My fifteen month old twins and I were dancing to Jess Glynne yesterday and Harry, one of my twins, discovered the volume button on the stereo for the first time and turned it up, very high, very quickly. He froze, just for a moment, then cried very loudly (louder than the music). My little girl, Edie, joined in. He stayed as far away from the stereo for the rest of the song, scared. This response to threat and fear is so universal, whether it’s a tiger in the room, a sudden loud noise or it could even be a vivid imagination about an event that hasn’t even happened yet. The amygdala plays a key part in this response (see below).
To understand more about how the brain works I love the site ‘The Brain from Top to Bottom’ (www.thebrain.mcgill.ca). If you are interested in finding out more about how the brain works, this is a great place to start. It covers different aspects of the brain’s function form a social, psychological, neurological, cellular and molecular level and in three different levels of difficulty. It received funding for ten years by The Canadian Institute of health Research Institute of Neuroscience, Mental Health and Addition.
| THE AMYGDALA AND ITS ALLIES |
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The amygdala is a brain structure that is essential for decoding emotions, and in particular stimuli that are threatening to the organism. As a result of evolution, many of our body’s alarm circuits are grouped together in the amygdala. Consequently, many sensory inputs converge in the amygdala to inform it of potential dangers in its environment. This sensory information comes to the amygdala either directly from the sensory thalamus or from the various sensory cortexes. |  |
But there are several other regions of the brain that project their axons to the amygdala; examples include the hypothalamus, the septum and the reticular formation of the brainstem.
The amygdala also receives numerous connections from thehippocampus. Since the hippocampus is involved in storing and retrieving explicit memories, itsconnections to the amygdala may be the origin of strong emotions triggered by particular memories. The hippocampus also specializes in processing sets of stimuli (as opposed to individual stimuli)–in other words, the context of a situation. Hence it is because of the hippocampus and its close connections with the amygdala that the entire context associated with a traumatic event can provokeanxiety. |  |
Major connections to the the amygdala also come from the medial prefrontal cortex. These connections appear to be involved in the process of extinction, whereby a stimulus that triggers a conditioned fear gradually loses this effect. This happens if that stimulus is repeatedly presented to the subject without the unconditional nociceptive stimulus that was initially associated with it to produce the conditioned fear.
The prefrontal cortex also seems to be involved in the final phase of confronting a danger, where, after the initial automatic, emotional reaction, we are forced to react and choose the course of action that can best get us out of danger. In people whose frontal cortex is damaged (people with “frontal syndrome”), planning the slightest task is very difficult, if not impossible.
Thus, the ability that our superior mental structures give us to voluntarily plan an emotional response suited to the situation is a wonderful complement to our system of rapid, automatic responses. The connections from the prefrontal cortex to the amygdala also enable us to exercise a certain conscious control over our anxiety. However, at the same time, this faculty can create anxiety by allowing us to imagine the failure of a given scenario or even the presence of dangers that do not actually exist.
Copyleft: The Brain from the Bottom to the Top
