Archives for posts with tag: oliver sacks

Your snout is able to determine over 10,000 different smells using about 500 nasal receptors.

However for some people, smell is but a memory.

They are unable to smell a whiff of anything and this total loss of smell is known as anosmia.

It currently affects around 5% of the US population, which means there are around 16 million people unable to smell leaking gas, smoke, or even worse, themselves (resulting often, undertandably, in some level of social anxiety).

As well as that, they sometimes can’t taste the flavours in food.

Your brain portion that controls smell is located at the base of your skull, so even mild head injuries to the back of the head can result in anosmia, however this is often temporary.

But for those whose smell never returns, hallucination of smells can form in their place where people think they smell coffee, smoke or other alarming substances even when there is none.

Hallucinated smells of a particularly vile smell kind are called cacosmia as described by Bonnie Blodgett in her book ‘Remembering Smell’ where she was plunged into a flurry of terrible smells from rotten eggs to chemicals, mould and sick.

On a more positive note, there have been recent studies to suggest that those who have a good sense of smell are more emotionally sensitive (thought to be because the two areas of the brain related to emotion and sense are in the limbic system), and science has taken steps closer to proving the simple truth that a memory can be triggered by a smell due to the proximity of the amygdala (the part of the brain responsible for emotional memory) to the hypothalamus and olfactory tracts (nose!).

So if you can smell the roses, be thankful. Some people are getting noses full of nothing, or worse.

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Facts found in Oliver Sacks’ newest book ‘Hallucinations’.

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Love can come in the most curious forms.

In his latest book ‘Hallucinations’, Oliver Sacks tells a story about his patient, Gertie C., who suffers intense visual hallucinations as a result of Parkinson’s postencephalictic disease – or ‘frozen’ disease (as described in Sacks’ book and film ‘Awakenings’).

Sometimes frightening, sometimes funny, hallucinations are an offshoot of the disease which is thought to be due to a build up of proteins in the parts of your brain that deals with sight and movement.

After some distress at her visualisations, Gertie decides to submit to the oddities her brain conjures, and embrace the experience instead…

In the form of a hallucinatory gentleman caller.

Every night, he arrives faithfully on her doorstep with flowers, presents, love and warm companionship.

Who says love isn’t real?

As well as exploring many other patient’s stories, Sacks’ own anecdote in his latest novel ‘The Mind’s Eye” (Picador, 2010) candidly talks about his experiences with an ocular melanoma in his right eye. The treatment required cutting the eye muscle to insert a radioactive plate for 72 hours, zapping the malignant cells. When unsuccessful, this is eventually followed by laser treatment which damages the fouvea – the part of your eye which delivers your central vision.

In the following weeks of recovery he experiences is extraordinary explosions of vision, with the brain suddenly spurting blowouts of bright light and colour as it tries to heal its burned, charred parts and reconnect tissues and messages between optical nerves and occipital lobe.

Colour becomes a riddle for him. Holding up a green apple in his peripheral vision, it is green, but when moved in front of his body (and thus it is viewed by the fouvea) it becomes black; same for bluebells in a meadow – with the untreated eye they remained blue but seen with the damaged eye the flowers became green with the grass.

Similarly, the scotoma or black hole in his central vision behaves as if a sci-fi beast, changing its pattern and colour to suit his surrounds; black when he opens his eyes, if looking at a white wall, the shape would suddenly change to white to match it, or to match the pattern when looking at brick walls, or chess boards.

The colour soon returns to the apples, and he experiences a heightened sense of vision whereby he sees images in his memory long after the event; a kind of heightened visual memory.

It’s an incredible cerebral experience told by such an eloquent physician.

Among his many books, Oliver Sacks has also written ‘The Man Who Mistook His Wife For A Hat’, ‘Awakenings’, and ‘Musicophilia’.
www.oliversacks.com

Oliver Sacks’ most recent book ‘The Mind’s Eye’ looks at the curious relationship between your brain and your eyes.

He follows the patient Sue, who was born stereo-blind (that is, without binocular vision which is necessary to construct a sense of depth). Born cross-eyed she had surgery at ages 2 and 7 buy was told there were no corrective exercises that would be done to help her gain a 3D vision of the world. In her 40’s, with the help of a developmental optometrist,  she decided to try corrective exercises anyway and realised her 3D vision was able to be activated, suddenly seeing the steering wheel and doors “popping out” into the world once the binocular cells in her brain were activated to see the world this way. Without exercises however, this ability faded and she lost her 3D vision, demonstrating the incredible elasticity of the brain’s capacities.

The fusiform face area (FFA) is a part of the human visual system which might be specialized for facial recognition, although there is some evidence that it also processes categorical information about other objects, particularly familiar ones.

Good news! That horrible feeling when you cannot, for the life of you, recognise that person enthusiastically greeting you like a long-lost friend, actually has a name – Prosopagnosia – or face-blindness. More than that, it’s a fairly common thing.

Up to 2% of the US population – that’s 6 million people – can’t quite recognise their husbands, children, wives, teachers and colleagues, but this strange impediment isn’t even a household name.

Recognition depends on knowledge; familiarity  is based on feeling, and thus has an entirely different neural base including the amygdala and hippocampi which store memory and emotion.

Prosopagnosia comes in the form of the “hyper-familiar”  – people who greet strangers at the bus stop enthusiastically feeling them know them, while also realising they don’t quite know where they know them from, if they know them at all.

The opposite is type Capgras syndrom, definitely the sadder of the two, where someone recognises a face but has no emotional memory of them – thus the Capgras patient will argue that the person (eg their daughter or son) cannot be the real thing – they must be imposters or counterfeits.

According to case studies, Prosopagnosia seems hereditary.

But with practice, the brain can be trained to remember people’s faces highlighting the plasticity of neural circuits adapting to create new memories… so there is hope for all those yet who can’t remember people’s faces!

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