1890–1958 · psychologist, Minnesota, Chicago, Harvard

he American psychologist Karl Spencer Lashley trained rats, damaged parts of their cortex and measured what they could still do. He worked at Minnesota and Chicago, from 1935 at Harvard, and later directed the Yerkes laboratories in Florida.

what he did

In Brain Mechanisms and Intelligence (1929) he reported that the loss in maze learning depended more on how much cortex was removed than on where: he called it mass action, and the capacity of remaining tissue to take over equipotentiality. His 1950 summary, "In search of the engram" (Lashley, K. S., 1950), confessed he had never found a memory trace in one place and could almost conclude that learning was impossible [paraphrase, not a quotation].

what is argued about

His rats could solve mazes with many senses at once, so lesions that removed one route left others; later work found memories localised more than he allowed (Josselyn, Köhler & Frankland, 2015). The word engram now names sets of cells that can be tagged, silenced and reactivated: see the engram.

why he is here

Lashley asked where a memory is, and the question has not gone away; it is now asked of networks too, in interpretability.

in the tour: the room called "The assembly and the engram" has a placard called "Where is it kept" ···

Primary works and sources

1. Lashley, K. S. (1950). "In search of the engram." Symposia of the Society for Experimental Biology, vol. 4, Physiological Mechanisms in Animal Behaviour. Cambridge University Press.
2. Josselyn, Köhler & Frankland (2015). Finding the engram. Nature Reviews Neuroscience. doi:10.1038/nrn4000

see also

	the engram
	Donald Hebb — his student
	timeline: memory