an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

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women and men: un discours sans fin

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Angel and Devil

Jacinta: Okay Canto, I rather hesitate to open up this subject, because I can’t see an end to it, but I want you to repeat here something you’ve said to me before about women and power, which goes to differences between men and women, an area subject to endless debate and contestation.

Canto: Ah well, I was considering how political power, in the world, is largely in the hands of men, and what the world would be like if the situation was reversed. It’s my humble opinion that the world would be less violent, more collaborative, and a lot more fun.

Jacinta: Well as a woman I’m obviously pleased to hear you say that, but we do try to look at evidence rather than personal opinion here, so what in the way of evidence leads you to this conclusion?

Canto: Well… where do we begin? Simone de Beauvoir famously wrote that women are made and not born, a highly contestable truism as it seems that women are actually wired differently from men, having less neurons but more connections between neurons, in toto and on average, so the very question of what it means to be a woman, or a man is one we’re unlikely to get to the bottom of, but I’d like to start with bonobos, always a favourite topic of mine. They appear to have diverged from chimpanzees only between a million and two million years ago, and they look very similar to chimps, which is likely why they weren’t identified as a separate species until the 1930s, and the differences seem to be far more social than anatomical. I mean, they share the same sexual dimorphism as chimps, and humans, and yet they’re essentially matriarchal, due it seems to social arrangements rather than individual size and strength. That gives me great hope for humans, especially now that physical size and strength are less relevant than ever as leadership qualities.

Jacinta: Ah, well now I get the fun part – you think a human matriarchal society will turn out to be a gigantic mutual wankfest. But what about civilisation? What about science and technology? Considering that women, regardless of culture or nationality, are more into astrology, fortune-telling, spiritualism, religion, naturopathy, and virtually every other pseudo-science and primitivism you care to mention, than men are.

Canto: Well, you’re talking about statistical differences, but you well know that there are many fine female astrophysicists, neurosurgeons, geneticists, experimental psychologists, whatever. You’re hardly the only female skeptic, even if they’re in a minority. And who knows what would happen if females were in a majority, with a history of being in a majority, with respect to leadership and power? Maybe you’d find then that it was men who were more into pseudo-science, statistically speaking.

Jacinta: True, and that brings me to a study analysed on the Skeptics’ Guide to the Universe recently. I had read, like you, that women, overall, had more white matter (the myelinated connections between neurons) than men – by a large factor, and that men had more grey matter, though this was concentrated around particular areas such as the amygdalae and the hypothalamus. However, in the study referred to, the researchers wanted to find if there were any categorical differences between male and female brains. They looked at 4 data sets of MRI and fMRI scans, checking out anatomical and connectional or networking differences, to make comparisons. According to SGU’s Steven Novella (a practising neurologist), the media over-simplified the findings as saying there were no differences, but in fact it was more interesting than that. Novella found this study to be essentially an exercise in examining how we categorise things (how do we define and categorise a disease, for example, or a planet, or a species). How we do so depends on a range of factors, and increasing knowledge, and better technology, helps us to develop parameters for categorising…

Canto: Though this also raises more problems… the more we know or learn, the more problematic our previous categories tend to become…

Jacinta: Anyway, in the case of female and male brains, the researchers distinguished between categorical differences and statistical differences. They used genitalia as a categorical difference. As Novella explains it, with genitalia we have a bimodal system, with male and female equipment…

Canto: I prefer to call it tackle…

Jacinta: And nothing really between. The vast majority of people, as subjects, can be placed in one category or another. Of course there are exceptions, but they are, always arguably, statistically insignificant. So, using this as a yardstick, the researchers wanted to know if there are categorical differences between male and female brains in the same way that there are categorical differences between male and female genitalia. One way to distinguish between categorical and statistical differences is whether, once you know which category an individual belongs to, that provides certainty about their particular traits. If it does, you have a categorical difference. So the researchers looked at about 40 different anatomical and functional aspects of the brain. They found that, generally speaking, there are statistical differences between males and females, in the size of various regions, the richness of the networks in various regions, but with a lot of overlap between the sexes; so it was statistical but not categorical. And the study didn’t look at causes of these differences, whether biological or social (we know that brains can be wired up through social conditioning to some degree). But they also did studies of individuals over the range of the 40 anatomical and functional features to determine how many were ‘typically’ male or female, or somewhere in between. One way to capture this was to ask – what percentage of people had 100% of their brain regions (those 40 features analysed) that were ‘typical’ of their sex? Among the 4 data sets, that percentage was 0 to 8%. So, very few men have ‘all-male’ brain regions, in terms of size and connections. Some 28% to 58% had a mixture of both.

Canto: So let me get this clear, the essential finding, according to Novella, was that though there were statistical differences in specific brain areas – and these are the differences described in ‘Do men and women have different brains?’ in How Stuff Works, from which the new ussr’s earlier post was largely derived – there is a lot of individual variation, which muddies the water rather a lot.

Jacinta: Yes, and I would say hopelessly, at least for those who want to think in stereotypes. As Novella puts it, people are mosaics of male and female traits. Another way of thinking about this, again put succinctly by Novella, is that we can’t assume that because a person is male – or female – we know what that person’s brain regions will be like. Statistical differences can’t automatically tell us about the brain region of any individual. There is no typically male or female brain in the way that there are typically male or female genitalia. And that is really interesting, and it might even mean that it’s illegitimate to say, ‘oh she’s female but she thinks like a man’, or ‘but she has a male brain’. There’s no male brain, or female brain, there are individual brains that are a product of all the influences, genetic, epigenetic, environmental, social, hormonal, psychological, whatever you can think of that influences brain activity and wiring.

