Semantic Memory and Semantic Dementia - When Knowledge Disappears

Semantic memory is the memory that contains knowledge about concepts and facts. On a neurobiological level it is assumed that these memory contents are processed and stored in modality-specific brain regions and then are further processed amodally in the anterior temporal lobes (ATL). This system enables us to generalise over semantic concepts. Patients with semantic dementia (SD), a form of fronto-temporal dementia, lose more and more knowledge about concepts and facts and their ability to generalise is heavily disturbed. Imaging results from SD patients confirm the role of ATL as a hub of semantic memory and simultaneously distinguish between SD and other forms of dementia, such as Alzheimer's disease. A special kind of semantic knowledge is the knowledge about cause-effect relationships. This is very important for goal-directed behaviour in our daily lives and, on a neural level, it is not only mediated by semantic memory regions, but also by dopaminergic midbrain regions, which are mainly activated during knowledge acquisition. However, the influence of SD on causal semantic memory is an understudied issue, so far.