Brain Rules by Dr. John Medina
Brain Rule # 6 (part 2)– Long-Term Memory - Repeat to Remember
In the previous rule, Medina presented Short-Term Memory and in the beginning of rule 6 he explained Working Memory, now he begins discussing Long-Term Memory. Up to this point, memory is short lived. However, understanding how to get something into our long-term memory remains very useful.
Next, our long-term memories are consolidated with other memories by current stimuli. For instance, a childhood memory of a German shepherd dog may be stimulated by watching a documentary about a dog of the same kind. Without the stimulus to remember, that childhood memory would remain dormant. Therefore, the ability to retrieve memories gains importance. “…our retrieval systems are powerful enough to alter our conceptions of the past while offering nothing substantial to replace them. Exactly how that happens is an important but missing piece of the puzzle.” (p. 127)
Two models of long-term memory have emerged: 1) memory passively imagines libraries; and 2) memory aggressively imagines crime scenes. (p. 127) Both of these models are correct. Early on our memory is like a library, but as time goes by it is more like a detective’s search. Sometimes a long-term-memory can be distorted as the detective fills in the missing pieces in an attempt to come up with the complete story.
Knowing that our memories can be inaccurate, it behooves us to provide our brains with repetition. “The typical human brain can hold approximately seven pieces of information for less than 30 seconds. If something does not happen in the short stretch of time, the information becomes lost.” (p. 130)
Three ways to reinforce memory:
a. Space Out the Input – the left inferior pre-frontal cortex is stimulated when one is retrieving a memory. (p. 132-133) According to the neurodevelopmental approach, we encourage short, frequent input.
b. Sparking Interest – As in a romance or what we often call falling in love, “long-term potentiation” is the idea that increasingly limited exposure can result in increasingly stronger responses. (p. 133-136) Neurodevelopmentalists recommend “intense” or “focused” input as a part of learning.
c. Steps in Long-Term Memory
1) “Sensory information comes into the hippocampus from the cortex, and memories form in the cortex by way of the reverse connections.”
2) “Long after the initial stimulus has exited the hippocampus and the relevant cortical neurons are still yapping (communicating) about it.”
3) “While these regions are actively engaged, any memory they mediate is labile and subject to amendment. But it doesn’t stay that way.”
4) “After an elapsed period of time, the hippocampus will let go to the cortex, effectively terminating the relationship. This will leave only the cortex holding the memory of the event.” P. 137-138
Finally, the last step is “forgetting.” “Forgetting allows us to prioritize events. Those events that are irrelevant to our survival will take up wasteful cognitive space if we assign them the same priority as events critical to our survival.’ (p. 143)
Medina summarizes Rule 6 with the following statements:
1) “Most memories disappear within minutes, but those that survive the fragile period strengthen with time.”
2) “Long-term memories are formed in a two-way conversation between the hippocampus and the cortex, until the hippocampus breaks the connections and the memory is fixed in the cortex – which can take years.”
3) “Our brains give us only an approximate view of reality, because they mix new knowledge with past memories and store them together as one.”
4) “The way to make long-term memory reliable is to incorporate new information gradually and repeat it in time intervals.” P. 147
With this, Medina completes his discussion of memory. As time goes on, we begin to understand more and more about how we are “fearfully and wonderfully made”, and yet we must be reminded that our understanding is still very limited because the Psalmist asks “who can know it?”