Tag: neurology

Posted in Psychology & Medicine

Fugue State

Posted on by Jinavie

Any computer user would have had an (unfortunate) experience where their computer crashed and all the information there was destroyed in a second. You may still be able to format it and use it without problems, but the data you had on the computer and any customisation you made would be lost. But what if this exact thing could happen to a human being?

There are many types of amnesia, with causes ranging from neurobiological (where trauma to the brain, a drug or some other pathology causes memory loss) to psychogenic (where there is no apparent biological cause for the amnesia). With psychogenic amnesia, one only experiences retrograde amnesia, where they cannot recall memories from the past. However, anterograde amnesia, where you cannot form new memories and keep forgetting what happened, is absent in psychogenic amnesia. Psychogenic amnesia is often caused by extreme stress or a traumatic event. One type of psychogenic amnesia is situation-specific amnesia, as seen in post-traumatic stress disorder (PTSD) that occurs after a severely stressful experience such as war, rape, child abuse or witnessing a brutal death. In this case, the patient tends to only lose memories regarding the event, as if the brain is trying to protect the person from the hurtful memories.

A more interesting and much rarer type of amnesia is global psychogenic amnesia, also known as a fugue state or dissociative fugue. Unlike situation-specific amnesia, patients in fugue states have absolutely no memory of their original identity and personality. Simply put, they (usually) retain all their functions such as speaking and social interactions, but their persona has been wiped out like a formatted computer. Fugue states often develop after severe stress and can happen to anyone. Similar to situation-specific amnesia, the brain blocks all memories of the past in an attempt to protect the person’s psyche. Due to the “deletion” of the previous persona, patients in fugue states often generate new identities and begin wandering (sometimes even travelling to another country) away from the place they lost their memories. This is most likely the brain attempting to leave the environment to avoid the stressor that caused the event. 

Fugue states are often short-lived, lasting from days to months. However, very rarely they can last for years. Once out of a fugue state, the patient recovers all of their past memories but have no recollection of what happened during the fugue state. This creates a hole in their memory. For obvious reasons, this usually causes intense confusion and distress in the patient and treatment is often based around helping the person come to an understanding about the episode and cope with the stressor that caused it.

Posted in Psychology & Medicine

Stroke

Posted on by Jinavie

A stroke is caused by a disruption in the supply of blood to the brain, which leads to cell death as oxygen is required. There are two types: ischaemic (where a clot cuts off blood supply to an area of the brain by blocking an artery) or haemorrhagic (when a blood vessel ruptures and leaks blood instead of delivering it to tissue). The most common cause of a stroke is a clot that made its way up to carotid arteries into the brain until it wedges in small vessel. There are many risk factors for blood clots, such as smoking, high cholesterol levels, atrial fibrillation and long distance flights.

Because the brain is always in high demand of oxygen (taking 20% of the total oxygen available), strokes can produce devastating effects within minutes. 5 minutes of oxygen deprivation can lead to irreversible cell death, a principle that is also used in cases of shock, where the blood pressure is too low to supply organs, or cardiac arrest. Therefore, it is crucial to recognise a stroke early so that an ambulance may arrive and deliver clot-busting medication such as streptokinase.

The FAST mnemonic is an effective way of remembering the common signs of a stroke. It is also useful in reminding people to respond fast.

  • F – Facial weakness: Is the person’s smile crooked? Disrupted brain function causes facial weakness on the opposite side. The weakness is usually seen around the mouth or eyes.
  • A – Arm weakness: Can the person keep both arms outstretched? This is related to motor function of the brain.
  • S – Speech difficulty: Is the person’s speech slurring or are they having problems understanding speech? This is a combined result of impaired motor function and speech centres of the brain.
  • T – Time to act: Call an ambulance. NOW.

Posted in Psychology & Medicine

Hypnagogia

Posted on by Jinavie

Every person has had the experience of having a few seconds of brilliance just before their consciousness slips into sleep. During this short moment, we have some of the most creative and innovative ideas. Unfortunately, this is all lost by the time we wake up. This state is known as the hypnagogic state and has been well known since ancient Greece. Many philosophers and writers such as Aristotle and Edgar Allan Poe have written on the subject and how they received some of their greatest ideas in this state. 

Recent researches show that during hypnagogia, thought processes and cognition vastly differs to normal wakefulness. It appears that hypnagogic cognition is more based on the subconscious mind, with people in this state being more open to suggestion (e.g. hypnosis). Ideas seem to flow in a fluid yet illogical way and they are based on external stimuli, thus explaining the heightened suggestibility as the brain incorporates the surrounding into its thought process. The thought process is also less restricted, leading to openness and sensitivity. A process called autosymbolism occurs where abstract ideas that we are thinking are converted into concrete images. This explains the artistic inspiration seen in hypnagogia.