Canto: And yet, and yet. Statistical differences do count for something don’t they? We still have the statistics showing that women are more into astrology and naturopathy than men…

Jacinta: Yes but what this study shows is that you can’t base this on some essentialist argument about female brains, and isn’t that a good thing?

Canto: Well, definitely, but then it works the other way. My argument that if women ruled we’d be so much better off can’t be based on anything essentialist either! Maybe being in power would turn their brains into something  like the statistically typical male brain. My hopes are turning to dust…

Jacinto: No, no, don’t despair Canto. Consider the bonobos of the jungle…

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Written by stewart henderson

December 20, 2015 at 11:42 pm

Posted in brain, gender, genetics, ideology, neurology, sex

Tagged with , ,

this one’s for the birds

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clevercrow1

Canto: If anybody doesn’t appreciate the beauty and complexity and general magnificence of birds they should pee off and never darken this blog again.

Jacinta: Right. Now what brought that on, mate?

Canto: Oh just a general statement of position vis-à-vis other species. Charles Darwin, an old friend of mine, was pretty disdainful of human specialness in his correspondence, but he kept a low profile – on this and everything else – in public. I want to be a bit more overt about these things. And one of the things that really amazes me about birds, apart from their physical beauty, is how much goes on in those teeny noggins of theirs.

Jacinta: Yes, but what really brought this on? I haven’t heard you rhapsodising about birds before.

Canto: You haven’t been inside my vast noggin mate. Actually I’ve been taking photos – or trying to – of the bird life around here; magpies, magpie-larks, crows, rainbow lorikeets, honeyeaters, galahs, corellas, sulphur-crested cockies, as well as the pelicans, black swans, cormorants, moorhens, coots and mallard ducks by the river, not to mention the ubiquitous Australian white ibis and the masked lapwing.

Jacinta: Well I didn’t know you cared. Of course I agree with you on the beauty of these beasties. Better than any tattoo I’ve seen. So you’re becoming a twitcher?

Canto: I wouldn’t go that far, but I’ve been nurturing my fledgling interest with a book on the sensory world of birds, called, appropriately, Bird sense, by a British biologist and bird specialist, Tim Birkhead. It’s divided into sections on the senses of birds – a very diverse set of creatures, it needs to be said. So we have vision, hearing, smell, taste, touch, and that wonderful magnetic sense that so much has been made of recently.

Jacinta: So we can’t generalise about birds, but I know at least some of them have great eyesight, as in ‘eyes like an eagle’.

Canto: Well, as it happens, our own Aussie wedge-tailed eagle has the most acute sense of vision of any creature so far recorded.

Jacinta: Well actually it isn’t ours, it just happens to inhabit the same land-form as us.

Canto: How pedantic, but how true. But Birkhead points out that there are horses for courses. Different birds have vision adapted for particular lifestyles. The wedge-tail’s eyes are perfectly adapted to the clear blue skies and bright light of our hinterland, but think of owl eyes. Notice how they both face forward? They’re mostly nocturnal and so they need good night vision. They’ve done light-detection experiments with tawny owls, which show that on the whole they could detect lower light levels than humans. They also have much larger eyes, compared with other birds. In fact their eyes are much the same size as ours, but with larger pupils, letting in more light. They’ve worked out, I don’t know how, that the image on an owl’s retina is about twice as bright as on the average human’s.

Jacinta: So their light-sensitivity is excellent, but visual acuity – not half so good as the wedge-tailed eagle’s?

wedge-tailed eagle - world's acutest eyes

wedge-tailed eagle – world’s acutest eyes

Canto: Right – natural selection is about adaptation to particular survival strategies within particular environments, and visual acuity isn’t so useful in the dark, when there’s only so much light around, and that’s why barn owls, who have about 100 times the light-sensitivity of pigeons, also happen to have very good hearing – handy for hunting in the dark, as there’s only so much you can see on a moonless night, no matter how sensitive your eyes are. They also learn to become familiar with obstacles by keeping to the same territory throughout their lives.

face of a barn owl - 'one cannot help thinking of a sound-collecting device, quoth researcher Masakazu Konishi

face of a barn owl – ‘one cannot help thinking of a sound-collecting device’, quoth researcher Masakazu Konishi

Jacinta: So they don’t echo-locate, do they?

Canto: No, though researchers now know of a number of species, such as oilbirds, that do. Barn owls, though, have asymmetrical ear-holes, one being higher in the head than the other, which helps them to pinpoint sound. It was once thought that they had infra-red vision, because of their ability to catch mice in apparently total darkness, but subsequent experiments have shown that it’s all about their hearing, in combination with vision.

Jacinta: Well you were talking about those amazing little brains of birds in general, and I must say I’ve heard some tales about their smarts, including how crows use cars to crack nuts for them, which must be true because it was in a David Attenborough program.

Canto: Yes, and they know how to drop their nuts near pedestrian crossings and traffic lights, so they can retrieve their crushed nuts safely. The genus Corvus, including ravens, crows and rooks, has been a fun target for investigation, and there’s plenty of material about their impressive abilities online.

seeing is believing

seeing is believing

Jacinta: So what other tales do you have to tell, and can you shed any light on how all this cleverness comes in such small packages?

