In an early attempt to physically locate the engram, Karl Lashley conducted experiments in which he created brain lesions in rats after they had learned to navigate a maze. He found that the rats retained the ability to find their way through the maze regardless of the size or specific location of the brain damage, demonstrating a lack of evidence for a localized memory trace.

Karl Lashley's Lesion Experiments

The equipotentiality hypothesis, formulated by Karl Lashley in 1950, posits that if a specific part of the brain involved in memory is damaged, another part of that same area can take over that memory function. Lashley developed this theory based on the animals' reactions in his lesion experiments, where rats could still navigate a maze regardless of the size or location of the lesion.

Equipotentiality Hypothesis

Karl Lashley was a psychologist who, about a century ago, investigated the physical basis of memory. His research methodology involved creating lesions, or intentional damage, in the cerebral cortex of animals like rats and monkeys. This was part of his pioneering search for the engram, the physical trace of a memory, which ultimately led to his formulation of the equipotentiality hypothesis.

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There have been a number of psychologists who have contributed to the study of memory. These include:
- Karl Lashley
- Hermann Ebbinghaus 

Important Figures in Memory Research

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Karl Lashley

Eric Kandel is a modern psychologist who has made significant progress in locating the physical traces of memory. He has spent decades studying the synapse and its critical role in controlling the flow of information through the neural circuits that are needed to store memories.

Eric Kandel

Endel Tulving is a notable cognitive psychologist who, along with his colleagues at the University of Toronto, conducted extensive research on memory. He is particularly known for his years-long study of patient K.C., whose case of severe amnesia provided significant insights into the functions of long-term memory.

Endel Tulving

In 1885, German psychologist Hermann Ebbinghaus pioneered the experimental study of memory. His methodology involved memorizing lists of nonsense syllables and then systematically measuring his own retention by testing his ability to relearn the lists at various time intervals. This work led to his discovery of the forgetting curve.

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