Memory

Memory encoding is done in two areas:

• The Hippocampus - Combines the incoming sensory information into a single memory trace.
• The Cortex:
  • The hippocampus plays the memory back to the cortex while we sleep or rest.
  • Factual data is stored in the temporal and frontal lobes as independent facts, without strong links to how you learned them
  • Episodic memories have their core sensory data stored in the cortex, but retain permanent links to the hippocampus for contextual details.

Concepts, categories, and memories are comprised of patterns of connections:

• The concept of Berlin is a network of millions of neurons firing together.
• The category of "German cities" is another network in which the Berlin network forms a part.
• The Anterior Temporal Lobe (ATL) is a kind of semantic hub that connects abstract words like "Berlin" to various features stored elsewhere.
• When you think "Berlin", electricity floods the relevant network and "leaks" or spreads out to closely connected networks such as WWII, Germany, Europe, etc

Memory retrieval requires brain networks to work together to provide personal and factual information to consciousness. For example, when thinking about "Berlin":

• Factual information such as "Berlin is the capital of Germany", which is stored across the lateral temporal cortex is s part of a semantic network of nodes that is activated.
• The left inferior frontal gyrus filters out irrelevant trivia and selects the facts you need.
• Memories of a visit to the city are stitched together by the hippocampus, which can signal the visual cortex to recreate the sights of monuments you saw and the auditory cortex to recall sounds you heard.
• The amygdala provides emotional content.
• The prefrontal cortex holds the facts and personal memories in working memory and acts as a filter, so that the desire to retrieve historical information will suppresses personal vacation memories

Attention moves across the content of memory due to shifts in electrical activation or chemical momentum:

• If the electrical leakage into a related concept grows strong enough, that concept may pop into conscious awareness.
• If the leakage remains below the necessary threshold, the related concept is still primed and can be more easily triggered by other thoughts, or external sights and sounds.
• The prefrontal cortex tries to keep you attention focused on your current task by sending inhibitory signals in the form of GABA, but the salience network may send a jolt of norepinephrine across the brain if it senses that an unconscious memory is highly important, emotional, or novel, and should be brought to conscious attention.
• In general, attention moves along the path of least resistance:
  • Pathways that you use frequently have more synaptic weight through stronger connections and attention will follow these well-worn paths
  • The amygdala heavily flags memories associated with strong feelings, so that emotional thoughts can easily pull your attention away from simple factual data.
  • When you relax, the default mode network lowers brain filters, allowing daydreaming where thoughts, facts, and episodic memories to freely drift, collide, and slip into one another.