Emotions are what makes us human; they shape our identities, often guide our decisions and influence our relationships. We express ourselves through emotions in sadness or anger, in happiness or surprise and even in fear. Yet, our emotions are electro-chemical in its composition and are complex reactions that involve physiological responses to our thoughts. How we experience life and interact with others are often a result of our emotional content that we carry with us. 

During our life, our emotions embeds itself in our memory. Through repeated exposure to stimuli all around us, our emotions associates itself to that stimuli and as a result develops learned emotional responses. We refer to this as emotional memory, which is a form of non-declarative memory that can easily be stored and retrieved without conscious effort.

The brain is a complex organ. Exploring its key structures that link to our emotions, several structures like the amygdala, the insula (or insular cortex), and the periaqueductal gray are important in shaping our emotions. Neurons from the prefrontal cortex, amygdala, and insular cortex connect to the periaqueductal gray, which in turn has reciprocal links with the central nucleus of the amygdala and projects to the thalamus, hypothalamus, brainstem, and deeper layers of the spinal cord.

The amygdala processes emotions, emotional behavior, and motivation. It is essential for interpreting fear, distinguishing allies from threats, and recognizing social rewards and how to achieve them. A well-known form of learning that relies on the amygdala is classical conditioning, which connects stimuli with rewards or punishments.

Through the insula, we experience feelings of happiness—such as a delight to a good experience—allowing us to enjoy those moments. The insula plays a role in the perception and anticipation of pain. It processes a wide range of inputs, generating subjective feelings that link emotions, internal physiological states, social experiences, and conscious actions.

Your brain’s ability to form memories and adapt based on experiences is due to changes at synapses. Synapses are tiny gaps where neurons communicate through chemical and electrical signals. This capacity for synapses to reshape is known as neuroplasticity. When a new long-term memory is formed, there are lasting alterations in the number and structure of synapses, along with changes in neurotransmitter release and the number of receptors on the postsynaptic membrane.

During information transmission, a presynaptic neuron converts an electrical signal into chemical messengers called neurotransmitters. These neurotransmitters diffuse across the synaptic gap to the postsynaptic neuron, which has receptors that interact with them. When neurotransmitters bind to these receptors, they trigger a series of events that convert the signal back into an electrical impulse. Afterward, neurotransmitters are either recycled back into the presynaptic terminal or broken down, allowing the postsynaptic receptors to receive new signals.

Two opposing processes are crucial for neuroplasticity: long-term potentiation (LTP) and long-term depression (LTD). LTP represents a sustained increase in synaptic strength, especially in the hippocampus, while LTD involves a decrease in synaptic effectiveness. Numerous studies have shown that LTP is essential for the consolidation of long-term memories.

LTP has been extensively studied in the hippocampus, a region vital for encoding new memories. The mechanisms of LTP can vary among neuron types, but it generally involves an increase in glutamate receptors on the postsynaptic neuron. Glutamate, the most common neurotransmitter in the nervous system, interacts with several receptor types.  An increase in the number of receptors on the postsynaptic cell strengthens the synapse by facilitating greater ion influx.

This molecular cascade is essential for transforming memories into long-lasting forms. Current understanding suggests that declarative memories are initially encoded in the hippocampus and later transferred to the frontal lobes for long-term storage. Over time, the hippocampus becomes less critical for retrieving older memories, a function increasingly taken over by the frontal cortex.

While the brain appears to have an unlimited capacity for long-term memories, short-term memories are limited to small amounts of information for brief periods. These memories are stored across various cortical areas. For example, recalling long-term memories but being unable to form new ones.

In contrast, working memory is a temporary type of declarative memory that allows you to hold information—like a phone number or visual image—for immediate use. The brain seems to have limitless capacity for long-term memories, while short-term memories are confined to relatively small data amounts for short durations. These memories are accessible during processing, but if not transferred to long-term storage, they can fade quickly. Working memory is particularly active when focusing on maintaining information, with studies indicating that neurons in the prefrontal cortex fire in bursts to keep information “online.” 

Emotions form part of who we are. Ignoring certain emotions can have significant consequences. It might provide temporary relief, but suppressing emotions often lead to increased levels of stress, anxiety, and physical health issues. If unresolved, over time,  emotions can manifest in various ways, such as irritability, emotional outbursts, burn out or even depression.