Does hippocampus associate discontiguous events? Evidence from event-related fMRI

To examine the hypothesis that the hippocampus is necessary to overcome temporal or spatial "discontiguity" (Wallenstein et al., Trends Neurosci 1998; 21:317-323), subjects were imaged by functional magnetic resonance imaging (fMRI) when they were making judgments as to whether two words were semantically related. Two words were presented, either at the same time (the Simultaneous Presentation Condition) or one after the other with a short unfilled rest period (the Delayed Presentation Condition). The latter condition, relative to the former, was proposed to involve the process of "discontiguity association." Event-related fMRI results of eight subjects showed that, relative to the binding of simultaneously presented words, the binding of delay presented words was associated with left hippocampus activity. This result provided direct neuroimaging evidence for the role of the hippocampus in "discontiguity association."