The retrogenesis of age-related decline in declarative and procedural memory

Abstract

The retrogenesis hypothesis proposes that the order of breakdown of cognitive abilities in older adults is the reverse of the developmental order of children. Declarative and procedural memory systems, however, have been empirically understudied regarding this issue. The current study aimed to investigate whether retrogenesis occurs in the developmental and decline order of the declarative and procedural memory systems. Besides, we further investigated whether retrogenesis occurs in declarative memory, which was tested through the recognition of familiar and unfamiliar items. Both questions were investigated by looking at 28 Chinese younger adults and 27 cognitively healthy Chinese older adults. The recognition memory task and the Serial Reaction Time Task were administered on two consecutive days in order to measure their declarative and procedural memory, respectively. The results showed older adults performed significantly worse than younger adults for both tasks on both days, suggesting a decline in both declarative and procedural memory. Moreover, older adults exhibited relatively preserved declarative memory compared to procedural memory. This does not follow the expectations of the retrogenesis hypothesis. However, older adults demonstrated superior performance and a steeper rate of forgetting for recognizing familiar items than unfamiliar items. This reverses the developmental order of different patterns in the declarative memory system. Overall, we conclude that retrogenesis occurs in the declarative memory system, while does not in the decline order of the two memory systems; this understanding can better help inform our broader understanding of memory aging.

Keywords: age-related decline in memory; declarative memory; memory; procedural memory; retrogenesis hypothesis.

Figure 1

Examples of picture stimuli from the Declearn Tasks. The pictures on the left-hand side represent real objects. Those on the right-hand side represent made-up objects.

Figure 2

Mean d-prime scores of Declearn Tasks reported by group and day. Larger d-prime scores imply better declarative memory ability. If d’ = 0, then declarative memory has failed, i.e., participant’s performance is equal to chance.

Figure 3

Mean d-prime scores of Declearn Tasks reported by group and condition on the day-one recognition phase.

Figure 4

Mean d-prime scores of Declearn Tasks reported by group and condition on the day-two retention phase.

Figure 5

Day-one mean normalized RTs of SRT tasks reported by block and group. The x-axis is the six blocks with the respective sequence types ‘RSSSSR’. The y-axis is the reaction time (z-score).

Figure 6

Day-two mean normalized RTs of SRT tasks reported by block and group. The x-axis is the three blocks with the respective sequence types ‘RSR’.