Memory: cognitive processes and mechanisms

Human Brain and Memory

Of the many intriguing mysteries of the human body, our capacity for memory and loss of memory is one of the most intriguing areas of study. Magda B. Arnold (1984) says that memory is the integration and articulation of the individual objects and experiences up to and including the present moment in our lives (p. 4). It is a mediated experience she contends, taking place in the brain's cortex (p. 4). Without memory, says Daniel L. Schacter (1996), everyone and everything in our daily lives would be strange and unknown; our relatives, our friends, our most common tools of daily use would all be foreign to us, new with each waking day and re-experience of the day (p. 2). Schacter points that out that except for the moments when our memory briefly fails us, or given to disease, our entire lives revolve our memory and we go about our day-to-day activities seldom thinking about where the organization out of chaos in our lives actually comes from. This brief study will explore memory, its capacity, its limits, and its susceptibility to disease and loss.

The Brain and Memory

While our memory serves us well, it has a tendency to be protective of us. It does this by throwing out the little bits of useless information that might otherwise become burdensome; and it stores in a remote region of the brain those experience or things that we do not want to deal with, cannot find the strength in ourselves to deal with at a particular point in time. Albert Einstein was always receiving questions by fans and others as to his great capacity for thinking and memory. He is credited with having responded to one question about how he maintained his brain's incredible capacity for problem solving by saying that he retained only the information that was useful and necessary, and discarded that information which was not useful or necessary. Perhaps Albert Einstein never said that at all, but it certainly gives rise to an interesting question: How does the process of retaining and discarding information work? Schacter says that the answer to questions about memory and memory processing begins with understanding what memory is (p. 4).

A different types of memory that enable us to hold information for brief periods of time, to learn skills and acquire habits, to recognize everyday objects, to retain conceptual information, and to recollect specific events. Acting in concert, these memory systems allow us to accomplish the tasks of our day-to-day lives while also supplying our intellect and emotions with ideas and feelings from the past that allow us to act with purpose and live rich emotional lives. But memory involves more than just our remembrance of things past. As we have come to learn that memory is not one single thing, we've opened up a whole new world of implicit, nonconscious memory that underlies our abilities to carry out effortlessly such tasks as riding a bicycle or playing a piano, without having to direct each movement consciously every time we attempt the task. Many of us think of this type of memory as being stored in our fingers, but new research is uncovering that specific brain systems are involved in the nonconscious effects of the past on the present.

We now know enough about how memories are stored and retrieved to demolish another long-standing myth: that memories are passive or literal recordings of reality. Many of us still see our memories as a series of family pictures stored in the photo album of our minds. Yet it is now clear that we do not store judgment-free snapshots of our past experiences but rather hold on to the meaning, sense, and emotions these experiences provided us. Although serious errors and distortions occur relatively infrequently, they furnish significant clues about how we remember the past because they arise from, and provide a window on, some of the fundamental properties of our memory systems (p. 5)."

There is a relationship in our memory to the present and events of the past, and they are in a sense inseparable (p. 5). Edmon T. Rolls (2000) discusses the stimuli that our brain responds to in triggering memories (p. 599). Rolls says:

Brain systems involved in rewards and punishers are important not only because they are involved in emotion and motivation, but also because they are important in understanding many aspects of brain design, including what signals should be decoded by sensory systems, how learning about the stimuli that are associated with rewards and punishers occurs, and how action systems in the brain must be built (Rolls 1999a) (Rolls, 2000, p. 599)."

Rewards and punishers, which Rolls says can be called emotions, and the understanding of how they might be classified as rewards or punishers is defined by that for which we would and will work for, and that which we would avoid or work to escape (p. 599). Those things that we choose to avoid are usually associated with frustration, anger, pain, fear, and alienation (p. 599).

Whether or not the memory associated with the event, object, person, or other relationship as to how it is stored in our memories would be related to whether or not the stimuli that triggers the memory is a reward or a punisher. Rewards, of course, are associated with pleasure, happiness, excitement, desire, and those emotions that we enjoy experiencing (p. 599). However, there are emotions that serve as warnings to us, too, that are associated with fear, pain and the punishers that we need to have to and we need to be stimulated to recall. For instance, most children learn very early in life that fire burns, causes pain and is, therefore, to be avoided. We avoid the punishment of pain by recalling the physical pain associated with fire. Conversely, certain foods serve as a trigger for us to recall a good and pleasant experience, like a birthday cake.

