exposures to this stimulus. Priming is central to the effectiveness of
advertising. Repeatedly seeing or hearing references to certain brand
names or political candidates will predispose us to pick that brand
or candidate when some future choice must be made. Advertising’s
goal is that we learn and remember, without being aware that we are
learning and remembering. In simple laboratory experiments, H.M.
showed evidence of priming.
After his death Henry’s brain was carefully removed, treated with
formaldehyde fixative, and cut into more than two thousand thin sec-
tions. High-resolution digital images were made of the brain sections,
and these images may now be accessed online—a resource available
for study by neuroscientists for years to come. Henry’s brain and the
data are archived at the University of California’s Brain Observatory in
San Diego.
Current thinking about long-term memory, both declarative and
nondeclarative, is that it is ultimately captured in the complex inter-
connectivity of neurons, such that changes in connections—forming,
eliminating, strengthening, and weakening of synapses—give rise
to changes in the patterns of activity that occur across large regions
of the cerebral cortex. Donald Hebb, in his classic 1949 book The Or-
ganization of Behavior, postulated that signal activity in networks of
neurons would somehow serve to strengthen synaptic connections
between the neurons and that this could provide a cellular mecha-
nism for memory storage: “When an axon of cell A is near enough
to excite a cell B and repeatedly or persistently takes part in firing it,
some growth process or metabolic change takes place in one or both
cells such that A’s efficiency, as one of the cells firing B, is increased.”
That is, repeated activation of a network strengthens the synaptic
connections within the network. Sometimes this is referred to as a