Abnormal spatial and non-spatial cueing effects in mild cognitive impairment and Alzheimer’s disease

Abstract

Our aim was to further characterize the clinical concept of mild cognitive impairment (MCI). We examined visual attention-related processing in 12 patients with amnestic MCI, 16 healthy older adults and 16 patients with Alzheimer’s disease (AD) by measuring performance on computer-based tests of attentional disengagement, alerting ability, and inhibition of return. Unlike the healthy older controls, the patients with AD and the patients with amnestic MCI exhibited a significant detriment in both the ability to disengage attention from an incorrectly cued location and the ability to use a visual cue to produce an alerting effect. The pattern of results displayed by the MCI group indicates that patients who only appear clinically to suffer from a deficit in memory also display a deficit in specific aspects of visual attention-related processing, which closely resemble the magnitude seen in AD.

The authors would like to thank the Bristol Research Into Alzheimer’s and Care of the Elderly (BRACE) Charity [Registered Charity Number 297965] for financial support. The authors would also like to thank all the participants taking part and Mr A. Hughes for statistical support.

Notes

The authors would like to thank the Bristol Research Into Alzheimer’s and Care of the Elderly (BRACE) Charity [Registered Charity Number 297965] for financial support. The authors would also like to thank all the participants taking part and Mr A. Hughes for statistical support.

In our previous studies examining attentional disengagement and alerting effects (Tales et al., 2002 a,b) covert cueing was employed. This covert paradigm is used specifically to elicit information regarding discrete attention-related processes without contamination by ocular function. However, the associated prerequisite sustained eye immobilization can lead to data loss if fixation cannot be maintained and puts extra demands on patients. As evidence suggests that overt and covert attention mechanisms are anatomically and functionally linked (Posner, 1978; Vandenberghe et al., 2001, Corbetta et al., 1998) the present study therefore employed overt cueing in which eye movements were allowed. This design removed the need for sustained fixation, thus making the task less demanding for the patients and reducing the potential for lost data due to eye movements, but still represented a typical situation in which the alerting, validity and IOR effects are expected to be manifest. The number of trials for each condition was also reduced, thus decreasing the time taken to complete the task and minimizing test fatigue.