The stimulus-driven learning process
We forge long-term memories, and learn nearly everything we retain by strengthening neural connections through repetition, and sometimes trauma or reward. Certain events can imprint permanent memories, simply by their magnitude, and their effects upon our lives and our emotions. Events such as Pearl Harbor, the assassination of President Kennedy, and the horror of 9/11 evoke strong associations, and any of us who lived through them remember where we were and what we were doing when we first heard about them. Few of us, however, could recall what we did on the preceding day. We are all familiar with that kind of memory imprinting and recall, but what about the normal, everyday kinds of things we try to remember – and sometimes fail. How does this neuroplasticity really work, and, most importantly, do we have any control over it?
The first step in memory formation is called “encoding,” which is a biological process, rooted in the senses, that begins with perception. As an example, think of meeting your first “crush.” When you met him or her, your visual system registered things like their physical appearance, the color of their eyes, the tilt of their head, and their smile. Your auditory system may have recorded the sound of their laughter. You may have experienced the smell of their after-shave or perfume. You may have even felt the touch of their hand upon your arm. These separate sensations traveled along neural pathways from different regions to a portion of your brain stem called the hippocampus, where they were integrated, as they occurred, and became one single experience – your experience of that specific person.
Imaging studies indicate that the hippocampus, along with another part of our brain, called the frontal cortex is responsible for analyzing these various sensory inputs and deciding if they’re worth remembering or not. If they are, they become part of our long-term memory. If not, they stay in short-term memory for a brief time, and are then forgotten. Do we have any control over what information is retained in long-term memory? Yes, we absolutely do, there are a couple of tools we can use to train our minds to commit information to long-term memory, one is repetition, and the other is mindfulness.
If we perform a task or recall some information that causes groups of connected neurons to fire in concert, it strengthens the connections between those cells, and they become what we call declarative memory, or memory we use in conscious decision-making. Eventually, if we strengthen them enough, these frequently-used pathways turn into what we call working or habit memory, and we can recall information, or perform certain tasks without the intervention or collaboration of our conscious mind! Practice makes permanent. The more times the network is stimulated, the stronger and more efficient it becomes.
To use another baseball analogy, there is nothing harder in all of sports than to hit a good major-league pitcher, but a great hitter never thinks about all the muscles that have to move in perfect coordination to hit the ball. He makes a decision in a few milliseconds, based upon his opinion of what the pitch is going to be, and well-developed neural pathways do the rest. A concert pianist does not consciously control his fingers while playing a piece he has practiced his whole life, any more than we think about the answer to 7 X 7, or our own social security number. These are things that have been committed to what we call “working or habit” memory. We don’t “think” about riding a bike, or turning on the tap when we’re thirsty, we just do it.
Many recent studies have concluded that “mindfulness” can play a major role in the retention of information, and thus the remolding of the brain. By mindfulness in this context, I am referring to simply “paying attention,” or being in the moment, and present to our lives. How many times have you been reading a book, and discovered you have “read” several pages and don’t remember a single one of them, because your mind drifted off to something else? Or you’re having a conversation with a friend, and suddenly discover that you can’t recall a single word they’ve said for the last minute or two? That’s what I mean, that’s how our mind works. We can focus for a time, but without some sort of mindfulness training, it’s difficult for us to keep ourselves from wandering off on some adventure or other. Simply paying attention is one of the best ways to improve our chances of not only retaining information, but also making major changes in the way we think, and how we perceive the world about us.
So, to briefly review: In response to a new experience or novel information, neuroplasticity allows either an alteration to the structure of already existing connections between neurons, or forms brand new connections between neurons, depending upon the experience or information. Either way, the brain is remolded to take in this new data, and if useful, retain it. When we are first exposed to something new, that information is entered into our short-term memory. If we decide that the information or experience is particularly important, it is repeated a number of times, or we are paying attention, it may become part of our long-term memory. If you want to increase your chances of remembering where you left your car keys last night, be sure you’re “present” when you set them down.
