2 - Temporal lobe structures and memory in nonhuman primates: implications for autism

Summary

Introduction

The medial temporal lobe (MTL), which includes the amygdala, hippocampal formation (dentate gyrus, CA fields and subicular complex) and a set of cortical areas (i.e. entorhinal, perirhinal and parahippocampal areas TH and TF) on the parahippocampal gyrus, has long been known to be implicated in memory processes and regulation of emotional behaviours. In experimental work with animals, the development of new surgical tools that have allowed more selective lesions of the amygdala and hippocampus (e.g. sparing adjacent temporal cortical areas), together with neuropsychological studies of the functions of the various medial temporal cortical areas have helped to clarify the contributions of each of these medial temporal lobe components to cognitive functions (Baxter & Murray, 2000; Brown & Aggleton, 2001; Eichenbaum, 2001; Lavenex & Amaral, 2000; Mishkin et al., 1997; Murray & Bussey, 1999; O'Reilly & Rudy, 2001; Yonelinas, 2002). Although controversies still exist in the field, the general picture that emerges can be summarized as follows. The perirhinal cortex, which receives perceptual information about objects, mediates item-specific memory, as well as learning of stimulus–stimulus, cross-modal and stimulus–reward associations. In turn, areas TH and TF, which receive more extensive spatial information about objects, are involved in spatial memory. Thus, these temporal cortical areas are involved in the storage and retrieval of stimulus representations, and are viewed as storing information or knowledge independently of the context in which they are learned (fact or semantic memory).