synaesthesia

Question 1

perception is a brain process

Answer 1

• Eyes, ears, nose, mouth and skin have receptors that convert physical signals to neural signals.
  
  • The brain perceives the world based on information from each sense, and form information from different senses and from stored knowledge of the world.
• Physical world not the same as the perceived world (e.g., visual and auditory illusions).

Question 2

multi-sensory perception

Answer 2

• Multi-sensory perception - the process by which information from different senses is brought together.
  
  • Advantages:
    1. More efficient and accurate than processing each sense separately.
    2. Enables us to establish a single coherent perspective of the world.
    
    3. Enables us to act on the world.

Question 3

• Colour influences taste.
  
  • Sound influences hardness.
    Vision influences sound.

Question 4

the McGurk illusion

Answer 4

• “BA” is presented to ears.
  
  • “GA” is presented to eyes
  • subject perceives “DA”.
• fMRI shows that silently looking at moving lips activates the auditory part of the brain (Calvert et al, 1997).

Question 5

what is synaesthesia?

Answer 5

• Concrete perceptual experiences (i.e., not imagination, memory association, or a ‘sixth sense’).
  
  • Elicited by stimuli in the external environment or by internal thoughts (i.e., not hallucinations which occur spontaneously).
• Automatic and cannot be suppressed (i.e., unlike thinking and imagining).

Question 6

developmental synaesthesia

Answer 6

• Runs in families and has a genetic component (Baron-Cohen et al 1996).
  
  • Equally common in males and females.
  • Present throughout the lifespan.
• Often triggered by linguistic stimuli (letters, numbers, words, etc).

Question 7

acquired synaesthesia

Answer 7

• Sensory deprivation or pharmacologically triggered.
• Effect are temporary not permanent.

Question 8

brain differences

Answer 8

• In synaesthetes, there is exuberant connectivity across whole brain.
• Not just in regions related to synaesthesia.

Question 9

is this for real?

Answer 9

• High internal consistency.
  
  • Functional imaging studies:
    1. Nunn et al, 2002:
    2. Synaesthesia activates - colour area (left v4)
    3. Controls do not - even if trained to associate colour, even if imagining colour.
• Synaesthetic stroop effect.

Question 10

links between vision and touch

Answer 10

• Blakemore et al, 2005, fMRI.
• Watching somebody else being touched activates our own somatosensory cortex (but watching an object touched does not).

Question 11

number-space synaesthesia

Answer 11

• Many synaesthetes see numbers in spatial arrays.
  
  • Small numbers = LEFT
  • Large numbers = RIGHT
  • But we all are faster at responding to small number with left and large numbers with right hand (Dehaene et al, 1993).
  • A universal mechanism?

Question 12

does everyone have synaesthesia

Answer 12

• Differences in genes, brain, cognition.
  
  • Some have synaesthesia, most people do not.
• Some synaesthetes have it stronger than others.

Question 13

summary

Answer 13

• Science has established that synaesthesia is a real phenomenon in which a few people can have different perceptual experiences from the rest of the world.
• Synaesthesia may shed light on general mechanisms, present in us all, that integrates different senses and links perception to language, thought and memory.