If you were forced at gunpoint to choose the part of the brain that plays the most important role in emotion, you might well plump for the amygdala. The amygdala is an almond shaped structure in the medial temporal lobe, roughly in the centre of the brain. While certainly not the only structure involved in emotional processes, it is the most extensively researched. Generally speaking, the amygdala is thought to play a role in mediating cognitive responses to emotional stimuli. Phelps (2006), in an Annual Review of Psychology article, provides an overview of the findings that have emerged.
If someone really did point a gun at your head, you'd probably be afraid, even if you are used to that sort of thing happening. But for some people with damage to their amygdala, this might reveal itself in a rather odd disconnect between what their body 'feels' and what they 'know'.
Phelps (2006) describes a patient with this type of amygdala damage who, while being able to conceptually understand immediate physical danger, cannot seem to understand it in what the rest of us might consider the most obvious way: bodily. Responses that can be conditioned physiologically into normal controls, cannot be elicited in this patient. When you point a gun at her head, she is afraid, but she doesn't start sweating like the rest of us would.
So there seems to be at least two different ways of 'being afraid'. Similarly, there is certainly more than one way of learning to be afraid. You can see someone else have a gun held to their head and that's enough to clue you in that it might not be a pleasant experience. Or someone can simply tell you. These have been investigated in so-called 'instructional' and 'observational' fear conditioning paradigms. As Phelps (2006) points out, the amygdala has been found to be important in both of these processes.
Emotion and Memory
Perhaps the most famous connection between emotion and memory is the idea that arousal enhances episodic memory. Reassuringly (for research psychologists at least) patients with damage to their amygdala do not show this particular enhancement of memory. So, again, the amygdala seems to be important in some way in mediating how memories are layed down.
More recent work, though, has suggested that it's not the memory that's actually being enhanced. Instead it might just be the perceived clarity of the event that's being increased, while the memory for the event itself remains unenhanced. Phelps (2006) uses the example of research examining people's memories of 9/11. Crucially, people's recall was not actually improved despite their significantly raised arousal at that time. Clearly there's something more complicated going on here.
Emotion, Attention and Perception
So, imagine that the guy with the gun is back again. Now the revolver is so close to your face that you can see the bullets loaded into the individual chambers. But it's dark and you're emotional so how can you see that? Phelps (2006) explains that there is some evidence that fear can actually enhance perception. One study carried out by Phelps herself found an increased sensitivity to contrast when subjects were primed with fearful faces (Phelps, Ling & Carrasco, 2006). It seems, then, that emotional situations can send your visual cortex into overdrive.
In the same way, there is also evidence that emotional situations can enhance your attention. Some research has suggested that normal cognitive processes like the attentional blink can be reduced when emotions are running high. Again, patients with certain types of damage to their amygdala do not show this enhancement, lending further weight to the amygdala's claim to emotional fame.
Emotions and Social Stimuli
You stare back into your assailants eyes, trying to work out whether he's actually more scared than you are. If you challenge him to shoot you, as they do in all the best cop shows, will he meekly hand you the gun or will he put a bullet in your brain? Phelps (2006) reports evidence examining the amygdala's role in processing fear on other people's faces. There is some evidence that the amygdala could once again come to your rescue. It seems to have a specialised role in processing fear, especially as, again, those with amygdala damage tend to have difficulties in this area.
But, Phelps (2006) points out that while there's some interesting research being produced on the amygdala's role in fear responses, this area is still wide open and there are still considerable controversies.
Down the Barrell
If you're looking down the barrell of a gun, the traditional dividing line in cognitive science between emotion and cognition is not so clear. Your emotional state can have marked effects on basic cognitive processes like learning, attention, perception and memory. And it's the amygdala that seems to play an important role in mediating these processes.
Phelps, E. (2006). Emotion and Cognition: Insights from studies of the human amygdala. Annual Review of Psychology, 57, 27-53. (Abstract)
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