I get this from passing references in many texts. When people talk about the amygdala they seem to imply that you have to be running for your life in abject fear or be screaming angry to be considered an emotional memory. What is missed is subtle shading of all memory consolidation - when something is just a little good or a little bad. As the semantic categories are formed the coloring allows you to choose between different choices as the relative “goodness” or “badness” of things is part of the learned properties. Being afraid of rejection by a mate, or a reduction in social standing among your peers, or disfavor of the boss is still fear.
Without this grounding from the subcortical structures, the semantic categories in the cortex are just arbitrary facts without any good or bad meaning.
What does it look like if this is missing?
In the Rita Carter book “Mapping the mind” chapter four starts out with Elliot, a man that was unable to feel emotion due to the corresponding emotional response areas being inactivated due to a tumor removal. Without this emotional coloring, he was unable to judge anything as good or bad and was unable to select the actions appropriate to the situation. He was otherwise of normal intelligence.
This lack of judgment learning is often described as “reduction in loss aversion.”
I call it lack of emotional weighting in semantic learning.
There is copious evidence that the chemical messengers from the amygdala modulate the learning rate due to this “emotional content:”
http://www.pnas.org/content/pnas/93/24/13508.full.pdf
“The amygdala has been associated with enhanced retention of memory. Because of this, it is thought to modulate memory consolidation. The effect is most pronounced in emotionally charged events.”
https://courses.lumenlearning.com/boundless-psychology/chapter/memory-and-the-brain/
In a symbolic form in speech:
http://www.pnas.org/content/pnas/96/18/10456.full.pdf
And more to the point in symbolic access:
The amygdala’s modulation of consolidation
The second stage of hippocampal memory formation is retention or storage. There is also evidence that the amygdala can influence the storage of memory. Hippocampal-dependent memories are not stored in an all or none fashion. After encoding, there is a period of time in which these memories are somewhat fragile and prone to disruption. It takes time for these memories to become more or less ‘set’, at which point their retrieval is less dependent on the hippocampus. This process is called consolidation. It has been suggested that one reason for this slow consolidation process is to allow an emotional reaction to an event an opportunity to influence the storage of that event.
https://pdfs.semanticscholar.org/2559/1f5d9fde558ce5cd7f49607ef87e48e6287f.pdf
“we speculate that the amygdala likely charges autobiographical memories with emotional, social, and self-relevance.”
“These findings suggested the possibility that endogenous stress-related hormones released by training experiences may play a role in regulating memory storage”
https://pdfs.semanticscholar.org/5414/12539e4557cbdb0f531e6f48e4575dbc21ba.pdf
I have dozens more papers like these but I think this shows the general ideas.