Posted in Psychology & Medicine

Sensory Illusion

The five senses we use to experience the world are simply wondrous. However, thanks to our not-so-perfect brain, these senses can easily be distorted. Illusions are a very good way to show how the brain processes sensory information and there are many fascinating examples.

Almost everyone has seen an optical illusion before, such as Penrose’s endless stairs or the Muller-Lyer illusion. There are countless more examples such as static pictures that appear to be moving and illusions in colour perception (A and B are the same colour). This is caused by the brain not recording images like a camera, but rather processing visual information and reconstructing an image. There are four main types of optical illusions: ambiguous (e.g. rabbit or duck), distortion (Café wall illusion), paradoxical (Penrose triangle) and fictional (only seen in hallucinations or by schizophrenics).

(Do you see the dolphins? Children cannot see the man and woman because they cannot comprehend it, whilst adults cannot overpower the sexual image)

Like vision, every other sense can be fooled in a similar fashion.
Auditory illusions that distort what we hear are fairly common, a good example being the infinitely ascending Shepard scale (which are just a series of the same ascending octave scale). Also, the McGurk effect shows how the brain uses a multimodal approach where it involves both hearing and vision when listening.

There are also tactile illusions. For example, if you pull your top lip to left and the bottom lip to the right, then prod the middle of the lips with a pencil, it feels like there are two. However, the more famous case is of the Phantom Limb, where an amputee’s brain still believes that the limb is there, causing it to “feel” the limb or even feel pain.

The other two senses aren’t as famous in terms of illusions, but definitely exist.
Smell is easy to fool through chemicals as it is the physiological method of detecting smell. It also exhibits olfactory fatigue where it becomes desensitised to a strong smell.
Taste illusions are more fascinating and easily seen. They are caused by two or more tastes forming a synergy to produce a completely different taste. For instance, mixing barley tea and milk produces a coffee milk taste, while cucumber and honey tastes like melons.
A more fascinating illusion involves Miracle Fruit Berries, which contain a substance called miraculin that distorts the taste of sourness to sweetness.

This shows how we can fool all five senses, and learn more about the mysterious organ that is the brain.

Posted in Psychology & Medicine

Ganzfeld Effect

To experience this peculiar effect, you require a ping-pong ball cut in half, tape, radio, headphones and a lamp tinted with red light (use cellophane).

  1. Set the radio to an empty station so that only white noise is playing.
  2. Plug the headphones into the radio and wear it.
  3. Place each half of the ping-pong ball over your eyes and secure it with tape.
  4. Shine the red light towards your eyes.
  5. Relax on a couch or a bed for over half an hour.

What you will experience after about half an hour are powerful visual and auditory hallucinations, the result of your brain trying to fill the void created by sensory deprivation. As the brain is in constant need of stimuli, complete deprivation of the senses results in the brain becoming confused, trying to interpret what is not there. It has been reported that people see things such as horses flying through clouds or hearing the voice of dead relatives.

Posted in Psychology & Medicine

Cranial Nerves

Nerves can be divided broadly as spinal nerves and cranial nerves: the latter which is directly from the brain. There are 12 pairs of cranial nerves:

  1. CN IOlfactory nerve (smell)
  2. CN IIOptic nerve (sight)
  3. CN IIIOculomotor nerve (eye movements, control of pupil and lens)
  4. CN IVTrochlear nerve (eye movements)
  5. CN VTrigeminal nerve (sensory information from face and mouth, chewing)
  6. CN VIAbducens nerve (eye movements)
  7. CN VIIFacial nerve (taste, tear and salivary glands secretion, facial expressions)
  8. CN VIIIVestibulocochlear nerve (hearing and sense of balance)
  9. CN IXGlossopharyngeal nerve (taste, swallowing, parotid gland secretion, sensory information from oral cavity, information about blood)
  10. CN XVagus nerve (sensory and motor signals to and from many internal organs, glands and muscles)
  11. CN XIAccessory nerve (movement of SCM and trapezius, which are neck/shoulder muscles)
  12. CN XIIHypoglossal nerve (tongue movements)

As there are so many nerves and the names are all varied, there is a simple (yet very obscene) mnemonic to help medical students remember the names and order of nerves:

Oh, Oh, Oh, To Touch And Feel Virgin Girls’ Vaginas And Hymens
Oh, Oh, Oh, To Touch And Feel A Girl’s Very Soft Hands
(where vestibulocochlear -> auditory)

It is also worth noting the mnemonic for the types of nerves is:

Some Say Marry Money, But My Brother Says Big Boobs Matter More

Perhaps the only way to survive medical school is through humour.

