Instantiating two learning systems in the brain: cognitive modeling and fMRI analyses of visual category learningPublic Deposited
The set of experiments described here test the hypothesis that the declarative memory system supported by the medial temporal lobe and habit/procedural memory supported by the basal ganglia are recruited when learning novel category representations. The theory guiding specific hypotheses about these neural systems and their operation in category learning are incorporated into a new cognitive model of category learning called PINNACLE (Parallel Interactive Neural Networks Active in Category LEarning). PINNACLE contains two competitive learning systems that simulate a fronto-MTL circuit that supports declarative memory and executive attention and cortico-striatal loops through the posterior caudate that support procedural learning. Chapter 1 reviews the relevant background literature on visual category learning including the hypothesized role of independent memory systems. This background includes recent behavioral, neuroimaging and neuropsychological studies examining the MTL and the caudate of the basal ganglia in learning visual categories either by verbalizeable rules or without awareness. Chapter 2 discusses two fMRI studies that preferentially engage either the MTL or caudate according to the learning strategy employed, demonstrating the capability of both of these systems in visual category learning. Chapter 3 describes the mathematical implementation of PINNACLE and some preliminary modeling results applied to fMRI data. Chapter 4 lays out the theoretical basis of the PINNACLE model, establishing the framework for the implementation of the theory into a neuro-cognitive model. The fifth chapter discusses the application of PINNACLE in enhancing and extending conventionally accepted fMRI data analysis techniques. The results of PINNACLE-based trial sorting both reinforce the original fMRI dissociation and demonstrate the benefit of combining these two methodologies. Finally, in the last chapter, several potential modifications to the mechanisms of the RB and II systems are suggested along with examples of the application of PINNACLE to other learning behaviors.