The brain hierarchically represents the past and future during multistep anticipation.

Memory for temporal structure enables both planning of future events and retrospection of past events. We investigated how the brain flexibly represents extended temporal sequences into the past and future during anticipation. Participants learned sequences of environments in immersive virtual reality. Pairs of sequences had the same environments in a different order, enabling context-specific learning. During fMRI, participants anticipated upcoming environments multiple steps into the future in a given sequence. Temporal structure was represented in the hippocampus and across visual regions (1) bidirectionally, with graded representations into the past and future and (2) hierarchically, with further events into the past and future represented in successively more anterior brain regions. Further, context-specific predictions were prioritized in the forward but not backward direction. Together, this work sheds light on how we flexibly represent sequential structure to enable planning over multiple timescales.

Aging shifts the relative contributions of episodic and semantic memory to decision-making.

Healthy aging is accompanied by well-characterized shifts in memory systems: episodic memory tends to decline with age while semantic memory remains relatively intact, with some knowledge domains strengthening. Beyond reflecting on the past, these distinct memory systems often guide decisions about the future. Yet how such age-related memory shifts influence simple value-based choices remain understudied. Here, younger (18-24 years) and older (61-75 years) adults completed a card game in which they could use task-relevant episodic memories to maximize the number of points they earned. Critically, they could also use task-irrelevant semantic memories to guide their choices. Both younger and older adults successfully used episodic memory to make decisions, but older adults did so less reliably than younger adults. Further, while younger adults strategically suppressed task-irrelevant semantic memories when a relevant episodic memory could be used, older adults used semantic memory to guide their decisions regardless of the relevance of episodic memory. We provide evidence that declining inhibitory control may play a role in how older adults arbitrate between competing memory sources when making decisions. These effects are consistent with the literature on age-related shifts in memory and cognitive control systems and add to a growing body of work on how episodic memories inform reinforcement learning and value-based decision-making. Our findings highlight how patterns of age-related memory differences can have consequences for value-based choices, which has implications for other types of decision-making, from the economic to the mundane. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Dynamic internal states shape memory retrieval.

Why do we sometimes easily retrieve memories, but other times appear to forget them? We often look to our external environment for retrieval cues, but another way to optimize memory retrieval is to be in a mental state, or mode, that prioritizes access to our internal representation of the world. Such a 'retrieval mode' was proposed by Endel Tulving (1983), who considered it a neurocognitive state in which one keeps the goal of memory retrieval in mind. Building on Tulving's proposal, we review converging evidence from multiple lines of research that emphasize the importance of internal states in the instantiation of retrieval modes that optimize successful remembering. We identify three key factors that contribute to a retrieval mode by modulating either the likelihood or the content of retrieval: (1) an intention to remember or forget (either in the present or the future), (2) attentional selection of goal-relevant memories and suppression of distractors, and (3) fluctuating levels of acetylcholine in the hippocampus. We discuss empirical evidence that these internal states individually influence memory retrieval and propose how they may interact synergistically. Characterizing these dynamic internal factors is an important key for unlocking our understanding of the organization and accessibility of our memories.