Canto: Well Birkhead has been studying guillemots for years. These are seabirds that congregate on cliff faces in the islands around Britain, and throughout northern Europe and Canada. They’re highly monogamous, and get very attached to each other, and thereby hangs another fascinating tale. They migrate south in the winter, and often get separated for lengthy periods, and it’s been noted that when they spot their partner returning, as a speck in the distance, they get highly excited and agitated, and the greeting ceremony when they get together is a joy to behold, apparently – though probably not as spectacular as that of gannets. Here’s the question, though – how the hell can they recognise their partner in the distance? Common guillemots breed in colonies, butt-to-butt, and certainly to us one guillemot looks pretty well identical to another. No creature could possibly have such acute vision, surely?

Jacinta: Is that a rhetorical question?

Canto: No no, but it has no answer, so far. It’s a mystery. It’s unlikely to be sight, or hearing, or smell, so what is it?

Jacinta: What about this magnetic sense? But that’s only about orientation for long flights, isn’t it?

Canto: Yes we might discuss that later, but though it’s obvious that birds are tuned into their own species much more than we are, the means by which they recognise individuals are unknown, though someone’s bound to devise an ingenious experiment that’ll further our knowledge.

Jacinta: Oh right, so something’s bound to turn up? Actually I wonder if the fact that people used to say that all Chinese look the same, which sounds absurd today, might one day be the case with birds – we’ll look back and think, how could we possibly have been so blind as to think all seagulls looked the same?

Canto: Hmmm, I think that would take a lot of evolving. Anyway, birds are not just monogamous (and anyway some species are way more monogamous than others, and they all like to have a bit on the side now and then) but they do, some of them, have distinctly sociable behaviours. Ever heard of allopreening?

Jacinta: No but I’ve heard the saying ‘birds of a feather flock together’ and that’s pretty sociable. Safety in numbers I suppose. But go on, enlighten me.

Canto: Well, allopreening just means mutual preening, and it usually occurs between mates – and I don’t mean in the Australian sense – but it’s also used for more general bonding within larger groups.

Jacinta: Like, checking each other out for fleas and such, like chimps?

Cant: Yeah, though this particular term is usually reserved for birds. Obviously it serves a hygienic purpose, but it also helps calm ruffled feathers when flocks of colonies live beak by jowl. And if you ever get close enough to see this, you’ll notice the preened bird goes all relaxed and has this eyes half-closed, blissed-out look on her face, but we can’t really say that coz it’s anthropomorphising, and who knows if they can experience real pleasure?

Jacinta: Yes, I very much doubt it – they can only experience fake pleasure, surely.

Canto: It’s only anecdotal evidence I suppose, but that ‘look’ of contentment when birds are snuggling together, the drooping air some adopt when they’ve lost a partner, as well as ‘bystander affiliation’, seen in members of the Corvus genus, all of these are highly suggestive of strong emotion.

Jacinta: Fuck it, let’s stop beating about the bush, of course they have emotions, it’s only human vested interest that says no, isn’t it? I mean it’s a lot easier to keep birds in tiny little cages for our convenience, and to burn their beaks off when they get stressed and aggressive with each other, than to admit they have feelings just a bit like our own, right? That might mean going to the awful effort of treating them with dignity.

Canto: Yyesss. Well on that note, we might make like the birds and flock off…

how the flock do they do that?

how the flock do they do that?

Written by stewart henderson

November 13, 2015 at 12:06 pm

exercise is medicine

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I read recently that regular moderate exercise sloshes up the blood, washing immune cells from vessel walls. This brings those cells back into the mainstream so to speak, where they can be more effective in combating infection. It makes no small difference – a simple study in which 500 adults were tracked for 12 weeks found that those who engaged in regular aerobic exercise sessions were found to suffer considerably less from upper respiratory tract infections – precisely my personal area of concern. Levels of immune cells in the blood double during exercise.

There’s also good news in this for those of us who couldn’t become gym junkies no matter how hard we tried. Too much exercise (but that means quite a lot) can undo all the good by raising levels of cortisol, noradrenaline and other stress hormones, which alter immune cell functioning. Stress, though, is another one of those complex indicators of health. Mild bouts of stress can be healthful, again boosting blood levels of immune cells. So don’t relax too much, but don’t overdo it.

Even so, exercise helps with everything, and that’s something worth promoting because the recommended dose of exercise isn’t being swallowed by the majority of people in the west. Of course we’ve always kind of known about the benefits of exercise, but the hard evidence has really been coming in lately. A really interesting study was published in the Lancet in 1953, at a time when the rising incidence of heart attacks was becoming a worry. It compared bus conductors to bus drivers on London’s busy double-deckers. The conductors, who spent much of their working day running up and down steps, had half as many heart attacks as their driver colleagues. This landmark study has of course been followed by many others that have confirmed the positive effects of exercise in reducing the incidence of stroke, cancer, diabetes, liver and kidney disease, osteoporosis, dementia and d barkepression.

