Depending on which part of the brain is suspected as the cause of dementia, the dementia may be classified as either cortical or subcortical.
The cortex of the brain is the part most people are familiar with - in appearance at least. The characteristic twists and turns of the outer layers play an important role in processing information and connecting functions such as language and memory. When the outer layers are affected, which is the case with Alzheimer's, Pick's disease, Binswanger's disease and Creutzfeldt-Jakob disease, there are characteristic problems with memory, the inability to recall words and as the disease progresses to understand what others are saying (aphasia).
As the term suggests, these are dementias believed to result in structures below the cortex. Huntington's disease, Parkinson's and AIDS dementia complex are three examples. It is more common to see changes in personality and a slowing down of thought processes with this classification of dementia. Language and memory functions appear largely unaffected.