Last summer I was invited by the lovely people at the Latitude Festival to participate in a debate at the Literature Tent on the impact of online pornography on society.
It was chaired by Dr Suzi Gage (@soozaphone) of Bristol (and by now Liverpool) University, known for her popular Guardian science column and podcast Say Why to Drugs. The other panelists were Martin Daubney (@MartinDaubney), former editor of lad’s mag Loaded for eight years and theatre-maker Christopher Green (@Kit_Green) creator and player of comedy Country ‘n’ Western heroine Tina C.
My role was to bring the neuroscience perspective, Martin the media perspective and Chris was taking the arts angle. I got prepared quite a few weeks in advance and was stunned by what I found lurking in the academic literature. So I thought I’d share my main findings with you here in this month’s blog.
When people think of addictions, compulsive consumption of various psychoactive substance is usually the first thing to spring to mind. Much research has demonstrated a hyper-responsiveness of the reward pathway – the ventral tegmental area in the midbrain and nucleus accumbens in the ventral striatum in particular – to drug-related images in the brains of people addicted to recreational drugs like, for example, cocaine. This body of research also demonstrates that the activity generated in the reward pathways of drug addicts to pleasant images of scenes unrelated to drugs, is somewhat diminished compared to non-drug takers. In other words, excessive consumption of drugs seems to subtly rewire the reward pathway so that it becomes more sensitive to visual scenes relating to their preferred recreational drug and less so (than normal) to everything else. It seems this is not just limited to drugs, a similar impact on brain function is seen in people who over-consume porn too.
It is important to bear in mind that the reward pathway is not only important for generating feelings of happiness when we participate in pleasurable activities, but it’s also instrumental in predicting what choices might bring us rewards in the future, which means it is critically involved in decision making. It’s role in helping us evaluate the benefits of one option over another extends to the point where this system, in combination with other nearby brain areas, can be thought of as providing the very drive that motivates us to pursue one course of action over another.
In recent times, research into excessive consumption of various products accessed through the internet – online gaming, gambling and pornography, to name but a few – also leads to behaviours that have all the hallmarks of addiction, not to mention the altered neurological responses outlined above. There has been some resistance to this idea in various academic communities, but the movement to have these “arousal” addictions included in handbooks of psychiatric illness symptom classification, and in particular the DSM-5, is starting to gather momentum.
On the basis of a huge survey investigating the pornographic consumption and sexual experiences of 28,000 Italian teenagers it seems that, for about one in ten boys who consume explicit online pornography on a daily basis, the habit is interfering with their ability to engage in real life sexual activities:
Carlos Forsta, President of the Italian Society for Andrology and Sexual Medicine.
This may at first glance seem to fly directly in the face of the stereotype of the ultra-horny teenage boy, brimming full of the very sex hormones that would usually ensure a hair-trigger sexual response to any possibility of coitus. But in light of research conducted many years ago by joint winner of the 1973 Nobel Prize for Physiology or Medicine, Nikolaas Tinbergen, it starts to make a lot more sense. In experiments conducted with “supernormal” stimuli, he observed that birds preferred to sit on larger than normal and / or more colourful eggs constructed from plaster, rather than their own real eggs. Similarly, herring gull chicks would peck harder and more often at a fake adult herring gull beak with brighter or more numerous red spots than the real thing, in a vain effort to elicit a regurgitated dinner. The point is that the larger than real life stimuli seem to have short-circuited the birds’ primal instincts leading to a preference that would ultimately be deleterious to the survival of the bird’s progeny.
It seems that the ubiquitous availability of explicit internet pornography is leading to a similar scenario in modern day internet addicted teenage boys. A subconscious preference for artificial, supernormal, explicit porn over actual sexual partners seems to be occurring with alarming regularity in adolescents who let their penchant for titillating pornographic films get out of control. In his TED talk entitled “Why I stopped watching porn” Ran Gavrieli gives an excellent and compelling account of some of the key differences between what pornographic films actually show and the relatively tame sensory stimuli involved in genuinely satisfying, intimate sexual behaviour between consenting adults.
Essentially, he points out that themes typically conveyed on free online porn sites, such as female subordination and extreme close ups of penetration to name but a few, are the human sexual equivalent of the brightly coloured, super-sized eggs and beak markings from Prof Tinbergen’s experiments (just not in so many words!). Porn is a supernormal stimulus, dominated by explicit close ups of penetration that you simply can’t reproduce in reality (the penis and eyeballs will always be separated by a set distance, unless you are exceedingly flexible, of course). Inevitably the real thing pales into insignificance by comparison after sufficient daily use of explicit porn of virtually infinite variety. No wonder boys are struggling to get it up!
