FUNCTIONAL INTERACTIONS BETWEEN THE MEDIAL TEMPORAL LOBES AND POSTERIOR NEOCORTEX RELATED TO EPISODIC MEMORY RETRIEVAL

We applied structural equation modeling to positron emission tomograph y data in humans to examine functional interactions between the right medial temporal lobe (MTL) and selected right neocortical regions in r elation to visual recognition memory. Using a priori knowledge about a natomical connections between these regions as a guiding constraint, w e modeled the pattern of interactions [i.e. covariances in regional ce rebral blood flow (rCBF)] associated with episodic memory retrieval of spatial location and compared it with the pattern for retrieval of ob ject identity. We also compared these patterns with those associated w ith perceptual matching of spatial location and object identity. Altho ugh displaying no difference in average rCBF across tasks, the right M TL showed domain-specific qualitative differences in interactions with posterior dorsal (parieto-occipital sulcus, supramarginal gyrus) and ventral regions (fusiform gyrus, superior temporal sulcus) hut not wit h a prefrontal region. MTL interactions involving dorsal regions were positive in the spatial retrieval task but negative for object retriev al. Interactions involving ventral regions showed the reverse pattern. No comparable changes were observed during perceptual matching. Using control models, we demonstrated the neuroanatomical specificity of th ese results. Our results provide support for the notion that the natur e of interactions between the MTL and posterior neocortex depends on t he domain of information to-be recovered.