So what exactly is the goldilocks zone for exercise? Well, anything is better than nothing, and most of us know we’re not doing enough. I’m not quite a senior citizen yet, but studies have been done with the elderly requiring them to do 40 minute walks three times a week, which is hardly strenuous. I catch a tram to work, which requires a ten-minute walk each way, and then a five minute walk each way to my workplace – 30 minutes a day, five days a week, though it would doubtless be better if those 30 minutes were continuous, and if I didn’t dawdle much of the time. The benefits of such a regime have been shown through before-and-after brain imaging. Expansion of the hippocampi, either through the growth of new brain cells, or greater synaptic connectivity, and a restoration of long-distance connections across the brain.

Mental exercise shouldn’t be forgotten either. It has been known for a couple of decades that intellectual stimulation can provide a kind of ‘cognitive reserve’ which can buffer us against the kinds of physical brain deterioration typical of Alzheimer’s and other forms of dementia, but clearer proofs of this have been gathered recently. Magnetic resonance imaging of Alzheimer’s sufferers has caught the goings-on in the brain while cognitive tasks are being performed. Highly educated people – brain workers  if you will – are better able to develop alternative neuronal networks to compensate for damaged areas. I would assume though that it’s not so much about education but about brain usage. Keep tackling new things. Keep using your brain in new ways. And your body for that matter.

Cognitive reserve is now seen as a real thing, and has been pinpointed as residing in the dorsolateral prefrontal cortex, a key area for learning, short term memory, attention and language. Increased activity in this area suggests flexibility in thinking and problem solving. Information processing efficiency is also a key to a healthy brain. Having a high IQ, something I’ve often been sceptical about in the past, is an indication of information processing efficiency, even if the information is often culturally specific. It appears that physical brain deterioration, from Alzheimer’s, stroke and and other causes, can be fended off by compensating neural network development and increased information processing efficiency in certain people, until the deterioration becomes too great to be compensated for, after which things tend to go downhill very rapidly. By the time the symptoms of Alzheimer’s appear in such people, the  physical damage is already well advanced.

A major message from all this is that you should try to develop lifestyle habits involving physical and mental exercise. Always a work in progress.

I note that one of the in terms these days is ‘hat tip’ (h/t), so h/t for this piece to New Scientist, the collection, edition 3: a guide to a better you.

Written by stewart henderson

November 20, 2014 at 8:19 am

Posted in diet, exercise, fitness, lifestyle

Tagged with , ,

aerosinusitis

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it's all about Boyle's Law, apparently (P1V1 = P2V2)

it’s all about Boyle’s Law, apparently (P1V1 = P2V2)

Aerosinusitis, also called barosinusitis, sinus squeeze or sinus barotrauma is a painful inflammation and sometimes bleeding of the membrane of the paranasal sinus cavities, normally the frontal sinus. It is caused by a difference in air pressures inside and outside the cavities.

The above quote is from Wikipedia, and it describes something I experienced on two flights recently (see previous post), though I experienced it, or felt I experienced it, in the ears (I’ve learned not to trust my own perceptions). On the first flight, I experienced a build-up of pressure until a sudden change as of a bubble bursting in some inner cavity, and then everything was fine. I’ve had similar, but less intense, experiences in a car when driving up into the hills near my home. In fact, they’ve been so mild that I’ve often looked forward to them as a physical sensation, and I know it’s common because people would ask around – have your ears popped yet? On my second flight, the pressure built up again on the descent, and I fully expected the bubble to burst as it always did. But the pain just increased, to an excruciating level, so that my face was all scrunched up and I was gasping, squealing and whimpering like a pup. By the time we landed, though, the worst of the pain was gone, and it gradually got better over the next hour or so, and although I could still ‘feel’ it 24 hours later, it was more a memory of a feeling than the thing itself. I don’t know whether my pain was severe or relatively mild as I’ve never felt other people’s pain. This was one of the first things I had ‘deep’ thoughts about as a child. When I was nine or ten years old I fell, while running, and bashed my shin against the edge of our front porch, and I still think that was the most extreme pain I’ve ever felt in my life. I screamed and screamed, and amongst the comforting remarks came the inevitable ‘come on now, stop squealing, it’s not that bad’. Of course this made me angry and resentful but it also raised the questions, ‘am I over-reacting? Would others react like this in the same circumstances? Would they feel the same pain? How could we ever know?’ And along with those questions was one that always ate at me, and probably still does – can I control my pain, can I obliterate it with the power of my mind? I’d sell my soul, FWIW, for total control. But that’s a rather too large side-issue for this post. The Wikipedia article, though, does classify aerosinusitis in terms of pain, along with other more measurable symptoms:

Grade I includes cases with mild transient sinus discomfort without changes visible on X-ray. Grade II is characterized by severe pain for up to 24 h, with some mucosal thickening on X-ray. Patients with grade III have severe pain lasting for more than 24 h and X-ray shows severe mucosal thickening or opacification of the affected sinus; epistaxis or subsequent sinusitis may be observed.

Annoyingly, my own intense but transitory experience doesn’t fit into any of those grades. I also find that this extremely technical article makes no mention at all of ear pain. Much of the focus is on the frontal sinuses, situated behind the brows and connected to the nose or nasal meatus, which naturally makes me uncertain about where my pain was located. Interestingly, the frontal sinuses still haven’t come into existence at birth, and aren’t fully developed until adolescence, and some 5% of people don’t even have them, which just complicates matters for me. As is mentioned above, the frontal sinuses are part of a whole labyrinth of hollows, bones, cartilaginous membranes and passageways known as the paranasal cavities. I’m hoping that the inner ear, or more accurately the middle ear cavity – technically called the tympanic cavity, is also part of that.

