The amygdala is at it again!

...Researchers used Positron Emission Tomography (PET) scans to analyze the brains of 72 healthy, right-handed adults (36 men and 36 women). The subjects were instructed to relax with their eyes closed while being scanned. When the scans were later studied, researchers found that not only was there a difference between the men and women as to which hemisphere's amygdala was more active, but also that the regions of the brain that the amygdala "talked" with were also quite different. In men, the right-hemisphere amygdala showed more connectivity with brain regions such as the visual cortex and the striatum. In contrast, the left amygdala in women was more connected to regions such as the insular cortex and the hypothalamus." - link

This isn't the first time the amygdala has cropped up on The Huge Entity (see: Whack my Bonobo! Sex, Emotion and the Female Amygdala). Thought, as it is, to be the seat of all emotion, the distinctions in amygdala activity in male and female brains says a lot to me about emotional control, or more specifically, lack of emotional control:

The amygdala (Latin, corpus amygdaloideum) is an almond-shape set of neurons located deep in the brain's medial temporal lobe. Shown to play a key role in the processing of emotions, the amygdala forms part of the limbic system. In humans and other animals, this subcortical brain structure is linked to both fear responses and pleasure. Its size is positively correlated with aggressive behavior across species. In humans, it is the most sexually-dimorphic brain structure, and shrinks by more than 30% in males upon castration.

It is now widely accepted that the right and left hemispheres of the brain play different roles in the nature of thought (known as the Lateralisation of brain function). The left brain is considered the centre of most logical, or rational activity, and the right brain concerns itself with emotional, or instinctive behaviour.

According to the research above most male amygdala activity takes place in the right brain, whereas for the female it happens in the left. Could this explain men's lack of control over the emotions? Or to define it conversely, when females experience emotion is it more in tune with aspects of rational thought than their male counterparts? When a man's amygdala kicks in it has less connections affirming a considered response - i.e. it acts upon regions of the brain defined by a more 'primitive' approach to the world. Thus men are more likely to act instinctively, maybe even thoughtlessly, when pressed into emotional situations.

The pseudo-evo-psychologist in me can imagine all manner of evolutionary reasons for this difference in the sexes. What interests me most deeply about the distinction between men and women though is how minutely different the construction of our brains is at the foetal stage of our development. Throw a handful of testosterone at a maturing foetus and sit back as life-long emotional behaviour is branded onto the brain.

I'd be fascinated to see this research extended to those members of society sitting on, or closer to, the gender fence. Hermaphroditic brains must surely reflect elements of both male and female brain function. Further still, the amygdalas of sex change patients and, possibly to a lesser degree, homosexuals would give us insight into the divergences in sexual reality.

How does your amygdala respond to all this?

Categories: Science, Sex, Consciousness, News, Links, Reality, Human

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