CROSSACTIVATION HYPOTHESIS

   In hallucinations research the term cross-activation hypothesis is a generic term for a group of hypothetical models that attribute the mediation of certain types of hallucinations to 'cross-talk' between two or more adjacent cerebral areas. The cross-activation hypothesis constitutes one of the major explanatory models for the mediation of * synaesthesias, i.e. phenomena in which the perceptual stimulation of one sensory modality leads to a hallucinatory experience in a second sensory modality. *Number-colour synaesthesias, for example, have been tentatively explained by the American neuroscientists Vilayanur S. Ramachandran (b. 1951) et al. as resulting from a genetically determined hyperconnectivity between cerebral colour and number areas. These areas are located within the fusiform gyrus (in so-called 'lower' number-colour synaesthetes), or within the angular gyrus (in so-called 'higher' number-colour synaesthetes). Theoretically, the cross-activation hypothesis might also be applicable to phenomena such as the * reflex hallucination, the * creative hallucination, the * functional hallucination, and the * Tullio phenomenon, which are all characterized by a hallucinatory experience occurring in reaction to a regular sense perception.

   References

   Ramachandran, V.S., Hubbard, E.M. (2001). Synaesthesia - A window into perception, thought and language. Journal ofConscious-ness Studies, 8, 3-34.