In this chapter we summarize the more important structures in the brain with which it is essential to be familiar when studying the pathological basis of dementia. As described in Chapter 3 many dementing conditions are impossible to distinguish on naked eye examination of the brain since they do not display gross regional pathology. In order to reach the correct diagnosis, it is necessary to select the appropriate areas for more detailed examination. To do that requires knowledge of the parts of the brain that are significant in the particular context of dementia. For more detailed information textbooks of neuroanatomy such as Paxinos (1990), Heimer (1995), Parent (1996), or Nolte (2001) should be consulted.
Chapter 1 has already emphasized the crucial importance of the cerebral cortex for the cognitive functions which deteriorate in dementia. The cerebral cortex can be divided anatomically into a phylogenetically older and simpler allocortex consisting of the hippocampus and closely related entorhinal cortex, subiculum and olfactory regions, and the remaining, much more voluminous and phylogenetically more recent, neocortex.
Hippocampus, subiculum and entorhinal cortex (archicortex allocortex)
These structures have already been mentioned in Chapter 1 but because of their importance it is worth providing a brief supplementary account here. Excellent reviews of the structure of the human hippocampus and related cortex can be found in Amaral and Insausti (1990) and Duvernoy (1988).
The entorhinal cortex lies in the uncus and anterior parahippocampal gyrus and forms an intermediate type of cortex between the complex six-layered neocortex of the temporal lobe and the simpler, basically three-layered, cortex of the hippocampus.