From Wikipedia, the free encyclopedia Engram (neuropsychology)
Engram (neuropsychology)
Engrams are a hypothetical means by which memory Later, Richard F. Thompson sought the engram in the
traces are stored as biophysical or biochemical changes cerebellum, rather than the cerebral cortex. He used clas-
in the brain (and other neural tissue) in response to ex- sical conditioning of the eyelid response in rabbits in
ternal stimuli. search of the engram. He puffed air upon the cornea of
They are also sometimes thought of as a neural net- the eye and paired it with a tone. (This puff normally
work or fragment of memory, sometimes using a holo- causes an automatic blinking response. After a number
gram analogy to describe its action in light of results of experiences associating it with a tone, the rabbits be-
showing that memory appears not to be localized in the came conditioned to blink when they heard the tone
brain. The existence of engrams is posited by some sci- even without a puff.) The experiment monitored several
entific theories to explain the persistence of memory and brain regions, trying to locate the engram.
how memories are stored in the brain. The existence of One region that Thompson’s group studied was the
neurologically defined engrams is not significantly dis- lateral interpositus nucleus (LIP). When it was deactivat-
puted, though their exact mechanism and location has ed chemically, the rabbits lost the conditioning; when re-
been a focus of persistent research for many decades. activated, they responded again, demonstrating that the
LIP is a key element of the engram for this response.[2]
Overview This approach, targeting the cerebellum, though suc-
cessful, examines only basic, automatic responses, which
The term engram was coined by the little-known but in- almost all animals possess, especially as defense mecha-
fluential memory researcher Richard Semon. nisms.
Karl S. Lashley’s search for the engram found that Studies have shown that declarative memories move
it could not exist in any specific part of the rat’s brain, between the limbic system, deep within the brain, and
but that memory was widely distributed throughout the the outer, cortical regions. These are distinct from the
cortex. One possible explanation for Lashley’s failure to mechanisms of the more primitive cerebellum, which
locate the engram is that many types of memory (e.g. dominates in the blinking response and receives the in-
visual-spatial, smell, etc.) are used in the processing of put of auditory information directly. It does not need to
complex tasks, such as rats running mazes. The consen- "reach out" to other brain structures for assistance in
sus view in neuroscience is that the sorts of memory forming some memories of simple association.
involved in complex tasks are likely to be distributed
among a variety of neural systems, yet certain types of
knowledge may be processed and contained in specific
References
regions of the brain.[1] Overall, the mechanisms of mem- [1] ^ Gerrig and Zimbardo (2005) Psychology and Life
ory are poorly understood. Such brain parts as the cere- (17th edition: International edition)
bellum, striatum, cerebral cortex, hippocampus, and [2] (James W. Kalat, Biological Psychology p. 392–393)
amygdala are thought to play an important role in mem-
ory. For example, the hippocampus is believed to be in-
volved in spatial and declarative learning, as well as con-
Further reading
solidating short-term into long-term memory. • Forgotten Ideas, Neglected Pioneers: Richard Semon and
In Lashley’s experiments (1929, 1950), rats were the Story of Memory, Daniel Schacter, 2001 ISBN
trained to run a maze. Tissue was removed from their 184169052X
cerebral cortices before re-introducing them to the • Holographic properties found in interference
maze, to see how their memory was affected. Increas- networks
ingly, the amount of tissue removed degraded memory, • Dudai, Y. (2004). The neurobiology of consolidations,
but more remarkably, where the tissue was removed from or, how stable is the engram? Annual review of
made no difference.[1] psychology, 55, 51-86.
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Categories:
• Memory
• Neuropsychology
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From Wikipedia, the free encyclopedia Engram (neuropsychology)
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