Wednesday, 14 July 2010

Snakes in a brain scanner!

Forget snakes on a plane, this was snakes in a brain scanner! To chart the neural activity associated with overcoming fear, Uri Nili and colleagues scanned snake-phobic participants' brains while they chose, with the press of a button, whether or not to bring a live, 1.5M long corn snake, located on a conveyer belt in the scanner room, nearer to their heads, or to shift it further away (watch video). A control condition replaced the snake with a teddy bear.

The subgenual anterior cingulate cortex (sgACC) - part of the frontal cortex buried under the corpus callosum - emerged as a key area involved when participants chose to overcome their fear and bring the snake closer to their heads - i.e. when they acted courageously. When people reported high fear but chose to bring the snake closer, sgACC activity increased, whilst physiological markers of fear dropped and activity in emotion processing regions, such as the amygdala, was reduced. Nili's team said this suggests the sgACC plays a role in dampening down fear-related bodily arousal. Consistent with this, the sgACC is known to be involved in regulating the paraysmpathetic nervous system (which is in opposition to the fight or flight response) and is deeply interconnected with brain structures involved in emotional processing.

In contrast, when courage failed and the participants chose to direct the snake further from them, sgACC activity dropped away (no longer correlating with fear levels), somatic signs of fear increased, as did activity in emotion-processing regions like the amygdala.

The only other brain region that was more active during displays of courage was the right temporal pole - a part of the brain that's known to be involved in modulating emotions triggered by visual stimuli, and also in the self-evaluation and monitoring of one's own emotions.

This new research has some important and exciting implications. From a practical perspective, the fact that bodily signs of fear were reduced during moments of courage, even while subjective fear was high, raises a concern with studies that use physiological measures (such as sweatiness of the skin) as a marker for fear. For example, studies of therapeutic interventions for phobias, which rely on physiological markers, risk mistaking what's in fact a display of courage for successful fear eradication.

Manipulating sgACC activity could also be a new target for therapy: 'Such interventions may range from training in meditation techniques that lead to greater activity in this region,' the researchers said, 'to transcranial magnetic stimulation similar to that attempted to alleviate depression.'
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ResearchBlogging.orgNili, U., Goldberg, H., Weizman, A., & Dudai, Y. (2010). Fear Thou Not: Activity of Frontal and Temporal Circuits in Moments of Real-Life Courage. Neuron, 66 (6), 949-962 DOI: 10.1016/j.neuron.2010.06.009

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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