FoundationalConceptsNeuroscience

recognize the experimenters, who were the same people working with
him day after day. But his performance on these tasks continued to
improve and was retained.
This revealed a key distinction within human memory: declarative
and nondeclarative. Declarative memories can be brought to mind in
words or describable images. This includes facts and other informa-
tional-type knowledge (semantic memory), as well as specific time-
and-place events from one’s experience (episodic memory). In declara-
tive memory H.M. was profoundly impaired.
Nondeclarative memory includes procedural memory, classical
conditioning, and priming. H.M. could accomplish this kind of learn-
ing and remember what he had learned, although he had no aware-
ness that he was learning and remembering. Procedural memory
involves performing a sequence of actions, such as maze tracing or
mirror drawing, or typing, swimming, riding a bicycle, or playing a
musical instrument. We can’t describe very well how to ride a bicycle,
and even if we could, it really wouldn't help us much in learning how
to actually ride one. Riding a bike is a “just do it” kind of task, with
knowledge about the task accessible only through performance, by ac-
tually engaging in the actions.
Classical conditioning is learning to associate together certain
stimuli and responses. For example, if a puff of air is directed at our
eye, we reflexively blink; and if a beep is sounded immediately before
the puff of air, we will learn to associate the beep sound and the air
puff. Very soon we will blink whenever we hear the beep, expecting
the air puff to follow the sound. This is classical conditioning. It is
another kind of learning without awareness of what we are learning—
it just happens. And it happened for H.M.
Yet another kind of nondeclarative memory results from priming
—when exposure to a stimulus influences one’s response to future