New research from scientists around the globe has produced the strongest evidence to date that there are two separate cognitive systems. Three unrelated studies from March of 2014 offer new clues to the inner workings of two very different cognitive systems. One is called the "implicit" system, the other is called the "explicit" system.
Implicit learning happens automatically and unconsciously through conditioning and practice. On the flip side, explicit learning requires the conscious, intellectual grasp of specific knowledge or procedures that you could memorize and articulate. Together, the explicit and implicit memory systems allow us to learn and remember the people, places, skills, and experiences that shape our perceptions and interactions with the world around us.
Implicit learning requires the person learning to actually perform and practice a task to master it. Things like riding a bike, serving a tennis ball, and tying your shoelaces all require implicit memory. Things like telling someone where you were born, your mother’s maiden name, or your cell phone number require explicit memory.
For more than a century, scientists have recognized the existence of “automatism” or implicit procedural memories which allow us to perform complicated actions without conscious thought or intention. Automatic skills based on implicit learning include most common daily activities skills we master through practice, practice, practice.
The Athlete’s Way philosophy is founded on the principle that to succeed in sports, or any type of skill that requires muscle memory and strategy, that you need to have an optimized balance between the function of your explicit and implicit brain regions.
Last week, I wrote a Psychology Today blog post about a new study from University of Pennsylvania which looked at specific neurons in the cerebellum—called Purkinje cells and climbing fibers—that are linked to implicit learning titled “Neuroscientists Discover How Practice Makes Perfect.”
The Unconscious Mind Can "Remember" Experiences that Occur Under Anesthesia
In the first study about the unconscious mind from March 2014, researchers at the American Society of Anesthesiologists (ASA) showed that a rats' brains can learn and remember odors they were exposed to while deeply anesthetized. These findings support a findings from a 1998 study published in the Journal of Neuroscience which found that the cerebellum plays an active role in human olfaction. Some scientists refer to the cerebellum as “the smell brain.”
These new findings suggest that our brain not only receives sensory information, but also registers information at an unconscious cellular level. While the rats had no memory of being exposed to the odor under anesthesia, changes in the brain tissue on a cellular level suggested the rats "remembered" the exposure to the unfamiliar scent under anesthesia.
"It raises the question of whether our brains are being imprinted during anesthesia in ways we don't recognize because we simply don't remember," said Yan Xu, Ph.D., lead author and vice chairman for basic sciences in the Department of Anesthesiology at the University of Pittsburgh School of Medicine. "The fact that an anesthetized brain can receive sensory information—and distinguish whether that information is novel or familiar during and after anesthesia, even if one does not remember receiving it—suggests a need to re-evaluate how the depth of anesthesia should be measured clinically."
Strong Evidence of Explicit and Implicit Cognitive Systems
In the second March 2014 study, cognitive neuroscientists found some of the strongest evidence to date of there being two separate and distinctive cognitve learning systems. "Our finding that there are distinct, discrete systems has implications for the fields of child development and cognitive aging," says lead researcher, cognitive psychologist J. David Smith, PhD, of the University at Buffalo.
"These distinct systems may have different developmental courses as the cortex matures," he says, "meaning that children may categorize differently than adults, using different systems at different ages. This would have educational and training implications in cases of developmental disability." Smith says the systems also may have different courses of decline in cognitive aging, which would have ramifications for remediation and compensation in dementia.
"Cognitive neuroscientists have hypothesized that humans have distinguishable systems for categorizing the objects in their world—one more explicit (i.e., conscious and available to introspection), one less so, or more implicit," says Smith.
"Because of the considerable controversy surrounding the question of whether we have more than one cognitive system, researchers have continued to seek models that distinguish the processes of explicit and implicit category learning," Smith says, "and this study presents the clearest distinction yet found between these systems.
"Implicit category learning," he says, "is a system that depends on trial-by-trial feedback of response correctness and incorrectness to establish the stimulus-response associations that allow implicit learning and responding." Smith adds, "In fact, the blocked-feedback technique made implicit category learning impossible. We then used extensive trial-strategy analyses and formal-mathematical modeling to demonstrate this conclusively.
