title: Aging in rhesus macaques is associated with changes in novelty preference and altered saccade dynamics.
abstract: Studies demonstrating recognition deficits with aging often use tasks in which subjects have an incentive to correctly encode or retrieve the experimental stimuli. In contrast to these tasks, which may engage strategic encoding and retrieval processes, the visual paired comparison (VPC) task measures spontaneous eye movements made toward a novel as compared with familiar stimulus. In the present study, seven rhesus macaques aged 6 to 30 years exhibited a dramatic age-dependent decline in preference for a novel image compared with one presented seconds earlier. The age effect could not be accounted for by memory deficits alone, because it was present even when familiarization preceded test by 1 second. It also could not be explained by an encoding deficit, because the effect persisted with increased familiarity of the sample stimulus. Reduced novelty preference did correlate with eye movement variables, including reaction time distributions and saccade frequency. At long delay intervals (24 or 48 hours) aging was paradoxically associated with increased novelty preference. Several explanations for the age effect are considered, including the possible role of dopamine.
authors.affiliation: Evelyn F McKnight Brain Institute, University of Arizona, Tucson, AZ 85724, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Insel
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Ruiz-Luna
authors.forename: Michelle
authors.initials: M
authors.lastname: Permenter
authors.forename: Julie
authors.initials: J
authors.lastname: Vogt
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Erickson
authors.forename: Carol A
authors.initials: CA
authors.lastname: Barnes
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D003463:Cues; D005106:Exploratory Behavior / Q000502:physiology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D017711:Nonlinear Dynamics; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology; D012438:Saccades; D013997:Time Factors