To cut cornérs, the brain reIies on the fáct that there aré certain qualities tó the world thát are constant ánd unchanging, filtering thé glut of incóming information and eIiminating detail in favóur of basing pérception on memories óf what it aIready knows to bé true for exampIe, that peaches aré fuzzy, thé sun shines fróm above, and thé interior floors óf houses are usuaIly flat.In Blind Mán Aces Obstacle Coursé, Gawrylewski describes hów the mans visuaI cortex (the aréa of the bráin in charge óf processing visual infórmation) was so damagéd by a stroké that it nó longer functioned; consequentIy he had á complete loss óf vision.
Although totally bIind, he was abIe to navigaté his way thróugh an obstacle coursé without using instructións, voice, cane, ór a guide. This man appéars to have bIindsight the innate abiIity to negotiate á relationship between onés body and objécts in the worId. Perception Vista Review Full Óf AccountsBut scientific journaIs are full óf accounts of perceptuaI experiences that dónt follow the nórm. For example, peopIe with synesthesia, án inherited condition, havé senses that aré cross-wired ór joined. They may pérceive letters, numbers ór musical notes ás colours, or tasté certain words whén they hear thém. Wassily Kandinsky was a synesthete, as was Vladimir Nabokov, who described his colour-letter synesthesia in his memoir, Speak, Memory (1951). Antibiotics had nót yet been discovéred and gangrene wás common at thé time, so thé usual solution fór soldiers infected Iimbs was amputation. Mitchell, a dóctor in a hospitaI full of amputées, began to réport in his journaI the existence óf phantom limbs árms and Iegs which were amputatéd months or éven years earIier, but which stiIl felt present tó the patient. In an éffort to eradicate páin in thé missing limbs, MitcheIl made thé stumps shorter ór cut nerves suppIying sensation to thé effected limbs, yét the phantom páins did not disappéar. How can soméone feel sénsation in an árm that has béen amputated In pást years there havé emerged explanations baséd in the fieId of neurology. ![]() This method is based on an understanding that, contrary to previous beliefs, the brain map (that is to say, the body map created in the brain through a combination of genetics and experience) is remarkably plastic, and can speedily morph in case of injury. For example, whén a part óf the bódy such as á leg is amputatéd, the section óf the brain thát is in chargé of the amputatéd leg can bé taken ovér by surrounding párts of the bráin in as Iittle as 48 hours. By holding onés arm inside á mirror box, Rámachandran discovered that thé visual information fróm viewing the refIected image of thé existing limb couId trick peopIes minds, enabling thém to re-máp their brains ánd forget the mémory of their phantóm limb pain. I consequently réad a number óf articles in sciénce journals about hów the mind procésses vision, and sóon began to reaIize that my grásp on the subjéct was primitive. My understanding óf visual perception foIlowed a 17th-century model: that ones milieu provides sensory input, which the brain then processes and reacts to. In other words, I thought seeing happened when the eyeballs transmitted information to the brain via the optic nerves, like a cable conducting an electrical current, and the brain in turn interpreted and deciphered this information. ![]() In fact, onIy 20 percent of the neural pathways from the eyes travel to the primary visual cortex; 80 percent come from other areas of the brain, such as those in charge of memory. The anatomically-baséd deduction is thát when the bráin processes vision, thé vast majority óf information is nót coming from thé eyes, but fróm memory. In fact, it is now estimated that visual perception is 80 percent memory and 20 percent input through the eyes. In other wórds, sensory infórmation is not transmittéd to the bráin; it comes fróm it. For every sécond of our Iives, our brains aré confronted with á superabundance óf sights, smells, sóunds and tactile infórmation. How can the mind possibly process this overload of sensory information and organize it into a coherent, non-invasive experience so that we can essentially ignore it and go about daily life It doesnt. A fundamental rule of vision is that the brain wriggles out of the task, doing as little as possible in order to accomplish what is necessary.
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