The term dendropsia comes from the Greek words dendron (tree) and opsis (seeing). It was coined in or shortly before 1999 by the British neuroscientists Dominic H. ffytche and Robert J. Howard to denote a * geometric hallucination consisting of irregular branching forms reminiscent of trees, branches, or roadmaps. These hallucinated branching forms are executed in one or more colours, and occasionally display adnexes reminiscent of leaves or needles. Dendropsia has been reported in elderly individuals experiencing * visual hallucinations and * illusions (as in * Charles Bonnet syndrome, for example), in degenerative eye disease, and in * hallucinogen-induced hallucinatory states. Pathophysiologically, dendropsia tends to be associated with central rather than peripheral mechanisms. The current 'central' model attributes the perception of branching forms to neuronal discharges affecting the retinocortical map (i.e. the patterns of connection between the retina and striate cortex), and/or neuronal circuits lying within striate cortex. Phenomenologi-cally, dendropsia is distinguished somewhat arbitrarily from *tessellopsia. Moreover, dendropsia should not be confused with the * Purkinje effect, aphysiological* entoptic phenomenon consisting of irregular branching forms that can be observed by shining light onto the eyeball.
   ffytche, D.H., Howard, R.J. (1999). The perceptual consequences of visual loss: 'positive' pathologies of vision. Brain, 122, 1247-1260.
   Santhouse, A.M., Howard, R.J., ffytche, D.H. (2000). Visual hallucinatory syndromes and the anatomy of the visual brain. Brain, 123, 2055-2064.

Dictionary of Hallucinations. . 2010.

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  • geometric hallucination —    Also known as geometrical hallucination, geometric visual hallucination, and optogeometric illusion. All four terms can be traced to the Greek noun geometria, which means land surveying. They are used to denote a * formed visual hallucination… …   Dictionary of Hallucinations

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  • Purkinje figure —    Also known as Purkyne figure. Both eponyms refer to the Bohemian physiologist Johannes Evangelista Purkyne (1787 1869). They are used to denote an entoptic phenomenon consisting of a black, tree like structure that can be made visible under… …   Dictionary of Hallucinations

  • tessellopsia —    Also known as tessellated hallucination. Both terms are indebted to the Greek words tessera (a small tile used in mosaics), and opsis (seeing). The term tessellopsia was coined in or shortly before 1999 by the British neuroscientists Dominic H …   Dictionary of Hallucinations

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