Though ‘ear-popping’ seems to be commonplace, aerosinusitis usually occurs in people who have head colds, or as the article puts it, it’s ‘typically preceded by an upper respiratory tract infection or allergy’. Of course, with my bronchiectasis, I’m effectively in a more or less permanent state of infection, so this may be a problem for me every time I fly.

So, what remedy? Well, the problem for me seems to be with the tympanic cavity or eustachian tube on one side. When I was eight, I perforated my ear drum and had to have an operation. I was told afterwards that I should never hold my nose tight while blowing it, as people do (making that horrible honking nose), as this might damage my eardrum. I remember being fascinated by this connection between the nose and the ears, and of course I’ve always followed the doctor’s advice. I didn’t want to blow my brains out of my ears.

Wikipedia suggests using decongestants or painkillers for mild forms of barotrauma, as does this useful site, which deals more with popping ears. First and foremost, though, it suggests gargling with warm salt water, which was my mother’s advice for many medical problems (she was a nurse).

I’m resisting any description of what I went through as ‘mild’.

Working the eustachian tube or tympanic cavity seems to be a good idea, for example by regular swallowing, chewing gum, sucking sweets, yawning, etc.

Sudafed is highly recommended. I’ll bear that in mind next time.

Written by stewart henderson

May 12, 2014 at 11:50 pm

what is autism and what causes it?

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Brain_Autism

The term ‘autism’ was coined in the 1940s by two physicians working independently of each other, Hans Asperger in Austria and Leo Kanner in the USA, to describe a syndrome the key feature of which was a problem with interacting with others in ‘normal’ ways. Sounds vague, but the problem was anything but wishy-washy to these individuals’ parents and families, and over time a more detailed profile has built up.

The term itself is from the Greek autos, or ‘self’, because those with the syndrome had clear difficulties in interpreting others’ moods and responses, resulting in a withdrawn, often antisocial state. Autistic kids often avoid eye contact and are all at sea over the simplest communication.

Already though, I feel I’m saying too much. When describing autism, it’s common to use words like ‘often’ or ‘sometimes’ or ‘some’, because the symptoms are seemingly so disparate. Much of what follows relies on the neurologist V S Ramachandran’s book The tell-tale brain, especially chapter 5, ‘Where is Steven? The riddle of autism’.

Autistic symptoms can be categorised in two major groups, social-cognitive and sensorimotor. The social-cognitive symptoms include mental aloneness and a lack of contact with the world of other humans, an inability to engage in conversation and a lack of emotional empathy. Also a lack of any overt ‘playfulness’ or sense of make-believe in childhood. These symptoms can be ‘countered’ by heightened, sometimes obsessive interest in the inanimate world – e.g. the memorising of ostensibly useless data, such as lists of phone numbers.

On the sensorimotor side, symptoms include over-sensitivity and intolerance to noise, a fear of change or novelty, and an intense devotion to routine. There’s also a physical repetitiveness of actions and performances, and regular rocking motions.

These two types of symptoms raise an obvious question – how are the two types connected to each other? We’ll return to that.

Another motor symptom, which Ramachandran thinks is key, is a difficulty in physically imitating the actions of others. This has led him to pursue the hypothesis that autism is essentially the result of a deficiency in the mirror neuron system.

In recent years there’s been a lot of excitement about mirror neurons – possibly too much, according to some neurologists. A mirror neuron is one that fires not only when we perform an action but also when we observe it being performed by others. They’ve been found to act in mammals and also, it seems, in birds, and in humans they’ve been found in the premotor cortex, the supplementary motor area, the primary somatosensory cortex and the inferior parietal cortex. It’s easier, however, to locate them than it is to determine their function. Clearly, to describe them as ‘responsible’ for empathy, or intention, is to go too far. As Patricia Churchland points out, ‘a neuron is just a neuron’, and what we describe as empathy or intention will likely involve a plethora of high-order processes and connections, in which mirror neurons will play their part.

With that caveat in mind, let’s continue with Ramachandran’s speculations on autism and mirror neurons. First, we’ll need to be reminded of the term ‘theory of mind’, used regularly in psychology. It’s basically the idea that we attribute to others the same sorts of intentions and desires that we have because of the assumption that they, like us, have that internal feeling and processing and regulating system we call a ‘mind’. A sophisticated theory of mind is one of the most distinctive features of the human species, one which gives us a unique kind of social intelligence. That autism would be related to theory-of-mind deficiencies seems a reasonable assumption, so what is the brain circuitry behind theory of mind, and how do mirror neurons fit into this picture?

Although neuro-imaging has revealed that autistic children have larger brains with larger ventricles (brain cavities) and notably different activity within the cerebellum, this hasn’t helped researchers much, because autism sufferers don’t present any of the usual symptoms of cerebellum damage. It could be that these changes are simply the side effects of genes which produce autism. Some researchers felt it was better to focus on mirror neurons straight-off, as obvious suspects, and to see how they fired and where they connected in particular situations. They used EEG (electroencephalography) as a non-invasive way to observe mirror neuron activity. They focused on the suppression of mu waves, a type of brain wave. It has long been known that mu waves are suppressed when a person makes any volitional movement, and more recently it has been discovered that the same suppression occurs when we watch others performing such movements.

