Karl S. 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 (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. Year 1890 (MDCCCXC) was a common year starting on Wednesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Monday of the Julian calendar). ... Jan. ... Davis is a town located in Tucker County, West Virginia. ... A psychologist is a person who studies psychology, the systematic investigation of the human mind, including behavior, cognition, and affect. ... Behaviorism (or behaviourism) is an approach to psychology based on the proposition that behavior is interesting and worthy of scientific research. ... Learning is the acquisition and development of memories and behaviors, including skills, knowledge, understanding, values, and wisdom. ... For other uses, see Memory (disambiguation). ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, speech lit. ... For other uses, see Engram (disambiguation). ... The human brain In animals, the brain (enkephalos) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ... For other uses, see Cortex. ...

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. The Johns Hopkins University, founded in 1876, is a private institution of higher learning located in Baltimore, Maryland, United States. ... John Broadus Watson (January 9, 1878–September 25, 1958) was an American psychologist who established the psychological school of behaviorism, after doing research on animal behavior. ... A postdoctoral (colloquially, post-doc) appointment is a usually temporary academic job held by a person who has completed his or her doctoral studies. ... This article does not cite any references or sources. ...

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. This article is about the oldest and largest campus of the University of Minnesota. ... This article is about the city in Minnesota. ... For other uses, see University of Chicago (disambiguation). ... Harvard redirects here. ... Orange Park is a town located in Clay County, Florida, USA. As of the 2000 census, the town had a total population of 9,081. ...

His work included research on brain mechanisms related to sense receptors and on the cortical basis of motor activities. Lashley studied many animals, including primates, but his major work was done on the measurement of behavior before and after specific, carefully quantified, induced brain damage in rats. He trained rats to perform specific tasks, then lesioned varying portions of the rat cortex, either before or after the animals received the training. The amount of cortical tissue removed had specific effects on acquisition and retention of knowledge, but where in the cortex it was removed from had no effect on the rats performance in the maze. This lead Lashley to conclude that memories are not localized but widely distributed across the cortex. Brain damage or brain injury is the destruction or degeneration of brain cells. ...

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. Equipotentiality refers to a psychological theory in both neuropsychology and behaviorism. ...

Notable publications

• 1923 "The behavioristic interpretation of consciousness." Psychological Bulletin
• 1929 "Brain mechanisms and intelligence."
• 1930 "Basic neural mechanisms in behavior." Psychological Review
• 1951 "The problem of serial order in behavior." Cerebral Mechanisms in Behavior

Year 1930 (MCMXXX) was a common year starting on Wednesday (link will display 1930 calendar) of the Gregorian calendar. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. ...

See also

• Sequence learning
• Engram (neuropsychology)
• Holographic properties found in interference networks