Integrating Memories in the Human Brain: Hippocampal–Midbrain Encoding of Overlapping Events

By Daphna Shohamy, Anthony D. Wagner. 2008

523 citations recorded by the source corpus.

SUMMARY Decisions are often guided by generalizing from past experiences. Fundamental questions remain regarding the cognitive and neural mechanisms by which generalization takes place. Prior data suggest that generalization may stem from inference-based processes that occur at the time of generalization. By contrast, it has been hypothesized that generalization may emerge from mnemonic processes that occur while premise events are being encoded. Here, participants engaged in a two-phase learning and generalization task, wherein they initially learned a series of overlapping associations, and were subsequently probed to generalize what they learned to novel stimulus combinations. Functional magnetic resonance imaging (fMRI) revealed that subsequent generalization performance was associated with coupled changes in learning-phase activity in the hippocampus and midbrain (ventral tegmental area/substantia nigra). These findings provide novel evidence for generalization based on integrative encoding, whereby overlapping past events are integrated into a linked mnemonic representation. Hippocampal–midbrain interactions support the dynamic integration of experiences, providing a powerful mechanism for building a rich associative history that extends beyond individually experienced events.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience

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Citations in the corpus

The Episodic Memory System: Neurocircuitry and Disorders (2009, unknown): “Relatively little functional neuroimaging work (with important exceptions, Shohamy and Wagner, 2008) has been performed on the contributions of thalamic, basal forebrain, and other subcortical regions to human episodic memory.”
Flexible Memories: Differential Roles for Medial Temporal Lobe and Prefrontal Cortex in Cross-Episode Binding (2010, background): “This finding contrasts a recent study where overlapping associations were acquired across repeated exposures that found no reaction time difference between learned and transfer probes in participants who successfully transferred (Shohamy and Wagner, 2008).”
The hippocampus and inferential reasoning: building memories to navigate future decisions (2012, methodology): “…(Klein et al., 2002; Buckner, 2010; Addis and Schacter, 2011) dates back to Tolman’s concept of a “cognitive map” (Tolman, 1948) and has been proposed as a key mechanism underlying successful inferential reasoning (O’Reilly and Rudy, 2001; Shohamy and Wagner, 2008; Zeithamova and Preston, 2010).”
Tracking the Emergence of Conceptual Knowledge during Human Decision Making (2009, unknown): “…Session): spatial vs non-spatial At a behavioral level, performance was well matched during spatial and non-spatial learning (RT: spatial 1.37 sec, non-spatial 1.36 sec, p=0.8; performance: spatial=74.9%, non-spatial=75.0%, p=0.9) and probe (performance: spatial 2.3, nonspatial 2.7, p=0.25) trials.”
Computational influence of adult neurogenesis on memory encoding. (2009, unknown): “…measures that correlate with human neurogenesis (Pereira et al., 2007) may permit the examination of the effect of neurogenesis on performance on psychological tasks that investigate the structure of human memories (Bakker et al., 2008; Schacter and Slotnick, 2004; Shohamy and Wagner, 2008).”
What Learning Systems do Intelligent Agents Need? Complementary Learning Systems Theory Updated. (2016, unknown): “…a substantial challenge to this account, however, has come from paradigms where individuals have been shown to rapidly utilize features that create links among a set of related experiences as a basis for a form of inference within or shortly after a single experimental session [4,5,90 – 95].”
Integrating memories to guide decisions (2015, background): “Indeed, there is some evidence that decisions based on retrospective integration can be computed as quickly as decisions that require no integration at all [43].”
Hippocampal Contributions to Model-Based Planning and Spatial Memory (2019, unknown): “Tests of relational encoding have even relied on tasks that are similar in logic to probes for model-based planning, like transitive inference or acquired equivalence (Dusek and Eichenbaum, 1997; Heckers et al., 2004; Shohamy and Wagner, 2008; Wimmer and Shohamy, 2012).”
Generalization of value in reinforcement learning by humans (2012, methodology): “Here, we used functional magnetic resonance imaging and computational model-based analyses to examine the joint contributions of these mechanisms to reinforcement learning.”