Posted in Psychology & Medicine


CPR stands for cardiopulmonary resuscitation – or in plain English, artificially (and partially) restoring the function of the heart and lungs of an unconscious, pulseless person. As blood flow (perfusion) is critical in the survival of major organs such as the brain, this procedure can save lives by prolonging a victim’s life until the paramedics arrive to provide professional medical care.

When the heart stops beating, or becomes inefficient due to erratic beating, blood flow stops. In the case of the brain, this means that the cells will start dying after 4~5 minutes if perfusion is not restored. CPR can restore about 30% of perfusion, delaying the onset of brain death.

This may be critical when someone suffers a heart attack (myocardial infarction) and paramedics will not arrive for over 10 minutes. Ergo, this is one of the most important emergency skills one should know to help people in need as soon as possible.

There are different guidelines for CPR in many countries, but here is a standard procedure guideline (NZ).
It is summarised into the acronym: DR’S ABCD (doctor’s ABCD), and is a flowchart that goes from one step to the next (detailed explanation after summary).

  1. Danger: check that area is safe and risk-free
  2. Response: check for patient response by shouting, shaking, pain
  3. Send for help: pick one person to call emergency services
  4. Airway: check airway, remove obstruction, tilt head back and lift chin
  5. Breathing: check for breathing, go to CPR if no breathing
  6. Circulation: check for pulse if breathing, if no pulse, start CPR (30 chest compressions : 2 breaths)
  7. (Defibrillation): follow AED instructions

The first rule of first aid is that you must not put yourself in danger. For example, if the patient is on the road, pull them to a safe area to minimise the risk to your own health.

Then, check for a response. The easiest way is to call loudly to them such as “Can you hear me”, and inflicting pain (such as rapping on their chest or shaking their shoulders) and see if they become conscious.

If they remain unconscious, immediately designate a person around you by pointing to them (otherwise they will be less likely to be responsible) to call the emergency service (111, 911, 119 etc.), alerting them the location and state of the patient.

This is the point when clinical skills come in.

Airway: An unconscious person may have their airway obstructed by vomit or their own tongue (which falls back by gravity into the throat). You must secure the airway by scooping out any material, and clearing the tongue out of the way. This is done by tilting the head back far (as if they are looking up), then using one hand to pull their chin out. This opens the airway up so that mouth-to-mouth becomes effective.

Breathing: Put one ear right next to the person’s nose and mouth and check for any breathing sounds or air flow. If they are breathing, check the pulse to see if they are pumping blood. If not, go straight to CPR.

Circulation: It is best to check the central pulses such as the carotid (side of neck, next to the Adam’s apple), brachial (squeeze inner side of biceps) or femoral pulses. The carotid is often the easiest as most people know how to take it. If you feel a pulse, put the patient in recovery position as they are just unconscious, breathing and has blood flowing. If not, proceed to CPR (as you do with when the patient is not breathing).

CPR is composed of two actions: chest compressions and mouth-to-mouth breathing. The former is the strong compression of the chest wall to squeeze blood in and out of the heart; the latter is breathing air into the patient’s lungs and letting exhalation come out naturally.

Chest compressions are often misrepresented in medical dramas, and is extremely important that you do it correctly. First find where the sternum is (centre of ribcage, between the nipples) and place the heel of your left palm on it, then spread your fingers out. Put your right hand over your left and close your fingers around it for a good grip. If the patient is lying flat on the ground (with head tilted back), kneel beside them and stoop over their chest with straight, locked arms (bent arms exert much less pressure).

You are now ready to begin chest compressions. Press down hard, until the chest wall is compressed to about 1/3~½ depth (the chest wall is a springy structure, and do not worry about broken ribs, as being alive is more important for the person), then ease pressure to let it bounce back up. Ideally the time pushing and the time letting it bounce back should be the same, giving a good rhythm. Repeat this 30 times at the beat of 100/min, or in easier terms: to the beats of the Bee Gee’s song Stayin’ Alive (scientifically proven).

