meaningful
Neural basis of chromesthesia
Auditory cortex
- superior temporal gyrus (STG), superior temporal sulcus (STS), middle temporal gyrus (MTG)
- secondary auditory cortex encompasses Wernicke’s area
- processes sound stimuli and plays a central role in auditory perception
Visual cortex
- Area V4
- responsible for colour perception
- activated during sound stimulation in chromesthesia –> linking auditory and visual experiences
study using diffusion tensor imaging
- showed enhanced structural connectivity between frontal lobe and visual and auditory association areas
- inferior fronto-occipital fasiculus (IFOF) = white matter tract connecting visual and auditory cortex association areas in occipital and temporal lobes with the frontal lobe (enhanced white matter connectivity in right hemisphere in chromesthesia)
Plausible causes:
Cross-activation theory
- ‘all born with but typically goes away at age 2’ (Salinas)
- arises from increased connectivity between adjacent sensory regions –> potentially due to reduced neural pruning during development
- diminished pruning may lead to excess neural connections, facilitating cross-activation between sensory modalities
Axonogenesis genes
- rare genetic variants perfectly co-segregating with the trait in three unrelated multigenerational families ( >5 affected)
Core set of six genes related to axonogenesis
- among other cortical sites –> expressed throughout development in auditory and visual cortex
- responsible for microtuble function-essential for axonal growth and guidance
- altered function may contribute to atypical neural wiring –> enhanced connectivity between auditory and visual brain regions
Disorders: Musicogenic epilepsy
- rare epilepsy syndrome
- seizures are elicited by music - develops later than epilepsy with audigenic seizures (average onset: 28 years)
- syndrome is associated with affective factors
- led to hypothesis: pathogenesis may relate more to the affective than auditory content of music - syndrome with focal-onset seizures
- origin is temporal lobe
- right-sided predominance
- functional signal change in regions associated with emotional processing
-> limbic structures: hippocampus, entorhinal cortex, cingulum, amygdala
–> nucelus accumbens
–> orbitofrontal and prefrontal cortex
- EEG and fMRI: signal changes within the bilateral frontal and right temporal lobes
Disorders: Musical hallucinations (MH)
= a rare type of auditory hallucination characterised by the perception of musical sounds in the absence of any external source of music
- content often familiar: vocal, instrumental, both
Causes
- peripheral: such as hearing impairement (strongly associated with MH)
- central: such as seizures or strokes (particularly temporal cortex), brain atrophy
- temporal lobe epilepsy
- intake of some pharmaceuticals
- psychiatric disorders such as depression or schizophrenia
- conjunction of aging with hearing impairment or other factors –> imbalance of inhibition and excitation towards a pathological activation of the auditory and musical systems of the brain
–> different from voluntary or involuntary imagery
Treatment:
- depends on underlying cause
- listening to actual music or increase in external auditory stimulation –> can reduce severity of persistent MH
Amusia
= tone deafness, tones are not recognised as tones
- neither pitch, melody or rhythm (therfore music too) are perceived as such –> all notes sound the same
- not linked to hearing impairment or other diseases
Congenital amusia
= disconnection syndrome caused by anomalous recurrent processing in the right frontotemporal (dorsal) network
- neurodevelopmental disorder
- coritcal anomalies in both right and left auditory cortex
- also structural abnormalities, specifically in the right and left inferior frontal gyrus
Acquired amusia
= tone deafness, common after stroke
- right temporal areas (superior and middle temporal gyrus)
- subcortical regions (striatum, globus pallidus)
- areas in the right frontotemporal network
- additionally, lesions in the insulation and frontoparietal operculum
Music therapy
- noninvasive, cheap and convenient
- improves gait, upper limb function, depression, cognitive function and pain
- can promote language function in aphasia patients after stroke
- many forms of music therapy –> melodic intonation therapy, singing, playing muscial instruments
Musical therapy: aphasia
Aphaisa = one of the most common symptoms after stroke
- impaired in the ability to comprehend and produce language
Melodic Intonation Therpay
= musical treatment program and widley used for the rehabilitation of patients with speech production disorders
- might restore language circuitry indirectly –> enhances shared components between music and language (pitch and/or rhythm)
- lyrics, rhythm and meldoy are considered to play an important role in improving the language function which mainly promotes the plasticity of the cerebral cortex and therefore language
