430 Neuroanatomy: Draw It to Know It
Memory: Classes
Here, we will create a diagram to categorize memory
types based on their duration. Note that the terms used,
here, demonstrate intertextual inconsistency because
they are derived from multiple memory theories gener-
ated over many decades. To begin, let’s divide memory
into three diff erent time spans: sensory, short-term, and
long-term. Sensory memory is the transitory retention
of a primary sensory stimulus; it is assumed that each
sensation has its own time duration, but show that sen-
sory memory as a class lasts from a fraction of a second to
a few seconds. Visual sensory memory is retained for an
exceedingly short period of time: a third of a second,
meaning every fraction of a second, our snapshot of the
world is refreshed. Th is explains why when we view a fan,
the blades appear continuous — the rapidly moving stim-
uli (the blades) overlap in our visual memory and conse-
quently blur. However, at slow enough fan speeds, if we
blink, we can visualize the individual blades. Auditory
sensory memory (aka echoic memory) retention is longer:
a few seconds. Just as we ask people what they were saying
we oft en “hear” them using our echoic memory.^9
Now, show that short-term memory lasts for roughly
3 to 30 seconds. Note, however, that the decay of short-
term memory begins within a few seconds; thus, we must
rehearse what’s available in our short-term memory in
order to preserve it (eg , a newly learned telephone
number). Th erefore, indicate that we need to divide
short-term memory into automatic processing , in which
a memory is not consciously manipulated, and eff ortful
processing (or as it is more commonly referred to, work-
ing memory), in which a memory is actively maintained
through various processes, such as subvocal rehearsal.
Indicate that working memory relies on at least two dif-
ferent storage mechanisms: the phonological loop,
which stores acoustic information through subvocal
rehearsal of words or sounds, and the visuospatial sketch-
pad, which stores visual and spatial information about
object characteristics and localization. Note that we
leave out of our discussion, here, for simplicity, the con-
cepts of the central executive and episodic buff er.^10
Next, show that long-term memory refers to memo-
ries that are anywhere from older than 30 seconds to our
most remote memories. Indicate that long-term memory
is parsed based on the presentation type of the memory,
basically its sensory form (ie, verbal, visual, olfactory,
etc.), and whether or not there is awareness of the
memory. Show that declarative (aka explicit) memories
are those that are consciously recalled (eg , reciting a
country’s capitals) and that nondeclarative (aka implicit)
memories are those that are unconsciously retrieved (eg,
riding a bicycle).
Indicate that declarative memory is most commonly
subdivided into episodic and semantic memory. Episodic
memory refers to our recollection of episodes, typically
autobiographical episodes, which have a strong contex-
tual stamp, whereas semantic memory refers to our
knowledge stores: our collection of facts or information,
which have no contextual stamp. Th e memories of times
spent with family are part of our episodic memory,
whereas the dates of family members’ birthdays and
anniversaries are part of our semantic memory.
Nondeclarative memory encompasses several diff er-
ent unconscious forms of memory; indicate that three
prominent forms of them are procedural memory, prim-
ing , and classical conditioning. Procedural memory
refers to our skills learning, such as riding a bicycle.
Priming refers to our improved ability to identify recently
perceived stimuli in comparison to new stimuli; for
instance, our processing speed for words recently read is
faster than that of our processing speed for more unfa-
miliar words. Classical conditioning refers to the trans-
formation of a neutral stimulus into a conditioned
stimulus with a conditioned response; for instance,
Pavlov observed that his laboratory dogs so strongly
associated his laboratory workers with meat powder that
the dogs would salivate at the site of them.^11