You can’t spell ‘Love’ without ‘Vole’ – The Neurobiology of Love.
Love. A source of great joy and agonising pain (wait, didn’t I also say that about western blots…?). When we talk about love, we talk about the heart – love is heart-warming, losing a love is heart-breaking, you should enter relationships based on your heart, not with your head!
Nope! Sorry! I don’t want to break any hearts with this, but love is ALL in your head.
A lot of studies have been carried out where the brain has been scanned (or imaged) while individuals are looking at particular photos or carrying out activities and tasks – this is called fMRI (functional magnetic resonance imaging). This method can detect areas of the brain that are receiving higher blood flow, and are therefore likely to be more active. Using this method, it has been discovered that the areas of the brain responsible for regulating your temperature overlap with the areas of the brain associated with social warmth, defined in the study as the feeling of being loved and connected to other people (Inagaki & Eisenberger 2013). These areas were the Ventral Striatum and the Middle Insula (see pictures below for an idea of where these are). The association between physical temperature and feelings of love went so far that when people in the study held a warm object, they reported stronger feelings of social warmth, and those that read meaningful and loving messages from friends and family reported the room as feeling warmer.
Here is a brain – my brain – with rough areas associated with love & reward drawn on. Left image from the side, right image from above.
Why would this be? How is that useful?
The authors suggest that it could be learnt from birth – many behaviours used to soothe a baby and show it love, such as rocking and being held, occur in close proximity to another person and subsequently cause a rise in temperature. We therefore learn that warmth is associated with being loved and cared for. And no one can deny that a warm hug (or Welsh ‘cwtch’) from a loved one feels pretty darn good!
The same brain areas identified in that study have also shown greater activation when people rate themselves as close to their romantic partner, this and was associated with longer relationship length. In fact a lot of brain areas have been linked to feelings of romantic love, and many of these, such the Hippocampus and Nucleus Accumbens (see previous picture!) are part of the reward system in the brain. The reward system is the network in our brains that makes us feel pleasure and happiness (a reward), often in response to a particular event or behaviour. Activation of this system makes us try to repeat the action that led to its activation in the first place, therefore resulting in another reward feeling – if spending time with a particular person activates our reward system, then we strive to see them again.
Dopamine is the signalling molecule that works within this reward system.
Prairie voles (super cute voles from North America) are the most frequently studied animal on the neurobiology of love- this is because they form monogamous relationships. Voles that had more receptors for dopamine (parts of the cell that are able to detect the presence of dopamine, allowing the cells to respond to it) had increased monogamous behaviour. This suggests that increased activity in the brain’s reward system may improve the longevity and fidelity of individuals in a relationship, because being with their partner feels particularly rewarding.
Oxytocin has the reputation of being The Love Drug.
Oxytocin is a neuropeptide – which means it is a molecule that is used by brain cells to communicate with each other, although oxytocin is also capable of working as a hormone around the body. Oxytocin is well known as being associated with pregnancy and lactation, but its effects are much broader than that! It can also stimulate social behaviour, such as increasing trust and empathy. Looking back to those adorable voles, monogamous animals had more oxytocin receptors in the Frontal Cortex, Nucleus Accumbens and Striatum, which are the same areas that show increased activity in humans when shown a picture of their partner. A release of oxytocin in the brain during mating was essential for the important bonding to a partner in voles.
Enough of voles – in humans, oxytocin is increased by hugs, social support, massages and orgasm.
In fact, when heterosexual male subjects were given oxytocin intranasally (up their nose!), they rated their partner’s face as more attractive than other women’s faces, and showed increased activation of their brain reward systems. The author stated that oxytocin could ‘improve the reward value’ of the subject’s partners…which is oh so romantic(!) A sniff of oxytocin in females improved their ability to determine the emotion felt by another person when just shown the eye region of their face – this is called the ‘reading the mind in the eyes test,’ or the slightly snappier ‘RMET‘.
As well as oxytocin, multiple other hormones have been implicated in the neurobiology of love – testosterone, cortisol and dopamine have all been identified as contributing to either the longevity or demise of romantic relationships. Cortisol is a hormone that is associated with responses to stress, and particularly high levels in couples during an argument were associated with increased hostility and relationship breakup, particularly if levels were high in both individuals. High levels of oxytocin, on the other hand, were associated with increased empathy. High levels of testosterone are associated with competitiveness rather than stability and trust – it is much higher in single men than in men in relationships who no longer need to compete with other males for a partner.
You can be ‘Crazy in Love’ – Beyoncé was right!
The early stage of a new relationship is considered to be a separate phase that creates different and unique responses in the brain. There is a dramatic increase in the love drug, oxytocin, which in turn increases the activation of dopamine-related brain areas. When these areas are so strongly activated, large areas of the cortex experience a reduction in activity, which means that we lose our ability for rational judgement – which is an effect many of us may have observed in our friends in a new relationship! The activation of the dopamine reward system may also make us temporarily ‘addicted’ to our new beau, as their ‘reward value’ is through the roof! It is thought that this early and temporary addiction serves the purpose of keeping us around that person for long enough to form a meaningful attachment.
So yes, it might all be in your head and love might make you crazy, but it’s also a real biological phenomenon. And don’t forget to be romantic – let your significant other know that they have a high reward value, then give ‘em a cwtch.