The ability to remember is fundamental to knowing who one is, and how to manage all the tasks of living. Decades of clinical and research experience as a neuropsychologist comes to this observation: the single most threatening brain disease or injury is memory loss.
No one has perfect memory. Memory does not work that way. It is not a file folder we can retrieve at will and open. Remembering past events is more a process of recalling details and elements, and then reassembling them in a plausible narrative. The result may not even be accurate, but it will feel true. In his 2017 book, The River of Consciousness, the neurologist Oliver Sacks wrote of his memory of a thermite bomb falling during the wartime blitz in the family’s garden in England. He had a detailed memory of being at home with his family, during the war, when the bomb fell. As his family later explained, he was not present, nor even living in the home, when it happened. It would appear he adopted his brother’s version of the event as his own true recall.
The things we remember are part mental record, part reconstruction, part blended with memory, but they always feel meaningful. Memory is the world we carry within us. It is our version of it, as best a simulacron as we have been able to assemble throughout our lives. It is part representative, part accurate. Nonetheless, we go on storing things in memory. The process is accurate enough for most purposes.
A neuropsychologist has a great deal of data to describe how peope of different ages learn and recall different kinds of material, how many errors they will typically make and what kinds of loss occur. This is the typical picture, or normative data, that shows the patterns of how a healthy memory normally works. Every once in a while someone comes along who shows eidetic, or near perfect recall, of information they have read or seen once. A person with this kind of memory can recall a visual image of great clarity, perhaps a page of text they had seen once before. The memory is clear and detailed enough to read again for content. This type of memory tends to fade, as do most recall mechanisms. It does not fail outright; over time it becomes just a more hesitant process. It is a glimpse of the sort of memory that is possible.
Mental functions gradually slow down with age. Retrieving a name, the right word, or a visual image from memory takes a little more time and effort. A few years back another neuropsychologist and I had a conversation in which he wanted to talk about the mediterranean fish soup, with lots of garlic…what was the name…I could not help. He knew it, I knew it, we struggled and then moved on to something else. Three days later I pick up the phone to hear his triumphant, “Bouillabaisse!”. It is a silly little story, but we tell it because it signalled that awareness that effortless recall was on its way out. We were getting older.
A lot of things in memory seem to recede farther down the road with age. Harder to get at. Retrieval is effortful. There is less certainty, as was the case of Oliver Sacks and the bomb, that what is retrieved is accurate.
When I became aware that my aging father was having memory troubles, I opened a mental file of behavioural observations. I paid attention, keeping track of events and complaints. I was watching for indicators of too much memory loss for age or signs that are pathognomic, specific to disease. Any signifiers of function outside the normal range. One day he could not find his way home, driving in the small city he had lived in for many years. The confusion eventually cleared and he made it home, but the event bothered him. It was as good as a clincher for me. I began making plans to have him formally evaluated. It resulted in a diagnosis of Alzheimer’s disease.
Any sort of memory loss is a pretty general event. It is not specific to any one cause. The problem can be inattention, worry, distraction, aging, illness. It can mean nothing important at all. Usually it means there is trouble retrieving the memory. The memory itself is not lost, it just won’t come when called.
There are rare cases in which the brain structures necessary for forming new memories are injured and can no longer function. In this situation, all the old memories are intact and can be retrieved without difficulty. The people in these situations know their families, where they went on vacation last year, whether they like modern architecture, and how to drive a car. What becomes impossible is recalling anything that happened after the event that injured them. They nonetheless remember who they are and how the toaster works.
Dementia is quite different. The central symptom of dementia is memory loss. It is progressive. It is not a retrieval problem; it is loss of the memories themselves. Those afflicted eventually fail to remember yesterday, who their family is, and how to operate a thermostat. People with dementia lose who they are and the knowledge of how to function in the world. In the early stages, people are aware something is wrong and they get worried and irritable. They lose track of their money, and may accuse others of stealing from them. While the disease continues its destructive course in the brain, the rest of the body remains healthy. The heart may tick on for years while mental function declines.
As the disease progressed, my father made poor decisions, one after another. He started recording his personal history, trying to hang on to his memories. I found pages of notes in his papers containing the names of his parents, brothers, other relatives, along with their birthdays and where they lived. He documented the memories on which he could not rely. One day, my stepbrother found my father on the floor of his house. He had fallen and could not get up. He did not know how long he had been on the floor. He was brought to hospital. It was clear to the admitting physician he was far too progressed in the disease to live safely at home, and would be discharged only to long term care. This most dangerous phase of trying to live with dementia had come to an end. In care, he would be supported. He would be safer. As in far too many cases, it was an emerging and real threat to life that precipitated the move to long term care.
