The process of fermentation has been practised since the early agricultural civilisations. But even now, no-one really knows how alcohol exerts the effects it does. As a neuroscientist, I am fascinated by the myths, and especially the mysteries, that surround alcohol and the brain.

One of the most frequently touted myths currently in the news, is that alcohol and cannabis have the same effects on the brain, hence if alcohol is legal, then cannabis might as well be. In my view, cannabis and alcohol are two very separate entities, working in very different ways within the brain.

But let’s look at how the two drugs actually work. Think of brain cells and the connections between them, a little like a huge jumble of telephone lines. Although these lines of communication might be potentially available in the adult brain they can, nonetheless, be temporarily out of service: like telephone lines that are actually in place, but simply not being used. The brain equivalent to an activated telephone line would be the process of ‘synaptic transmission’. A synapse is the narrow gap which separates one brain cell from another. And it is here, at the synapse, where the analogy of telephone lines literally breaks down. Imagine an electrical signal buzzed, as indeed it is, all the way down to the end of the cell at speeds of some 250 miles an hour. But then the synapse presents a natural barrier, an electrical signal just won’t cross the gap. As the electrical signal reaches the end ‘terminal’ of the brain cell, it causes a chemical to finish the job, and transmit the signal across the gap. The chemical ‘transmitter’ comes in many different shapes and sizes. It is made in the brain cell and stored in small packets. Once the electrical signal has acted as a trigger, then some of these small packets empty their contents into the gap. The transmitter then rapidly crosses the gap and locks into a specialised molecule on the outer surface of the target brain cell. This molecular complexing, is like a boat going into a dock, - although my own favourite analogy is that of a molecular handshake. Once the transmitter binds to its special ‘receptor’, then a new electrical impulse is generated in the receiving cell, and the whole process starts again. In the brain, we can interfere with the otherwise passive process of the spread of an electrical current and this is where drugs come in.

Alcohol interferes with this process of synaptic transmission by preventing the phone call in the first place. Its key action is to impair the communication between one brain cell and another. Alcohol destabilises the molecular configuration of the wall of the neuron, and once the parallel barriers in the walls start to buckle, then the electrical signal will not be able to be sent as normal. If you have been drinking, therefore, it will be very hard for your brain to function as fast as normal. Hence the problems that we have all experienced, in sensory motor coordination, of walking along a white line, or of touching your nose with your finger. Alcohol may work with other transmitters, that slow down activity in the brain. Because of its actions in slowing brain cell functioning, alcohol is known as a CNS ‘depressant’.

Although alcohol enters the brain easily, it requires at least 7,000 mg (1/2 pint of beer, or a small glass of wine) to have a perceived effect on one’s consciousness. Cannabis inhaled in a reconstructed cigarette has a harder time gaining access to the brain cells, yet it can have an effect as low as 0.3mgs! Cannabis acts so efficiently due to the existence of specialised molecular targets, ‘receptors’, by which the drug can exert its custom-made action. The effects of cannabis can be realised at the strategic molecular hot-spots, where its effects can be concentrated. Hence, the active ingredients of cannabis,-9-tetrohydrocannabinal (THC), fit into their own custom-made molecular gloves, their specialised receptors. The reason that receptors for THC exist, but not those for alcohol - is that cannabis has its own naturally occurring agent. Hence there is a world of difference between kidding the brain into thinking that an impostor has been released (as with cannabis), and merely slowing down generalised processes of communication (as with alcohol). Another difference between naturally occurring agents, such as those for cannabis or morphine, and the drug equivalent, is that the drugs will not be destroyed as quickly, and hence will have a much longer-term effect in the brain. If we pursue the handshake analogy a little further, it is a little like squashing someone’s hand so much that the hand becomes numb. Brain researchers speak of receptors for different transmitters, and those that are affected by different drugs, as becoming less sensitive. No such receptors exist for alcohol. This might be why there is another big difference between cannabis and alcohol, that is that cannabis notoriously enhances the risk of psychotic episodes, and schizophrenic side-effects, even in individuals that have never exhibited such symptoms before.

Moreover, with merely moderate social use, there are different risks of long-term effects. With cannabis, but not with alcohol, it has been shown that even when the drug is no longer used, long-term impairments on cognition and attention can persist. Another big difference between the two drugs is the duration in the body: cannabis can be cumulative over days, whilst it takes only one hour for one unit of alcohol to clear from the body.

