Memory definitions

Memory - Some Keywords and Concepts

Learning changes the brain


autobiographical memory


BDNF - brain-derived neurotrophic factor

declarative memory



long-term memory



nondeclarative memory


semantic memory

short-term memory


working memory

Acetylcholine is essential for learning. This neurotransmitter helps the brain pay attention, and sharpens memories. It also contributes to feelings of brightness, alertness, and engagement.

Autobiographical memory is also called episodic memory. It is one type of explicit (declarative) memory, and a form of conscious long-term memory. Episodic/autobiographical memory enables our recollection of personal experiences, events in our lives, and their contexts - e.g., celebrating a graduation, losing a job, etc. The degree of emotion connected to personal experiences and events affects whether or not they are stored in memory, as well as how strongly we remember them. Usually, the stronger the emotion, the stronger the memory.

BDNF, brain-derived neurotrophic factor, is a protein that is active in the hippocampus, cortex, and specific areas of the frontal lobe - areas of the brain that are vital to learning, memory, and higher order thinking processes. It's been called Miracle-Gro or fertilizer for the brain because it increases synaptic connections and strengthens communication between neurons. BDNF is also important for long-term memory. BDNF levels tend to be critically low in people with depression. Sugar suppresses BDNF, but exercise boosts BDNF levels in the brain.

Declarative memory is also called explicit memory. It is a form of long-term memory, and requires conscious thought - such as remembering the names of countries and capitals of South America, or dates and events in world history.

Declarative memory is subdivided into episodic memory, which is autobiographical, and semantic memory, such as general knowledge and textbook learning.

Dopamine is associated with the brain's reward and pleasure centers. It contributes to our experiencing life as positive and pleasurable. It is called the reward transmitter because it is triggered in the brain when we accomplish something positive and important to us. When we master a new skill or learn a new concept, a surge of dopamine induces feelings of excitement and the pleasure of achievement. We feel ready and motivated towards achieving additional rewards. The release of dopamine also consolidates learning by strengthening the neuronal connections that led to the accomplishment.

Long-term memory is stored information that may be minutes, days, or years old. Some memories are stronger and relatively easier to retrieve than weaker memories that may require prompting or reminding.

Long-term memory may be conscious (declarative, explicit), like remembering facts, concepts, events, etc. Other memories are unconscious (nondeclarative, implicit), and do not require conscious thought, like riding a bike.

We understand memory to be the process by which the brain encodes, stores, and retrieves information.

Encoding is the process of transforming the information we receive from the outside world through our senses into the electrical and chemical signals that activate our brain cells.

Storing refers to the changes that happen in the brain to keep information over periods of time.

Retrieving is the process of locating information stored in the brain to make it available to us - i.e., remembering.

When we store information, we are creating a memory. What the information is, and how long we store it, determines what type of memory it is.

Nondeclarative memory is also called implicit memory. It is a form of long-term memory, but unlike explicit/declarative memory, does not require conscious thought. Implicit/nondeclarative memory is unconscious memory. It allows us to perform learned skills and procedures by rote - i.e., without having to think about the steps or process involved. Implicit memory is subdivided into procedural memory, which is our "how to" knowledge, and priming - i.e., experience may trigger speedier memory retrieval.

Semantic memory is one type of explicit (declarative) memory, and a form of conscious long-term memory. General knowledge about the world, and information learned from textbooks and schools, are stored and retrieved as semantic memory. Level of knowledge and frequency of recall will affect the speed of retrieval and strength of the memory.

Short-term memory is temporary. This information is not stored. It is kept in mind for a short time before it is transferred to long-term memory, or dismissed - i.e., lost to memory.

The term working memory is often used interchangeably with short-term memory.

Working memory is a term often used interchangeably with short-term memory. However, working memory suggests a more specific and active idea of the brain keeping information - e.g., a name of phone number - "in mind" just long enough for immediate use, after which the information is lost to memory.

Short-term memory refers more generally to temporarily holding information and determining if it will be transferred to long-term memory or dismissed.

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