Thursday, June 3, 2010

Do you want to hallucinate? Watch this image. #medtweeps #psychiatry

"A hallucination is a percept experienced in the absence of an external stimulus to the corresponding sense organ" - Oxford textbook of psychiatry

Jaspers suggested the following defnition 'a false perception which is not a sensory
distortion or a misinterpretation, but which occurs at the same time as real
perceptions’.

You are having a visual hallucination when there is no external object, but you are still percieving that there is an object. Visual hallucinations are seen in some psychiatric illness.Recently i came across this interesting image in Scientific American. Its called the Yorick's Skull. This was the image.

doodle.png  on Aviarydoodle.png on Aviary.

 

The site says, 'To experience a vintage afterimage illusion, stare at the X in Yorick’s left eye socket for about 30 seconds. Then look away at a wall or piece of paper, and you will see a ghostly apparition.'

 

When we stare at a wall after seeing the image, there is no external object. But we are still able to percieve the image of the ghost. So is this an illusion?? or is it that we are hallucinating??

Posted via web from Inquisitives' posterous

6 comments:

Anikethana G V said...

did u really appreciate anything.. i couldnt appreciate any ghostly after image or anything.. and how can u call this as an hallucination.. it can just be the residual firing of the neurons.. to call it a hallucination it is not just sufficient to c something tat doesnt exist; u should also not realize that it doesnt exist.. so its neither illusion nor hallucination.. its just residual after image; this is my opinion...

docspike said...

absolutely correct man...we should also lose insight that it doesnt exist...bingo! and explanation is correct too...When you stare at an image, the neurons in your retina eventually adapt to this unchanging stimulus and stop responding to it. If you then look away, you can see a ghostly afterimage during the brief period that it takes for your neurons to reset to their responsive state...

and u must be able to see it...light the room adequately....and watch for 30 sec correctly and then stare at wall for atleast ten seconds...

Sitaram said...

nice info

docspike said...

Thank you

Nizam Raj Banerjee said...

great post

Nizam Raj Banerjee said...

Great Post!