It seems like you see with your eyes but in fact they merely detect light and convert it into electrical signals from which dedicated brain areas create what you perceive as vision. Similarly, it feels like you hear with your ears, but again they mainly convert sound information into electrical impulses which are interpreted as the sounds you hear in brain regions dedicated to hearing. In the same way, sex might feel like it takes place in your genitals, but in fact it is all experienced inside your brain.
The part of your brain that ultimately triggers sex drive is called the paraventricular nucleus (PVN) of the hypothalamus. It can release the neurohormone “oxytocin” into the bloodstream (via the pituitary gland) AND use it as a neurotransmitter in the neurons which coarse down the spinal cord en route to the genitals. When activated by a sexually-arousing sensory experience, or thought, the PVN prepares the body for sex by sending a torrent of electrical activity along neurons that descend down the spinal cord exiting at the level of the sacrum and ultimately release a cocktail of neurotransmitters into the tissues of the genitals. In both men and women this leads to vasocongestion whereby the genitals become engorged with blood. In men this leads to an erection and in women this increases lubrication, diameter and depth of the vagina. As I devoted last month’s brain post to female sexual arousal, this month I will place greater emphasis on the male.
Acetyl Choline (ACh), Vasoactive Intestinal Peptide (VIP) and Nitric Oxide (NO) are the names of the three neurotransmitters released by the neurons (many neurons in a bundle constitute a nerve) which terminate in the twin blood reservoirs that run alongside the urethra – the tube that carries urine / seminal fluid through the underside of the penis to the outside world. These blood reservoirs are called the corpora cavernosa and the presence of the ACh, VIP and NO increases levels of another pair of neurotransmitters – cAMP and cGMP – which are both cyclic nucleotides. It is these cyclic nucleotides that are responsible for releasing the grip of those finger-like smooth muscles which, in the unaroused and flaccid penis, hold the corpora cavernosa blood reservoirs tightly closed – preventing blood from entering (see “Flaccid” cross section image, right). However when the tension in these smooth muscles is relaxed by the presence of the cyclic nucleotides, blood can rapidly enter these reservoirs, inflating them (see “Erect” cross section image; left) until they press tightly against the tunica albugina – an inflexible cylinder of tissue that defines the extension limit of an erection. At this point the blood pressure within these vessels rises to 100 mmHg (as opposed to the usual 70-90 mmHg) under which pressure the blood vessels carrying blood away from the penis are closed. This is how the brain induces an erection, next we will encounter factors that can eliminate an erection.
cAMP and cGMP are constantly being eliminated by the action of an enzyme called phosphodiesterase-5. Maintenance of an erection requires constant activity within the hypothalamic PVN in order for electrical messages to be sent down neurons of the spinal cord to ensure continuous release of the NO, VIP and ACh which in turn keeps levels of cAMP and cGMP up sufficiently to prevent the finger-like muscles of the trabeculae from contracting and squeezing all the blood out of the penis (detumescence). This can also be triggered by impulses within the sympathetic nervous system, operating antagonistically alongside the parasympathetic nervous system which is responsible for inducing the erection. The sympathetic nervous system kicks in after ejaculation, explaining the detumescence that usually follows orgasm, but can also oppose the arousing influence of the parasympathetic innervation in response to perceived (or imagined) danger, or any other cause of anxiety. Sildenafil (aka Viagra), tadalifil (Cialis) and vardenafil (Levitra) are drugs prescribed for erectile dysfunction in men which induce and erection by chemically inhibiting the phosophodiesterase-5 enzyme so that the cAMP and cGMP are not broken down ensuring that the blood reservoirs of the penis stay full of blood.
In addition to these monthly brainposts you can catch my regular 140 character dispatches relating to new breakthroughs in brain research (#braintweet) by following me on Twitter.
MTV is the last place you’d expect to find a neuroscientist, right? Wrong! Tonight (Wed 16th Nov 2011) at 8pm GMT I make my second appearance on MTV’s Plain Jane. Yes, I know, it’s a makeover show. You may well be of the opinion that I should choose the series I contribute to better. And you might be right. However, in my defence I would say that, as my aim is to make neuroscience interesting and accessible to the widest possible audience, contributing to such a show allows me to reach people that are wholly unlikely to tune into anything vaguely scientific whether on the BBC, Channel 4, Sky or Discovery. So I saw Plain Jane as an opportunity to raise the profile of neuroscience in the minds of a new audience and to offer my knowledge of dating behaviour that increases the chances of getting the brain of a young lady’s romantic target into the state we know as love.
Tonight’s candidate, Jamie from Chicago, is a lovely girl with a big crush on a young man by the name of Adam. She lacks nothing but a bit of self-confidence and few fashion tips from Louise. As part of the preparation for her big date in Lake Como (lucky girl) we met in Spitalfield’s Market one windy Sunday last summer in trendy London’s favourite shopping/nightspot – Shoreditch.
