Visual-discrimination learning ability and beta-amyloid accumulation in the dog

Young, middle-aged, and old beagle dogs were tested on several visual-discr imination tasks: reward- and object-approach learning, object discriminatio n and reversal, long-term retention of a reversal problem, and a size-discr imination task. beta-Amyloid accumulation in the entorhinal, prefrontal, pa rietal, and occipital cortices was quantified using immunohistochemical and imaging techniques at the conclusion of cognitive testing. Middle-aged and old dogs were impaired in size-discrimination learning. In each task, a subset of aged dogs was impaired relative to age-matched peers . beta-Amyloid accumulation was age-dependent. However, mot all middle-aged and old dogs showed beta-amyloid accumulation in the entorhinal cortex. Th e error scores from dogs tested with a nonpreferred object during visual di scrimination learning and from reversal learning were correlated with beta- amyloid in the prefrontal but not entorhinal cortex. Size-discrimination an d reward and object-approach learning error scores were correlated with bet a-amyloid accumulation in the entorhinal but not prefrontal cortex. The res ults of these studies support an association between cognitive test and the location and extent of beta-amyloid pathology. (C) 1998 Elsevier Science I nc.