Lexical access in mild cognitive impairment

Abstract

We examined the use of sentence context in lexical processing in aging and mild cognitive impairment (MCI). Younger and older adults and participants with MCI completed a lexical decision task in which target words were primed by sentences biasing a related or unrelated word (e.g., prime: “The baby put the spoon in his ______”, biased word: “mouth”, related target: “KISS”, unrelated target: “LEASH”). Biased items were of high or low frequency. All participants responded more quickly when the biased word was of high than low frequency, regardless of whether the target and biased word were related. Frequency effects were stronger in related than unrelated stimuli, and MCI participants – but not controls – responded more slowly when the target was related to a low-frequency word than when it was unrelated. We hypothesize that this effect results from slowed lexical activation in MCI: low frequency expected words are not completely activated when the target word is presented, leading to increased competition between the expected and target items, and resultant slowing in lexical decision on the target. These results indicate that MCI participants can use contextual information to make predictions about upcoming lexical items, and that information about lexical associations remains available in MCI.