SEMANTIC PRIMING IN AN OBJECT DECISION TASK IN NORMALS AND ALZHEIMERS-DISEASE - AN ELECTROPHYSIOLOGICAL STUDY

Semantic memory deterioration is a major symptom observed in dementia of the Alzheimer's type (DAT). However, the nature of this deficit rem ains uncertain, some researchers postulate difficulty in accessing and retrieving semantic information while others point to a degraded stor ing. In this study, we used the event-related potential, specifically the component N400, to assess semantic functions. Ten DAT patients and 10 controls were visually presented with 120 prime-targets pairs, 50% of them belonging to the same category and the other 50% mismatching the prime. Statistical analysis revealed significant differences just for the incongruent targets while the amplitude of the congruent ones was similar for both groups. The lack of this component in DAT patient s appears to indicate that there is a lack of efficient access and def icient associative links within the semantic network and therefore see ms to indicate a breakdown in the structure and organization of semant ic memory.