Posts Tagged ‘Explicit memory’

Cognitive Neuroscience of Memory

September 6, 2019

The title of this post is the same as the title of an important book by Scott D. Slotnick. He writes in the preface, “The human brain and memory are two of the most complex and fascinating systems in existence. Within the last two decades, the cognitive neuroscience of memory has begun to thrive with the advent of techniques that can non-invasively measure human brain activity with spatial resolution and high temporal resolution.

Cognitive neuroscience had not been created when HM was a graduate student. The field is quite new. In cognitive psychology we studied cognitive processes, of which memory was central, but little was known about the neuroscience underlying memory.

Before getting into neuroscience it is important to understand what memory encompasses. Most people think of memory as something they need to use to pass exams, are frustrated by exam failures, and by an inability to remember names. Readers should be aware of the function of memory. Memory is a tool for time travel. We use it to help us predict and deal with the future. The more we learn, the more we have information for dealing with the future. Moreover, there are many types of memory.

The first pair of memory types is explicit memory and implicit memory. These refer to conscious memory and nonconscious memory. They differ in that all forms of explicit memory are associated with conscious experience/awareness of previously experienced memory, whereas all forms of implicit memory are associated with a lack of conscious experience/awareness of the previously experienced information.

Skills are one type of implicit of memory. After a skill is learned, performance of that skill reflects nonconscious memory. Once a person has learned to ride a bike, she doesn’t think about rotating the pedals, steering, breaking, or balancing. Rather, their conscious experience is dominated by where she wants to ride or whatever else she happens to be thinking about. Repetition priming is another type of implicit memory that refers to more efficient or fluent processing of an item when it is repeated. When a television commercial is repeated, that information is processed more efficiently (and when the item from the commercial is seen again while shopping, implicit memory presumably increases the chance that it will be purchased.) Skill learning can be assumed to be based on repetition priming.

The remaining memory types are types of explicit memory. A second pair of memory types is long-term memory and working memory. Working-memory is often referred to as short-term memory. A recognition memory experiment will be described to help make the distinction between long-term memory and working memory. During the study phase of both long-term memory and working memory, items such as words or objects are presented. After the study phase, there is a delay period that will last as a function of specific amount(s) of time. During the test phase, old items from the study phase and new items are presented, and participants make “old” or “new” judgments for each item. This is termed old-new recognition. A greater proportion of “old” responses to old items than “old” responses to new items indicates the degree of accuracy of the memories.

Long-term memory and working memory differ with regard to whether or not information is kept in mind during the delay period. Typically there are many items in the study phase and the delay period is relatively long (typically minutes to hours). Obviously participants do not actively maintain information from the study phase during the delay period. In working memory experiments, there are typically a few items in the study phase, the delay period is in seconds and participants are instructed to actively maintain information from the study phase in their mind.

Another pair of memory types is episodic memory and semantic memory. Episodic memory consists of the memories we have of our experiences. Semantic memory refers to retrieval of, hopefully, factual memory that is learned over periods of time such as the definition of a word. Unfortunately, semantic memory also consists of misinformation and erroneous beliefs. And, unfortunately, this misinformation and erroneous beliefs can be further amplified via technology and social media.

Another pair of memory types is “remembering” and “knowing.” “Remembering” refers to the subjective mental experience of retrieving details from the previous experience, such as someone retrieving where they parked their car in a parking lot. If any details are recalled from a previous experience, this constitutes “remembering.” “Knowing” is defined by the lack of memory for details from a pervious experience, such as when someone is confident they have seen someone before but not where or when they saw them. Remembering is usually assumed to be related to context memory, as it is thought to occur whenever contextual information is retrieved. “Knowing” is typically assumed to be related to item memory and semantic memory. The last pair of memory types is recollection and familiarity. The terms recollection and familiarity can refer to mathematical models of these two kinds of memory, but more commonly refer to all the forms of detailed memory (episodic memory, context memory and “remembering”) and non-detailed memory (semantic memory, item memory, and knowing). Dr. Slotnick writes, “It may be useful to think of context memory and item memory as measures of task performance, “remembering” and “knowing” as measures of subjective experience, and recollection and familiarity as general terms that describe strong memory and weak memory, respectively.”


