Engram (neuropsychology)

An engram is said to be a memory trace, one possible explanation for the persistence of memory. Fundamentally, an engram is posited to be a physical, biochemical change in the brain (and other neural tissue) in response to external stimuli, thus forming a memory. It is not to be confused with Enneagram, a personality typing system.

The term egram was coined by Karl S. Lashley an American behaviorist well-remembered for his influential contributions to the study of learning and memory. His failure to find a single biological locus of memory (or "engram", as he called it) suggested to him that memories were not localized to one part of the brain, but were widely distributed throughout the cortex.

Lashley argued for distributed representations as a result of his failure to find anything like a localized engram in years of lesion experiments (src: Early work, Connectionism).

Later researcher, Richard F. Thompson, sought the engram of memory in the cerebellum instead of the cerebral cortex.

Thompson and his colleagues used classical conditioning of the eyelid response in rabbits in their search for an engram. They puffed air upon the cornea of the eye and paired it with a tone. This airpuff normally causes an automatic blinking response. After a number of trials they conditioned the rabbits to blink when they heard the tone even though the airpuff was no longer administered. During the experiment, they monitored several brain cells to try to locate the engram.

One brain region that they monitored that they thought was a possible part of the memory engram was the lateral interpositus nucleus (LIP), when chemically deactivated, it resulted in the rabbits, who were previously conditioned to blink when hearing the tone, to act as if the conditioning never took place; however, when they re-activated the LIP, they responded to the tone again with an eyeblink. This gives evidence that the LIP is a key element of the engram for this behavioral response. (James W. Kalat, Biological Psychology p.391-393)

It is important to stress that this approach targeting the cerebellum, though relatively successful, only examines basic, automatic responses. Almost all animals have these (especially as defense mechanisms) and it is fairly difficult to resist them. Imagine trying to avoid blinking when someone shoots something at your eye. Ideally, research by Thompson and others could eventually lead to isolation of more complicated engrams that control more abstract, declarative memories, like how one remembers one's name or the capital of France.

The problem here is that considerable studies have shown declaritve memories tend to move about the brain between the limbic system (deep within the brain) and the outer coritcal areas. This contrasts with the more "primitive" set-up of the cerebellum, which controls the blinking response and receives direct input of auditory information. Thus, it does not need to reach out to other brain structures for assistance in forming simpler memories of association.

Engrams are a central concept in L. Ron Hubbard's Dianetics psychoanalysis techniques and the associated beliefs of Scientology. NLP or Neurolinguistic programming also makes similar use of the use of the engram concept (Drenth 2003)[1] especially in relation to the clearing or treatment of traumas (Andreas & Faulkner, 1994).

References

• . ISBN 0688146198. {{cite book}}: Missing or empty |title= (help); Unknown parameter |Author= ignored (|author= suggested) (help); Unknown parameter |Publisher= ignored (|publisher= suggested) (help); Unknown parameter |Title= ignored (|title= suggested) (help); Unknown parameter |Year= ignored (|year= suggested) (help)

• Drenth, J.D. (2003) Growing anti-intellectualism in Europe; a menace to science. Studia Psychologica, 2003, 45, 5-13