Objective: To investigate whether changing recognition stimuli from words to pictures would alter response bias in patients with Alzheimer disease (AD).
Background: Response bias is an important aspect of memory performance in patients with AD, as they show an abnormally liberal response bias compared with healthy older adults. We have previously found that despite changes in discrimination produced by varying the study and test list length, response bias remained remarkably stable in both patients with AD and older adult controls.
Methods: Patients with mild AD and healthy older adults underwent two separate study-test sessions of pictures and words. For both pictures and words, increasing study-test list lengths were used to determine whether bias changed as a factor of discrimination or task difficulty.
Results: Consistent with apriori hypotheses, healthy older adults showed increased discrimination and shifted to a more liberal response bias for pictures compared with words. In contrast, despite their higher level of discrimination for pictures, patients with AD showed a similar response bias for both pictures and words. Bias was consistent across varying study-test lengths for both groups.
Conclusions: These results suggest that response bias is a relatively invariant factor of an individual with AD that remains liberal regardless of discrimination or stimulus type.
*Center for Translational Cognitive Neuroscience, Geriatric Research Education Clinical Center, Edith Nourse Rogers Memorial Veterans Hospital, Bedford
†Department of Neurology, Boston University Alzheimer's Disease Center, Boston University School of Medicine, Boston
‡Department of Psychology, Boston College, Chestnut Hill, MA
This material is the result of the study supported with resources and the use of facilities at the Edith Nourse Rogers Memorial Veterans Hospital in Bedford, MA.
Supported by National Institute on Aging grants K23 AG031925 (BAA), R01 AG025815 (AEB), and P30 AG13846.
Reprints: Brandon A. Ally, PhD, Edith Nourse Rogers Memorial Veterans Hospital, GRECC, Building 62, Room B31, Bedford, MA 01730 (e-mail: firstname.lastname@example.org).
Received for publication June 24, 2008
accepted June 29, 2009