In such a condition of insufficient memory, one can not survive. Where did I put my wallet? Did I buy groceries? Who paid the utility bill? One has to rely on others to provide food, shelter, clothing and security.
Memory may fail us in ways that reflect not just a specific disease process, but might speak to the priorities of storage. In normal aging, it is the newest memory that is most elusive. Well rehearsed older memories are more robust. In the case of someone with damage to crucial memory structures in the brain, new memories stop abruptly with the injury. In the situation where one is distracted or busy, some events of information may fly by. These things are unattended and unregistered. They form fleeting memories at best.
The more you think about and anayze something, the stronger the memory and the fewer errors in later recall. If as a child you spent hours learning how to fashion the letters of the alphabet and reciting the times tables, these will stick and be retained throughout life. Your name and gender are likewise solid memories. This is material that has been rehearsed so many times it can be described as ‘overlearned’.
In contrast, if you witness a fast moving dramatic event, such as a car accident or bank robbery, you have limited time to collect all the facts. Unless you are a trained observer, there will be little time to register the details let alone encode in any depth and remember. Eye witnesses are famously wrong about details. So, sustained attention and cognitive engagement are important.
Dr. Schacter, memory researcher at Harvard University, wrote in The Seven Sins of Memory (1999), information can be forgotten if it is poorly encoded in the first place. Information can be distorted due to misattribution, suggestibility and bias. A lack of accurate registration can result in poor memory. If the context in which a memory is learned and stored is at fault, the memory again can fail to accurately represent the initial event. Poor encoding, the time, focus of attention and complexity of thought that goes into the initial stage of learning, leads to less accurate memory.
Another variable is context. Are you familiar with the item or situation to be remembered, or is it novel? The more you already know about a subject, the greater your own personal context into which this is to be slotted, the better the memory. This suggests that memory storage benefits from context, or memory connectors if you will, and that if you do not have to build the context from scratch, it is easier to form a strong memory.
The level of emotion raised by the initial exposure to an event is also a factor. Repeated exposure with intense negative emotional responses can result in blocked memory, or even the intrusive nature of memories in post traumatic stress disorder. Positive emotional responses are associated with frequent rehearsal, because it feels good to go over these memories, and rehearsal improves memory. Some emotional memories become quite robust. These are the so called flashbulb memories, such as where you were and what you were doing when a majour event such the explosion of the Challenger rocket, or the attack on the World Trade Towers, occurred.
There is a different mechanism in play for the recall of information when the need is not how to make a reuben sandwich or the name of the spouse of the department head, but how to address a larger conceptual question. The question is more an issue of organization.
In his 2017 book, The River of Consciousness, Oliver Sacks gave some examples of inspired ideas. The chemist Kekule spent months working on the problem of how a specific carbon based molecule might be structured. He dreamt of a snake, biting its tail in a circle. Kekule awoke, realizing that a benzene molecule could be formed by a ring of carbon molecules. This conceptual breakthrough was the beginning of organic chemistry. The mathematician Poincare also spent months working on a complex mathematical problem. One day, while stepping onto a bus, the solution abruptly came to him in its entirety.
In both cases, the inspiration was accompanied by clarity, detail and a sense of truth. All of the information these two had about the problem at hand was retrieved from memory, in its entirety, but in a new configuration. Their memories of the facts at hand were rearranged. The memories were not faltering, or lost, or inaccurate, just organized differently. The facts were not altered; the ways in which they were connected were changed, and there was new meaning to be taken from the arrangement.
Memory is a general concept encompassing (at a minimum) attention, registration, analysis, storage, organization and retrieval. The examples above describe a few aspects of the memory process: storage, reorganization and survival. What becomes clear is that memory is a complicated process. It includes a number of mechanisms, handles different types of information, stores information in multiple ways, actively sorts and reorganizes as needed and makes the contents available by recall, question, context and recognition. Very simply stated, there are a lot of ways for information to be brought in and a lot of ways to bring it back out again. There is a lot of redundancy in this system. The basic lesson of biology is that what is most important for survival gets the most resources. Memory looks to qualify in the arena of mental activity.
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