So researchers used EEG (involving electrodes placed on the scalp) to monitor neuronal activity in a medium-functioning autistic child, Justin. Justin exhibited a suppressed mu wave, as expected, when asked to make voluntary movements. However, he didn’t show the same suppression when watching others perform those movements, as ‘neurotypical’ children do. It seemed that his motor-command system was functioning more or less normally, but his mirror-neuron system was deficient. This finding has been replicated many times, using a variety of techniques, including MEG (magnetoencephalography). fMRI, and TMS (transcranial magnetic stimulation). Reading about all these techniques would be a mind-altering experience in itself.

According to Ramachandran, all these confirmations ‘provide conclusive evidence that the [mirror neuron] hypothesis is correct.’ It certainly helps to explain why a subset of autistic children have trouble with metaphors and literality. They have difficulty separating the physical and the referential, a separation that mirror neurons appear to mediate somehow.

A well-developed theory of mind which can anticipate the behaviour of others is clearly a feature of understanding our own minds better. In Ramachandran’s words:

If the mirror-neuron system underlies theory of mind and if theory of mind in normal humans is supercharged by being applied inward, towards the self, this would explain why autistic individuals find social interaction and strong self-identification so difficult, and why so many autistic children have a hard time correctly using the pronouns ‘I’ and ‘you’ in conversation. They may lack a mature-enough self-representation to understand the distinction.

Of course, tons more can be said about the ‘mirror network’ and tons more research remains to be done, but there are many promising signs. For example, the findings about lack of mu wave suppression could be used as a diagnostic tool for the early detection of autism, and some interesting work is being done on the use of biofeedback to treat the disorder. Biofeedback is a process whereby physiological signals picked up by a machine from the brain or body of a subject are represented to the subject in such a way that he or she might be able to affect or manipulate that signal by a conscious change of behaviour or thinking. Experiments have been done to show that subjects can alter their own brain waves through this process. Some experimental work is also being done with drugs such as MDMA (otherwise known as the party drug ‘ecstacy’) which appear to enhance empathy through their action on neurotransmitter release.

So that’s a very brief introduction to autism. Hopefully I’ll come back to it in the future to explore the progress being made in understanding and treating the syndrome.

Written by stewart henderson

October 23, 2013 at 10:25 am

What do we currently know about the differences between male and female brains in humans?

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Having had an interesting conversation-cum-dispute recently over the question of male-female differences, and having then listened to a podcast, from Stuff You Should Know, on the neurological differences between the human male and the human female, which contained some claims which astonished me (and for that matter they astonished the show’s presenters), I’ve decided to try and satisfy my own curiosity about this pretty central question. Should be fun.

The above link is to How Stuff Works, which I think is the written version of the Stuff You Should Know podcast, that’s to say with more content and less humour (and less ads), but I do recommend the podcast, because the guys have lots of fun with it while still delivering plenty of useful and thought-provoking info. Anyway, the conversation I was talking about was one of those kitchen table, wine-soaked bullshit sessions in which one of the participants, a woman, was adamant that nurture was pretty well entirely the basis for male-female differences. I naturally felt sympathetic to this view, having spent much of my life trying to blur the distinctions between masculinity and femininity, having generally been turned off by ultra-masculine and ultra-feminine traits and wanting to push for blended behaviour, which obviously suggests we can control these things through nurturing such a blending. However, I had just enough knowledge of what research has revealed about the matter to say, ‘well no, there are distinct neurological differences between males and females’, but I didn’t have enough knowledge to give more than a vague idea of what these differences were. The podcast further whetted my appetite, but writing about it here should pin things down in my mind a bit more, here’s hoping.

I’ve chosen the title of this post reasonably carefully, with apologies for its clunkiness. For the fact is, we still know little enough about our brains. I’ve mentioned humans, but I expect there are gender differences in the brains of all mammals, so I’m particularly interested in that part of the brain that distinguishes us, though not completely, from other mammals, namely the prefrontal cortex.

Here’s an interesting summary, from a blurb on a New Scientist article by Hannah Hoag from 2008;

Research is revealing that male and female brains are built from markedly different genetic blueprints, which create numerous anatomical differences. There are also differences in the circuitry that wires them up and the chemicals that transmit messages between neurons. All this is pointing towards the conclusion that there is not just one kind of human brain, but two. …

Men have bigger brains on average than women, even accounting for sexual dimorphism, but the two sexes are bigger in different areas. A 2001 Harvard study found that some frontal lobe regions involved in problem-solving and decision-making were larger in women, as well as regions of the limbic cortex, responsible for regulating emotions. On the other hand, areas of the parietal cortex and the amygdala were larger in men. These areas regulate social and sexual behaviour.

The really incredible piece of data, though, is that men have about 6.5 times more grey matter (neurons) than women, while women have about ten times more white matter (axons and dendrites, that’s to say connections) than men. These are white because they’re sheathed in myelin, which allows current to flow much faster. On the face of it, I find this really hard, if not impossible, to believe. I mean, that’s one effing huge difference. It comes from a study led by Richard Haier of the University of California, Irvine and colleagues from the University of New Mexico, but this extraordinary fact appears to be of little consequence for male performance in intellectual tasks as compared to female. What appears to have happened is that two different ‘brain types ‘ have evolved alongside and in conjunction with each other to perform much the same tasks. Other research appears to confirm this amazing fact, finding that males and females access different parts of the brain for performing the same tasks. In an experiment where men and women were asked to sound out different words, Gina Kolata reported on this back in early 1995 in the New York Times:

The investigators, who were seeking the basis of reading disorders, asked what areas of the brain were used by normal readers in the first step in the process of sounding out words. To their astonishment, they discovered that men use a minute area in the left side of the brain while women use areas in both sides of the brain.

