The Lifespan Trajectory of the Encoding-Retrieval Flip: A Multimodal Examination of Medial Parietal Cortex Contributions to Episodic Memory

Abstract

The formation of episodic memories is associated with deactivation during encoding and activation during retrieval in the posteromedial cortex (PMC). We hypothesized that the encoding/retrieval (E/R) flip is a critical component of episodic memory across the lifespan because structural and metabolic changes in the PMC coincide with the fine tuning of the episodic memory system in development and the reductions of memory performance in aging. The aims of the present study were, first, to describe lifespan trajectories of PMC encoding and retrieval activity in 270 human participants (167 females) from 6 to 80 years of age. Our second goal was to construct a model for episodic memory development in which contributions from brain activity, cortical thickness (CT), and structural connectivity are accounted for. We found that modulation of neural activity in response to memory encoding and retrieval demands was not fully developed until adolescence and decreased from adulthood through old age. The magnitude of the E/R flip was related to source memory and 55% of the age-related variance in source memory performance during childhood and adolescence could be accounted for by the E/R flip, CT, and mean diffusivity together. However, only CT and the E/R flip provided unique contributions with which to explain memory performance. The results suggest that neural dynamics in the PMC is related to the development of episodic memory during childhood and adolescence. The similar trajectories of the E/R flip and episodic memory emergence and decline through development and aging further suggests that a lifelong relationship exists. Modulation of neural activity in the posteromedial cortex (PMC) in response to memory encoding/retrieval (E/R) demands (E/R flip) does not reach its peak until adolescence and decreases from adulthood through old age. The magnitude of the E/R flip is related to source memory and 55% of the age-related variance in source memory performance during childhood and adolescence can be accounted for by the E/R flip and brain structure together. The results suggest that neural dynamics in the PMC is related to the development of episodic memory function during childhood and adolescence and the similar trajectories of the E/R flip and episodic memory performance through development and aging suggests that a lifelong relationship exists.

Age-Related Differences in Functional Asymmetry During Memory Retrieval Revisited: No Evidence for Contralateral Overactivation or Compensation

“…Overall this suggests that age-related deficits in the brain activity associated with memory retrieval can drive lower asymmetry in older brains. This is in line with the well-established view that aging is associated with the dedifferentiation of previously specialised neural systems (Park et al 2004(Park et al , 2012Park and McDonough 2013;Koen et al 2019), and may also reconcile well with studies demonstrating that the regionally-dependent dynamic range of activity available to older adults may be lower across varying task conditions (Garrett et al 2011(Garrett et al , 2013Kennedy et al 2017;Amlien et al 2018), a potential alternative account that may explain findings of lower-toabsent negative memory effects in older adults (Mattson et al 2014;de Chastelaine et al 2015). In particular, our finding that absent negative effects explained all instances of apparent over-activation in older adults agrees well with a similar report during retrieval (Morcom et al 2007).…”

Medial Temporal Lobe Subregional Atrophy in Aging and Alzheimer's Disease: A Longitudinal Study

“…restricting analyses to linear models when investigating the effects of age (Chen et al, 2016). In line with previous findings, visual inspection of the trajectories indicates that the HPC and ERC volumes remained stable or expanded until middle age and then declined substantially (Ziegler et al, 2012;Fjell et al, 2013;Coupé et al, 2017;Amlien et al, 2018;Li et al, 2018;Nobis et al, 2019;Langnes et al, 2020;Nyberg et al, 2021). As entorhinal cortical-hippocampal circuits are important in episodic memory processing, this pattern might partly explain the similar trajectory of age-related episodic memory deficit (Rönnlund et al, 2005;Nyberg et al, 2012).…”

Episodic Memory Dysfunction and Effective Connectivity in Adult Patients With Newly Diagnosed Nonlesional Temporal Lobe Epilepsy

“…In further support of this, several studies have found the parietal cortex to be involved in episodic memory tasks (21)(22)(23)(24)(25). Interestingly, the lateral parietal cortex has direct anatomical connections with several key brain areas, such as the dorsolateral prefrontal cortex and the temporal cortex, and has reciprocal connections with structures in the MTLs, such as the entorhinal, parahippocampal, and hippocampal regions (23).…”