Rolls describes the punisher and awards mechanisms this way:

When an environmental stimulus has been decoded as a primary reward or punishment, or (after previous stimulus-reinforcer association learning) as a secondary rewarding or punishing stimulus, then it becomes a goal for action. The animal can then perform any action (instrumental response) to obtain the reward, or to avoid the punisher. Thus, there is flexibility of action, and this is in contrast with stimulus-response, or habit, learning, in which a particular response to a particular stimulus is learned. The emotional route to action is flexible not only because any action can be performed to obtain the reward or avoid the punishment, but also because the animal can learn in as little as one trial that a reward or punishment is associated with a particular stimulus by stimulus-reinforcer association learning. Animals must be built during evolution to be motivated to obtain certain rewards and avoid certain punishers. Indeed, primary, or unlearned, rewards and punishers are specified by genes that effectively specify the goals for action. Rolls (1999a) proposes that this is the solution that natural selection has found for how genes can influence behavior to promote their fitness (as measured by reproductive success), and for how the brain could flexibly interface sensory systems with action systems (2000, p. 599)."

Rolls helps us understand a little bit about the emotional/memory connection, but it is here that it begins getting a little more physical and a little more complex. It probably helps to have a visual of the portion of the brain where memory takes place, the hippocampus. (the University of Wisconsin, found online at http://whyfiles.org/184make_memory/2.html,2008).

The brain is a place of immense activity and electrical impulses being transmitted, transported and firing. All of these functions serve the overall mind process in various ways of cause and effect. The hippocampus is the area of the brain where the visuals that we recognize are connected with the memory sources that transmit to our cognitive processes the understanding of what we are seeing (McNamara, Patrick, 1999, p. 72). Patrick McNamara (1999) describes the relationship between the functions of recognition and memory taking place in the hippocampus. He says:

medial archicortical trend originating in the hippocampus and the proisocortex of the medial wall of the frontal lobe gives rise to the anterior cingulate cortex and to supplementary motor cortex and inferior frontal sulcus. The lateral trend begins in the olfactory cortex, peripaleocortical proisocortex of the insula, and proceeds superiorly up the lateral convexity, the superior temporal lobe and inferior parietal sites and thence to somatosensory area II. Again, the trend in each case is for greater differentiation of cellular layers as the trend proceeds toward its "termination" sites. The two trends interact in dosolateral prefrontal cortex. Goldberg (1987) argues that the lateral trend is overepresented in posterior portions of the brain, especially the parietal cortex, and thus the parietal and frontal lobes operate in a kind of mutual inhibitory balance. The great superior longitudinal fasiculus connects frontal and parietal sites, allowing for nuanced interactions between anterior frontal systems and posterior parietal systems. The frontal lobes rely on processing of internal information, including memories, in order to guide behavior, while the parietal lobes specialize in processing of externally-based sensory information, in order to guide behavior. Both sources of information are needed to self-regulate one's own behaviors but internal mnemonic sources are crucial to resist enslavement to external and salient events (p. 72)."

While McNamara has explained the technical functions taking place in the hippocampus, he ends his explanation above by helping us understand, in short, the hippocampus is our "self-regulation" of our behavior, or our personality (p. 72). It is how we, or others, might describe us.

Injury or disease can interrupt or alter the processes taking place between the frontal systems and the posterior parietal systems, and since the frontal lobes rely on processing information, including memories, damage can result in how that information is processed and can impact, of course, the personality since the hippocampus is the regulator of personality (p. 72).

McNamara says:

The frontal lobes were only supposed to assist other neuroanatomical structures (e.g., the hippocampus) in doing the real work of memory. The role of the frontal lobes was restricted to helping develop strategies to facilitate encoding, storage, or retrieval. Patients with frontal lobe dysfunction, for example, do not spontaneously use categorization or chunking strategies to memorize large amounts of material. They do not efficiently encode contextual information, such as time and place, surrounding an event (or an experimental trial). They do not easily recall where or how they acquired or learned a new piece of information (source amnesia), nor can they say which piece of information, among an array of similar items, they learned most recently. Finally, patients with frontal lesions are not as proficient as controls at making judgments and predictions about their own memory abilities. All of these deficits seem to involve memory operations, rather than memory content per se, so it is not surprising that before the advent of PET scanning, the role of the frontal lobes in memory was assumed to be important but indirect and peripheral to the main action (p. 74)."