After 30 compressions, tilt the patient’s head back, lift their chin up, and lock your mouth over their mouth and nose to make an airtight seal. It is crucial that you use a face shield to prevent the spread of disease. Be aware that breaths are less important than the compressions, so if you do not have a face shield, let someone else do the breathing and focus on chest compressions. Pinch the nose closed to ensure air does not escape.
Forcefully breathe into them and look for the chest rising. Let go of the nose and pull away so that they can breathe out. Repeat once, then return to chest compressions.

After 2 minutes of CPR (30 compressions : 2 breaths, repeat 4 times), change places with another person capable of CPR, as otherwise you will tire out and become inefficient.

Defibrillation is only possible if you are near an AED (automated external defibrillator). Nowadays, AEDs are designed to be completely user-friendly so simply follow the instructions on the machine.

It is important to note that not all abnormal heart rhythms are “shockable” (see Flatline). Follow the AED’s instruction, as it will state whether shock is advised or not. Make sure that CPR is still happening continuously.

Repeat until help arrives.

As a final note, remember that the patient is dead whether you do CPR or not, so there is nothing to lose. Believe it or not, this will be of incredible help in calming your mind when struck with such an emergency. Even with CPR, there is a maximum 30% chance the patient will survive, 10% if it occurs outside the hospital. But if you do nothing, their survival chance will be 0%, so put all your energy into resuscitating them, and you may just save a life.

Posted in Psychology & Medicine

Brain Freeze

When you quickly eat or drink something cold, you experience a sudden onset of a painful headache. This is commonly known as brain freeze, or medically, a sphenopalatine ganglioneuralgia.

Although the cause is not perfectly understood, it is believed to be due to the coldness on the palate (roof of mouth) causing a sudden cooling and rewarming of the sinus capillaries, which causes them to suddenly constrict and then rapidly dilate. Dilation of blood vessels in this area causes pain due to receptors in the vessels. This phenomenon is similar to the cause of a flushed face when exposed to cold wind, and why it sometimes causes headaches.

The only way to prevent a brain freeze is to slowly let the mouth get used to the cold, warming the food or beverage in the mouth instead of quickly swallowing it. Warming the palate with your tongue is another effective way to shorten the duration of a brain freeze.

Posted in Psychology & Medicine

Locked-in Syndrome

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?

Posted in Psychology & Medicine


In medicine, a person’s way of walking is termed gait. By analysing a person’s gait, a trained professional can gain insight into what pathologies the person may be suffering from. For example, just from the way the patient limps, the doctor may discover that the patient has an incurable degenerative brain disease.

The most common gait abnormality is the antalgic gait, or limping due to pain. Most people would have experienced the difficulty of walking with a sprained or broken ankle, muscle ache or knee problems. This is easy to spot as the patient quickly switches to the other feet when leaning on the affected leg due to the pain. Therefore, the side that stays on the ground less than the other is the affected leg.

Sometimes, you can see a person “waddling” along as they swing from one side to the other. This may be a waddling gait, also known as Trendelenburg’s gait, caused by a weakness in the hip muscles that support the pelvic girdle, either due to muscle or nerve damage. As the patient cannot support their weight on the affected side, their pelvis tilts towards the opposite side. To avoid falling over, the patient lurches their body towards the other side, causing them to waddle. Looking at the tilt and lurch gives insight into what side is affected.
Another rather common gait is the steppage gait, where the person lifts one leg higher than the other, while their foot drags on the ground. This is caused by nerve damage leading to the loss of ability to lift the foot up (termed foot drop).

As the brain controls the motor system, damage to the brain also leads to motor dysfunction. A common example is a stroke.
If the stroke damages a significant part of the motor cortex, the patient suffers from hemiparesis/hemiplegia, or weakness/paralysis of one half of the body. This causes the limbs on the affected side to stiffen, as seen by an extended leg pointing inwards and retracted arm. The patient has to swing the affected leg around while they walk as they cannot flex the hip, known as a hemiplegic gait.
If the cerebellum is damaged, balancing becomes an issue. This causes the patient to suffer from ataxia, where they cannot coordinate their movements and are prone to toppling over. These patients tend to sway violently from side to side as they try to walk in a straight line.