THC will remain in different parts in the body differentially. In blood, it will have declined to less than 20% within a few hours: however, in the brain it will reach its peak concentration at 12 hours, yet remain at some third of that concentration for up to 120 hours. Meanwhile, over that same period, there is a slow escalation of cannabis in the fat of the body. Hence different people will respond differently accordingly to the amount of body fat they have. Moreover, if anyone takes a further dose of THC then clearly there will be an accumulation in their body tissue that no-one would have predicted.

But perhaps the most important difference of all is that cannabis, not alcohol, seems to exert a very powerful pain-killing effect. If this is true, - and as yet the jury is still out, since clinical trials need to be properly performed, - then the conclusion is that it must be having a huge long-term impact on the central nervous system! There is also a strong risk of dependence on cannabis that is not seen with a social use of alcohol. 10% of cannabis users who want to stop are having problems doing so, and there are withdrawal effects after only three days of cannabis use.

Although the effects of cannabis are longer-lasting and far more powerful than alcohol, both will be working to change the number of ‘telephone lines’ active at any one time. So how might these drugs, cannabis and indeed alcohol, actually have the effect they do on the way we see the world?

When we talk about a ‘mind’ we are normally emphasising simply the personal aspects of the way we see the world, as in ‘I don’t mind’, ‘broad-minded’, ‘develop one’s mind’, etc. But it is impossible surely for something you feel, ultimately not to have some physical basis in the body: even a personal view will be just that, - the personalisation of the brain through the configuration of brain connections through experience. Viewed in this way, we can see that we would always be evolving as people. You are not the same individual, arguably, as you were five years ago or even a week ago. Every experience you have, will change the way that you see the world. Brain connections therefore are all-important. If alcohol works on these connections, however temporarily, it is easy to see how, in the short term, as with cannabis in the long term, our view of the world might change. Initially, we evaluate the world in sensory terms: how sweet, how fast. how loud, but gradually these abstract sensations will coalesce into people and objects and, in turn, they will become memories. Sometimes something very banal may have a highly personal significance, by activating an excessive number of connections because it is important, ie triggering off a further series of very extensive connections. With long-term cannabis use therefore, there may be long-term quasi-permanent changes in how one sees the world. The cannabinoid system and the natural equivalent of THC work as normal tools in the development of neurons, and may therefore change brain connections and, with it, associations in the longer term.

Alcohol is, as we have seen, less potent, and does not have a role in the development of the brain but, nonetheless, because of its action, however much more temporary on neuronal connections, we might see a similarly temporary change in the way in which we see people and places in the world: they may come to mean ‘less’. Alcohol then, I am suggesting, can affect your mind. The more you drink, the more it will sabotage the neuron connections so that inner thoughts can no longer dominate: instead you are more immersed in a world of immediate sounds, sights and sensations. The greater the consumption of alcohol, the less the individual mind will feature, the more you will be, as are children, a passive recipient of the senses.

But if alcohol can affect the mind in this way, what about the other way around? What about our own personalised brain connections - our minds - influencing our particular view of alcohol? This question might help us understand a very great mystery: why do individuals respond to alcohol differently? For example, why do some - albeit a minority of 2% of women and 6% of men in the UK- need to seek oblivion in alcohol? One answer is to blame it on the genes, - there may be a genetic predisposition to alcoholism, but we need to understand exactly what that means. Alcoholism can’t be locked into the structure of DNA any more than can ‘good housekeeping’ or being witty. After all, a gene will merely make a protein. We need to know what that protein does in the landscape of the brain and, indeed, how that landscape corresponds to the individual configuration of brain cell connections that occurs even in clones, ie identical twins. There are a mere 30,000 or so genes in body, whereas there are 1,000,000,000,000,000 brain connections: so even if every gene in your body were each to account for a single brain connection, there would be a deficit of 1010! Genes are important to the brain, just as sparking plugs are important to a car engine, but there is a big difference between something being necessary and sufficient.The potential of a sparking plug is only realised once it is placed it an engine, and the engine in a car and the car has a driver, and indeed wheels. So if a protein that is made from a gene within the brain must, in turn, be able to operate in the context of all the sophisticated neuronal circuitry and chemistry that makes up brain regions which, in turn build up to form what we call a brain. If the sparking plug is defective, and a gene is defective, then an impairment, such as a predisposition to alcohol, may become apparent: but that’s not to say that that is the whole story. Genes alone are not sufficient. The expression of a protein, even in the correct micro-environment has to be nested in the hierarchy of integrated brain circuits and overlapping brain regions and, indeed, I would argue placed within a whole body, in order for the effects, the final behaviour, to be apparent.

