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Acquired Synesthesia in Retinitis Pigmentosa

Acquired Synesthesia in Retinitis Pigmentosa,10.1093/neucas/5.4.293,Neurocase,K. C. Armel,V. S. Ramachandran

Acquired Synesthesia in Retinitis Pigmentosa   (Citations: 30)
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Patient PH developed retinitis pigmentosa in childhood and progressively lost his vision until he became completely blind at 40 years old. At age 42, he started experiencing vivid 'synesthesia'; tactile stimuli on the hand evoked a vivid visual sensation of 'movement', 'expansion' or 'jumping'. Intriguingly, the synesthesia was much more vivid when the hand was in front of the face rather than behind. The effect is unlikely to be confabulatory since touch thresholds (Semmes Monofilaments) were normal and identical for hand in front versus hand behind the head, while 'thresholds' for evoked visual sensations were significantly higher for the 'behind' condition. Also, the critical fusion frequency for the tactile sensation was much higher than the visually evoked ones. We propose three explanations. (i) 'Remapping' or 'cross-talk'. As a result of de-afferentation, sensory input to the somatosensory pathways (e.g. insular cortex) also innervates extrastriate visual areas. (ii) When a person is touched, there may be spontaneously evoked tactile associative 'memories' that would not normally evoke actual visual qualia because of competing 'spontaneous activity' from the visual pathways. However, upon de-afferentation, the associations may be experienced as synesthesia. (iii) After de-afferentation, the 'back projections' to somatosensory areas from visual areas may be strengthened.
Journal: Neurocase , vol. 5, no. 4, pp. 293-296, 1999
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    • ...Additionally, Ramachandran and colleagues have reported two further cases where touch is the trigger, causing either experiences of movement and jumping (Armel & Ramachandran, 1999), or of powerful and consistent emotions (eg, depression) which were verified by skin conductance responses (Ramachandran & Brang, 2009)...

    Julia Simneret al. The color of touch: A case of tactile–visual synaesthesia

    • ...Additionally, Ramachandran and colleagues have reported two further cases where touch is the trigger, causing either experiences of movement and jumping (Armel & Ramachandran, 1999), or of powerful and consistent emotions (eg, depression) which were verified by skin conductance responses (Ramachandran & Brang, 2009)...

    Julia Simneret al. The color of touch: A case of tactile–visual synaesthesia

    • ... Partial evidence supporting this idea comes as sensory deprivation and deafferentation (i.e., loss of sensory input through the destruction of sensory nerve fibers) can lead to synesthetic-like experiences. For example, after early visual deprivation due to retinitis pigmentosa, touch stimuli can produce visual phosphenes ...

    David Branget al. Survival of the Synesthesia Gene: Why Do People Hear Colors and Taste ...

    • ...We suggested too, that some forms of the condition might result from hypertrophy or hyperactivity of ‘back projections’ (Armel & Ramachandran, 1999) that are known to exist linking difference stages in the virtual hierarchy; eg, high level visual areas representing more abstract shapes might feedback and activate lower sensory maps...

    David Branget al. Visual field heterogeneity, laterality, and eidetic imagery in synesth...

    • ...Although rare, touch-color synaesthesia has been noted in synaesthetes who later became blind (Steven & Blakemore, 2004; Wheeler & Cutsforth, 1921), in a blind person who subsequently acquired synaesthesia (Armel & Ramachandran, 1999), and in developmental cases of synaesthesia in sighted individuals (Smith, 1905; Ward, Banissy, & Jonas, 2008)...

    Jörg Jewanskiet al. A Colorful Albino: The First Documented Case of Synaesthesia, by Georg...

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