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Open Access Publications from the University of California

Scholarly Works (40 results)

  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2012)
Episodic memory is central to the human experience. In typically developing children, episodic memory improves rapidly during middle childhood. While the developmental cognitive neuroscience of episodic memory remains largely uncharted, recent research has begun to provide important insights. It has long been assumed that hippocampus-dependent binding mechanisms are in place by early childhood, and that improvements in episodic memory observed during middle childhood result from the protracted development of the prefrontal cortex. We revisit the notion that binding mechanisms are age-invariant, and propose that changes in the hippocampus and its projections to cortical regions also contribute to the development of episodic memory. We further review the role of developmental changes in lateral prefrontal and parietal cortices in this development. Finally, we discuss changes in white matter tracts connecting brain regions that are critical for episodic memory. Overall, we argue that changes in episodic memory emerge from the concerted effort of a network of relevant brain structures.
    Cover page: Neural changes underlying the development of episodic memory during middle childhood
    • Thesis
    • Peer Reviewed
    UC Davis Electronic Theses and Dissertations (2023)

    Decision-making is an integral part of life; however, little research has been done with regards to decision-making in young children. Across three studies, I investigated how response latencies and eye-movements were related to toddlers’ decision-making and to later developing metacognition. Study 1 examined whether toddlers response latency and eye-movement behaviors indicate awareness of decision difficulty or uncertainty. Results revealed that 25- to 32-month-olds had lower accuracy rates for harder decisions, responded more slowly during inaccurate trials, and switched their gaze between response options more frequently during harder decisions; suggesting that toddlers are indeed aware of decision difficulty. Study 2 examined whether responses latencies and eye-movements measured at 2 years of age were longitudinally related to emerging uncertainty monitoring at age 3. Results showed that gaze transitions in 25- to 32-month-olds, but not response latencies, were positively associated with uncertainty monitoring when they were 36- 60-months-old, suggesting that toddler’s visual exploration may help to provide a foundation for emerging uncertainty monitoring. Finally, Study 3 examined how 26- 32-month-olds use their memories in service of a goal. Results showed that when asked to report on their memories, only a subset of the toddlers showed reduced novelty preferences and high accuracy. An attentional manipulation reduced novelty preferences and increased gaze transitions and accuracy, suggesting that although attention to novelty seems to interfere with memory decisions, it can be countered with attentional manipulations.

      Cover page: Emerging Decision-Making and Metacognition between 2 and 4 years of age
      • Thesis
      • Peer Reviewed
      UC Davis Electronic Theses and Dissertations (2024)

      When babies are born into the world, they have no concept of how much there is to learn and know about the world. As they age and grow, infants make and retain memories with rapid improvements in recollection for the unique spatio-temporal circumstance. Three studies investigate episodic memory in toddlers, emphasizing the role of the hippocampus in encoding and retrieving spatio-temporal and context-specific memories. Through innovative research methods including behavioral experiments, neuroimaging during natural sleep, and eye-tracking techniques, it was found that hippocampal activation correlates with the ability to retain episodic details and distinguish between similar events. Key findings across the chapters highlight that while spatial associative memory capacities are more robust earlier in development, the abilities to process temporal sequences and perform context discrimination are also evident in the second and third year of life and are linked to hippocampal function. These insights contribute to our understanding of the foundational aspects of memory development and its implications for cognitive development in early life.

