Memory and Its Underlying Brain Structures

A variety of Healthymemory Blog posts have discussed the various brain structures underlying memory. As a book1 I have been reading has provided a succinct overview describing the interacting structures and areas of the brain that are responsible for memory I have decided to write the following post.

The initially encoding is done in the hippocampi (there is one hippocampus in each of the two brain hemispheres) from which it is distributed throughout the rest of the brain. This distribution is needed to determine the meaning, or lack of meaning, of this information. This takes place in short term or working memory. Meaningless information is quickly lost without further processing. Even the current instance of meaningful information will be lost without further processing (for example I need to meet Fred for lunch or I need to remember this for the examination). This working memory is maintained in an active mental state within the dorsolateral prefrontal cortex of the frontal lobes. Maintaining information here requires glucose metabolism.

This glucose metabolism is the physiological indication of paying attention. So when you are performing a task that requires you to pay attention, glucose metabolism is required. It is interesting to note that as you become more proficient in performing the task, the rate of glucose metabolism actually decreases. This indicates that you need to pay less attention due to your increase in proficiency.

The successful storing of information in long term memory via the hippocampi requires the establishing of links to other items in long term memory. Mnemonic techniques are developed to make what appears to be inherently meaningless into something meaningful so it can be linked to other items I long term memory for later retrieval. There is no central memory center in the brain. Rather information is stored throughout the brain. Sensory information in the sensory portions, motor information in the motor portions, and verbal and semantic information is the associative portions. Information that you know well likely has many many links to other items of information. Some memory theorists have likened human memory to a hologram. Holograms differ from photographs in that the entire image can be reconstructed from portions of the hologram. So if you break a hologram into two pieces, the entire hologram can be reconstructed from either piece, but the resulting image will be less distinct.

Memory theorists make a distinction between information being available in memory and information being accessible in memory. Information that can be readily retrieved is said to be accessible. However, if you cannot retrieve something at a given time, it is likely that that information is still not available in memory, but it is still accessible. Moreover, even after you have consciously given up trying to recall this information, it sometimes happens that at a later point in time when you are consciously thinking about something else, that this apparently lost memory pops into consciousness.

So how does this relate to maintaining and growing a healthy memory? Engaging in activities requiring significant amounts of attention increase the metabolic activity going to your working memory. This metabolic activity will decrease as you become more proficient in the activity. In many respects this is analogous to the effects of physical activity on cardiopulmonary activity. It should be noted that this practice effect is the result of transferring information to long term memory so less attention is required.

To maintain and grow long term memory developing new associative pathways throughout the brain is required. This will not be done by simply surfing the internet (which is primarily a working memory exercise). Long term memory growth is a matter of pursuing knowledge and skill in more depth to develop and strengthen associative pathways so that they are more resistant to forgetting. In other words, increasing the accessibility of the information. The very act of retrieving information is beneficial even if your initial retrieval attempts are unsuccessful. The searching for information activates memory pathways, some of which might have been long inactive. The memory search can reactivate them. Moreover, your memory will likely continuing working even after you have consciously given up the attempt.

1Restak, R., (2009). Think Smart: A Neuroscientist’s Prescription for Improving Brain Performance. New York: Riverhead Books.

© Douglas Griffith and, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

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