Implicit and explicit memory explained

Many individuals have thought of something they needed to do, and as soon as they step into another room, that thought that was so urgent a few seconds ago vanishes faster than pizza at a child's birthday party. Or during a conversation you experience "Presque vu", otherwise known as the tip of the tongue phenomenon.

Healthy Ageing | Memory and concentration

Dr. Owen Wiseman, ND

03 October 2019

What are implicit and explicit memory?

Explicit memory is declarative and involves the conscious recollection of information. Explicit memory can be further divided into the following categories:

  • Episodic memory – this is your autobiographical memory containing the memories of your life and past.
  • Semantic memory – this is your fact and knowledge memory.

These categories of explicit memory are often invoked simultaneously because as you recall parts of your past, they may include facts or knowledge that you share during the recollection. This form of memory tends to activate regions of the hippocampus and prefrontal cortex.

Implicit memory is nondeclarative and involves the unconscious skills and habits that have been acquired throughout life, including the recall of events based on certain prompts. In a sense, this can be referred to as 'muscle memory' as you most likely don't talk yourself through how to tie your shoes each time.

Do they both decline with age?

While it is well-understood that explicit memory declines with age, implicit memory tends to stay intact with healthy aging. Certain studies have demonstrated that results of tests of implicit memory often do not differ significantly between older and younger individuals. The rate of explicit memory decline is actually highly indicative of the progression into dementia.

How could you test the different forms of memory?

Testing explicit memory can prove interesting and is a testament to how fallible this form of memory truly is. For explicit memory, individuals may be shown a clip of a motor vehicle accident between two cars. One group is asked to estimate how fast the car was traveling when it "bumped" into the other vehicle while the other group is asked the same question, but when the car "smashed" into the other vehicle. Unsurprisingly, the smashed group consistently indicates the vehicle was traveling faster than the bumped group estimates, but both parties insist their memory of the collision is more accurate.

Tests of implicit memory could be perceptual, conceptual, or non-verbal including tasks such as word stem completion, object decision, or word association respectively.

Word stem completion involves providing a number of letters of a larger word and the individual tries to complete the word as quickly and accurately as possible. Object decision involves viewing a variety of pictures or words, then other items are presented briefly in full form or broken down slightly and participants identify them. For word association, certain word pairs exist such as beach-sand, and one of these words will be presented on its own and the participant will need to complete the word.

What are some steps you can take to improve your memory?

In a trial looking at 48 elderly men, those taking ginkgo demonstrated improved blood flow to certain areas of the brain, a reduction blood viscosity, and improved global cognitive function. Another study looked at the effects of an extract of ginkgo known as EGb 761 on age-related mental decline in 60 participants. Those taking the extract demonstrated improvements in reaction time and vigilance. The effect was more pronounced in those who were further deteriorated. Based on these studies, the leaf may indeed be a choice to treat early cognitive deficits and it can be found in products as a homeopathic tincture (Ginkgoforce) which won't interact with the many medications that elderly individuals often find themselves taking.

Optimizing nutrition can have a significant benefit on all aspects of the body, including memory. A group of healthy, elderly participants were placed on the Mediterranean diet including 30g of nuts a day and 1L of olive oil. They demonstrated improvements in overall cognition, frontal executive function, and memory. The Mediterranean diet is rich in both poly- and monounsaturated fats, so if there are factors keeping you from wholly adopting the Mediterranean diet, adding omega-3 fats to your diet is beneficial. While research has not yet indicated fish oil benefits memory issues in those with Alzheimer's, it does have benefits in age-related cognitive decline. It can improve attention, processing speed, learning, and performance on cognitive tasks. If you want to add more omega-3 to your diet but find yourself adverse to the taste of fish, then it may be worth considering a vegetarian alternative like VegOmega 3 sourced from flaxseed and algal oil.

What are some other aspects of memory issues to consider?

Cognitive decline can also be associated with psychological distress and mental health concerns such as depression and anxiety. Therefore, it's important to consider treating the person as a whole as opposed to only treating their memory deficits.

Mind-body practices such as yoga and tai chi are aerobic exercises, and when practiced daily for one month and weekly for three additional months, participants demonstrated improvements in immediate and delayed recall, reduced symptoms of depression and agitation, as well as increased brain volume.


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