Context Memory Encoding and Retrieval Temporal Dynamics Are Modulated by Attention across the Adult Lifespan

Abstract

Episodic memories are multidimensional, including simple and complex features. How we successful encode and recover these features in time, whether these temporal dynamics are preserved across age, even under conditions of reduced memory performance, and the role of attention on these temporal dynamics is unknown. In the current study, we applied time-resolved multivariate decoding to oscillatory electroencephalography (EEG) in an adult lifespan sample to investigate the temporal order of successful encoding and recognition of simple and complex perceptual context features. At encoding, participants studied pictures of black and white objects presented with both color (low-level/simple) and scene (high-level/complex) context features and subsequently made context memory decisions for both features. Attentional demands were manipulated by having participants attend to the relationship between the object and either the color or scene while ignoring the other context feature. Consistent with hierarchical visual perception models, simple visual features (color) were successfully encoded earlier than were complex features (scenes). These features were successfully recognized in the reverse temporal order. Importantly, these temporal dynamics were both dependent on whether these context features were in the focus of one’s attention, and preserved across age, despite age-related context memory impairments. These novel results support the idea that episodic memories are encoded and retrieved successively, likely dependent on the input and output pathways of the medial temporal lobe (MTL), and attentional influences that bias activity within these pathways across age.

Significance Statement The events we learn and remember in our lives consist of simple context details like color and more complex ones like scenes. Whether we learn and recognize these memory details successively or simultaneously, and whether attending to some features but not others impacts when we encode and retrieve them is unknown. Using high temporal resolution neural activity patterns, we found color details were successfully encoded earlier than scene ones but recognized in the reverse order. Importantly, these temporal dynamics depended on which feature was in the focus of one’s attention and were preserved across age. These findings elucidate the successive manner in which the features that constitute our memories are encoded and retrieved and the conditions that impact these dynamics.