Spatial reversal learning is impaired by age in pet dogs

Abstract

Aged dogs spontaneously develop progressive decline in both cognitive and behavioral function, in addition to neuropathological changes, that collectively parallel several aspects of human aging and Alzheimer's disease progression and likely contribute to the development of canine cognitive dysfunction syndrome. In the current study, ethologically relevant spatial learning, retention, and reversal learning tasks were conducted, with the goal of expanding canine neuropsychological testing to pet dogs. Initially, dogs (N = 44, aged 7.8 ± 2.8 years, mean ± SD) had to learn which of two alternative routes successfully led out of a T-maze. Two weeks later, long-term memory retention was assessed, immediately followed by a reversal learning task in which the previously correct route out of the maze was reversed compared with the initial learning and memory retention tasks. No effects of age were evident on the learning or retention tasks. However, older (≥ 8 years) dogs were significantly impaired on the reversal learning task compared with younger ones (< 8 years). Moreover, trial response latency was significantly increased in aged dogs across both the initial and reversal learning tasks but not on the retention task, which suggests that processing speed was impaired by increasing age during the acquisition of novel spatial information but not during performance of previously learned responses. Overall, the current study provides a framework for assessing cognitive function in pet dogs, which should improve understanding of the effects of aging on cognition in the dog population.

Fig. 1

Representation of the T-maze employed in the study. A door in the center of the front wall leads into the start compartment (1 × 1 m; a). A sliding panel divides the start and the central compartment (1 × 1 m; b), from where two identical and symmetrical openings lead into the lateral arms of the maze (3 × 1 m at their narrowest point; c). Each of these arms terminates with an aperture (0.8 m in height), equipped with a remotely operated sliding panel. Sliding panels are represented in black in the picture

Fig. 2

Mean errors ± SD committed by younger (<8 years, N = 15) and older (≥8 years, N = 12) dogs in the learning and reversal learning tasks. Tukey’s post hoc test; *P < 0.001