As a human, you are born with pretty much all your brain cells, but it is the connections between neurons that account for the growth of the brain after birth. When we are born, our brains are the same size as that of a chimp, but then our brain grows, as the connections proliferate, cross, re-cross and fight for survival. It is a jungle in there, where survival of the fittest, the most hard-working neurons will triumph. Brain scientists call this ceaseless dynamism in the brain, plasticity. Plasticity is an astonishing phenomenon where the brain can rewire itself, for example after damage. This remarkable feature of the brain is particularly apparent in the very young. There are even cases where, following surgery due to epilepsy, a child has had up to half their brain removed, but recovered full function. Such effects can persist into old age, for in cases of stroke, patients can make near full recovery of function, after a relatively short period of time.

The brain works on a ‘use it or lose it’ principle a recent study showed that taxi-drivers have a larger hippocampus than others.This area of the brain contributes to memory: taxi-drivers use their memory more than most of us, as they have to remember street names. Another interesting example shows that five-finger piano exercises can enhance brain territory relating to the digits, and a similar phenomenon will even occur following mental practice, not the mechanical practice of fingers to keyboards. The basis of this enhancement in brain territory is the growth of connections between brain cells, more particularly the growth in the branches of brain cells, which enables it to form connections. We know that in rats brought up in an enriched environment with ladders and wheels, compared to those in simple conditions, these branches are much denser even in adults. Similarly, as people age, it is these same branches, with the potential to form connections, that are pruned back, giving rise to symptoms of senility.

So, I hope I’ve convinced you that these connections form the basis of the mind, so that even if you are a clone, ie an identical twin, you will have a unique configuration of brain cell connections. It is these connections and how they are incessantly changing and forming, that could account for the creativity that is so treasured in humans, and is never found in computers. As the famous physicist, Neils Bohr, once admonished a student: "You are not thinking, you are just being logical". The mind then, is not an abstract philosophical notion, nor a fixed, inviolate entity, but rather an endlessly dynamic and exquisitely sensitive web of neuron connections that determines how we see the world, whilst at the same time being changed by that world. And alcohol is very much part of our world. I would like to suggest that it is the ‘blowing of the mind’ or the ‘losing of one’s mind’ with excessive alcohol, say, that may account for how we view alcohol, and how we see it as a palliative for life’s ills, as well as explaining how, when taking an excess, we can literally ‘blow our minds’.But how exactly does alcohol wreak its effects on our state of mind? why should we do so? This is where we come to the other great mystery. How does alcohol actually give us pleasure? This is perhaps the hardest but most exciting question that we can ask, because it actually touches on the final ultimate secret of the brain, how it generates subjective sensations of consciousness.

My own view is that it is neither brain region, nor genes, but the middle level of organisation where we should look: namely at the synchronised activities of assemblies of brain cells that can work together over fractions of a period of time. The bigger the assembly, the ‘deeper’ the degree of consciousness. Although we speak about the depth of consciousness every day, in everyday life, up until now, scientists have normally viewed the phenomenon as all-or-none: you are either unconscious or conscious. We now know that this may not be the case.

Certainly, during anaesthesia and sleep we know that the brain has different stages, different degrees of unconsciousness, and surely if you can have different depths of lack of consciousness then, conversely, you should have different degrees of consciousness too. My own suggestion has been that consciousness is what happens when there is synchronised activity of brain cells - the more working together in an ever bigger assembly, the deeper the degree or depth of consciousness. A rat will be conscious, but not as conscious as a dog, and a dog will be conscious, but not as conscious as a primate, and similarly, a small child will be conscious,but not as conscious as an adult. If consciousness grows as the brain grows, then it makes sense that the foetus has a rudimentary type of consciousness, similar to that initially of very primitive animals, which gets more sophisticated as the brain accommodates sophisticated physiological functions. Seen this way, consciousness is like a dimmer switch, it grows as brains grow.

