Prefrontal cortex and the organization of recent and remote memories: an alternative view.

摘要: The last three assumptions form the basis of what is called standard theory systems consolidation (Squire and Alvarez 1995). major premise this that there a dynamic reorganization in location memories as function their age. As new are formed, old get moved from hippocampus to cortex. In its strong form, predicts that, provided enough time, once dependent on can survive even if completely removed. Numerous studies humans other animals with damage have been conducted evaluate view. Recently, Bontempi, Frankland, colleagues (Bontempi et al. 1999; Frankland 2004; Maviel 2004) applied different methodology investigate retention memories. They measured neuronal activity brain regions induced by test thought initially depend hippocampus. Their important finding was prefrontal cortex (PFC) changed significantly age memory. For recently acquired memories, high low PFC regions, whereas opposite pattern observed for older (Fig. 1). recent review work, Bontempi (2005) interpreted these results context consolidation, suggesting play same role retrieving plays Thus, become consolidated into cortical areas, being critical locus because broad patterns interconnectivity areas (which similar hippocampus). hypothesis accounts why regional memory inactivating relevant has no effect but impairs retrieval an (Frankland 2004). Alternative We suggest alternative explanation leverages existing theories emphasize importance cognitive control top-down attention (O’Reilly Miller Cohen 2001). Specifically, we argue differential involvement simply reflects consequences natural forgetting. Due either decay or interference, weaker more difficult retrieve. These require additional activation be retrieved. There considerable evidence human literature strategic recall (Fletcher Henson 2001; Miyashita Ranganath Furthermore, mechanisms proposed enable activated response potential failure. example, weak (old) may lead diffuse neural trigger conflict detectors anterior cingulate (Botvinick Indeed, Bontempi’s work revealed region becomes active when mice were According our view, does not represent component trace region. Instead, it represents failure cues access degraded trace. case, provide signal boost contain New unaffected inactivated they easily retrieved through hippocampal traces (see Fig. 2). support idea degrade age, reported less than Although forgetting always behavioral measures used studies, clear (1999) experiment. Where absent, would enabled successful retrieval. subtle reveal had degraded. known ages, broader range stimulus (i.e., generalization gradient broadens; Riccio 1992). two contribution empirically evaluated. key implication account correlate, variable determining will activated. strength To degree weak, neurons should possible reverse age-related changes effects at time One testing Our 1Corresponding author. E-mail: JRudy@Clipr.Colorado.Edu; fax: (303) 492-2967. Article published online ahead print. publication date http://www.learnmem.org/cgi/doi/10.1101/lm.97905.