Spatial negative priming in early Alzheimer’s disease: Evidence for reduced cognitive inhibition FRANCES L. VAUGHAN, 1,3 ELIZABETH A. HUGHES, 2 ROBERT S.P. JONES, 1 ROBERT T. WOODS, 1 and STEVEN P. TIPPER 1 1 School of Psychology, University of Wales Bangor, Bangor, United Kingdom 2 Psychology Department, South Essex Partnership NHS Trust, Essex, United Kingdom 3 North Wales Brain Injury Service, Conwy & Denbighshire NHS Trust, United Kingdom (Received August 13, 2005; Final Revision January 30, 2006; Accepted January 31, 2006) Abstract Some studies of negative priming and other tasks assumed to reflect inhibitory functions suggest a decline in inhibitory processes in Alzheimer’s disease. However, none of the measures used in previous studies can be interpreted as an unambiguous reflection of distractor inhibition. The present study investigates whether reductions in negative priming associated with Alzheimer’s disease reflect reduced distractor inhibition, rather than perceptual review processes. Individuals with early Alzheimer’s disease were predicted to show reduced negative priming on a spatial localization task designed to provide an unambiguous measure of distractor inhibition. Sixteen clinical participants showed significantly less negative priming than old and young healthy control groups, which is interpreted as evidence for reduced distractor inhibition in early dementia. A second analysis indicated that, within the clinical sample only, negative priming effect size was significantly correlated with prime trial response speed. Clinical participants showing the least negative priming were slower to respond to an initial stimulus. The results may mean that people with early Alzheimer’s disease have a reduced capacity to use excitatory as well as inhibitory processes in selection. ( JINS, 2006, 12, 416–423.) Keywords: Alzheimer disease, Dementia, Inhibition, Attention, Cognitive science, Neuropsychology INTRODUCTION Recent studies and literature reviews indicate that atten- tional impairments develop earlier in Alzheimer’s disease (AD) than was previously recognized, after the onset of memory difficulties but before aphasic, apraxic, agnosic, and visuospatial deficits are detectable (Parasuraman & Haxby, 1993; Perry & Hodges, 1999, 2000). Furthermore, progressive changes in attentional capacity correlate with other cognitive impairments and functional decline (Rizzo et al., 2000). These findings have implications for the neuro- psychological assessment of early AD and our understand- ing of the cognitive processes that are compromised. Some forms of attention are affected more than others in early AD. Parasuraman and Haxby (1993) reported that selec- tive attention, divided attention, and the movement of spa- tial attention are all altered at an early stage. Perry and Hodges (1999) reached a similar conclusion, and later reported evidence that impairments of selective attention and the shifting of attention develop before impairments of sustained and divided attention (Perry et al., 2000). Perry and Hodges (2000) conclude that selective attention and semantic memory tests are the most likely to detect cogni- tive changes (other than episodic memory problems) during the earliest stages. Studies of executive function in early AD also indicate selective attention difficulties. For exam- ple, Collette et al. (1999) obtained widespread evidence of executive dysfunction and found “inhibition abilities” to be particularly affected. It is widely assumed that the capacity to attend to one salient feature while ignoring others is facilitated by active inhibitory mechanisms that suppress irrelevant information (Houghton & Tipper, 1994). Opponent processes of activa- tion and inhibition are thought to operate throughout the central nervous system (e.g., Rafal & Henik, 1994) and to play a fundamental role in the control of cognitive process- Correspondence and reprints requests to: Dr. Frances Vaughan, School of Psychology, University of Wales Bangor, Brigantia Building, Penrallt Road, Bangor, Gwynedd LL57 2AS, UK. E-mail: f.vaughan@bangor.ac.uk Journal of the International Neuropsychological Society (2006), 12, 416–423. Copyright © 2006 INS. Published by Cambridge University Press. Printed in the USA. DOI: 10.10170S1355617706060504 416