One of the more pronounced phenomena of hypnagogia is insight. It has been noted by many people throughout history that the moment before sleep is when we have the best ideas. For example, a chemist called August Kekulé realised that benzene was a ring structure after seeing an image of snakes biting each other’s tails to form a ring. Because of this, many famous artists and inventors tried to harness the power of hypnagogia through techniques such as the Dalí nap. Thomas Edison, Isaac Newton, Beethoven and Richard Wagner also practised similar techniques to gain insight into a problem that they were trying to solve or bring fresh ideas.

Another fascinating side of hypnagogia is the strange sensory phenomena associated with it. As in the case of sleep paralysis (which usually occurs in hypnapomp – the state between sleep and waking up), people often report strong hallucinations in the form of bright colours, geometric shapes, or even nightmarish visions (such as a ghost sitting on your chest). Other senses are affected as well, such as hearing whispering (commonly associated with the nightmarish hallucinations mentioned above) or out-of-body experiences. Hypnic jerks are also common, where the person jerks awake just before drifting off to sleep. This is thought to be caused by the brain misinterpreting sleep as “death” or the body shutting down, leading it to jolt the system back to life. 

Finally, an interesting psychological phenomenon is the Tetris effect, where people who have spent a prolonged time on one activity cannot stop seeing images and thinking about that activity in the hypnagogic state. This was seen in people who had played too much Tetris seeing coloured bricks before they went to sleep. Other common versions of the Tetris effect include chess boards and pieces, feeling waves after being at sea and seeing words and numbers after working on documents for a long time.

The combination of insight, creativity and sensory illusions leads to hypnagogia causing strange “experiences”. Ergo, hypnagogia is now thought to explain many supernatural experiences such as ghost sightings, UFO abductions, premonitions and visions.

Posted in Psychology & Medicine

Phantom Limb Pain

Posted on by Jinavie

In up to 80% cases of amputations, a strange phenomenon occurs where the amputee reports sensation or even severe pain where the limb has been amputated. It was noticed in field hospitals during wars when a soldier would wake up and ask someone to scratch his leg – which was no longer attached to his body. The sensation can be so powerful that victims actively believe that their phantom limb can interact with real objects. For example, there have been case reports of patients trying to pick up a cup with an amputated arm and becoming frustrated with their inability to.

Phantom limb pain may persist even after the amputee realises the limb is no longer there. The basis for phantom limb pain is a neurological system called the cortical homunculus. The cortical homunculus is a concept that the part of the brain responsible for sensation and movement is mapped out so that each part corresponds to a part of the body (see picture). For example, the top of the primary somatosensory and motor cortices (said parts of the brain) is responsible for foot sensation and movement while the side receives information from and sends signals to the face. It lets the brain construct an image of what the body looks like from sensory information it collates from various body parts. It is suggested that phantom limb pain is caused by a remapping of the cortical homunculus, fooling the brain to think that the limb is there even if it has been physically cut off. This also explains a similar condition called supernumerary phantom limb, where the brain believes there is an extra limb (e.g. a third arm).

As the homunculus concept is a recent idea, treatment options had not advanced much until the late 1990s. In 1998, a neuroscientist called Dr. Vilayanur S. Ramachandran devised a method called the mirror box treatment. He noticed that victims of phantom limb pain (PLP) had paralysis or pain in the limb just before the amputation (such as tightly gripping something before the arm got blown up by a mine), suggesting that PLP may be a form of learned paralysis. This means that the brain believes that the arm is still paralysed and any movement causes an uncomfortable sensation as the brain thinks the limb is contorted into a painful position. To fix this problem, Dr. Ramachandran invented a box with two holes, each going into a separate compartment. One compartment is for the good arm while the other has a mirror positioned on an angle to reflect the other arm (instead of seeing the stub they put in the hole). He would then instruct the patient to perform symmetric movements with both hands while looking at the reflected arm. For example, he would tell the patient to squeeze their “fists” tightly as possible and then let go. Through this procedure, the brain is retrained to let go of the perceived paralysis and pain as it is tricked in to thinking that the arm is healthy again. The mirror box therapy drastically improved the outcome and quality of life of PLP patients through the power of illusions.

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Posted in Psychology & Medicine

Alien Hand Syndrome

Posted on by Jinavie

There is a very rare, disturbing and interesting medical condition called alien hand syndrome (AHS). An individual with this neurological disorder has full sensation in the rogue hand, but is unable to control its movements and does not feel that it is a part of their body. The hand becomes personified, as if it has a will of its own, and its owner will usually deny ownership of the limb.

Though AHS was first identified in 1908, it was not clearly defined until 1972. Depending on the cause of the injury, the movements may be random or purposeful, and may affect the dominant or non-dominant hand. The symptoms are brought on by an injury to the brain, such as head trauma, stroke, tumour, or infection. It can also be a side effect of a certain kind of brain surgery where the patient has the two hemispheres of the brain separated to relieve severe epilepsy.

