Some physicians and researchers split dementia into two broad categories the cortical dementias and the subcortical dementias based on what part of the brain is affected. Cortical dementias arise from some sort of disorder affecting the cerebral cortex, the outer layers of the brain that play a critical role in cognitive processes such as memory and language. Alzheimer's and Creutzfeldt-Jakob disease are two forms of cortical dementia. Cortical dementia patients typically show severe memory impairment and aphasia. Aphasia is the inability to recall words and understand common language.
Subcortical dementias result from dysfunction in the parts of the brain that are beneath the cortex.
Usually, the memory loss and language difficulties that are characteristic of cortical dementias are not present. Rather, people with subcortical dementias, such as Huntington's disease and AIDS dementia complex, tend to show changes in their personality and attention span, and their thinking slows down. Of course, it is not always easy to categorize dementia, and many dementias show signs of both cortical and subcortical disease. In multi-infarct dementia, for example, both parts of the brain tend to be affected. That Resemble Dementia Pseudodementia Pseudodementia, or masked depression, is the term used to describe symptoms that look like dementia but are in fact due to depression and not any underlying organic disease.