Functional MRI Studies of the Hippocampus

Developments in tasks and imaging techniques applied over the last decades have yielded substantial support for the hypothesized role of the hippocampus in mnemonic processes. Human imaging research has now moved on to disentangle the contributions of the different hippocampal subregions and adjacent cortices, so as to bridge the gap between rodent and human data. Besides the importance of such studies for basic research, the investigation of hippocampal (dys)function has clinical relevance for diseases ranging from neurological disorders such as Alzheimer's disease or epilepsy to mental disorders such as schizophrenia or anxiety disorders. So far, most of the present review articles and books about the hippocampus and its functions focus on traditional declarative memory paradigms and 'encoding versus retrieval'. In this chapter we concentrate on a less travelled, but not less important, route concerning the role of the hippocampus in a well-established associative learning (encoding) paradigm: pavlovian fear conditioning. Fear conditioning is hypothesized to model aversive associative learning on a nonpathological level and is further assumed to recruit the same networks that are relevant for anxiety disorders, with the hippocampus being specific for contextual fear conditioning. We highlight the findings in humans by addressing its role in mediating spatial and temporal aspects of a context, involving different kinds of a fear-conditioning procedure (delay vs. trace conditioning), and its role in extinction, both from a theoretical and clinical perspective.