If the AHS is caused by separation of the corpus callosum (the area of the brain that connects the two halves of the brain) by surgery or injury, the movements are usually complex purposeful behaviour, such as compulsive manipulation of tools, undoing buttons, or tearing clothes. For example, a right-handed person is left-hemisphere-dominant, thus their left hand (controlled by the right hemisphere) will become “alien”. Sometimes the sufferer is completely unaware of what the hand is doing until it is brought to his or her attention, or until they happen to see it themselves. 

Strangely, many of the alien hand’s actions are the complete opposite of what the person is doing with the other hand. For example, if they start packing a suitcase, the alien hand will unpack it. It is believed that one half of the brain (usually the right brain) is unaware of why the other hand is doing something (due to the lack of connection between the two hemispheres) and so proceeds to “correct” it. There are also reports of the alien hand attacking the patient by hitting them or even trying to strangle them in their sleep. 

There is currently no treatment for alien hand syndrome, but the symptoms can often be relieved by giving the rogue hand an object to manipulate, to keep it occupied. One patient whose alien hand had a compulsion of holding on to door handles or other objects to stop the man from walking was given a cane. The alien hand would grab on to the cane and not interfere with the patient’s walking.

There is currently no treatment for alien hand syndrome, but the symptoms can often be relieved by giving the rogue hand an object to manipulate to keep it occupied. One patient whose alien hand had a compulsion of holding on to door handles or other objects to stop the man from walking was given a cane. The alien hand would grab on to the cane and not interfere with the patient’s walking.

Although it is a distressing condition, some patients learn to live with the disease. For instance, when one patient’s alien hand kept throwing away the cigarette her dominant hand put in her mouth, she shrugged and said: “I guess ‘he’ doesn’t want me to smoke that”. Perhaps the alien hand is simply a way for the subconscious mind to physically act on the conscious mind.

Posted in Science & Nature

Piquance

Posted on by Jinavie

When the word taste is mentioned, people often think of sweet, sour, bitter, salty, savoury and spicy. But among these, only the first five are officially “tastes”. Spiciness is technically not a taste; it is rather a type of pain.
Due to the confusion between the words hot (which could mean temperature) and spicy (suggesting there are spice, but not specifying what type), scientists devised a new word called piquance to correctly name the sensation.
Piquance is caused by chemicals such as capsaicin stimulating the densely packed nerve fibres in mucous membranes in the mouth, causing pain. This sensation can be sensed anywhere covered by thin skin or membrane such as the eye. Tear gas and pepper spray exploit this by attacking the eyes, disabling sight, and the respiratory system, crippling breathing by inducing cough reflexes, to nullify the target.

Being a sensation, piquance can be seen as a subjective measure. Is there an objective way of measuring the piquance of a food?
In 1912, an American pharmacist called Wilbur Scoville utilised the fact that piquance is due to capsaicin to create something called the Scoville Scale. This scale’s unit is 1 Scoville Heat Unit (SHU) and is proportionate to the level of capsaicin.
The following is a list of many types of chilli and their SHU:

  • Paprika: 0
  • Peperoncini: 100-150
  • Jalapeño pepper/Tabasco sauce: 2,500-8,000
  • Chungyang red pepper: 10,000-23,000
  • Habanero chilli: 100,000-350,000
  • Red Savina habanero: 350,000-58,0000
  • Naga Jolokia: 1,067,286
  • Naga Viper: 1,382,118
  • Trinidad Scorpion Butch T pepper: 1,463,700 (currently the world’s hottest pepper)
  • Tear gas/pepper spray: 5,300,000
  • Pure capsaicin: 16,000,000

Posted in History & Literature

Darkness

Posted on by Jinavie

When you close your eyes, what do you see? When you look into the night sky, what do you see? Most people describe darkness as pitch black, but this is not quite true.
The colour that we see in perfect darkness is not black, but more of a dark grey colour. This colour has a special term called eigengrau, which is German for “intrinsic grey”. Similarly, when you look into the night sky the actual colour is a deep navy.

The reason for this is that the brain uses relative contrast to determine true black rather than the absolute brightness. So when you see darkness, the optic nerve still fires off some signals that the brain interprets as eigengrau. When you see a black object, the brain compares it to the surrounding to cancel this effect out to see true black.

The night sky is lit with stars and the moon, giving it a darker colour than eigengrau due to contrast, while retaining the blue hue produced by the dust diffracting light in a particular manner. Because of this, ninjas actually wore dark navy clothes instead of the black that we associate with them in the present.

An interesting point regarding darkness is that people often see it as a symbol of the negative side (e.g. The Dark Side). However, darkness is technically the opposite of light. It is in fact defined by the absence of light, which in other words suggests it is the default state.

