Memory

The problem of adverse brain effects of molecules derived from food is under-recognized. There are a host of clues that link the food supply to mysterious and threatening neurological diseases. We suggest that a prudent person suffering early brain-dysfunction symptoms would be wise to pursue vigorous, thorough diet revision at the earliest opportunity. Because some brain dysfunction compromises judgment learning and motivation, family members, friends and professional advisor often have to provide the right direction and support.

Information coming in from our sense organs must be encoded into patterns of electrochemical activity in the brain. Some of this electrochemical activity is then fixed into a more enduring form referred to as memory. If an experience is important and reinforced by repetition, a permanent memory pattern can be established. The ability to sequence tasks is disrupted by forgetting what you just did or were supposed to do. If you cannot remember what you just did or wanted to do, cognitive performance is impaired, you become disorganized and life becomes difficult. Recent memory seems to involve the most dynamic, distributed activity in the brain and is easy to disrupt.

The flow of information through our brain is prodigious; we couldn't possibly remember everything. We now have and use so much information that we cannot store all we need to know in our own brains and must rely on external devices which expand our information access. Increasingly, we need to remember how to get information from books, newspapers, files, tapes, radio, television, computers, and other storage devices. Selective retention of the most relevant information is the secret to mental success.

Memories are of several types. Two categories are recognized: explicit memories for experiences and facts and implicit memory which consists of knowledge, skills, and awareness that cannot be stated in a clear, explicit manner. Often implicit memory is in the form of mental maps and patterns. Our most skilled activities using body movement are all implicit memory. A concert pianist does not think about the movement of his fingers; the performance flows automatically out of implicit memory. When we talk we do not know what we are going to say in advance, our speech flows out of implicit memory.

Explicit memory involves packets of information necessary for daily interactions with other people and useful for passing exams or winning games of trivial pursuit. Memories are associative, meaning that new information is linked to information already stored. Recall is a separate process which also works in an associative manner. Tricks for recalling numbers and random letter arrays involve associating these difficult-to-remember items with already familiar items. The medial temporal lobe, especially the hippocampus, is the area of the brain most involved in explicit memory storage. Without normal medial temporal lobe function, immediate memory cannot be translated into longer-term storage. Squire and Zola-Morgan suggested:^{^[i]}

"The medial temporal lobe memory system is needed to bind together the distributed storage sites in neocortex that represent whole memory... as time passes after learning, memory stored in the neocortex gradually becomes independent of medial temporal lobe structures."

The physical procedures involved in storing and retrieving memories involve a sequence of biochemical steps, some of which require structural changes in the brain. If protein synthesis in the brain is blocked, long-term memory is impaired. A stream of molecules, originating in the food supply passes through the brain. This molecular stream will either facilitate the brain changes required for memory or will interrupt them.

The integrity and reliability of discrete and explicit memories are often exaggerated. The dependence of courts, for example, on reports of crimes and identification of perpetrators is naïve at best. The idea of a reliable long-term storage of single episodes would seldom hold up to scientific scrutiny. Single events are not remembered well if at all, since reliable long-term memory is dependent on a three or four stage process to imprint the memory in long-term storage by neuronal reorganization. An event must be repeated to be securely stored.

Daniel Schacter [i] suggested: “A key point of agreementbetween cognitive and biological theories is that memories donot preserve a literal representation of the world; memories areconstructed from fragments of information that are distributedacross different brain regions, and depend on influences operatingin the present as well as the past. By studying memory distortionsand illusions from a cognitive neuroscience perspective, it shouldbe possible to gain useful insights into the neural underpinningsof this constructive process…neuroimaging research highlights a distinction between strategic effort and consciousrecollection in memory retrieval."

Much human conflict revolves around discrepancies in remembered events. Two witnesses of the same event will seldom agree on the details. Loving couples sharing many experiences will argue frequently about who said what and when. When one spouse tells a story to friends, the other spouse will usually have something to add or details to correct. Sometimes the discrepancies in memory occur because one person remembers an event more accurately, but most of the time, no one remembers accurately -- they recall different things or the same things differently.

Philosophers interested in cognition and cognitive scientists have indulged in elaborate discussions and arguments about the distinction – implicit and explicit. These discussions involve detailed considerations of language and knowledge. The heart of the problem is that explicit memory or knowledge that can be declared is stored and recalled by procedures that are implicit and not accessible as a discrete recollection.

The distinction between implicit and explicit is not necessarily a real distinction but a convenient bookmark that separates the study of different aspects of memory. The distinction is useful to move away from the common misunderstanding that all memory consists of episodes and is explicit and declarative.

[i] Daniel L. Schacter. Illusory memories: A cognitive neuroscience analysis . Proc. Natl. Acad. Sci. USA Vol. 93, pp. 13527-13533, November 1996

[i]Squire LR, Zola-Morgan The medial temporal lobe memory system. Science 1991:253; 1380-1386