I set her the rather unusual challenge of offering unsuspecting passers by a hand massage to give her the opportunity to practice some flirting tactics. Sounds a bit odd admittedly but my thinking was this. Number 1: if she was physically holding onto them then they couldn’t get away until she was done with them. Number 2: physical contact between two humans causes the release of oxytocin in the brain.
If you’re trying to get someone to fall in love with you oxytocin-release is what you’re after. It is a vital neurohormone for creating a social bond between two humans as it makes a person feel safe, happy and secure. There are many things you can do to increase release of oxytocin in a person brain: offer words of support when a person is scared or vulnerable, do someone a favour in their time of need – pretty much any altruistic gesture of support will do it. But physical contact is certainly one of the most potent ways to achieve this goal when standing in the middle of a pedestrianised shopping precinct.
The other tip was to avoid typical topics of conversation that flit into a person’s head when they haven’t really thought about it: like what a person does for a living, what they had for breakfast etc. Of course, the aim of effective flirting is to excite the date not bore them to death.
On the whole people love nothing more than to hear the sound of their own voice; ideally talking about themselves. So I encouraged her to give them ample opportunity to do so by steering them onto subject matters that are likely to boost their self-esteem. Using a simple mnemonic technique using the Palm of the hand, Thumb and Forefinger I suggested that she try and steer them into topics involving their Passions, Talents and Fantasies. That way the brain areas involved in creating feelings of excitement and pleasure should be maximally stimulated. The idea is to forge subconscious associations between being in your presence and positive emotional states to make them want more of the same.
I have no idea whether she employed any of that advice in her luxurious date on the banks of Lake Como. Regardless, my main aim was that these neuro-informed brain tips would help viewers find romance in their real lives and realise that knowing how the brain works can be both interesting and come in useful from time to time. The very artificial and impersonal set up Jamie had to endure was always going to make her job of kindling love under the bright lights and watchful eye of cameras very difficult. My fingers are crossed that, despite the tough circumstances, she manages to get her guy tonight at 8pm GMT on MTV.
In addition to these fortnightly brainposts you can get a daily #braintweet by following me on Twitter.
On Tues 2nd November a beautifully shot episode of “Plain Jane” airs across Europe on MTV at 21.00 (GMT). British fashion journalist, Louise Roe, takes sweet but slightly awkward, inelegant young women and transforms them into confident, gorgeous divas.
The aim: to hone their raw potential into a final product that enables them to win their secret crush.
In a nutshell: Louise meets “Jane” who explains why she just can’t seem to make a good impression, they go shopping, “Jane” gets some expert date training, confronts phobias via adrenaline sport and then turns up to a lavish date in an exotic location to seduce her man – a man who has no idea who his date for the night will be. Sure, you’ve heard it all before, except that in this particular makeover show they’ve injected some brain science!
Last summer, MTV invited me out to the beautiful alpine lake town of Montreaux (directly opposite the iconic mountains of Evian bottle fame) to provide a little brain-informed date training.
Having a neuroscientist provide inspiration to a girl trying to get ahead in the love game may sound a bit odd, but at the end of the day it is the brain after all that produces the experience of love in the first place.
The “Plain Jane” of this episode goes by the name of Sarah – a tomboy by day and a little bit too slutty by night. Her difficulty essentially boils down to the fact that she simply tries too hard and becomes clumsy when in the company of guys she really likes.
Once her shopping trip to Geneva and morning at the local Swiss finishing school were successfully completed, I coached her with a few choice tips on how to get the best out of her brain when chatting with the hottest young gentlemen that the Swiss Alps had to offer.
She was given the opportunity to practice putting this advice into action with a medley of men from the European brat pack in a beautiful hotel that looks out across the serene grace of Lake Geneva.
On a date, if one person perceives the other to be uncomfortable then that makes them feel uncomfortable too, setting up a downward spiral.
However by thinking about the signals that your body language, tone of voice, enthusiasm with which you embrace certain topics of conversation sends out, an explosion of dopamine and serotonin can be triggered in the other person’s brain to make them feel comfortable and happy.
I explained to Sarah the mechanisms at work in her brain that lead to her trying too hard to impress and the influence that this subsequently has on her date’s brain state. I spoke with her about how the adrenaline and cortisol release that can put a person on edge can also be harnessed to produce a spark of excitement. I explained ways in which she can wield the power of the oxytocin neurohormone that, when released in the brain, leads to feelings of trust, comfort and bonding; luring that man into her spell.
How much of this ends up hitting the cutting room floor and how much into the final cut remains to be seen. Either way I think that MTV deserves a little credit for being forward-thinking enough to employ a neuroscientist as one of their dating coaches in the first place! Personally I’m going to be watching on Wed at 9pm because I’m really keen to find out whether or not she got her guy. She was firing on all cylinders when I last saw her so I’m cautiously confident that it might just have gone her way. Plain Jane, 9pm, Wed 2nd Nov, MTV.
In addition to these fortnightly brainposts you can also get my daily #braintweet – pearls of brain science that I distil into 140 characters – by following me on Twitter.