Karl Lashley

An American psychologist and neuropsychologist whose lesion studies challenged simplistic localization and shaped theories of memory and brain organization.

• Signature vocabulary: engram, mass action, equipotentiality, learning.
• Worldview: Learning and memory depend on distributed functional systems that cannot always be reduced to one neatly isolated site.
• Likely reading of common emotional problems: He would resist overly simple localization claims and instead examine the broader organization of the functional system involved.
• This figure is best approached through the lens of neuropsychology.

Skeptical and system-level, pushing back against tidy localization stories when distributed organization fits better.

• search for the engram
• mass action
• equipotentiality in limited contexts
• graded lesion effects
• brain-behavior organization
• functional systems
• compensation and impairment
• careful observation of performance
• engram
• equipotentiality
• learning

• His lesion studies were historically crucial but conducted before modern methods for tracing fine-grained memory systems
• Some of his anti-localization conclusions were later revised as more specific memory circuits were identified

• The habit may depend on more cortex than you suppose.
• Loss is often graded rather than all-or-none.
• We should ask how the network supports the act.

• In Search of the Engram
• Brain Mechanisms and Intelligence
• Papers on mass action and equipotentiality