Segunda parte: Sistemas de memoria de largo plazo: Memoria episódica, sistemas de memoria no declarativa y memoria de trabajo

According to recent evidence, memory can be conceptualized as a series of subsystems working together to reach the same final goal. In the present time, most authors coincide in proposing a main division or long-term memory systems in mammals. This division separates memory in two categories: declarative and not declarative, often conceptualized also as explicit and implicit memories, respectively, although the latter terms are more appropriate to describe the role of consciousness during the development of codification and recovery tasks in regard to the information of each system. Declarative memory, as indicated by its name, includes a variety of memories implicating information that can be verbalized and effectively transmitted from person to person. This type of memory is conceptualized as conformed by two distinct memory sub-categories sometimes collaborating and coinciding in the use of memory. The first of these sub-categories is semantic memory, the one including the information about concepts and precise facts, and it is frequently defined as «general knowledge». It also makes reference to conceptual information lacking from the temporal-spatial frame (this issue is detailed in the first part of this paper). The second sub-category is episodic memory, which refers to the memory for personal experienced events, or the memory used for «what?, where?, and when?», in regard to the occurrence of a given personal event. Altogether, autonoesis (the conscious concept of a personally experienced event), subjective temporal consciousness (or subjective temporal frame about when a given event occurred), and self-consciousness are considered indispensable for the definition of episodic memory. In spite of these characteristics, there is yet controversy on whether this type of memory could be observed in animals. In this regard, some researchers have demonstrated that the processes needed to define episodic memory are effectively employed by non-human primates and rodents. In regard to the functional anatomy of episodic memory, an active role of the temporal lobe in the codification of some components of this memory is known from long time ago. Experimental studies employing hippocampal electro-physiological recordings have demonstrated that this region participates in two main components of episodic memory: i) the strong links of the subject with the environment or the spatial context, and ii) the temporal organization of the stored information. Some studies have clearly demonstrated the important participation of specific hippocampal cell areas (CA1 and CA3) for the resolution of behavioral tasks requiring episodic memory. However, clinical studies employing functional imaging have shown a considerable diversity of cortical areas as involved in the several processes of codification or recovery of episodic information, going from prefrontal medial and left ventrolateral regions to medial and lateral temporal regions, retrosplenial cortex, posterior cingulus posterior, and even the cerebellum.