INCREASED SEMANTIC PRIMING IN PATIENTS WITH DEMENTIA OF THE ALZHEIMERS TYPE

Semantic priming on a lexical decision task(LDT) was examined in 50 pa tients with mild to moderate dementia of the Alzheimer's Type(DAT), an d 25 normal age-matched controls. DAT patients were slower in their re sponses, and showed significantly greater priming effects (mean 54 ms vs. 27 ms in controls). The size of the priming effect correlated with the speed of response on the LDT task for the individual DAT patients but not for controls. Twenty of the DAT patients (vs. one control) sh owed priming greater than 60 ms. This subgroup of DAT patients with '' hyperpriming'' was slower than the nonhyperpriming group on ''yes'' re sponses to targets preceded by unassociated prime words and more impai red on tests of clock drawing and verbal fluency. Slowing of responses alone, however, seems unable to account for the presence of increased priming in DAT patients. Its presence may reflect semantic memory def icits, as well as impaired attentional processing and supervisory cont rol systems. The exact mechanism of this increased priming remains to be established.