synaesthesia

what is synaesthesia?

a neurological phenomenon where the stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second, unrelated pathway

state five key characteristics of synaesthesia

• consciousness

• consistency

• idiosyncrasy

• unidirectionality

• automatic

what percentage of the population is reported by simner (2006) to experience synaesthesia?

4%

how are crossmodal/cross-directional correspondences different ffrom synaesthesia?

there is no conscious experience to CDCs- it is more likely that they simply influence synaesthesia

how many self-reported types of synaesthesia are there?

~75, and it is common for a synaesthete will have more than one type of synaesthesia

state a limitation of theories of synaesthesia

there is no way no genuinely validate self-report synaesthesia

describe the familial link of synaesthesia

40% of people with synaesthesia report having one or more first degree relatives with synaesthesia (it was originally thought to be linked to the X chromosome, but this has sicne been debunked by simner (2006)

which chromosomes is auditory-visual synaesthesia linked to?

• 2q

• 5q

• 6p

• 12p

which chromosome is linked to coloured sequence synaesthesia?

16q

what are the five clusters of synaesthesia subgroups?

• coloured music synaesthesia

• coloured sequence synaesthesia

• coloured sensation synaesthesia

• non-visual sequela synaesthesia

• spatial sequence synaesthesia

describe the neonatal synaesthesia theory

infants have connections between sensory stimuli which are usually segregated in adulthood. synaesthesia is caused by less pruning of seemingly non-functional arbitrary connections in childhood, causing hyper-connectivity

true or false; synaesthesia develops at some point during life, according to the neonatal synaesthesia theory?

false; simner (2006) stated that most synaesthetes have had it all their life

describe hubbard and ramachandran’s cross-activation theory of synaesthesia

cross-wiring between areas responsible for processing information is used to explain synaesthesia; this was mainly proposed to explain grapheme-colour synaesthesia, which was thought to be the most common type at the time.

what is the disinhibited feedback theory of synaesthesia?

the theory that feedforward activation travelling in the area of multiple pathway integration feeds back down another pathway due to specific disinhibition

describe the re-entrant theory of synaesthesia

similar to disinhibited feedback theory; it was adapted mainly to explain grapheme-colour synaesthesia as it includes proposed specific cortical areas involved. it states that higher-level processing feeds back to grapheme and colour processing areas, however it is critically assumed in this theory that the grapheme is identified before concurrent is triggered

name one difficulty across all theories of synaesthesia

they are all simply based on grapheme-colour synaesthesia. this is an issue due to the existence of many different types of synaesthesia

describe the link between mental imagery and synaesthesia

synaesthetes report to have higher levels of mental imagery, however this is specific to the types of synaesthesia which a person has

is synaesthesia linked better by research to autism-spectrum disorder or anxiety disorder?

anxiety; a link was found by Carmichael et al (2018), who did not find a link with ASD

how does grapheme-colour synaesthesia change and develop with age?

• children aged 6/7 have fixed colour associations with ~30% of graphemes

• children aged 7/8 have fixed colour associations with ~50% graphemes

• children aged 10/11 have fixed colour associations with ~70% graphemes

• therefore, number of fixed colour associations increases with age throughout childhood

what are the two types of explicit measures for synaesthesia?

• consistency measures (e.g. synaesthesia battery)

• self-report questionnaires

what is the main implicit measure used for synaesthesia?

the synaesthesic stroop task

what is the stroop task?

an explicit measure of synaesthesia in which synaesthetes are asked to pair the inducer (e.g. grapheme) with the congruent/incongruent concurrent (e.g. colour). this can show that there is interference, if it takes longer to complete a task when the inducer and concurrent are not congruent

which five experiences can cause the development of synaesthesia later in life?

• sensory deprivation

• brain damage

• recreational drug use

• hypnosis

• training

describe the case study linking sensory deprivation to synaesthesia

JF developef braille-colour synaesthesia after going blind in adulthood, as well as sequence-space and sequence-colour synaesthesia

describe two case studies in which brain damage caused synaesthesia

• in one case, a lesion in the right thalamus in adulthood created sound-touch synaesthesia

• it has been noted that auditory-visual synaesthesia can also develop from brain damage AND sensory deprivation

which three hallucinogenic drugs are reported to cause synaesthesia-like experiences?

• LSD

• mescaline

• psilocybin

which two types of synaesthesia have been reported from LSD use?

• grapheme-colour

• sound-colour

which type of synaesthesia can be induced in non-synaethetes through hypnosis?

grapheme-colour

which characteristics do induced synaesthesia-like experiences have to meet for them to be classified as developmental synaesthesia?

• inducer specificity

• consistency

• automaticity

• consciousness

how long does induced synaesthesia last for each method of induction?

• drugs/hypnosis; short term

• training; longer, but extinguishes

• sensory deprivation/brain damage: years +