FoundationalConceptsNeuroscience

Are memories stored in some particular part of the brain? This
question was addressed by Karl Lashley (1890-1958) early in the
twentieth century. He studied the ability of rats to navigate in mazes
—how to go from start to finish without making wrong turns and
entering blind alleys—for which they were rewarded with tasty treats.
Lashley then made lesions to various places in the rat’s cerebral cortex
and measured their effects on performance in the maze. He found that
lesioned rats made errors in navigating the maze, as if their memory
for the maze had been damaged. Moreover, he established that the
number of errors made in navigating the maze was proportional to
the size of the cortical lesion, but not its location in the cortex. From
this Lashley concluded that memory was not localized to any particu-
lar region of the cerebrum.
Building on this idea, Donald Hebb (1904-1985) suggested that
networks of many neurons, extending throughout the cerebral cortex,
represent the information stored in memory. Memory is distributed;
somehow large portions of the brain work together in the formation
and retrieval of memories. Indeed, memories often contain multiple
kinds of sensory and emotional information. Consider a favorite
restaurant, one that you have visited many times. Particular occasions
may stand out in memory, but most of your visits probably meld to-
gether into a landscape of sights, sounds, smells, tastes, actions, and
feelings. These varied aspects of memory related to a particular place
and set of associated experiences involve many different regions of
the brain.
Specific regions of the brain may nonetheless be required for cer-
tain stages of memory storage, and studies of patients who developed
amnesia following neurosurgical procedures have contributed greatly
to ideas about brain mechanisms of memory. Among all the people