Saturday, February 14, 2009

The Science of Love and Hate

For all of those who believe love and hate are the same thing, they’re not. Love and hate, in two fMRI studies done, showed distinct neural networks.

Hate was actively visualised in the insula, premotor cortex, putamen, and frontal medial gyrus while the superior frontal gyrus showed deactivation.

Interestingly, there was no activation in the amygdala, an area associated with instinct and emotional memory and learning. As well, the hippocampus, an area involved in forming new memories, showed no activity. And well there was no visualisation of activity in the amygdala, this region is functionally connected with the insular cortex which did show activation.

The insula is involved with emotions of anger, fear, disgust, happiness and sadness. Interestingly, it is also associated with pain. So while such emotions may be stored in the instinctual amygdala, hate, like pain, is not remembered as evidenced by the inactivity of the hippocampus. Environmental and cultural influences which play a role in types of hate such as racial prejudices can as such become a default response to emotional stimuli. The insula, also showing brain activation with feelings of love, is also involved with addiction.

The amygdala did appear in association with love, but as a deactivation. A recent study suggests that impaired amygdala function corresponds with reduced (emotional) pain sensitivity, thereby suggesting that when painful stressors occur within the context of love, we feel them less than we would otherwise.

Also showing de-activations in the love-brain were the prefrontal, parietal and middle temporal cortices. The authors cite an article demonstrating that de-activation of these areas is associated with happiness while activation is associated with depression. A different study claims the opposite:

"Sadness was accompanied by specific activations of the subgenual cingulate area (BA) 25 and dorsal insula, specific deactivation of the right prefrontal cortex BA 9, and more prominent deactivation of the posterior parietal cortex BAs 40/7. Anxiety was associated with specific activations of the ventral insula, the orbitofrontal and anterior temporal cortices, specific deactivation of parahippocampal gyri, and more prominent deactivation of the inferior temporal cortex BAs 20/37".

Another study demonstrates “disgust and happiness imagery provoked activation of the insula, anterior cingulate cortex, and parietal cortex. Trait disgust was negatively correlated with localized brain activation (e.g. insula, amygdala, parietal cortex, anterior cingulate cortex) during disgust imagery.” With all the studies being done on happiness and sadness, there is much contradiction in the results. This is not surprising given the complexity of and variety within such emotions.

The other brain area love shares with hate is the putamen. The putamen functions in motor activity as well as memory, specifically implicit and reinforcement learning. Therefore, the more you are exposed to feelings of love or hate, the more likely you are to develop these feelings more deeply. This explains the we-covet-what-we-see-everyday and let’s-be-friends-if-you-don’t-like-me-now-because-eventaully-you-will strategies to courtship.

Another area imaged with feelings of love is the anterior cingulate cortex (ACC) which functions in autonomic functions (heart rate, blood pressure), conscious emotional awareness, reward-based learning, and empathy. The caudate nucleus (also seen in love) shares some similar functions with the ACC in the role of learning. Additionally, a dysfunctional caudate nucleus is associated with obsessive-compulsive disorder.

Also interesting is that disgust is associated with love. And isn’t this so very true? The exchange of bodily fluids, not liking the way a particular part of their body looks, being annoyed with their mannerisms, pretending to care when you actually don’t because it’s socially expected. This could also explain how we becoming blinded by love (or hate). Not wanting to admit to either ourselves or the object of our affections (dislike) that they fall short of our expectations and desires (or that they exceed contradict our feelings of hate), we reinforce the deep and passive learning of the emotion.

Euphoria inducing drugs activated the same regions as those in the love study suggesting love being an euphoric state. The authors also found that sexual arousal differed neurologically from love, though the regions of the brain activated in arousal were adjacent to those activated in love. Also, the feeling of love is very specific with only a few, well defined areas in the brain showing activations and deactivations.

An fMRI study of your brain before entering into marriage would be an interesting way of determining whether or not you are really in love.

Following is a formula I developed to rate the probability you are in love:

PL= ∫0 →t [(N(t)-U(t))(H) + d/SG]

= ∫0 →t[(N-(D+P))(H) + d/SG]

(where t=length of relationship)

N(t) = Need = (Tothers/Talone)(A)

A=Your age, Tothers=Time spent with others (besides your partner) during course of relationship, Talone=Time spent alone during course of relationship

U(t) = Unhappiness = D(t)+P(t)

D=Time spent disgusted with other person, P=Time spent in pain caused by other person.

H(t) = Happiness = h(t)/s(t)(X+I)

h(t) = #happy days during time together, s(t) = #sad days during time together

X = Sex = (#times sex was good/#times sex was bad) + (#times sex was adequate)/2

I = Income (of partner) = (actual income/desired income)

D = # digits of pi your partner can recite

SG = # of episodes of Summer Glau tv you have watched

For other relationship formulas check out this site and The Math of Love.

References: 1, 2, 3, 4

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