The reward-driven learning process
Above, we discussed stimulus-driven learning, in which the emotional content, novelty, significance, or perhaps the mindfulness we applied were the primary determinants in whether or not new experiences or information would be incorporated into our long-term memories, creating or strengthening neural pathways. We also mentioned feedback-driven learning, or the use of repetition to strengthen previously-existing neural pathways. There is another learning process, much stronger, and more primitive than any we have discussed thus far. Headquartered in a part of our brain that evolved hundreds of millions of years ago, is the system that incentivizes us to eat, reproduce, defend ourselves, protect our young, and other important functions that are key to our survival, and the survival of our species. It’s called the Reward Pathway, or Limbic system, and it’s one of the most powerful and complex systems we have.
Sometimes referred to as our “reptile brain,” because of it’s early evolution, this system organizes the behaviors that are life-sustaining, provides some tools necessary to take the desired actions, and then rewards us with pleasure when we do. Research shows that almost any normal activity we find pleasurable, from eating a chocolate chip cookie, to hearing great music, or seeing a beautiful face, can activate the reward system. When this happens, not only are we stimulated, but these circuits enable our brains to encode the circumstances that led to the pleasure, so that we can repeat the behavior, and the reward in the future.
A critical component of the system is a chemical, called dopamine, which is released from neurons in the reward system circuits and functions as a neurotransmitter, heightening our awareness and focusing our attention. I know, I promised I wouldn’t talk about chemicals, but understanding the effects of the release of this important component of the reward system is the key to understanding the system itself. As a matter-of-fact, the reward system is sometimes referred to as the “dopamine” system. Many other areas of the brain are wired-into this system as well, including decision-making areas, such as the frontal cortex. I’m not going to discuss other areas that are involved, because they’re not important for our purposes, and they vary from drug-to-drug anyhow.
One thing that I want you to understand, though, is that we are talking about our most basic survival mechanism here, and the established neural pathways that are used by this system are some of the most-used, and therefore strongest pathways in our entire brain. There is no other system, no other stimulus that will drive the formation of new connections, or the strengthening of existing ones’ faster then the reward, or limbic system. The limbic system connects the higher and lower functions of our brains, and serves as its’ emotional center. If we, as Humans, had to consider one part of our brains to be the core of our personal consciousness, it would be the limbic system and, especially, the interaction between it and the cortex. Physical disruption of the limbic system causes major behavioral changes, and, as we shall see in a later section of this chapter, it is this system that is hijacked by addiction.
The memory formation process is virtually the same for reward-driven memories as it is for stimulus-driven. The key difference between the two is that following the initial encoding or acquisition phase, the stronger emotions and already well-established neural pathways involved with the reward system can, and often does lead to much more rapid formation of declarative and working or habit memory. Again, declarative memory is that long-term memory which we use for concious decision-making, while habit memory is that which is called into play without our concious mind being involved.
When a person experiences a positive, pleasurable outcome from an action or event, the release of dopamine alters the brain circuitry, providing tools and encouragement to repeat the event. The memory circuitry stores cues, or triggers, to the rewarding stimulus, so previously neutral cues (a perfume, a particular location) become important. Our brains map the environment in which we experience the rewarding activity by recording the place, the people, the smells – in fact the entire experience. Triggers alone are not enough; actions are necessary to get a reward. The brain’s reward system is organized to engage the areas of the brain that control our ability to take action.
When we experience a rewarding event, the “thinking” portions of our brain are engaged. It remembers the actions used to achieve the reward and creates the capacity to repeat the experience. So, not only does a pleasurable experience result in pleasant memories, but also the executive center of the brain provides motivation, rationalization, and the activation of other brain areas necessary to repeat the experience. Each time the experience is repeated, all of these brain changes and reorganizations become stronger and more ingrained.
(Excerpted from Chapter 2 of the forthcoming book: “Powerless No Longer” Copyright© 2011, Pete Soderman)