Transverse patterning, aging, and neuropsychological correlates in humans.

Transverse patterning is a learning and memory adaptation of the 'rock/paper/scissors' problem that has been though to depend on the hippocampus, is sensitive to aging, and requires pattern separation to solve. Previous investigators dichotomized cognitively normal older adults who passed a cognitive screening into impaired and unimpaired subsets, and found that impaired older adults were disproportionately deficient in pattern separation abilities. However, this variability in pattern separation ability has not been examined using a transverse patterning task. Our aims, then, were two-fold: First, to determine if impaired older adults were inferior on transverse patterning compared to unimpaired older adults and young adults; second, to identify the neuropsychological correlates of transverse patterning. Our findings revealed that impaired older adults required more trials to criterion on the transverse patterning task than both young adults and unimpaired older adults. Unimpaired older adults also required more trials to criterion than young adults. A detailed analysis of the transverse patterning task confirmed that the aforementioned group differences were only observed in high interference conditions when pattern separation demands were at their peak. Finally, regression analyses showed that both memory and executive functioning neuropsychological composite scores were related to different indices of transverse patterning performance. Consistent with the pattern separation literature, and despite passing a cognitive screening, we found disproportionate transverse patterning deficits in impaired older adults. Forthcoming work should determine if transverse patterning performance is similar between impaired older adults and patients with Mild Cognitive Impairment. © 2016 Wiley Periodicals, Inc.

Age-related changes in place learning for adjacent and separate locations.

The effect of spatial interference on place learning was examined in young and old rats. Rats were trained on a radial 8-arm maze to discriminate between a reward arm and a nonreward arm that either were adjacent to each other (high spatial interference) or separated by a distance of 2 arm positions (low spatial interference). Each rat was tested until reaching a criterion of 9 correct choices out of 10 trials across 2 consecutive days. The data revealed that old rats committed significantly more errors than young rats when the arms were adjacent and spatial interference was high. However, no group differences were detected when the arms were separated and spatial interference was low. Group differences also were not detected in the number of trials required to reach the learning criterion in either condition. The results indicate that age-related brain changes result in increased errors during place learning, particularly when spatial interference is high, suggesting that spatial pattern separation might be less efficient in aged animals.

Age-related differences in the anticipation of future rewards.

The present study examined the anticipation of future reward in 7-mo- and 26-mo-old Fischer 344/Brown Norway rats. Young and old rats were divided randomly and assigned into one of two conditions. In the Contrast Condition, subjects were given a water solution containing 2% sucrose for 3 min followed immediately by a water solution containing 32% sucrose for 3 min. In the No-Contrast Condition, subjects were given a water solution containing 2% sucrose for 3 min followed immediately by a water solution containing 2% sucrose for 3 min. Across 10 days of testing in the Contrast Condition, young rats showed significantly less intake of the less preferred 2% sucrose solution, whereas old rats showed increased intake of the 2% sucrose solution. Young rats showed a significant increase in intake of the preferred 32% sucrose solution compared to aged rats across the 10-day testing period with the exception of days 8-10 where intake did not differ between groups. In the No-Contrast Condition, there were no significant differences between young and old rats, with both groups consuming significantly more of the first 2% solution than the second 2% solution. Therefore, these data suggest that age-related changes may impair the ability to anticipate future rewards.