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synesthesia

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types, theories and research

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synesthesia

  1. 1. 1 MPCL Arathi 1537316 Anjana 1537314 Joel 1537305 Grace 1537326 Rejin 1537307
  2. 2. • Voluntary stimulation of one sensory or cognitive pathway leads to involuntary stimulation of another. • People with synesthesia are called synesthetes. • Topic of intense research in early 19th – 20th century. • Synesthesia aids creative processes
  3. 3. Diagnosis • Diagnosis pattern suggested by Richard Cytowic - Involuntary - Projected - Durable and generic -Memorable - Emotional • Synesthetes tend to be in general women, Neurologically normal people, left handed people and can also be a hereditary phenomenon.
  4. 4. Types of Synesthesia
  5. 5. • Chromesthesia the sound to colour synesthesia, which is a type of synesthesia in which heard sounds automatically and involuntarily evoke an experience of colour.
  6. 6. • Grapheme-Color Synesthesia • This is one of the most common types of synesthesia. • A person who experiences this may associate/see individual letters or numbers with a specific color. Usually, two people won’t report the same color for letters and numbers.
  7. 7. • Hearing- touch Synesthesia It is a very rare condition in which an individual develops tactile feelings or senses upon hearing some sounds. For instance, people have claimed that they are feeling some physical discomfort especially with the background noise of the plane.
  8. 8. • Lexical-gustatory synesthesia  one of the more rare synesthesia types.  Synesthetes who experience this kind of synesthesia evoke different kinds of tastes when they hear certain words or phonemes.  According to research, associations between the words and what a synesthete is able taste are constrained by tastes he or she has experienced early in life. So, if an individual hasn’t had mashed potatoes or bacon, they won’t be tasting those flavors as a result of this variation. What a shame!
  9. 9. • Mirror-touch synesthesia a condition which causes individuals to experience the same sensation (such as touch) that another person feels. Example: if someone with this condition were to observe someone touching their cheek, they would feel the same sensation on their own cheek.
  10. 10. Number-Form Synesthesia  A number form is essentially a mental map that consists of numbers. When a person with number-form synesthesia thinks about numbers, a number map is involuntarily visualized.  It is sometimes suggested that the number forms are a product of “cross-activation” between regions in the parietal lobe – a part of the brain that is involved in numerical and spatial cognition.
  11. 11. Ordinal-linguistic personification  An individual who experiences this will associate ordered sequences with various personalities. Ordered sequences may include numbers, letters, months and so on.  For example, a person with OLP may look at the letter ‘A’ and think in his mind that ‘A’ is a rude letter.  In addition to thinking that certain ordinal sequences have a personality, a synesthete may also imbue a personality within an object.
  12. 12. Time-Space Synesthesia  People with time-space synesthesia literally experience a time-space connection. They feel like the phenomenon of time must have a physical reality.  To them, time is like the applications and icons in an iPad screen laid out for them. They can physically point at specific dates in space like you could flip or touch-select an icon in a touchpad. They see time in definitive sizes, dimensions, locations and even color
  13. 13. Tactile-emotion synesthesia  Touch-emotion synesthesia has been documented by two researchers David Brang and Vilayanur Ramachandran.  Condition in which individuals develop some emotions when they touch particular surfaces with some texture  Studies suggests that touch-emotional synesthesia is caused by the cross activation of the samatosensory cortex and the insula. The samatosensory cortex is responsible for processing the body's sensory information while insula which is located in the temporal lobe is responsible of the emotions
  14. 14. Why is 7 red? Why do you hear the colours? Why is the rainbow warm? Grace Maria Jochan 1537326
  15. 15. Learned Association Theory (Estranged Theory) • Mary Calkins • Learned association between stimuli causes multiple sensory experiences ie; distinct memories of sensory and auditory associations • Does not explain the hereditary nature of synesthesia
  16. 16. Evolutionary Theory • Focus on natural selection of traits essential for survival • Synesthesia may be was once essential and may have been present in a larger population • Synesthesia not required now, therefore only among few • Does not give explanation for what use it served in human past except for art • Synesthesia- recently discovered, so can’t compare with generations past
  17. 17. Awareness Theory • Synesthetic interactions may be common but only a few are conscious or aware of it • Cytowic (1993)- Theory of cortical suppression synesthesia occurs in the subcortical regions of limbic system and only come to conscious when cortical areas are suppressed
  18. 18. Neural connectivity Theories • Maurer (1997) – Neonatal synesthesia theory Neural connections between visual and auditory areas are found in infants. Later these connections are pruned normally • Ramachandran (2001) – Cross –wiring Theory Synesthesia occurs due to functional connections between specific senses either through excessive proliferation or defective pruning of connections
  19. 19. RECENT RESEARCH REPORTS
  20. 20. A Single Case fMRI Study of Visually Induced Olfactory Perception. (Chan, 2014)  In this study we describe a single individual (LJ) who experiences a concurrent olfactory stimulus when presented with congruent visual images. For some visual stimuli, he perceives a strong and automatic olfactory percept, which has existed throughout his life. In this study, we explore whether his experiences are a new form of synesthesia or simply vivid imagery. Unlike other forms of synesthesia, the concurrent odour is congruent to the visual inducer. For example, a photograph of dress shoes will elicit the smell of leather.  LJ and several control participants were introduced with 75 images of everyday objects. Their task was to indicate the strength of any perceived odours induced by the visual images. LJ rated several of the images as inducing a concurrent odour, while controls did not have any such percept. Images that LJ reported as inducing the strongest odours were used, along with colour-matched control images, in the context of an fMRI experiment.
  21. 21. Cont..  There was an increased BOLD response in the piriform cortex (primary olfactory cortex) for the odour-inducing images compared to the control images in LJ. There was no difference in BOLD response between these two stimulus types in the control participants.  A subsequent olfactory imagery task did not elicit enhanced activity in the piriform cortex in LJ, suggesting his perceptual experiences may not be based on olfactory imagery.
  22. 22. Colored-Speech Synesthesia Is Triggered by Multisensory, Not Unisensory, Perception. (Bargary, GaryBarnett, Kylie J.Mitchell, Kevin J.Newell, Fiona N. 2009)  Researcher tested 9 linguistic-color synesthetic and found that the colors induced by spoken words are related to what is perceived (i.e., the illusory combination of audio and visual inputs) and not to the auditory component alone. Research findings indicate that color-speech synesthesia is triggered only when a significant amount of information processing has occurred and that early sensory activation is not directly linked to the synesthetic experience.
  23. 23. References  Chan, J. J. (2014). Synaesthesia or Vivid Imagery? A Single Case fMRI Study of Visually Induced Olfactory Perception. Multisensory Research, 27(3/4), 225-246.  Bargary, GaryBarnett, Kylie J.Mitchell, Kevin J.Newell, Fiona N. 2009. "Colored-Speech Synaesthesia Is Triggered by Multisensory, Not Unisensory, Perception." Psychological Science (Wiley-Blackwell) 20, no. 5: 529-533. Psychology and Behavioral Sciences Collection, EBSCOhost (accessed September 6, 2015).

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