This isn’t to say that there is no place for pornography in society. Regardless of your attitudes on this topic, it certainly isn’t going away any time soon. However it may be useful for porn fans to bear in mind the concept of everything in moderation. Once one genre of porn is no longer arousing there are many other categories to choose from. Once the relatively soft porn is no longer stimulating, casual browsing will always yield more explicit options. Eventually the kind of sexual activities we are likely to have access to in real life become insufficient to yield an erection for long enough to reach climax, which will inevitably lead to relationship problems. And nobody wants that.
The good news is that abstinence from pornography is usually sufficient to enable normal biological sexual function to eventually return. Interestingly, in older men this takes two months, whilst in younger men it can take much longer: four to five months. Find out more in the Latitude Podcast of the Porn Perspective Debate.
Spring has finally hit London. And like many people I found myself motivated to get outside and do some exercise.
I went down to the park where I spent most of my childhood and, as I jogged, stretched and sprinted, I found myself marvelling at the wonders of biology.
The trees were in full blossom, swarms of insects buzzing around, helping with the vital job of carrying pollen from flower to flower.
Male magpies and blue tits were showboating – swooping, diving, in an incessant chase – competing for the amorous attentions of the female onlookers.
Male pigeons were getting all ruffed up, pirouetting like whirling dervishes, in the hope of taking the fancy of their target lady pigeon.
My attention then landed on a group of humans sat on the grass directly in front of me, as I exercised atop a council-provided rowing machine, where I observed courtship behaviours that were not dissimilar.
Six males and six females, somewhere in their mid-teens and freshly discharged from school, were sat in a disjointed huddle.
All the boys had their shirts off – despite it only being warm – far from the sweltering weather that usually triggers bare-chested exposure in the city.
These young lads had their own method of peacocking, namely running around, wrestling good-naturedly, draping a fraternal arm over each others shoulders to emphasise what great friends they all were.
All the while they flashed furtive glances at the girls to see whether or not these displays were eliciting approving looks from the young ladies.
The girls, despite determinedly fixing their faces into expressions of nonchalance, were also quite flagrantly advertising their fledgling sexual wares.
Only one girl in the group, for instance, had their shirt completely unbuttoned; she happened to be the only one in the group whose sexual hormones had already sculpted mature breasts.
Another was at the opposite end of this spectrum – her ovaries had yet to unleash the torrent of oestrogen and progesterone that would one day increase the curvaceousness of her body.
In the meantime, her growth hormones had clearly been surging and the resulting growth spurt had dramatically elongated her body and limbs.
She had opted to roll her demure school-issue skirt up around the waist to reveal as much leg as possible – a strategy I distinctly recall the girls I used to hang around with as a teenager describing as: “standard”.
Was it a coincidence that each of these girls happened to respond to the pleasant weather by advertising the assets they perceive to be most alluring to the boys? I think not.
Was it a coincidence that the male humans and magpies responded to the sunshine by larking around to advertise their strength and agility? Of course not.
It may not have been a conscious decision on their part, but nonetheless, both the males and the females of the group were engaging in behaviours indicating a desire to be noticed and approved of by the others.
All of these behaviours are orchestrated by the action of sex hormones upon regions of the hypothalamus that govern sexual behaviours including courtship displays.
And when boiled down to their bare bones these courtship displays are surprisingly similar despite the considerable differences in cerebral sophistication of the different species.
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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.
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The G-spot was named in honour of the gynaecologist Ernst Graefenberg M.D., who first proposed the presence of an “erotogenic zone” (an area of tissue that swells and evokes erotic sensations in response to touch) just inside the vagina alongside the urethra, in a paper published in 1950. Despite the testimony of thousands of women that a particularly sensitive region of the vagina resides at this location, its existence is still contested in the medical literature to this very day.
Earlier this year an academic paper was published claiming to have finally confirmed the existence of the fabled G-spot (on the basis of a post-mortem dissection of a 83 year old cadaver). The author was promptly pounced upon by distinguished colleagues and so the dispute rages on with medics and scientists continuing their debate over whether or not a distinct anatomical structure exists close to the opening of the vagina in its anterior wall (that is: the wall of tissue that is closest to the abdomen). For those to whom the anatomical details are considerably less interesting than the functional impact that stimulation of this area makes in the pursuit of sexual satisfaction there is much to be said for this unobtrusive patch of vaginal tissue.
Stimulation of the clitoris – or the clitoral glans to be specific – which nestles directly beneath a hood of tissue that protects this extraordinarily sensitive sensory structure, is generally regarded to be the most effective way to stimulate the female genitalia in the pursuit of orgasm. Effective as this may be for many women in reaching climax efficiently, the orgasm that results tends to be highly localised to the immediate vicinity of the clitoris itself. Vaginal stimulation, on the other hand, can result in an orgasm that manifests itself throughout the entire body.