After lesions to the left hemisphere, men more often develop aphasia (problems with understanding and formulating speech) than women.

While I’m a bit sceptical about the extent of the differences between grey and white matter in terms of gender, it’s clear that these and many other differences exist, but they’re difficult to summarise. We can refer to different regions, such as the amygdala, but there are also differences in hormone activity throughout the brain, and so many other factors, such as ‘the number of dopaminergic cells in the mesencephalon’, to quote one abstract (it apparently means the number of cells containing the neurotransmitter dopamine in the midbrain). But let me dwell a bit on the amygdala, which appears to be central to neurophysiological sex differences.

Actually, there are 2 amygdalae, located within the left and right temporal lobes. They play a vital role in the formation of emotional memories, and their storage in the adjacent hippocampus, and in fear conditioning. They’re seen as part of the limbic system, but their connections with and influences on other regions of the brain are too complex for me to dare to elaborate here.  The amygdalae are larger in human males, and this sex difference appears also in children from age 7. But get this:

In addition to size, other differences between men and women exist with regards to the amygdala. Subjects’ amygdala activation was observed when watching a horror film. The results of the study showed a different lateralization of the amygdala in men and women. Enhanced memory for the film was related to enhanced activity of the left, but not the right, amygdala in women, whereas it was related to enhanced activity of the right, but not the left, amygdala in men.

This right-left difference is significant because the right amygdala connects differently with other brain regions than the left. For example, the left amygdala has more connections with the hypothalamus, which directs stress and other emotional responses, whereas the right amygdala connects more with motor and visual neural regions, which interact more with the external world. Researchers are of course reluctant to speculate beyond the evidence, but as a non-scientist, but as a pure dilettante I don’t give a flock about that – just don’t pay attention to my ravings. It seems to me that most female mammals, who have to tend offspring, would be more connected to the flight than the fight response to danger than the unencumbered males would be??? OMG, is that evolutionary psychology?

It’s interesting but hardly surprising to note that studies have shown this right-left amygdala difference is also correlated to sexual orientation. Presumably – speculating again – it would also relate to those individuals who sense from early on that they’re born into ‘the wrong gender’.

Neuroimaging studies have found that the amygdala develops structurally at different rates in males and females, and this seems to be due to the concentration of sex hormone receptors in the different genders. Where there’s a size difference there appears to be a big difference in number of sex hormones circulating in the area. Again this is difficult to interpret, and it’s early days for this research. One brain structure, the stria terminalis, a bundle of fibres that constitute the major output pathway for the amygdala, has become a focus of controversy in the determination of our sense of gender and sexual orientation. As a dilettante I’m reluctant to comment much on this, but the central subdivision of the bed nucleus of the stria terminalis is on average twice as large in men as in women, and contains twice the number of somatostatin neurons in males. Somatostatin is a peptide hormone which helps regulate the endocrine system, which maintains homeostasis.

What all this means for the detail of sex differences is obviously very far from being worked out, but it seems that the more we examine the brain, the more we find structural and process differences between the male and female brain in humans. And it’s likely that we’ll find similar differences in other mammals.

It’s important to note, though, that these differences, as in other mammals, exist in the same species, in which the genders have evolved to be codependent and to work in tandem towards their survival and success. Just as it would seem silly to say that female kangaroos are smarter/dumber than males, the same should be said of humans. The terms smart/dumb are not very useful here. The two genders, in all mammals, perform complementary roles, but they’re also also both able to survive independently of one another. The amazing thing is that such different brain designs can be so similar in output and achievement. It’s more impressive evidence of the enormous diversity of evolutionary development.

Written by stewart henderson

October 6, 2013 at 9:30 am

the latest on dolphin language

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I wrote, or semi-podcasted, on the brain of the dolphin a while back, and much of my focus was on language, often described as the sine qua non of cerebral complexity and intelligence. In that piece, posted about eight months ago, I reported that there there was little clear evidence of any complex language in dolphins, but there had been some interesting research. Allow me to quote myself:

Dolphins do sometimes mimic the whistles of other dolphins too, particularly those of their closest relatives, but signature whistles as a form of recognition and differentiation, are a long way from anything like language. After all, many species can recognise their own mates or kin from the distinctive sounds they make, or from their specific odour, or from visual cues. However, a clever experiment carried out more recently, which synthesised these whistles through a computer, so that the whistle pattern was divorced from its distinctive sound, found that the dolphins responded to these patterns even when produced via a different sound. It seemed that they were recognising names. It’s undoubtedly intriguing, but clearly a lot more research is required.

So it was with some interest that I heard, on a recent SGU podcast, an account of what seemed an elaboration of the experiments conducted above, further confirming that dolphins recognised names. Or were they just reporting the same experiments? Having re-listened to the SGU segment, I find that they didn’t give any details of who did the study they were talking about, the only mention was to a news article. So I’ll just report on anything I can find, because it’s such a cool subject.

