Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
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Oxytocin has been known for years, but not as a brain peptide. Let’s leave the ewe to nuzzle her lamb, and visit the nearby milking shed. Here we see them milking cows the old-fashioned way. Each squeeze of a teat is followed, a few seconds later, by a squirt of milk. Oxytocin does that. A squeeze (or a suckle)
is sensed by
the hypothalamus, which sends a pulse of oxytocin down to the pituitary
and into the blood. This acts on the udder (or breast, in humans)
which squirts out the milk. If you watch a gaggle of tiny rat
pups suckling their mother, every few minutes you see them wriggle
mightily; they’ve just received a shot of milk, the result of a
pulse of oxytocin in their mother’s blood. Some
lactating women have been known to squirt milk across the room!
Next door, there’s a ewe giving birth. Her womb (uterus)
contracts hard in waves to expel the newborn lamb. Oxytocin
again. Women near term can be induced to give birth by being
infused with oxytocin (more usually, with an artificial peptide
closely resembling it). As the baby, or little lamb, snuggles up
to its mother, more oxytocin ensures a good supply of milk.
Oxytocin is clearly an essential part of the process of giving birth
(rats lacking it can’t give birth properly) and of the delivery
system for feeding the baby. How extraordinary, then, that it took so long for its role in the brain to be discovered – a role that fits so well with its other actions. For good mothering needs not only a successful birth, and an efficient supply of milk, it also needs the mother to be ‘maternal’. That is, to be motivated to care for her young (provide food, warmth, protection, a shelter) and to make sure the baby stays close, and to look for it if it strays. To do that, the limbic system cleverly makes the baby a prized object, something the mother doesn’t want to lose. Its called ‘attachment’ or ‘bonding’ or ‘motherly love’ and oxytocin, a little peptide of only eight amino-acids, may be an essential chemical signal responsible for it………
We know curiously little about what happens in the brain of any species to make a female behave maternally. We do know that there has to be some way of ensuring that sensory information from the pups (their smell, the sounds they make, their movements) are decoded and register with that part of the brain that is ‘maternal’. Where is this part? Many scientists in the field now think of a ‘maternal circuit’ – a collection of interconnected bits of brain that, together, represent what we describe as maternal behaviour….
A human mother is attached to her little child; she also bonds with her mate (partner) and both feel strong affiliations to their parents. In each case, there is a strong attachment to a particular person (which may exclude others). Three words – bonding, attachment, affiliation - with essentially the same meaning. There’s a fourth, which you won’t find mentioned much in the neuroscientific literature, because neuroscientists find it troubling. It’s called love, and poets have no problems with it.
I am not so concerned here with the psychological aspects of love, on which there is a literature, as with the biological functions of love and its neural basis. Love, attachment, whatever you call it, implies that a particular person becomes special, in that social interaction (and usually proximity) is rewarding, that loss (temporary or permanent) is both feared, avoided and, if it happens, is treated as a serious adversity, and great efforts are made to rectify this loss or deficit....... Just as there are two levels of understanding for, say, hunger (what is its function? how does it happen?) so there are for love. The biological function of love (its role in survival) lies in the fact that attachment implies an individually-distinct interaction……….
Bonding is part of what all social animals, including our species does as part of its interaction with the rest of society. We have a particularly complex system of assessing those to whom we should behave in a particular way; either because we would lose something if we did not, or because we feel ’affection’ for them or ‘obligation’ towards them. We are bound by social rules that we learn as we grow up. These processes require some of the most complicated activities of the human brain, way beyond the capacity of the limbic system. In particular, they rely upon a region of the cortex called the prefrontal lobe…….
Scientific and literary quotes.