Partial knowledge of abstract words in patients with cortical degenerative conditions

Partial knowledge is a common but rarely studied consequence of damage to conceptual representations and is characterized by the retained ability to retrieve crude, superordinate information but not specific, detailed information about a conceptual entity. Previous studies have described partial knowledge for concrete items particularly following semantic dementia (SD). The present study was designed to investigate the occurrence of partial knowledge effects in the conceptual domain of abstract words. A novel 3-level synonym comprehension test was administered to 9 patients with SD, 20 patients with probable Alzheimer's disease (AD), and 40 healthy control subjects. All subject groups showed weaker performance on tasks requiring a fine specification of word meaning compared with those for which a broad sense of meaning or valence was necessary. However, this gradient of partial knowledge was significantly greater for SD and AD subjects than for controls. These results demonstrate that partial knowledge is a general property of a degraded knowledge base and is not restricted to the concrete word domain. It constitutes a normal phenomenon that is exacerbated in the context of neurodegenerative disease.