Karl Lashley

Karl Spencer Lashley
Born	June 7, 1890 Davis, West Virginia
Died	August 7, 1958
Nationality	United States
Alma mater	Johns Hopkins University
Known for	learning and memory
Scientific career
Fields	psychology

Karl Spencer Lashley (1890–1958), born in Davis, West Virginia, was an American psychologist and behaviorist well-remembered for his influential contributions to the study of learning and memory. His failure to find a single biological locus of memory in the rat's brain (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 Cerebral cortex.

Career

While working toward his Ph.D. in genetics at Johns Hopkins University, Karl Lashley became associated with the influential psychologist John B. Watson. During three years of postdoctoral work on vertebrate behavior (1914-17), he began formulating the research program that was to occupy the remainder of his life.

In 1920 he became an assistant professor of psychology at the University of Minnesota, Minneapolis, where his prolific research on brain function gained him a professorship in 1924. He was later a professor at the University of Chicago (1929-35) and Harvard University (1935-55) and also served as director of the Yerkes Laboratories of Primate Biology, Orange Park, Florida from 1942 to 1955.

In 1938, he was elected a Member of the American Philosophical Society, the oldest learned society in the United States, dating to 1743. Since 1957, the Society has awarded the annual Karl Spencer Lashley Award in recognition of work on the integrative neuroscience of behavior.

Lashley's work included research on brain mechanisms related to sense receptors and on the cortical basis of motor activities. His major work was done on the measurement of behavior before and after specific, carefully quantified, induced cortical damage in rats. He trained rats to perform specific tasks (seeking a food reward), then lesioned varying portions of the rat cortex, either before or after the animals received the training depending upon the experiment. The amount of cortical tissue removed had specific effects on acquisition and retention of knowledge, but the location of the removed cortex had no effect on the rats' performance in the maze. This led Lashley to conclude that memories are not localized but widely distributed across the cortex. Today we know that distribution of engrams does in fact exist, however, the distribution is not equal across all cortical areas, as Lashley assumed. His study of the V1 (primary visual cortex) led him to believe that it was a site of learning and memory storage (i.e an engram) in the brain. He reached this erroneous conclusion due to imperfect lesioning methods.

By 1950, Lashley had distilled his research into two theories. The principle of "mass action" stated that the cerebral cortex acts as one—as a whole—in many types of learning. The principle of "equipotentiality" stated that if certain parts of the brain are damaged, other parts of the brain may take on the role of the damaged portion.

Notable publications

• 1923 "The behavioristic interpretation of consciousness." Psychological Bulletin
• 1929 "Brain mechanisms and intelligence."
• 1930 "Basic neural mechanisms in behavior." Psychological Review
• 1932 "Studies in the dynamics of behavior." University of Chicago Press.
• 1935 "The mechanism of vision", Part 12: Nervous structures concerned in the acquisition and retention of habits based on reactions to light. Comparative Psychology Monographs 11: 43–79.
• 1950 "In search of the engram." Society of Experimental Biology Symposium 4: 454–482.
• 1951 "The problem of serial order in behavior." Cerebral Mechanisms in Behavior

External Links

• Dewsbury, Donald A (2002), "Constructing representations of Karl Spencer Lashley.", Journal of the history of the behavioral sciences, vol. 38, no. 3, pp. 225–45, doi:10.1002/jhbs.10060, PMID 12115785
• Dewsbury, D A (2002), "The Chicago Five: a family group of integrative psychobiologists.", History of psychology, vol. 5, no. 1 (published 2002 Feb), pp. 16–37, doi:10.1037/1093-4510.5.1.16, PMID 11894885 {{citation}}: Check date values in: |publication-date= (help)
• Sapetskiĭ, A O (1999), "[A physiologist's dialog with a psychologist]", Zhurnal vyssheĭ nervnoĭ deiatelnosti imeni I P Pavlova, vol. 49, no. 6, pp. 909–18, PMID 10693270
• Bruce, D (1986), "Lashley's shift from bacteriology to neuropsychology, 1910-1917, and the influence of Jennings, Watson, and Franz.", Journal of the history of the behavioral sciences, vol. 22, no. 1 (published 1986 Jan), pp. 27–44, doi:10.1002/1520-6696(198601)22:1<27::AID-JHBS2300220104>3.0.CO;2-Y, PMID 3511136 {{citation}}: Check date values in: |publication-date= (help)
• Roofe, P G (1970), "Some letters from the Herrick-Lashley correspondence.", Neuropsychologia, vol. 8, no. 1 (published 1970 Jan), pp. 3–12, doi:10.1016/0028-3932(70)90021-7, PMID 4941968 {{citation}}: Check date values in: |publication-date= (help)
• CARMICHAEL, L (1959), "Karl Spencer Lashley, experimental psychologist.", Science, vol. 129, no. 3360 (published 1959 May 22), pp. 1410–2, doi:10.1126/science.129.3360.1410, PMID 13658968 {{citation}}: Check date values in: |publication-date= (help)
• WALSHE, F M (1958), "Karl S. Lashley.", Neurology, vol. 8, no. 11 (published 1958 Nov), p. 870, PMID 13590401 {{citation}}: Check date values in: |publication-date= (help)
• Weidman, Nadine (2002), "The depoliticization of Karl Lashley: A response to Dewsbury.", Journal of the history of the behavioral sciences, vol. 38, no. 3, pp. 247–53, discussion 255–7, doi:10.1002/jhbs.10061, PMID 12115784

See also

• Sequence learning
• Engram (neuropsychology)

External links

• Holographic properties found in interference networks