Cognition in Alzheimer's disease: disorders of attention and semantic knowledge.

Alzheimer's disease leads to a selective decline of cognitive skills, particularly semantic knowledge and visuospatial attention. Recent advances suggest that, although the two systems responsible for these skills can interact, the semantic memory deficit seen in Alzheimer's disease cannot be solely attributed to attention or retrieval deficiencies. This is consistent with a modular view of cognition, which postulates that disruption to these systems is selective in Alzheimer's disease. Cortico-cortical disconnection of association areas may disrupt widespread networks mediating attention and semantic knowledge in Alzheimer's disease.