Posted in Science & Nature

Vision

Consider this: if you see something that is not there, or not see something correctly, is that due to a problem in your eyes or your brain? An interesting anatomical fact is that the eyes are part of the brain. They originally evolved from the brain and drifted further and further forwards, connected to the brain by the optic nerves. If you lift a brain out from the skull, the eyes would be pulled backwards too. But technically speaking, eyes are distinct organs by themselves that have merely originated from a portion of the brain. It does not think or make decisions by itself. Just like a camera, an eye records things as it sees it and transmits it to the brain via the optic nerve via electrical signals. The brain then processes the signals in the occipital lobe, located at the back of the head (this is why you “see stars” when you bang the back of your head).

This means that vision can be altered anywhere along the pathway. If you have cataracts, where the lens of the eye becomes clouded, you lose portions of your visual field. If you have a large pituitary gland tumour, it presses on the optic nerve and causes double vision (diplopia) or vision loss. If you have a stroke in the occipital lobe, you can lose your vision. The brain’s role in producing vision can easily be demonstrated in the form of optical illusions. The eye merely records and transmits what it sees, but the brain becomes confused by what information it receives and tries to make sense of it. In the process, we experience bizarre illusions such as static images moving by themselves.

Because of this intricate pathway, some pathologies present with fascinating symptoms. A condition called Anton’s blindness (or Anton-Babinski syndrome) causes a patient to “see” despite being blind. Patients with Anton’s blindness are adamant that they can see perfectly clearly, and will even describe what they are seeing. However, what they “see” is completely different to what the object actually looks like. For example, if the patient looked at a blonde woman wearing a yellow blouse and a red skirt, they may describe her as a brunette woman wearing a blue shirt and black jeans.

The reason for their blindness is that their occipital lobe was damaged (usually by a stroke), leading to an inability to process the information from the eyes. Although the eyes are pristine and record what they see in perfect detail, the brain is incapable of interpreting the signals. The brain then goes on to confabulate, where the brain fills the gap by conjuring up false information. This makes Anton’s blindness quite hard to pick up on as the patient will not complain of it. It is only found when someone pays close attention to the patient and notices subtle cues like the patient bumping into furniture or talking in the direction where they think a person is at (even after they move). Ergo, the patient adamantly believes that they can see as their brain thinks it is seeing things (even though it is not receiving the information from the eyes properly).

Seeing is not believing. You see what you believe.

Posted in Psychology & Medicine

Korsakoff’s Syndrome

It is a well-known fact that excessive drinking leads to a so-called “blackout”. This form of memory loss is common in normal people and cannot be seen as a major illness. However, there is another disease that can be caused by excessive drinking called Korsakoff’s syndrome. Strictly speaking, this is not caused by alcohol but due to a thiamine (vitamin B1) deficiency and is commonly found in alcoholics and malnourished patients (it has also been reported to be caused by mercury poisoning and after centipede bites in Japan).

The six characteristic symptoms of this syndrome are: anterograde (cannot form new memories) and retrograde (cannot remember old memories) amnesia, confabulation, lack of detail in conversation, lack of insight and apathy.

Korsakoff’s syndrome patients show a very peculiar behaviour. As stated before they suffer from both anterograde and retrograde amnesia so not only can they not remember the past but they cannot make new memories either. Ergo, the brain uses information from its surroundings and attempts to recreate the lost memories, the result being confabulation. Confabulation is essentially what happens when the brain tries to fill in blanks in memories with false information. Confabulation is seen in everyday life too with healthy people but in the case of Korsakoff’s patients the effects are significantly more profound. For example, if you ask a patient what she did yesterday, she may look at your horse-print tie and claim she was horse-riding. If you ask the same question an hour later without your tie and instead holding a book with a photo of a Ferris wheel on the cover, she’ll state that she was at the amusement park. As one of the leading causes of amnesia and confabulation, Korsakoff’s should be suspected in any alcoholic or very underweight patient who keeps changing their stories around. 

As previously explained, the disease is caused by thiamine deficiency – therefore, the treatment is administering thiamine. But if the syndrome has persisted for a long time, the brain injury may be permanent. Also, treating the underlying alcoholism and malnutrition is important. 

If the thiamine deficiency is prolonged, it may lead to another disease called Wernicke’s encephalopathy. This is known as Wernicke-Korsakoff’s syndrome and in addition to the above symptoms, the patient may also experience confusion, tremors, nystagmus, paralysis of eye muscles, ataxia, coma and can eventually lead to death. All because of a deficiency of a single vitamin.

Who said nutrition is not important?

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(NB: Dory from Finding Nemo is one of the most accurate portrayals of amnesia in films)