Wednesday, 24 September 2014

Mind's eye

Your mind’s eye is the ability you have to visualise things that are not physically in front of you – your ability to ‘see’ things using just your mind. Throughout history philosophers and doctors have consistently tried to localise where the mind’s eye resides – although not all agree that it can be localised to a specific area.  Those that believe it can tend to focus on an area of the brain called the pineal gland, an area that possesses unusual properties, such as being one of the only areas of the brain not in a pair on either neural hemisphere.

The pineal gland is where Hippocrates determined as the area where the mind and the brain joined together, and in more recent times has been suggested as the area where the mind’s eye is located. The evidence for this is that the pineal gland supposedly secretes the psychedelic molecule dimethyltryptamine (DMT). DMT is a powerful hallucinogenic compound that dramatically affects human consciousness. However, this evidence is not agreed on by all and is mainly the musings of Dr Rick Strassman, who was also the first person in the U.S. granted with the ability to carry out research with psychedelic substances on humans after a 20-year intermission. Previously only animal tests were allowed. This jump in research allowed for Strassman to produce unprecedented results. Strassman also suggests that the production of DMT by the pineal gland is what accounts for dreams and near death experiences.

The 'mystical' pineal gland 

Although most of us are able to take our mind’s eye for granted, for some the case is entirely different. In 2005, a 65-year-old man referred to as “MX” went to hospital complaining that his mind’s eye had gone blind. Upon further examination, it was revealed that MX had recently gone to hospital for surgery to treat his coronary arteries, and during this had felt a tingling in his left arm, but didn’t think to mention it to doctors. Four days later, he realised he could no longer visualise anything when he closed his eyes – his mind’s eye had gone blind. Doctors at the time grabbed this opportunity to study the mind’s eye in more detail, and MX was put through a battery of tests. It was found that he performed pretty much the same as the other men (with ‘seeing’ mind’s eyes) who were selected as controls in the tests. However, when faced with Roger Shepard’s classic ‘Mental Rotation of Three-Dimensional Objects’ test, MX performed differently. In this test, a subject is given two images of 10 cubes stacked into an object. The subject must then determine if the two images are of the same object shown from different perspectives, or of different arrangements altogether. Normally you would expect to see that the more different the two images, the longer the amount of time taken to distinguish. This is because your mind’s eye is rotating the image in your head. However, in the case of MX, there was no difference in the time taken to solve the puzzle – and he got every one right. The doctors studying MX noticed that his case was similar to patients suffering from the phenomenon ‘blindsight’.
Images similar to what MX would have been shown 

Blindsight (or Anton-Babinski syndrome) is a condition in which a person has a damaged primary visual cortex, but is still able to tell where an object is, even though they claim they cannot see it. This is a form of anosognosia – a condition in which a person suffers a disability but is unaware of its existence. Those with blindsight have damage to the neural pathways that link visual information and consciousness, and the doctors working with MX speculate that it may be possible to process visual images without actually seeing it in the mind’s eye. The mechanism behind blindsight appears to be that missing sensory information is ‘filled in’ with confabulation (which is similar to lying but has no intent to deceive – the person genuinely believes that what they see is true).

A cartoon showing blindsight testing

The mind’s eye has long been the subject of debate, but it is still not well understood. Some brain scanning studies (using fMRI) have shown that specifically the lateral geniculate nucleus and area V1 of the visual cortex are activated when subjects are asked to visualise an image – but does this really tell us anything? Unfortunately scientists are currently unable to say much more than the fact that the same neurons that fire when you look at an apple are firing when you imagine an apple. Interestingly, these neurons fire at nearly the same rate, even though the intensity/vividness of an image conjured up by your mind’s eye is significantly less than a physical object in front of you.

What are your thoughts?

3 comments:

  1. This is an interseting post. I wonder if the minds eye can be trained like a uscle as sometimes it is difficult to imagine a certain thing without the mind wandering - thats what mediatation is i suppose.

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  2. This is something that I really struggle with being dyslexic.

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  3. Your posts are always so fascinating :) I studied philosophy so I know about the brain in that regard but it's so interesting to read about the science in such an accessible way

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