As our understanding of memory and how it stored, retrieved begins to take shape, we readily see that there is much more to memory, memory storage, and memory retrieval than probably most people might have thought there was to it. But the understanding the hippocampus, our personality, where it comes from and how it works with our memory in the way we respond to stimuli is just a small part of the overall process.

Learning and Memory

Old theories and beliefs about memory and the brain have been revised over the past two decades of research. Technology has contributed to this revised understanding, and what has been learned thanks to the technological advances in medicine and science are intriguing and fascinating insights into how memory works. Judy Willis (2007) discusses these new insights, saying:

It was a long-held misconception that brain growth stops with birth and is followed by a lifetime of brain cell death. Now we know that although most of the neurons where information is stored are present at birth, there is lifelong growth of the supporting and connecting cells that en rich the communication between neurons. These "dendrites" sprout from the neuron's arms (axons) or cell body (p. 310)."

While this new information is still being studied and analyzed, certain tests have, as reported by Willis, shown that certain learning activities, such as learning to juggle or learning a second language, produce certain changes in the brain (p. 310). Willis says that engaging in learning actually increases one's capacity to learn (p. 310). However, when learning ceases, for instance, when the juggler stops juggling, the result is that the chemical (in the case of juggling) the gray matter that was created by the brain and directly associated with juggling, ceased being created by the brain. The juggling was the stimuli that created the chemical creation and release of the gray matter in the brain that was observed in the occipital lobes, or the visual memory areas (p. 310). In other words, in the instance of juggling, the juggler would have had a greater degree of visual memory ability as a result of the activity of juggling; when the activity ceased, so did the increased ability that existed in the visual memory relationship (p. 310).

This would be a good scientific explanation to a judge as to why a group of individuals witnessing the same event might describe it differently from one person to the next. Unless the person describing the event is engaged in an activity or event on a regular basis that stimulates the brain to create the visual memory relationship, as in the case of the juggler; then an individual's visual memory might not be as keen from one person to the next.

It is also why policemen are deemed memory credible, because the activity of observation and paying close attention to the details of what is taking place around them is a continual activity.

Schacter says:

Connectionist or neural network models are based on the principle that the brain stores engrams by increasing the strength of connections between different neurons that participate in encoding an experience. When we encode an experience, connections between active neurons become stronger, and this specific pattern of brain activity constitutes the engram. Later, as we try to remember the experience, a retrieval cue will induce another pattern of activity in the brain. If this pattern is similar enough to a previously encoded pattern, remembering will occur. The "memory" in a neural network model is not simply an activated engram, however. It is a unique pattern that emerges from the pooled contributions of the cue and the engram. A neural network combines information in the present environment with patterns that have been stored in the past, and the resulting mixture of the two is what the network remembers. The same conclusion applies to people. When we remember, we complete a pattern with the best match available in memory; we do not shine a spotlight on a stored picture (1996, p. 71)."

McNamara discusses the selectionist theory of memory model, saying:

any selectionist theory of memory must be composed of at least three processing components: a generation (or proliferation) phase, a selection phase, and a cumulative retention or amplification phase (p. 38)."

Both Schacter and McNamara are talking about the levels of processing theory introduced in 1972 by Craik and Lockhart, whose theory held that there were levels of memory processing: depth of processing, maintenance and elaborative rehearsal, implicit and explicit memory, and update (Craik, Fergus and Lockhart, R.S., 1972, p. 301)."

Creative Testing

It is possible to test Willis' and McNamara's theories and models using our example of the policeman. The hypothesis is: A policeman's memory will fit the description of the models (both of which are based on the Craik and Lockhart levels of processing theory). The policeman's memory will, by virtue of his continuous use of his memory and attention to detail, much like the juggler, will have a higher level of gray matter (the visual to memory relationship) in the brain than will a witness selected from a category of employment whose work does not involve the continuous attention to detail - like a rock musician.

We might test the memory of the musician and against that of the policeman for an accuracy of visual details with specific test that employs a series of actions using a series of items. We might, for instance, take a crime scene from the hit movie Heat (1995), directed by Michael Mann. There is a bank robbery scene towards the end of the film, and there are a series of events that are detailed and numerous and require the viewer to pay attention closely to be able to follow the remainder of the film. We will show the selected three-minute segment of the film to a group of police officers, and to a group of musicians, whose daily lives involve the sensory memory as opposed to the visual memory.