Ecem Aşık

1. Ecem Aşık

2. Outline • Definition of synesthesia • Types of synesthesia • Neurological basis of synesthesia • Non-idiopathic Synesthesia • Idiopathic Synesthesia • Uninhibited Natural State Hypothesis • Neonatal Synesthesia Hypothesis • The Cross Talk Hypothesis

3. What isSynesthesia? • Perceiving a stimulus of one sensory modality within other senses • A neurological condition in which stimulation in one sensory modality triggers involuntary sensory experiences in another modality • Hearing the word “Thursday”  orange taste • Eating a broccoli  seeing the color blue

4. More about Synesthesia • Many synesthetic do not know their unusual perception • 50% more likely to co-occur • More common in children and women (72%) • Generally having synesthesiasince childhoodand disappears after puberty • Hereditary

5. Types of Synesthesia • It is estimated that there are 61 different types of synesthesia • Common types: • graphemes (letters or numbers)color • days of week/months of year  color • sounds  color • smells  color • words tastes • vision sounds

6. Synesthesia and the Brain • Causesof synesthesia may be • non-idiopathic:resultingfrom aknown etiology or mechanism which is acquired and produced synesthesia • Spinal Cord Damage Induced • Drug Induced • Brain Damage Induced • idiopathic:the person having experienced synesthesia as long as they can remember • Uninhibited Natural State • Neonatal Synesthesia Hypothesis • The Cross Talk Hypothesis

7. Non-Idiopathic Synesthesia • Spinal Cord Damage Induced: • Atouch above a lesion causes a local sensation a sensation in other, unrelated parts • Brain Damage Induced: • A damage to anterior portions of the brain, often the optic nerve • Drug Induced: • Drugs,especially hallucinogenic compounds,such as mescaline, peyote or LSD.

8. Uninhibited Natural State Hypothesis • Everyone is synesthetic in an unconscious level • A stimulus causes a rebalancing of regional metabolism • With synesthesia, the stimulus causes parts of the brain to become electrically disconnected from one another • The normal processes of the limbic system are released and can be sensed in our conscious state. • Little evidence

9. Neonatal Synesthesia Hypothesis • A normal phase in development. • Allbabies experience sensory input in an undifferentiated wayup to about 4 months. • At a critical period, the senses may become increasingly modular to make more rapid and efficient information processing. • In adults with synesthesia,the process of modularization of the senses may not have been completed. • Connections between different sensory modalities in synesthetic may have either grown or not died off.

10. The Cross Talk Hypothesis • The area in the brain responsible for recognizing letter/numeral graphemes(in green) is located in the left hemisphere just next to the color perception area called V4 (in red). • Everytime there is activation of neurons representing the recognition of numbers in the cortex, these neurons also trigger the activation of the neurons which represent color perception.

11. Conclusion • An extremely complex phenomenon • The cross-talk hypothesis is more widely applicable and testable

12. References • Cytowic, R.E. (1995). Synesthesia: Phenomenology and neuropsychology. Psyche, 2(10), 1-22. • Grossenbacher, P. & Lovelace, C.(2001). Mechanisms of Synesthesia:Cognitiveand Physiological Constraints. Trends in CognitiveNeurosciences, 5(1), 36-41. • Ramachandran, V. & Hubbard, E. (2001). Psychophysical Investigations into the Neural Basis of Synaesthesia. Proceedings of the Royal Society of London, 268, 979-983. • Ramachandran, V. & Hubbard, E. (2001). Synaesthesia- A window into perception, thought, and language. Journal of Consciousness Studies, 8(12), 3-34. • Simner, J. Mulvenna, C., Sagiv, N., Tsakanikos, E., Witherby, S., Fraser, C., Scott, K. & Ward, J. (2006). Synaesthesia: The prevalence of atypical cross-modal experience. Perception, 35, 1024-1033. • Simner, J. (2012). Defining synaesthesia. British Journal of Psychology, 103,1-15.