The default state of the universe is nothing.

Posted in Science & Nature

Taste Of Water

Posted on by Jinavie

It is a common chemical fact that water is flavourless and odourless. However, most people will know that water “tastes” subtly different each time.
Taste is composed of information from taste buds on the tongue, combined with the sense of smell from your nose. Although water itself has no flavour or smell, it has many things dissolved in it such as gases and minerals that can be tasted.
This is why tap water can taste bad due to the chlorine used to treat it, or metals such as copper that have come off the pipes. 

It is also well known that temperature affects the taste of water. The ideal temperature is between 10~17°C, where oxygen saturation is sufficient, giving the water a “refreshing” taste. Any hotter and the oxygen escapes, giving the water a flat taste, just like distilled water. Warm water also causes the brain to think it is saliva or mucus, sometimes producing an uncomfortable sensation. Any colder, the tongue is numbed and it loses its ability to taste.

When making tea, the ideal temperature is 70~80°C. A simple way to achieve this is by leaving a cup of boiled water for a minute or two before putting the teabag in. This is the temperature when the dissolving of the various chemicals in tea leaves is optimal. If it is too hot, bitter-tasting tannins and catechins are released in excess, whereas if it is too cool, not enough dissolving occurs.

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Posted in Psychology & Medicine

Madness

Posted on by Jinavie

“As mad as a hatter” – this is a well-known English idiom, particularly famous after Lewis Carroll created the Mad Hatter character in his work Alice in Wonderland. However, what is less known is the fact that this idiom is based on actual events.

In the 18th and 19th centuries, hatters used mercury to treat felt (traditionally made from rabbit fur or the more luxurious beaver fur). Unfortunately, mercury is a highly toxic heavy metal, which causes severe damage in the human body. In the case of mercury poisoning (also known as Minamata disease or the Mad Hatter disease), it infiltrates neurons to cause severe neurological symptoms. For example, it can impair vision and hearing, cause paresthesia (pins and needles), anxiety, depression, tremors and hallucinations. The famous physicist, Isaac Newton, also suffered from Mad Hatter disease.

Another mad character from Alice in Wonderland is the March Hare. As one may deduce from his name, he is modelled after a normal hare. The reason why the March Hare is mad is that March is around the time when rabbits enter their mating season, and male hares are in heat. They then have only one thing in mind: sex. 

Maybe, as the Cheshire Cat explains, “we’re all mad down here”.

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Posted in Psychology & Medicine

Locked-in Syndrome

Posted on by Jinavie

Imagine that one day, you wake up, but then no matter how hard you try, you cannot move a single part of your body. Trying to roll out of bed, lifting your arm, or even moving your fingers is impossible. You think it is merely sleep paralysis, but you soon realise that it is not as simple as that, or even a dream. No voice escapes your throat.
The only thing you can do is blink and roll your eyes around.

Welcome to the world of Locked-in Syndrome (LIS), a neurological condition where your brain has no connection to all the muscles in your body. The actual symptoms list is: quadriplegia, paralysis of most facial muscles, inability to speak, with complete preservation of cognitive function (sometimes sensation too). In simpler terms, a LIS patient’s mind is essentially trapped inside an unmoving body, with only the senses and eyes to interact with the real world.

It is caused by damage to a part of the brainstem known as the pons, which not only carries motor nerve fibres to the spinal cord (where it then carries on to supply the muscles of the body), but is also the origin of some cranial nerves. This explains the symptoms of paralysis, even the face (e.g. damage to the facial nerve, or CN VII). More specifically, the damage only affects the pons and not the brain itself, meaning that cognition (thinking), intelligence, memory and sensation (if the fibres are spared in the brainstem) are completely functional.
This can be caused by trauma, stroke, drugs, degenerative neuropathies, or anything that can selectively damage the pons.

Due to the nature of the disease, there are no treatment or cures for LIS. Prognosis is very poor and most patients are not expected to regain motor control. This can be very distressing news to LIS patients, as it essentially means that they will be trapped in a motionless, voiceless body for the rest of their natural lives, which could feel like eternity. Although over 90% of the patients die within 4 months, some continue to survive for much longer periods. To improve their quality of life, methods have been developed to allow the patients to communicate, such as Morse code (by blinking eyes) or alphabet boards. Technology is allowing even better options such as eye-tracking and brain-computer interfaces, where a machine tries to interpret a pattern in brain activity, trying to relate a certain action to a pattern. This may allow simple communication such as yes/no answers.

Because of the almost complete paralysis, even professional neurologists often miss this condition, diagnosing the patient as being in a vegetative state.
What would it be like to be trapped in your own body – or “living corpse” as described by Alexandre Dumas in The Count of Monte Cristo – and not be able to tell others that you were still in there?