An Inspirational and Informative Case of Memory Loss

October 9, 2011

A recent article1 reported a case of memory loss that was both inspirational and informative. This was the story of Lonni Sue Johnston who was an accomplished illustrator, musician, pilot, and farmer. She had done half a dozen covers for the New Yorker magazine. Then a virus invaded her brain causing encephalitis and severely injury her hippocampus. As readers of the Healthymemory Blog know, the hippocampus is a subcortical structure that plays a key role in the formation of new memories. Initially she had trouble walking, talking, and eating. Her cognitive functioning was severely affected. She recognized only a few people, her mother, her sister, and a few faces from her childhood. She could no longer draw.

Her mother had her daughter try to copy simple shapes. Although progress was slow, she eventually was able to draw again. A friend, who was a puzzle-maker, dropped off word search books. These exercises enabled her to rebuild her vocabulary. She started making grids with words hidden in them and created her own puzzles. She created elaborate word lists, then puzzles from the lists, and them images from the puzzles. A grid of words for things that hang in the closet formed the shape of a coat hanger. Words related to trousers formed a pair of pants.

She still can’t recognize art that she adored before her illness, Van Gogh’s “Starry Night” for instance, but she can recognize her own past work. Although she has not reached the degree of proficiency that she once had, she has improved enough to have her own exhibition at The Walters Art Museum in Baltimore.

It is instructive to consider what she can and cannot do. She remembers how to fly an airplane, but doesn’t remember the death of her father. She doesn’t remember that she was married for ten years, but she can play Bach suites on her viola. When her mother thanks her for playing, she does not remember that she has played.

She continues to rise at 5:30 in the morning and spends most of her working hours drawing and creating puzzles. Her family is keeping everything she has produced, hoping that it will offer insight into the relationship between neural science and creativity.

It is interesting that most of what has recovered has been what is termed implicit memory (see the immediately preceding blog post, “Explicit and Implicit” memory). Motor skills are primarily in the domain of implicit memory, which appears to be more robust than explicit memory. She had developed an interesting technique for rebuilding her vocabulary, which seems to capitalize on using implicit to make memories explicit.

For another inspirational story of recovery from memory loss, see the Healthymemory Blog Post, “An Amazing Example of the Neuroplasticity of Memory.”

1Pancake, J. (2011). A “self” portrait of an artist with memory loss. Washington Post Style Section, September 19.

© 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.

Explicit and Implicit Memory

October 5, 2011

When we normally think of memory, we are thinking of explicit memory. Memory techniques and most of the posts on memory in this blog are concerned with explicit memory. Implicit memory refers to memory that occurs without your consciousness awareness. Implicit memory covers a wide range of activities. Classical conditioning, habit learning, emotional memory, procedural and motor memory typically are implicit. So implicit memory involves both maladaptive behaviors, such as bad habits and addiction, but it is also involved in the development of optimal strategies in skill acquisition. Implicit learning could also be helpful for amnesiacs and Alzheimer’s patients.1

Theorists have wondered why we have two types of memory. Although theorists wonder about this, it is nice to have a type of memory that requires little or no consciousness. Although consciousness might not be required, trials or repetitions are required. For example, classical conditioning in which a conditioned stimulus, say a bell, is paired with an unconditioned stimulus, say food, before the sound of the bell alone will cause you, or a dog, to salivate. Similarly habits take repetitions to develop, and procedural and motor skills can take a great deal of practice to perfect. On the other hand, emotions, depending on the strength of the emotion, can be learned quite rapidly.

I think it is obvious why we have explicit memory. Explicit memory involves consciousness. Had we only implicit memory we would be acting like Zombies, behaving and learning with little or no understanding as to why. So it is understandable that most educational practices and most of the Healthymemory Blog posts involve explicit memory. But we should be thankful for these implicit memory processes. Consider how burdensome it would be if all memories were explicit.

We do need to learn more about implicit memory. Much athletic and artistic performance is a matter of practicing to the point where skills become automatic. Usually performance falters when the performer or athlete starts to think about what they are doing. Implicit memory also offers a path into the memories of those for whom explicit memory has been lost such as Alzheimer’s patients and other suffering from traumas to the medial temporal lobes.

1Much of this blog post is taken from an article by David W.L. Wu. Implicit Memory: How It Works and Why We Need It. The Joournal of Young Investigators, Vol. 22, Issue, 1, July 2011.

© 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.