The effect of repeated prime-target presentation in manipulating attention-induced priming in persons with dementia of the Alzheimer's type.

The present experiment manipulated attention-induced semantic priming in seven persons with dementia of the Alzheimer's type (DAT) and 16 healthy aged controls in a word-nonword lexical decision task by means of repeated prime-target presentations. The experimental paradigm allowed for the simultaneous comparison of automatic processing and attention-induced strategic processing. The results showed that both the healthy aged subjects and the subjects with DAT demonstrated semantic facilitation in the automatic processing of information. The two groups differed, however, on the attention-induced component of the task. The control subjects consciously generated a strategic response bias favoring the real word targets and thus used their processing of the prime to induce an expectancy about the following target. The DAT subjects showed no such attention-dependent expectancy, a deficit which is most probably related to the general cognitive impairments which are a hallmark of the disease.