There’s a nice TED talk, from February 2013, on dolphin language and intelligence here, which is about researches over many years in the Bahamas with Atlantic spotted dolphins. As always, I suggest you listen to the talk and do the ‘research on the research’ yourself, as I’m not a scientist and I’m only doing this to educate myself, but hopefully I can also engage your interest.

Dolphins have a brain- to-body ratio (a rough but not entirely reliable guide to intelligence) second only to humans, they pass the mirror self-awareness test (another standard for intelligence that’s been questioned recently), they can be made to understand very basic artificial human language tests, and they’re at least rudimentary tool users. But the real interest lies in their own, obviously complex, vocal communication systems.

I probably misrepresented the information on signature whistles before: they’re only what we humans have been able to isolate from all the ‘noise’ dolphins make, because they’re recognisable and interpretable to us. Denise Herzing, in her TED talk, refers to ‘cracking the code’ of dolphins’ communication systems. She and her team have been working with the dolphins over the summer months for 28 years. They work with underwater cameras and hydrophones to correlate the sounds and behaviours of their subjects. This particular species is born without spots, but is fully black-and-white spotted by age 15. They go through distinct developmental phases making them easy to track over the years (dolphins live into their early 50s). The distinctive spotted patterns make them easy to track individually. Females are sexually mature by about age 9, males at around 15. Dolphins are very sexually active with multiple partners, so paternity is not always easy to determine, so this is worked out by collecting fecal matter and analysing its DNA. So, over 28 years, three generations have been tracked.

What really interests me about the dolphin communication question is their relation to sound and their use of sound compared to ours. Herzing describes them as ‘natural acousticians’ who make and hear sounds ten times as high as humans do. They also have highly developed vision, so they communicate via bodily signals, and they have taste and touch. Sound is of course a wave or vibration which can be felt in water, the acoustic impedance of tissue in water being much the same as on land. Tickling, of a kind, does occur.

Signature whistles are the most studied dolphin sounds, as the most easily measured. They’re used as names, in connecting mothers and calves for example.  But there are many other vocalisations, such as echo-location clicks (sonar), used in hunting and feeding, and also socially, in tightly-packed sound formations – buzzes, which can be felt in the water. They’re used regularly by males courting females. Burst-pulse sounds are used in times of conflict, and they are the least studied, most hard to measure of dolphin sounds.

Interestingly, Herzing notes that there’s a lot of interaction and co-operation in the Bahamas between spotted and bottle-nose dolphins, including baby-sitting each others’ calves, and combining to chase away sharks, but little mention is made, in this talk at least, of any vocal communication between the two species. When she goes on to talk about synchrony, I think she’s only talking about within-species rather than between species. Synchrony is a mechanism whereby the dolphins co-ordinate sounds and body postures to create a larger, stronger social unit.

As I’ve mentioned, dolphins make plenty of sounds beyond the range of human hearing. Underwater equipment is used to collect these ultrasonic sounds, but we’ve barely begun to analyse them. Whistle complexity has been analysed through information theory, and is highly rated even in relation to human languages, but virtually nothing is known about burst-pulse sounds, which, on a spectrogram, bear a remarkable similarity to human phonemes. Still, we have no Rosetta Stone for interpreting them, so researchers have developed a two-way interface, with underwater keyboards, with both visual and audible components. In developing communication, they’ve exploited the dolphins’ natural curiosity and playfulness. Dolphins, for example, are fond of mimicking the postures and vocalisations of humans, and invite the researchers into their play. Researchers have developed artificial whistles to refer to dolphins’ favourite toys, including sargassum, a kind of seaweed, and ropes and scarves, so that they can request them via the keyboard interface. These whistles were outside the dolphins’ normal repertoire, but easily mimicked by them. The experiment has been successful, but of course it isn’t known how much they understand, or what’s going through their minds with all this. What is clear, however, is that the dolphins are extremely interested in and focused on this type of activity, which sometimes goes on for hours.

This research group has lately been using an underwater wearable computer, known as CHAT (cetacean hearing and telemetry), which focuses on acoustic communication. Sounds are created via a forearm keyboard and an underwater speaker for real-time Q and A. This is still at the prototype stage, but it uses the same game-playing activity, seeking to empower dolphins to request toys, as well as human game-players, through signature whistles. It’s hoped that the technology will be utilisable for other species too in the future.

All of this is kind of by way of background to the research reported on recently. This was really about dolphin memory rather than language – or perhaps more accurately, memory triggered by language. Dolphins recognise the sounds of each others’ signature whistles, but would they recognise the whistle of a dolphin they’d not been in contact with for years. And for how many years? Researcher Jason Bruck tested this by collecting whistles of dolphins in captive facilities throughout the US. Dolphins are moved around a lot, and lose contact with friends and family. Sounds a bit like the foster-care system. Bruck found that when dolphins heard the signature whistles of old companions played to them through an underwater speaker, they responded with great attention and interest. One dolphin was able to recognise the whistle of a friend from whom he was separated at age two, after twenty years’ separation. As biologist Janet Mann put it, this is a big breakthrough but not so surprising, as dolphins are highly social animals whose lives, like ours, are criss-crossed by profound connections with others, with effects positive, negative and equivocal.  It’s important, too, for what it suggests – the capacity to remember so much more, in the  same coded way. in other words, a complex language, perhaps on a level with ours. Will we ever get to crack this code? Why not. Hopefully we won’t stop trying.

Written by stewart henderson

August 24, 2013 at 3:55 pm