Background: Memory disorder is a significant symptom during early-stage Alzheimer's disease (AD). Changes in semantic memory are frequently seen in terms of forgetting names, loss of word meanings, and difficulties in linguistic expression. Significant semantic degeneration is not a normal phenomenon in elderly persons, and it may be an important sign in the early stages of progression of AD.
Methods: Thirty-four participants aged between 60 and 86 years were recruited for an experiment with a 3 × 4 × 2 factorial design that was conducted to explore the differences in semantic memory performance among controls with normal cognitive performance (NC), individuals classified as mildly cognitively impaired (MCI), and individuals with AD.
Results: The performance of participants diagnosed with mild AD was poorest for the attribute category, and there was no difference in response to different word frequencies. Although those diagnosed with MCI performed similarly to healthy elderly participants in terms of semantic memory, their performance profiles for different semantic hierarchies were similar to those of participants with AD.
Conclusion: Semantic memory had degraded among participants with AD and MCI, and the rate of semantic degeneration was different in different semantic hierarchies.