The defining characteristic of<unk>  is decreased performance on tasks that require<unk>  memory. This includes difficulty with naming pictures and objects, single word comprehension, categorizing, and knowing uses and features of objects.<unk>  patients also have difficulty with spontaneous speech creation, using words such as "this" or "things" where more specific and meaningful words can be used. Syntax is spared, and<unk>  patients have the ability to discern syntactic violations and comprehend sentences with minimal lexical demands.<unk>  patients have selectively worse concrete word knowledge and association, but retain knowledge and understanding of abstract words.<unk>  patients are able to retain knowledge of numbers and music, but have more difficulty with concrete concepts with visual associations. Impairments of processing of phonemic structure and prosodic predictability have also been observed.
Semantic dementia
Subcortical dementia
Vascular dementia
Lewy body dementias
Dementia with Lewy bodies
Frontotemporal dementia
Normal pressure hydrocephalus
Alcohol-related dementia