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
Music therapy and Parkinson’s
- music-based rehabilitation for gait, motor timing,
coordination, postural control, and balance improvement
–> considered an effective for patients with
PD and other motor disorders
Networks implicated in movments
- basal ganglia-thalamo-notor cortices
- cerebellar-thalamo-motor cortices
–> are also conntected to auditory cortex
- auditory stimuli can reinforce the remaining activity of the basal ganglia-thalamo-motor cortices and cerebellar-thalamo-motor cortices networks –> ameliorating motor defecits
- dopamine release is higher when listening to familiar music rather than aleatory (random) music
Music therapy and dementia
- people with dementia enjoy music –> ability to respond to it is preserved even when verbal communication is no longer possible
- familiar music as mnemonic source, eliciting emotions and associations that had been long forgotten –> access to memories and thoughts that had seemingly been completly lost
- sense of community in group sessions
- significantly imporved verbal and language fluency
- reduced behavioural and psychological symptoms (anxiety, depression, apathy)