One way that we as adults can re-visit the state of an earlier, less sophisticated consciousness, is dreaming. Here, because the brain cells will not be recruited into a big assembly, by a powerful stimulation of our senses, it follows that we could have a rather flimsy, haphazard, sequence of assemblies active for one moment and then lost. It would be a bit like a small stone or pebble being placed on the gently on the water’s surface, so few ripples emanated. The third way we might achieve the child-like press of the moment type of consciousness, would be in fast-paced sports, where the competition for one assembly would quickly supersede the other, preventing it from forming properly. Indeed, if we look at children dreaming, and fast-paced sports, we know that all are characterised by the press of the moment, a premium on the purely sensory, and arguably a loss of one’s mind: there is little reasoning with the chance of high pleasure. Clearly human beings enjoy being in the state where they are the passive recipient of their senses, and are again like children in a throbbing, sensual world.

Now let’s return to alcohol, and to the model of the ripples. If those ripples are caused by the connections and the ease with which they work and if, as we have seen, alcohol dampens down those connections, it follows that here we have a direct way of entering this ‘small assembly state’ - the world of the child, the dreamer, or the fast-paced sports: the world of pleasure. It could be therefore, that alcohol works by changing the ease with which brain cells can normally form large assemblies, and therefore brings us into a sensual, sensory, present. The more alcohol we have, the greater the restriction on the formation of assemblies of brain cells. Hence initially we may merely see less meaning in the past or the future and difficult abstract concepts, concentrating more on the immediate moment. As we drink more, and the assembly reduces further, then gradually the world shrinks from one of highly personalised meaning, to one of pure sensations and feelings, where nothing really matters, it is of no significance, literally. If we persist in taking more alcohol, then gradually we will start to lose consciousness altogether, because the assembly will be just too small.

Because the effects of alcohol are so determined by the landscape of an individual’s brain, and the external environment and context in which drinking takes place, it is surely unwise to make sweeping statements or assumptions about alcohol consumption that might inspire blanket policies encompassing indiscriminately the entire population. Government strategy should strive to reduce alcohol misuse by focusing on the consequences - be they social, general health or psychological/neurophysiological - of that misuse, not by targeting the substance itself.

Nevertheless, we should never underestimate some individuals’ capacity to wreak havoc with the way their brain sees the world. The need for personal responsibility on the part of those who drink is at least, if not more, important than public policy on alcohol. Personal responsibility is often overlooked and under-resourced: but it is vital to spend resources on disseminating information to provide a base for individual choice.

It is vital that, for their part, scientists also take responsibility of helping the public understand the technical jargon and seemingly arcane and obscure facts that provide the back-drop to a real appreciation of what is happening in their brains and bodies when they take alcohol, or other types of drugs. In fact there should be a three way partnership between the public, the scientific community, and the media. Previously the public have instead been the hapless victim of mutual distrust and prejudice between the other two constituencies. But surely both media and scientists have a fundamental duty to keep the public as accurately informed as possible. And they can do so best, by working together.

If science research itself were more centre stage, I would like to see specific studies exploring some of the myths and mysteries we have discussed here. For example, to the best of my knowledge there has been no direct laboratory comparison between the toxicity of alcohol and cannabis on brain cells grown ‘in vitro’, in a dish that allows precise measurements to be made. Secondly, we need to examine the actual relation between wholesale brain operations and the protein or proteins, expressed or absent, as a result of aberrant activity in the gene or genes ‘for’ alcoholism. Finally, it might even be possible one day to test my particular theory of consciousness, and use brain imaging to monitor assembly size of neurons as subjects experience the pleasure of alcohol.

But in the meantime, we can still reflect on the most interesting issue for most of us - that we would not want that kind of sensation, even of being mildly drunk, all the time: those that do we tend to regard as unfulfilled in their lives. On the other hand we all know the importance of ‘letting your hair down’, ‘letting yourself go’. Moderate drinking can even have demonstrable health benefits to some groups in the population. The important challenge to being human therefore, surely, is to balance these two drives. Interestingly enough, the prophet Tiresias in Euripides’ Bacchae, described this dichotomy almost two and half thousand years ago. He counselled that we had bred forth the need, the logic, organisation, and a sense of tomorrow and yesterday, but this had to be balanced by the force that enabled us to live for the moment from time to time. It was of course derived from the god the Bacchae worshipped, Dionysos, the God of Wine.

Alcohol on the Brain: Myths and Mysteries was delivered as a speech at the Royal Institution as the sixth top table talk sponsored by The Portman Group in February.