Form constants: Difference between revisions

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[[File:Form constant.jpg|300px|thumb|right|An example of a form constant.]]'''Form constants''' are one of several geometric patterns which are recurringly observed during hallucinations and altered states of consciousness. Form constants can be categorized into four types: lattices (including honeycombs, checkerboards, and triangles), cobwebs, tunnels, and spirals.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>

Form constants appear in near-death experiences and sensory experiences of those with [[synesthesia]]. Other triggers include psychological stress, threshold consciousness ([[hypnagogia]]), insulin hypoglycemia, the delirium of fever, epilepsy, psychotic episodes, advanced syphilis, sensory deprivation, photostimulation, electrical stimulation, crystal gazing, migraine headaches, dizziness and a variety of drug-induced intoxications. These shapes may appear on their own or with eyes shut in the form of [[phosphenes]], especially when exerting pressure against the closed eyelid.

Form constants appear in near-death experiences and sensory experiences of those with [[synesthesia]]. Other triggers include psychological stress, threshold consciousness ([[hypnagogia]]), insulin hypoglycemia, the delirium of fever, epilepsy, psychotic episodes, advanced syphilis, sensory deprivation, [https://en.wikipedia.org/wiki/Photostimulation photostimulation], electrical stimulation, crystal gazing, migraine headaches, dizziness and a variety of drug-induced intoxications. These shapes may appear on their own or with eyes shut in the form of [[phosphenes]], especially when exerting pressure against the closed eyelid.

It is believed that the reason why these form constants appear has to do with the way the visual system is organized, and in particular in the mapping between patterns on the retina and the columnar organization of primary visual cortex. Concentric circles in the retina are mapped into parallel lines in visual cortex. Spirals, tunnels, lattices and cobwebs map into lines in different directions. This means that if activation spreads in straight lines within the visual cortex, the experience is equivalent to looking at actual form constants.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>

It is believed that the reason why these form constants appear has to do with the way the visual system is organized, and in particular in the mapping between patterns on the retina and the columnar organization of the primary visual cortex. Concentric circles in the retina are mapped into parallel lines in the visual cortex. Spirals, tunnels, lattices and cobwebs map into lines in different directions. This means that if activation spreads in straight lines within the visual cortex, the experience is equivalent to looking at actual form constants.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>

==External links==

*[[wikipedia:Form constant|Form constant (Wikipedia)]]

==References==

@@ Line 1: / Line 1: @@
 [[File:Form constant.jpg|300px|thumb|right|An example of a form constant.]]'''Form constants''' are one of several geometric patterns which are recurringly observed during hallucinations and altered states of consciousness. Form constants can be categorized into four types: lattices (including honeycombs, checkerboards, and triangles), cobwebs, tunnels, and spirals.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>
-Form constants appear in near-death experiences and sensory experiences of those with [[synesthesia]]. Other triggers include psychological stress, threshold consciousness ([[hypnagogia]]), insulin hypoglycemia, the delirium of fever, epilepsy, psychotic episodes, advanced syphilis, sensory deprivation, photostimulation, electrical stimulation, crystal gazing, migraine headaches, dizziness and a variety of drug-induced intoxications. These shapes may appear on their own or with eyes shut in the form of [[phosphenes]], especially when exerting pressure against the closed eyelid.
+Form constants appear in near-death experiences and sensory experiences of those with [[synesthesia]]. Other triggers include psychological stress, threshold consciousness ([[hypnagogia]]), insulin hypoglycemia, the delirium of fever, epilepsy, psychotic episodes, advanced syphilis, sensory deprivation, [https://en.wikipedia.org/wiki/Photostimulation photostimulation], electrical stimulation, crystal gazing, migraine headaches, dizziness and a variety of drug-induced intoxications. These shapes may appear on their own or with eyes shut in the form of [[phosphenes]], especially when exerting pressure against the closed eyelid.
-It is believed that the reason why these form constants appear has to do with the way the visual system is organized, and in particular in the mapping between patterns on the retina and the columnar organization of primary visual cortex. Concentric circles in the retina are mapped into parallel lines in visual cortex. Spirals, tunnels, lattices and cobwebs map into lines in different directions. This means that if activation spreads in straight lines within the visual cortex, the experience is equivalent to looking at actual form constants.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>
+It is believed that the reason why these form constants appear has to do with the way the visual system is organized, and in particular in the mapping between patterns on the retina and the columnar organization of the primary visual cortex. Concentric circles in the retina are mapped into parallel lines in the visual cortex. Spirals, tunnels, lattices and cobwebs map into lines in different directions. This means that if activation spreads in straight lines within the visual cortex, the experience is equivalent to looking at actual form constants.<ref> Bressloff, Paul C.; Cowan, Jack D.; Golubitsky, Martin; Thomas, Peter J.; Weiner, Matthew C. (March 2002). "What Geometric Visual Hallucinations Tell Us About the Visual Cortex" Neural Computation (The MIT Press) 14 (3): 473–491. | http://www.mitpressjournals.org/doi/abs/10.1162/089976602317250861</ref>
+==External links==
+*[[wikipedia:Form constant|Form constant (Wikipedia)]]
 ==References==
 <references/>