This chapter shows how various functions correspond to different areas of the cerebral cortex. The brain consists of a cluster of neural structures which have evolved over time. Some structures such as the brainstem are relatively ancient in evolutionary terms and perform necessary but rudimentary functions such as coordinating respiratory rhythm and fulfilling basic aims of life such as consciousness. The chapter discusses four case histories and describes how organic disease can affect brain function helps provide a link between the symptoms of a psychiatric disease such as senile dementia and the neuropathology that underlies it. A new case of dementia deserves a very full medical assessment to exclude treatable causes of dementia including a full history, thorough physical examination, blood and other investigations and additional assessments such as occupational therapy. Some clinical features tend to distinguish between causes — Alois Alzheimer's is characterised by short-term memory loss, relentless progression, dysphasia, dyspraxia and behavioural changes such as wandering.