Pattern Completion and Pattern Separation Mechanisms in the Hippocampus

There is great interest in how pattern separation and pattern completion in the hippocampus contribute to its functions in memory and spatial function (Giocomo et al. 2011; Jezek et al. 2011; Leutgeb et al. 2007; McHugh et al. 2007; Nakashiba et al. 2012; Nakazawa et al. 2002, 2003; Wills et al. 2005), and among those who have made many contributions in this area are Ray Kesner and his colleagues (Hunsaker and Kesner 2008, 2013; Kesner 2007, 2013; Kesner et al. 2012; Rolls and Kesner 2006). This chapter describes some of the different types of pattern separation and pattern completion in the hippocampal system, and the mechanisms that implement them. More comprehensive descriptions of my theory of hippocampal function, and of differences between the primate and rodent hippocampal neuronal representations and the implications for understanding human memory are provided elsewhere (Rolls 2008, 2010b, 2013; Rolls and Kesner 2006; Rolls and Xiang 2006; Kesner and Rolls 2015). The theory has been developed through many stages (Rolls 1987, 1989a, b, c, 1990a, b, 1991, 1995, 1996b, 2008, 2010b; Rolls and Deco 2010; Rolls and Kesner 2006; Rolls and Treves 1998; Treves and Rolls 1991, 1992, 1994), has as a predecessor developments made by David Marr (Marr 1971) (though he never identified the CA3 system as an autoassociation network), and has benefitted greatly from collaborations with many whose names appear below in the citations, including Alessandro Treves and Simon Stringer. The operation of pattern association networks, autoassociation networks, and competitive networks has been described elsewhere (Hertz et al. 1991; Rolls 2008; Rolls and Treves 1998; Rolls 2016).