Visual Hallucinations: Another Argument for Brain Equals Behavior

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Visual Hallucinations: Another Argument for Brain Equals Behavior

A hallucination is defined as a sensory perception in the absence of an externally generated stimulus (4). They are different from illusions in that in an illusion an external object actually exists and is perceived, but is misinterpreted by the individual (4). Main forms of hallucinations are be visual, auditory, and olfactory, but since we have been discussing vision and interpretation of reality lately this paper will focus only on those that are visual. And I will attempt through the examination of two different types of visual hallucinations - release hallucinations and those experienced by schizophrenics - to make an argument for brain equals behavior.

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For example, patients hallucinating in color showed activity in an area known to be the color center in the fusiform gyrus while a patient hallucinating in black and white showed activity outside of this region (3). Likewise, activity was found in the middle fusiform gyrus which responds to visual objects in a patient who hallucinated objects, and in the collateral sulcus which responds to visual textures in patients who hallucinated things like fences and brickwork (3). So it seems that whatever is responsible for hallucinations of this sort stimulates them through the same means we use to interpret our visual reality under normal circumstances.

These hallucinations are experienced identically to normal seeing, however they are distinguishable from reality because of their content and the fact that they often appear in clearer and greater detail than Charles Bonnet patients (whose visions have been impaired or lost) would naturally see (3). These "release" hallucinations are often not reported to doctors and psychologists because the individuals experiencing them are aware that what they are seeing are hallucinations and are afraid of being judged as crazy by those people that they might tell (5).

These are different from the visual hallucinations experienced by people suffering from schizophrenia because schizophrenics most often cannot
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