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Emotions and the brain

Fear, Anxiety and Anguish

Original modules
Experiment Module: Identifying the Brain Structures Involved in Conditioned Fear Identifying the Brain Structures Involved in Conditioned Fear

Just as we do for most other structures in the brain, we have two amygdalae, one in each hemisphere. The left amygdala seems to be more sensitive to voice intonations, while the right amygdala responds more to facial expressions.


Just because a given region of the brain is assigned a particular name rarely means that all of its neurons are homogeneous. On the contrary, these neurons are typically organized into specialized sub-groups. Each of these specialized groups of neurons within a given structure is called a “nucleus”.

The amygdala, a brain structure that plays a key role in fear reactions, contains a number of distinct nuclei. The lateral nucleus seems to act as the main gateway into the amygdala. It is through this nucleus that the amygdala receives messages warning of danger, whether they come by the fast, direct route from the thalamus or by the slower route via the cortex.

Another nucleus, the central nucleus, acts as the exit from the amygdala. The commands for the bodily responses associated with fear leave the amygdala from the central nucleus. In between the lateral nucleus and the central nucleus, several other nuclei gather information, process it, and send it on out via the central nucleus. Though not all of these nuclei are involved in the fear reaction, they do represent the centre of the body’s alarm system.

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