the proposition that different content-based memory systems exist and are located in different areas of the brain.
Memory is divided essentially into short-term, meaning seconds, minutes or hours, depending on the investigator, and long-term, meaning everything longer than that included in short-term (Markowitsch, 2001). Long-term memory is further subdivided into episodic memory, semantic (knowledge system) memory, procedural memory and priming. Episodic memory covers events and autobiographical data; semantic memory contains context-free facts; procedural memory covers various skills (e.g. motor, cognitive); and priming memory refers to the ability to reidentify previously perceived stimuli.
The immediate processing of information (working memory) is thought to occur cortically, with some involvement of the prefrontal and parietal lobes (Markowitsch, 2001). Long-term memory has not been definitively localized because of the diverse mechanisms and routes for its processing and storage. The transfer from short-term memory stores to long-term memory stores is related to a conglomeration of subcortical and allocortical structures collectively referred to as the limbic system. The limbic system consists of three primary regions: the medial temporal lobe, containing the hippocampal region; the medial diencephalon, including the medial thalamic and the mamillary nuclei; and the basal forebrain region. The mediodorsal nucleus is interconnected most intensely with the prefrontal cortex, the basal forebrain has numerous cholinergic connections with diverse cortical regions, and the hippocampal region is widely associated with the temporal cortex.
The problem of defining the true neural basis of memory stems in part from the fact that there is still little concrete evidence for actual sites of memory storage in the human brain (Markowitsch, 2001). The fact that patients with complete bilateral damage to the limbic bottlenec...