Neuroscientist Dr Zarinah Agnew came to the Secret Garden Party this summer to teach us about the coital corners of the cortex in her new lecture, Dirty Brains. Here, she gives us the goods on how neuroscientists have probed our privates. 


Zarinah, introducing us to the “dirty” bits of the brain at the Dirt Banquet at the Secret Garden Party this summer.

Trying to make science sound interesting whilst balanced and educational is somewhat of a challenge, but one that I consider to be a central part of being a scientist. I have been working with Guerilla Science for the last few years; we have done a number of events, festivals and parties and it’s been a pretty good ride. This year the theme from their funders the Wellcome Trust is “Dirt” and given that my (very general) theme is brains, I put in a proposal to talk about Dirty Brains: mapping out how the erogenous zones arerepresented in the brain.

The idea stemmed from a couple of lectures I saw at a conference in the US a few years ago: in light of the fact that most of what we know about genitals in the brain has been drawn from studies of men, researchers had decided to instead go to great lengths to map out the female genitals in the brain using real women. Of course my talk (done in conjunction with Dr Aidan Horner of UCL) was accompanied by a fairly long and drawn out description of what these experiments entailed: “mechanical self stimulators” and so forth.

In fact, this new group in the US managed to map out the female sexual organs in pretty amazing detail, locating the precise whereabouts of the vaginal wall, cervix, nipples and clitoris in a part of the brain known as the the primary somatosensory cortex, a strip of brain tissue on the surface of the cortex going down the side of the middle of the brain, from the top of your head to just behind your ear.

This is interesting, as the original studies done by pioneering neuroscientist Wilder Penfield in Montreal in the 1930s had not revealed much about the genitals at all. He painstakingly mapped out how the body is represented both in the primary motor cortex and the somatosensory cortex by opening up the skulls of 126 patients already undergoing surgery for another procedure (such as the treatment of intractable epilepsy) and electrically stimulating different parts of these regions with a probe.

He recorded that simulating the primary motor cortex elicited involuntary movements – hence the name motor cortex: this part of the brain is crucial for controlling movement. The same stimulation given to the somatosensory cortext resulted in sensation in different parts of the body – patients would report strong feelings in various parts of their bodies, when only their brains were being touched. In this way, Penfield mapped out where in the body different parts of the body are controlled and perceived.

Penfield’s pioneering maps of the brain: motor cortex on the right, somatosensory on the left.

Despite mapping out the toes, feet, legs, trunk, hands, arms, mouth, lips and face, there are were almost no reports of elicited sensation on the penis (although Penfied did remark that this may have been due to a sense of modesty). The famous “homunculus”, which shows how big our body parts would be if they corresponded to how much of the brain is devoted to that body part, reflects this: the genitals are underrepresented.

Anything look unlikely to you?

Luckily for science, these days people are much less shy. There are now a plethora of studies looking at self-stimulation, mechanical stimulation, fantasies and orgasm – all of which made for perfect fodder for our talk on Dirty Brains.

In fact, this whole subject area gave us the perfect opportunity to make this point: the amount of brain that is dedicated to a body part is dictated not by the size of that body part, but by how sensitive that body part is. We made this point a bit more tangible with a small game where we asked people to inflate a long thin pink balloon to a size that they thought might represent how much of their brain was dedicated to the penis.

How big is yours then?

Much hilarity ensued: apparently people like to see slightly pink faced scientists talking about rude things. We finished the demonstration by showing a quite unpleasant but updated somatosensory homunculus and hopefully teaching everyone something interesting about body representations in the brain.

Quite unpleasant.

We finished off talking about a form of brain scanning known as “magnetic resonance imaging” (my technique of choice) and what it has taught us about moving parts of the body that we cannot see. Our speech organs for example are extremely mobile and flexible when speaking, but of course we never get to see this. MRI is the perfect way to demonstrate what is happening when you speak: check out this video of me speaking in an MRI scanner.

Only recently has fornication inside an MRI scanner taken place: we showed a video of this incredible performance, and talked our way through the anatomy.  As this was a cross section, it is quite alarming as the woman appears to have no legs. All in all it was a pretty dirty evening.

Working with Guerilla Science has been a fantastic experience: it has helped me to develop my ideas and taken me to audiences I would never have reached otherwise. I believe it is important to communicate science with non-scientists and to talk about what it is like being an academic; Guerilla Science provides the perfect opportunity to make this happen. Highly recommended.