05 May 2010

Me and My Big Amygdala?

Controlling our emotional responses can feel like a struggle. We may feel logical and capable, reasonable and calm, before we face a social challenge. But often, when the time comes to use our logic and serenity in dealings with others, we react in an emotional "knee-jerk" manner.

Emotional responses are multifaceted and are not purely the result of one specific brain area. Current theories are based upon a group of interconnected structures near the brain stem known as the limbic system. Within the "layer cake" context of the brain, with evolutionarily "newer" parts stacked above and around "older" parts, the limbic system structures can be seen as an early development.

The amygdala (or more correctly amygdalae: one in each hemisphere) is part of this conceptual limbic system and it plays a role in many of our responses to different types of social interaction. For example, it is involved in our recognition of and reaction to sexual stimuli (direct or indirect); it interacts with the hippocampus in the process of forming emotional memories; it is involved in fear responses and also in "predatory" and "affective" aggression.

Affective aggression is "display" behaviour, such as making warning noises and adopting defensive postures e.g. when a cat hisses and arches its back in the presence of a dog. Humans often display affective aggression, although not usually in the form of hissing and arching. The sympathetic nervous system (SNS) is involved in this behaviour; bringing about and contributing to a host of "symptoms" over which we may feel we have no control. Examples of this are blushing; racing heartbeat; dry mouth; shaking; sweating.

There is some evidence that a human amygdalectomy (destroying all or part of the amygdala by electrical or chemical surgery) can reduce aggressive behaviour. But this type of psychosurgery would nowadays be considered a drastic procedure of last resort.

I am speculating here but it appears to me that "blurting" responses often come about in extremely quick succession to the SNS responses. We sometimes seem to respond harshly to a challenge to our "authority" or "self-image", perhaps with shouting or expletives, before we have a chance to "think through" our response. I know a few people who think that's a good thing: "Get it off your chest"; "It's better out in the open". But, more often than not, it isn't for the best. Humans have a highly-developed neocortex. If we respond harshly, before taking the time to fully process the information through that "new" structure, we may regret our initial emotion-laden response.

This may all seem to imply that having a bigger amygdala would make you more prone to aggressive behaviour; and that men must have larger ones than women. In fact, women have larger amygdalas than men: some ten percent larger. The amygdalas of gay men can be around twenty percent larger.

This appears contradictory until you think of the amygdala in terms of a seat of "emotional intelligence". The amygdala has a strong role in the recognition of the emotional responses of others. This could mean an aggressive emotional feedback loop but instead it often means an empathetic feedback loop. You recognise the emotional response of another human to your cues: your expression, your tone etc; and you respond appropriately to those cues, creating a positive "loop". It's a kind of "mirroring" behaviour. Women and gay men are particularly well-adapted to it.

So, positive social interaction with other humans isn't simply a matter of thinking everything through before expressing an opinion. Certainly it requires logic and tact, but it also requires emotional intelligence; and that requires the timely involvement of the amygdala.