"So we were able to selectively unplug one category-learning system—the implicit system—but leave the explicit-conscious system functioning and intact," he says. Smith et al. even found that, facing a task that could only be learned implicitly, participants with blocked feedback turned futilely to conscious strategies that were inadequate, because this was all they could do when implicit category learning was defeated.
Induced "Out-of-Body" States Disrupt Formation of Explicit Memories
In a third study from March 2014, scientists at Karolinska Institutet and Umeå University in Finland demonstrated for the first time that there is a close relationship between body perception and the ability to form explicit memories. Because the cerebellum is responsible for proprioception, this finding implies to me that the cerebellum may be working in concert with the cerebrum, hippocampus, and other brain regions to optimize explicit learning and memory.
According to researchers, in order to be able to store new memories from our lives, we need to feel that we are in our own body. These results could be of major importance in understanding the memory problems that psychiatric patients often exhibit.
"It is already evident that people who have suffered psychiatric conditions in which they felt that they were not in their own body have fragmentary memories of what actually occurred," says Loretxu Bergouignan, principal author of the FInnish study. "We wanted to see how this manifests itself in healthy subjects."
It then turned out that the participants remembered the "out-of-body" interrogations significantly worse than those experienced from the normal "In body" perspective. This was the case despite the fact that they responded equally well to the questions from each situation and also indicated that they experienced the same level of emotion.
The researchers' interpretation of the results is that there is a close relationship between body experience and memory. Our brain constantly creates the experience of one's own body in space by combining information from multiple senses: sight, hearing, touch, and more.
When a memory is created, it is most likely the task of the hippocampus to link all the information found in the cerebral cortex and the cerebellum into a unified explicit memory. During the experience of being outside one's body, this memory storage process is disturbed, whereupon the brain creates fragmentary memories… or no conscious memories at all.
"We believe that this new knowledge may be important for future research on memory disorders in a number of psychiatric conditions such as post-traumatic stress disorder, borderline personality disorder and certain psychoses where patients have dissociative experiences," says Loretxu Bergouignan.
H.M. Lost His Hippocampus... and His Explicit Memory System
The famous neurosurgery patient "H.M." had his entire hippocampus accidentally removed in a botched attempt to treat epilepsy. He went on to suffer amnesia and the ability to form any new explicit memories. However, with a cerebellum in tact he was able to learn puzzles and retain implicit-procedural memories although he had absolutely no cerebral or conscious recognition of learning these implicit skills.
This inability to store new long-term memories literally froze his personal history and knowledge to the date of his operation. For example, after his operation, H.M. could no longer recall a list of words a few minutes after hearing it. He also had difficulty with new words that became popular in the 1960s such as “jacuzzi” and “granola.”
However, H.M.’s implicit memory, as well as his memories of the distant past, were intact. For example, he could acquire and master new skills, such as tracking a target or copying an object in a mirror, and building a complex wooden block structure called “The Hanoi Towers.” But again, he could not remember having ever practiced these skills in the past.
This separation of his explicit memory from his other forms of memory contributed greatly to the identification of explicit and implicit learning systems decades ago. H.M. revealed that despite an inability to form conscious memories, someone can still acquire procedural skills held in the implicit memory system.
Conclusion: Explicit and Implicit Memory Systems Complement One Another
Chapter ten of my book, The Athlete’s Way is titled “Sticking With It” and gives practical advice for breaking bad habits and creating better habits through a combination of explicit and implicit learning techniques.
In my first book I presented a split-brain model that refers to the unconscious ‘non-thinking’ cerebellum as the seat of implicit memory and the cerebrum as the seat of explicit learning and memory. This is a revolutionary idea which the latest neuroscience seems to support.
Clearly, more clinical studies are necessary to fine tune how the implicit and explicit memory systems can be optimized and to see if there is in fact a brain region associated with each these two systems.
If you'd like to read more on how implicit and explicit cognitive systems coordinate with the cerebrum and cerebellum please check out my Psychology Today blog posts: