This is Your Brain on Caffeine Quiz

Answer: Stimulant

Stimulants are a class of drugs which, broadly speaking, make you feel more alert by increasing heart rate, blood pressure, breathing and blood glucose levels. Other stimulants include amphetamines, cocaine and ecstasy.

Answer: Adenosine

Adenosine is one of the neurotransmitters responsible for making us sleepy. Because caffeine has a similar molecular structure (i.e. shape), it is able to bind to the adenosine receptors in the brain. By stopping the adenosine reaching our brain, coffee keeps us alert and stops us getting sleepy. The downside is that the brain fights back by making more adenosine receptors, which means more caffeine is needed to block the adenosine from getting through. This can cause regular coffee drinkers to build up a tolerance to caffeine, which means they need more coffee to keep them alert.

Answer: Adrenaline

Scientists still have a lot to discover about neurochemicals, and quite often many different neurotransmitters are involved in one reaction. There is often a cascade effect, whereby an increase or decrease in one neurotransmitter will affect others. It's possible that any of these neurotransmitters are affected by caffeine, however the one responsible for the "fight or flight" response is adrenaline - also known as epinephrine.

By blocking adenosine, caffeine lets excitatory neurotransmitters move about the brain more freely. This results in an increase in neuron firing which leads to the pituitary gland springing into action and releasing hormones which activate the adrenal glands, which in turn release adrenaline.

Adrenaline affects the body by increasing blood pressure, elevating heart rate, opening airways, redirecting blood to the muscles and causing the liver to release sugars. The overall effect of this complicated chain of events is that coffee makes you feel more energetic - it's also responsible for giving you the "jitters" if you drink too much of it.

Answer: Pleasure

Dopamine is known as a feel-good chemical. Increased levels of dopamine in the brain are associated with eating and exercise as well as with addictive substances. There's always some dopamine in the brain, but elevated levels lead to improved mood. Caffeine doesn't increase the amount of dopamine your brain makes, but by blocking its reabsorption into the body it allows you to have higher amounts of dopamine floating around your brain.

Answer: Yes

Differences in genes can cause differences in the chemicals the body produces. Three genes which affect a person's sensitivity to coffee are the CYP1A2 gene, the AHR gene and the ADORA genes.

The CYP1A2 gene affects a person's ability to produce the enzyme CYP1A2 which the liver uses to metabolise caffeine. Differences in this gene can affect a person's ability to eliminate caffeine from the body. The AHR gene regulates the turning on and off of the CYP1A2 gene, which indirectly affects the amount of CYP1A2 produced. If the level of CYP1A2 is such that the liver is able to metabolise coffee quickly, this will lead to caffeine insensitivity, whereas someone whose liver can only metabolise caffeine slowly would be extremely sensitive to caffeine.

The ADORA genes affect the structure of the adenosine receptors in the brain. Caffeine's structural similarities to adenosine are what allows it to bind to the adenosine receptors, preventing the adenosine from making us sleepy. Some people's genes produce adenosine receptors which are shaped so that caffeine cannot bind to them properly. This leaves them unresponsive to the stimulating effects of caffeine.

Answer: Prefrontal Cortex

A subject's brain can be monitored using fMRI while they complete a task. Researchers view an image of the brain on a screen, and monitor changes in brain activity, represented by different parts of the image changing colour.

For this experiment, two groups were asked to complete a memory and concentration task. One group were given a cup of strong coffee, while the other group were given a caffeine free alternative. After 20 minutes they were asked to complete the task while researchers monitored their brain activity using fMRI.

It was found that during the task, all the participants showed some activation of the part of the brain associated with working memory, but those who received caffeine had significantly greater activation in the areas of the prefrontal lobe known to be involved in executive memory, concentration, planning and monitoring.

"Does caffeine modulate verbal working memory processes? An fMRI study." Koppelstaetter et. al. Neuroimage. 2008 Jan 1;39(1):492-9.

Answer: Learning and memory

The hippocampus is associated mainly with long term memory. It is where the brain forms new memories. If the hippocampus is damaged, a person can still recall old memories while being unable to create new ones.

The 2009 study showed that ingestion of a moderate amount of caffeine over a 7 day period slowed down the growth of new neurons in the hippocampus. A single dose of caffeine had no effect. The implication of this is that extended caffeine use could affect learning and long term memory in humans. Interestingly, extremely high doses of caffeine had the opposite effect, increasing production of new neurons.

Answer: Alzheimer's Disease

Various studies have been conducted investigating the link between caffeine consumption and onset or progression of Alzheimer's disease. Studies have linked caffeine intake with lower risk of Alzheimer's and dementia, and shown that drinking a moderate amount of coffee could slow or stop the transition from mild cognitive impairment to dementia.

While the mechanism is not yet fully understood, some studies have concentrated on the fact that caffeine appears to reduce the build up of beta-amyloid, a destructive protein which is commonly found in the brains of patients with Alzheimer's.

Answer: Sneezing

Caffeine keeps us awake, and too much caffeine at the wrong time of day can keep us awake when we'd rather be asleep. Too much coffee can also cause digestive symptoms such as diarrhoea and gastrointestinal reflux. And its stimulating effects include an increased heart rate, which can be an unpleasant sensation if it increases too much.

Ingested in the normal way, coffee is not known to cause sneezing.

Answer: Temporary Blindness

There has been much debate about whether caffeine should be classed as addictive. On the one hand, research has shown that caffeine does not activate the reward pathways in the brain that are normally associated with serious addictions to nicotine, alcohol, drugs and gambling.

However it is not unusual to experience a physiological dependence on caffeine which means that if you don't get your usual dose your body makes sure you know about it. Symptoms of caffeine withdrawal include headaches, muscle pain and stiffness, lethargy, nausea, vomiting, depressed mood, and marked irritability. Withdrawal normally begins within 12-24 hours after stopping caffeine intake and could last as long as nine days.