Long Term Memory: The Brain's Storage System

Description: Long-term memory is "where" we store and retrieve information. It's capacity is unknown, but is thought to be somewhere around a million billion connections. It is permanent, but not always accurate.

Types of Memory Storage- there are two categories of memory storage.
1. Procedural Memory- "how" you know how to do something, not "what" you know. There are 2 sub-categories, both of which are implicit,
meaning you do them without being consciously aware:
a. nondeclarative- these are skills. It is our brains ability to store automatic processes for routine actions like walking, driving, decoding
words. These skills become automatic after repetition. Our conscious has a hard time accessing its rules of operation because it has
become automatic. Nondeclarative memory represents something we just DO.
b. priming- being influenced by a past memory without awareness of remembering the event that caused the memory. The indication is that
our memory can be influenced by experiences we can't necessarily remember. Having seen something previously enhances our ability to
recall it later.
2. Declarative Memory- ability to store and recall information we can speak and write about. This type of memory is reflective, not reflexive...in
other words, we can't do it automatically--it requires thought. There are two types of declarative memory:
a. episodic- aka "source" memory because it involves remembering where and when information was acquired. It records faces, music, facts,
and individual experiences. The downside of episodic memory is that you don't so much recall a memory so much as you reconstruct it.
Sometimes our brains forget the details of and event. As we retell them we tend to make them more elaborate until the "refabrication"
becomes the memory itself. Memory of an event can be vivid, but the details can be fuzzy.
b. semantic- is usually accurate. It includes words and symbols, rules for manipulating those words and their definitions, grammar rules,
math computation, etc. It is basically your general knowledge...the result of education.
*Knowing that 6 x 7 = 42 is semantic memory at work. Knowing what grade you were in and who your teacher was when you learned your times tables is episodic memory at work.

Cellular Basis of Memory-underlying all memory there is a physiological basis of storing and retrieving information.
  1. The term Long-Term Potentiation (LTP) represents a current hypothesis that the synapse ("connector") between neurons (brain cells representing experiences) becomes strengthened ("potentiated") over time.
  2. Memory entails firing of neurons similar to how the neurons fire when you actually experience an event.
  3. It is thought that this is possible because when two or more neurons are active at the same time, the more sensitive they become. The more often this pattern repeats, the stronger the synapse.
  4. The increased strength of the synapse makes it more efficient and is what is known as LTP.
  5. Growth of Synapses- enriching environments lead to changes in the actual architecture of the brain.
Bottom Line for the Educator: the learning methods we use to educate our students can affect the strength and duration of the changes that happen when neurons connect.

How Memories are Stored
  • In his book, Inside the Brain, Ronald Kotulak uses the following metaphor:
    • The brain gobbles up its external environment in bites and chunks through its sensory system: vision, hearing, smell, touch, and taste. Then the digested world is reassembled in the form of trillions of connections between brain cells that are constantly growing or dying, or becoming stronger or weaker, depending upon the richness of the banquet.
  • There is no such thing as a "storage department" in the brain. Instead, various networks of brain cells are used many times to recall similar lines, colors, smells, etc. For example, the cells that allow us to perceive the color red can be used to see a red rose or a red heart.

How Memories are Recalled
  • Memories aren't exactly recalled, like files from a file cabinet. Instead the ability to remember is a reconstruction or reactivation.
  • Your brain doesn't reconstruct the whole memory, only the defining elements. The brain fills in the rest.
  • Depending on the type of cue, only certain fragments of the total memory may be activated.
  • If the cue is unclear or weak, what is reactivated may belong to another episode or differ from the original memory. (This is why eye-witness accounts are unreliable and demonstrates how false memories can be planted by faulty questioning.)

Consolidation-memory is not formed at the exact moment it is acquired. It strengthens over days, months, etc. The process (which is unconscious) through which it strengthens is called consolidation.
  • enhanced through rehearsal, or practice.
  • essentially, consolidation is not just a process, but also a length of time. Learning motor skills sets in motion neural processes that continue to evolve (or gel...or consolidate) long after the actual practice of that motor skill has ended.
  • sleep plays a role in consolidation, too.
  • during REM sleep, the brain takes a break from the constant input of information.
  • If you think about it, our own dreams often contain fragments of the day. This is how the brain replays those experiences, making sleep critical in the development of long-term memory.
Bottom Line for the Educator: this is why instruction that allows students to hook new information to previous experiences enhances the strength of the neural connection/retention of information.

Educational Implications:
  • We know consolidation must occur after the learning of a new concept and that the introduction of a new concept too soon can interrupt retention of the old concept. No one knows how much time is needed for consolidation.
  • There is the suggestion that allowing time to process information more in depth may increase the strength of learning...and herein lies the reason why many educators say "We need to teach a lot less a lot better."

Teaching for Long-Term Memory:
  • As learners, we need to expend some effort to make certain that we'll be able to recall information when we need it.
  • The speed at which we must teach curriculum works against that need, ensuring that we only cover content superficially, which does not build strong neural connections.
  • Rote rehearsal does not produce long-term declarative memory, elaborative rehearsal does.