• Spring is in the Air by Dr Jack

    magpiesSpring 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.

    In the parkSix 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.

    Pigeon CourtingThe 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.
    Peacock_Flirting

    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.

     

     


    These brain blogs are currently a monthly, for daily instalments of life through the eyes of a neuroscientist, please consider following me on Twitter.

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  • Lust, Love & Long-Term Bonding by Dr Jack

    What is the human body’s most important sex organ?

    The brain.

    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.

    First things first – it is very important to bear in mind the differences between sex drive, love and long-term bonding; in terms of how and why they evolved in the first place.

    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.

    In addition to these brainposts I also tweet a thrice daily #braintweet. If this sounds interesting then please do consider following me on Twitter.

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  • Crash course in brain anatomy anyone?

    The terminology associated with brain anatomy can seem intimidating to the uninitiated, but really there’s no need to be intimidated.

    A pair of cartoon rodents (Pinky and the Brain) managed to get their heads around it and so will you.

    Here’s their quick guided tour to the different parts of the human brain.

    It’s a shame they don’t really mention the role of each area they name.

    I guess that would have made making the lyrics rhyme even more complicated!

    To supplement their guide to neuroanatomy (what bit is where) I’ve given a quick overview of what each bit does in the order they’re covered in the cartoon:
     

     

    1) Neocortex – the whole large sheet of brain cells on the brain’s outer surface, folded up into the skull giving it the appearance of a walnut.

    2) Frontal lobe – the region of the neocortex at the front of the brain, behind the forehead, which is much larger in humans than our monkey cousins and enables us to do all those complex functions that other primates cannot.

    3) Brainstem – the part of the brain that ninja assasins aim for with their deadly chop where neck meets skull, it is involved in coordinating all the vital bodily functions that keep us alive e.g. breathing and heart rates.

    4) Hippocampus – key brain area at the core of the temporal lobes (which run horizontally down the sides of the head from the temple to behind the ears) which is heavily involved in not just creating, but also retrieving memories. It also creates new brain cells in response to exercise!

    5) Neural node – erm, I think they just needed something sciency sounding to rhyme with the other lines. The image THE BRAIN enlarges with the magnifying glass is a single brain cell complete with nucleus (which contains all the DNA) at it’s centre, the dendrites (receiving information from other brain cells) plus a single axon (along which electrical messages are sent to other brain cells).

    6) Right hemisphere – the left and right sides of the neocortex are separated by a fluid filled gap yet are connected by a massive bundle of neuronal connections called the corpus callosum that bridge the gap enabling left and right sides to send and receive information between them.

    7) Pons – All of the commands travelling from parts of the neocortex involved in motor control (i.e. body movements) pass through the pons which sits on top of the brainstem which is at the very top of the spinal cord through which the brain controls all the muscles of the body.

    8) Cortex visual, usually referred to as the visual cortex, sits right at the back of the brain. So the eyes quite literally detect light striking the retina, at the back of the eyeball, and send this information all the way to the back of the brain before we can see anything!

    9) Pineal, usually referred to as the pineal gland, is about the size of a grain of rice and produces melatonin which regulates the sleep/wake cycle. Daylight in the morning switches off melatonin production to make us feel awake, switching production back on in the evening so we can sleep.

    10) Cerebellum left and right, critical for balance and co-ordinated muscle contractions important for effective speech, walking, running, swimming and all sporting activities etc.

    11) Synapse – the gap between one neuron and the next. Electrical signals arriving at the end of one neuron releases tiny packets of brain chemicals that travel across the synapse, bind with special receptors on the other neuron to trigger or inhibit electrical signals its own electrical messages.

    12) Hypothalamus – the most important site of hormone production and release that powerfully regulates innumerable body and brain functions.

    13) Striate, a. k. a. striatum – enormously important subcortical brain area (deep in the brain not on the surface of the neocortex) involved in reward and motivation, planning and modulation of movements, named thus due to its stripy appearance.

    14) Axon fibres – as mentioned before this is the part of the brain cell that sends electrical messages to other brain cells.

    15) Matter grey, usually know as the famous Grey Matter. This is darker than the white matter as this is where all the synapses and cell bodies are. So it is in the grey matter that all the computational power of the brain is unleashed.

    16) Central tegmental pathway: the tegmentum is a part of the midbrain – which lies between the striatum and the brain stem. Activation of the ventral tegmental area, i.e. the “belly” of the tegmentum, causes the feelings of intense pleasure when people eat, drink, have sex or take drugs.

    17) Temporal lobe – the upper surface of the temporal lobes is the part of the brain we hear with.

    18) White core matter, usually referred to as White Matter, consists of millions and millions of axonal fibres that ferrying electrical signals from one brain area to the next.

    19) Forebrain – we’ve done that already

    20) Skull – the bone in which our brain is cradled

    21) Central fissure – the name for the fluid filled gap described earlier which separates the left and right hemispheres

    22) Cord spinal, usually known as the spinal cord, through which axons pass sending messages from brain to body and body to brain.

    23) Parietal – one of the lobes of the neocortex – involved in spatial awareness, focusing attention and mathematical calculations.

    24) Pia mater – is the innermost of the three brain sacks (or meninges) which cushion and protect the brain.

    25) Meningeal vein – blood vessels taking waste materials away from the outer parts of the neocortex.

    26) Medulla oblongata – lower part of the brain stem, also involved in triggering reflexes like vomiting, sneezing, coughing etc.

    27) Lobe limbic – usually known as limbic system, deep inside brain beneath the temporal lobes, involved in generating emotions.

    28) Microelectrodes – there is not a microelectrode in sight so just ignore that lyric!

    In addition to these monthly brain posts you can follow me on Twitter for my thrice daily #braintweet.

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