Inspection of the adjacent illustration will reveal that the glans is quite literally just the tip of the clitoral iceberg. The clitoris also extends to incorporate both the left and right crus clitoris (dark pink) and the bulb of the clitoral vestibule (light pink). Considering the close proximity of the bulb of the clitoral vestibule to the anterior (upper, in this diagram) wall of the vagina – it is clear to see why pressure upon this region (location of the highly contested G-spot) is thought by many experts in the field to actually mediate its effects via stimulation of the clitoral bulbs. The paraurethral glands (a.k.a. Skene’s glands or female prostate) are also unavoidably stimulated by this same pressure and from which an ejaculatory fluid may be expelled at climax in some women.
Orgasms resulting from stimulation of the vagina tend to involve muscular tension that gradually builds up throughout the whole body, culminating in an intense euphoria and muscular convulsions that cause involuntary spasms in the limbs, torso and face at the moment of climax. Yet another different type of orgasm altogether can be elicited by stimulation of the cervix; the “neck” of the womb or uterus which lies at the far end of the vagina and has its very own system of nerve fibres carrying touch information to the brain. Touch information is relayed to the somatosensory cortex – a strip of brain tissue dedicated to processing tactile sensation from all over the surface of the human body. Although the different brain areas dedicated to processing touch at the tongue/mouth/throat, face, hand, arm and trunk are located in a strip on the outer surface of the brain, those that receive tactile information at the leg, foot and toes are positioned on the part of this strip that spills over onto the inner surface of the brain where the two hemispheres face each other.
Stimulation of the clitoris is primarily carried to the brain via the pudendal nerve, vaginal stimulation mainly by the pelvic nerve and cervical stimulation mainly by the hypogastric, pelvic and vagus nerves. Simultaneous stimulation of the clitoris, vagina and cervix can result in a “blended” orgasm incorporating the various qualities of each. For further reading I would highly recommend the “Science of Orgasm” by Komisaruk, Beyer-Flores and Whipple.
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What is the human body’s most important sex organ?
In this, the first in a series of brainposts investigating how our brains orchestrate sexual behaviour, I provide a short introduction into this fascinating (and often overlooked) branch of neuroscience.
Libido, lust, desire is a drive that promotes relatively indiscriminate sexual activity and is fundamentally dependent on adequate levels of testosterone in men and women to ensure neural pathways that orchestrate sexual arousal are well maintained. Lust ensured that every single one of your direct line of ancestors managed to pass their genes on to the next generation, by hook or by crook. It is not an emotion, nor a feeling, so much as a fundamental, goal-directed, motivation to act – hence the term sex drive.
Love evolved much later to promote more selective sexual behaviours. Romantic love is thought to involve elevated levels of dopamine and noradrenaline in combination with low serotonin to produce sensations of intense euphoria, energy and excitement whilst also compelling us to obsess over our single specially-chosen beloved deemed superior to all the others.
Long term bonding is a third system, seemingly dependent on the action of the neurotransmitter vasopressin, which mediates behaviours promoting long-term partnership with one individual; known as monogamous pair bonding. This evolutionary benefit of such behaviour relates to the importance of nuture, i.e. ensuring that parenting duties are fulfilled. Committed parenting helps offspring to fulfil their genetic potential, improving the quality of mates that they attract, facilitating passage of genes into a third generation.
These three systems, although inter-related, are largely independent of each other. At any stage in post-pubertal life the three systems can be perfectly aligned or pull in different directions. No wonder the tabloids are full of stories of public figures sleeping around, and /or falling in love with people other than those with whom they are engaged in long term relationship. Understanding how we are wired up for sex, love and commitment can help us navigate the traps and pitfalls of the love game. If we can anticipate the antagonisms that develop between these systems, we can develop decision-making strategies that favour contentment in the long term, as opposed to immediate, but fleeting, satisfaction. For further reading on the evidence behind this conception of coupling as a three stage process I would highly recommend Helen Fisher’s books such as “Why We Love.”
Sex drive, or libido, evolved in mammals to promote the act of sex, or coitus. Coitus is captured in the below image, which is, believe it or not, an MRI image of a couple having sex inside the scanner! I’ve taken the liberty of adding some pink coloured dots to delineate the border of the woman’s body and blue dots to delineate the outer surface of the man. The green dots show the path that the sperm takes at the point of ejaculation: passing from the testis up and over the pelvic bone (white oval) and bladder (black/grey semi-circle), through the seminal vesicle / past the prostate gland (which together inject the constituents fluids of which semen consists), along the length of the penis where it is deposited right next to the cervix (neck) of the woman’s uterus (womb). Under optimal conditions the uterus rhythmically contracts to “suck” this seminal fluid up into the uterus and even on into whichever of the two fallopian tubes is most likely to have an ovum (egg) ready for fertilisation.
I added the red dots to help readers orient themselves with regard to the key erogenous zones in the female anatomy. The clitoris is marked with a large red dot and the position of the G-spot has been illustrated with several smaller red dots to convey that fact that it’s exact location on the anterior (front) wall of the vagina appears to be highly variable from person to person.
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