Lastly, degenerative brain diseases can also affect gait. There are two main examples.
In Parkinson’s disease, the patient suffers from what is called hypokinesia and bradykinesia – reduced and slow movement. This leads to a shuffling gait where the patient walks slowly by shuffling their feet in small steps. They are also stooped over and are often seen with a pill-rolling tremor of their hands – a cardinal symptom of the disease.
In Huntington’s chorea, the opposite (hyperkinesia) occurs. This causes flailing as the muscles contract in an uncoordinated manner, including both the arms and legs. Ergo, their gait is quite jerky and interrupted by bouts of flailing, termed choreiform gait, but their balance is fine so walking in a straight line is still possible.

Knowledge of these disorders may help one appreciate the suffering a patient walking along the street has to undergo everyday of their life.

(Video demonstrations:

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?


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

Posted in Science & Nature

Murphy’s Law

In 1947, an aerospace engineer named Edward A. Murphy Jr was involved in high-speed rocket sled experiments led by the US Air Force. The aim of the experiment was to research the effect of sudden deceleration on the human body so to improve the safety of jet fighter pilots. To study this, a flight surgeon named Dr John Stapp devised a “sled” attached to a rocket that could be used on a long track. The rocket would propel the sled to a massive speed and brakes would induce as sudden deceleration. However, they found that the machines that were used to measure the G-force (force of deceleration relative to the force of gravity) were unreliable. Murphy proposed that they use electronic strain gauges attached to the harness of the test subject to measure the G-force, something he learned while working with centrifuges.

The idea was great but there was one problem: the gear kept failing, showing no reading whatsoever. Murphy soon found that the sensors were attached correctly but were wired backwards. This simple mistake frustrated Murphy, who blamed the incompetency of his assistant, stating that “if that guy has any way of making a mistake, he will.” This became the famous Murphy’s law, now simplified to “Anything that can go wrong will go wrong”.

Murphy’s law actually played a fundamental role in defensive design, where the worst-case scenario is always assumed and prepared for. Thanks to this system, the rocket sled experiment was successful and in 1954 Dr Stapp became the fastest man in the world – travelling at a speed of 1011km per hour and decelerating at a force of 46G (it was hypothesised that a human being could not survive past 18G). Not only did he survive (albeit with broken limbs, ribs, hernias, detached retina and temporary blindness), Dr Stapp went to build bigger rockets to further test the limits of the human body.

Interestingly, there’s another side to the Murphy’s law involving psychology. People suffer from a fallacy called appeal to probability, where they believe that because there is a possibility of something can happen, it will happen. The brain is surprisingly inefficient in dealing with probabilities and has a tendency to ignore that there is a relatively miniscule possibility and instead focuses on the absolute fact that there “is” a probability. This is the best explanation for why people are compelled to buy lottery tickets and why every student believes they will grow up to be rich and successful. 

Posted in Psychology & Medicine

Egg Of Columbus

After returning to Spain after his discovery of the New World, Christopher Columbus was dining with some nobles. One noble approached him and said:

“Even if you had not discovered the West Indies, another fine Spaniard would have gone to discover it anyway.”

Columbus did not respond and merely smiled. He then asked for an egg, which he placed on the table and asked:

“I bet that no one can make this egg stand by itself.”

All the nobles tried but were unsuccessful and the egg would continue to fall down. Columbus stepped forward and grabbed the egg, which he tapped on the table so that one end would be cracked and flattened. The egg would now stand on its flattened base.
Although the nobles initially complained that they knew that was the solution, the message was loud and clear: once the feat is done, everyone knows how to do it.

This is known in psychology as the historian’s fallacy – a logical fallacy that can be summarised in the words: “I told you so”. Essentially, people assume that people had the same information in the past or that they would not have made the same mistake if they were placed in such a situation. It is another example of cognitive dissonance where the brain finds conflict between a problem and information that could have prevented said problem (which the other person did not have at the time). Therefore, the brain immediately convinces itself that it would have made the right decision as it already knows the answer. This means that we are almost incapable of putting ourselves in other people’s shoes. We label those people as idiots, because they apparently had the same information (they did not) and still could not make the right decision.

People never realise that given the foreknowledge we have now, the Americans would have known about Japan’s plan for attacking Pearl Harbour or that Germany would not have invaded Russia. Although they say “those who cannot remember the past are condemned to repeat it”, we have a tendency to think that people in the past were stupid and we would never make the same mistakes.

Hindsight is 20/20.