memoria

Salud Mental 2010;33:85-93

Sistemas de memoria: reseña histórica, clasificación y conceptos actuales

Sistemas de memoria: reseña histórica,
clasificación y conceptos actuales.
Primera parte: Historia, taxonomía de la memoria, sistemas
de memoria de largo plazo: la memoria semántica
Paul Carrillo-Mora1
Actualización por temas

SUMMARY
Memory is a fascinating brain function by meansof which the nervous
system can codify, store, organize, and recover a variety of information
relevant to the subject. The formal study of memory started more
than a century ago, providing in this time a considerable amount of
scientific information on memory functioning. The actual knowledge
of memory allow us to consider it far from being unique, isolated or
static function, but more as acomplex net of memory systems working
in parallel for a common goal. Historic evolution of memory concepts
and their classifications have progressed simultaneously to our
knowledge on these systems.
The first empiric approaches to memory description were found
in ancient Greece by authors like Plato and Aristoteles, and were based
on philosophy, thinking, and introspection and logic methods.However,
the first real scientific approaches appeared in the XIX century, by
authors such as Ebbinghaus and Lashley, who initiated the experimental
study of memory in humans and animals, respectively.
The contribution of the intellectual group known as «behaviorist»
in the beginning of XX century, was also relevant during this period,
and was represented by scientists like Pavlov, Watson,Skinner, and
Thorndike, who detailed a variant of learning recognized in our days
as associative learning. In turn, this variant can be divided into classic
conditioning (associates a stimulus with a response) and instrumental
or operant conditioning (associates a stimulus with a specific
behavior). Behaviorists claimed that only on observational basis of
behavior is possible to knowprocesses linked to learning. However,
these authors clearly made a mistake when they stated that knowledge
on processes occurring in the brain will always be far of the
understanding of the investigator.
Later on, one of the hardest evidences for the study of memory
processes came from clinic studies of patients with focal cerebral
lesions. Penfield, Scoville, and Milner, during the 60’s,documented
the effects of surgical lesions of temporal lobe on declarative memory,
finding selective alterations, such as severe anterograde amnesia
and retrograde amnesia with temporal gradient. These findings were
accompanied also by a description of memory subsystems remaining
intact, despite of those temporal lobe lesions (procedural memory,

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long-term memory, etc.). Based on thesefindings, medial temporal
lobe was described as a key structure for the acquisition of declarative
information. In parallel to clinic studies, a first attempt to coordinate
psycho-psychiatric research with the knowledge and scientific protocol
of biology occurred in the 60’s, thus allowing the emergence of
disciplines known as cognitive neuroscience and cognitive psychology
or psychophysiology, bothcreated in an effort to explore the cellular
and molecular mechanisms responsible for the storage of memory
information. The list of significant findings provided by these two
scientific disciplines is extensive, but among the most important are
probably those derived from the study of the most elementary memory
processes (i.e. habituation and sensitization) in invertebrate animal
models,such as Aplysia spp. These researches established the basis
for the basic cellular requirements for elementary learning, as well
as the molecular basis for short-and long-term memory.
The conjugation of these clinical descriptions together with
experimental evidence led to the postulation of the first classifications
of memory systems during the 80’s. One of these classifications
divided...