        • Article
        • Peer Reviewed
        UC Davis Previously Published Works (2021)
        Accurate memories are often associated with vivid experiences of recollection. However, the neural mechanisms underlying subjective recollection and their unique role in decision making beyond accuracy have received limited attention. We dissociated subjective recollection from accuracy during a forced-choice task. Distractors corresponded either to non-studied exemplars of the targets (A-A' condition) or to non-studied exemplars of different studied items (A-B' condition). The A-A' condition resulted in higher accuracy and greater activation in the superior parietal lobe, whereas the A-B' condition resulted in higher subjective recollection and greater activation in the precuneus and retrosplenial regions, indicating a dissociation between objective and subjective memory. Activation in insular, cingulate, and lateral prefrontal regions was also associated with subjective recollection; however, during a subsequent decision phase, activation in these same regions was greater for discarded than for selected responses in anticipation of a social reward, underscoring their role in evaluating memory evidence flexibly based on current goals.
          Cover page: Distinct neural mechanisms underlie subjective and objective recollection and guide memory-based decision making
          • Article
          • Peer Reviewed
          UC Davis Previously Published Works (2015)
          The present research examined whether eye movements during retrieval capture the relation between an event and its temporal attributes. In two experiments (N=76), we found converging evidence that eye movements reflected the veridicality of memory for temporal order seconds before overt memory judgments, suggesting that these movements captured indirect access to temporal information. These eye movements did not entirely depend on the amount of contextual cueing available (Experiment 1) and reflected the unique ordinal position of an event in a sequence (Experiment 2). Based on our results, we conclude that eye movements reflected the absolute temporal order of past events.
            Cover page: Eye Movements Provide an Index of Veridical Memory for Temporal Order
            • Article
            • Peer Reviewed
            UC Davis Previously Published Works (2021)
            We examined how subjective assessments of recollection guide decision making. Subjective recollection was dissociated from accuracy during a forced-choice recognition task. Distracters were either similar to targets (match condition) or to other studied, but untested items (nonmatch condition). We assessed 223 participants (112 males) across three experiments (137 White, 37 Asian-American, 7 African-American, 4 American-Indian, 32 mixed race, 6 undisclosed). In Experiment 1, 6- to 10-year-olds and adults (N = 119) were less accurate (d = 0.70), but more likely to claim subjective recollection and make memory selections in anticipation of a reward in the nonmatch condition (ds = 0.64-0.70). This pattern was eliminated in 6- to 7-year-olds when we limited the number of selections (Experiment 2, N = 52), but was replicated when we required the selections to be counted (Experiment 3, N = 52), underscoring the effects of decision complexity on children's self-reflections.
              Cover page: Developmental Differences in Subjective Recollection and Its Role in Decision Making
              • Article
              • Peer Reviewed
              UC Davis Previously Published Works (2018)
              Nonhuman research has implicated developmental processes within the hippocampus in the emergence and early development of episodic memory, but methodological challenges have hindered assessments of this possibility in humans. Here, we delivered a previously learned song and a novel song to 2-year-old toddlers during natural nocturnal sleep and, using functional magnetic resonance imaging, found that hippocampal activation was stronger for the learned song compared with the novel song. This was true regardless of whether the song was presented intact or backwards. Toddlers who remembered where and in the presence of which toy character they heard the song exhibited stronger hippocampal activation for the song. The results establish that hippocampal activation in toddlers reflects past experiences, persists despite some alteration of the stimulus, and is associated with behavior. This research sheds light on early hippocampal and memory functioning and offers an approach to interrogate the neural substrates of early memory.
                Cover page: Memory-related hippocampal activation in the sleeping toddler
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2020)
                Episodic memory, or the ability to remember past events with specific detail, is central to the human experience and is related to learning and adaptive functioning in a variety of domains. In typically developing children, episodic memory emerges during infancy and improves during early childhood and beyond. Developmental processes within the hippocampus are hypothesized to be primarily responsible for both the early emergence and persistence of episodic memory in late infancy and early childhood. However, these hypotheses are based on non-human models. In-vivo investigations in early human development of hippocampal processes have been significantly limited by methodological challenges in acquiring neuroimaging data, particularly task-related functional neuroimaging data, from infants and toddlers. Recent studies in adults have shown neural activity in the brain regions supporting episodic memory during slow-wave sleep using functional magnetic resonance imaging (fMRI), and fMRI has been increasingly utilized in infancy and early childhood to address other research questions. We review initial evidence and present preliminary data showing the promise of this approach for examining hippocampal contribution to how infants and toddlers remember individual events, and their association with information about the context in which the event occurred. Overall, our review, integrated with the presentation of some preliminary data provides insight on leveraging sleep to gain new perspectives on early memory functioning.
                  Cover page: Neuroimaging the sleeping brain: Insight on memory functioning in infants and toddlers.
                  • Article
                  • Peer Reviewed
                  UC Davis Previously Published Works (2018)
                  Episodic memory is a critical capacity that involves remembering past events along with their spatial and temporal contexts. Relatively little is known about the relations between spatial and temporal information in long-term memory in children or adults. The present research examined the influence of the mental timeline (linear horizontal display extending from the left to right direction for English speakers) on memory for events and their spatial and temporal features in 7-year-olds, 9-year-olds, 11-year-olds and young adults (N = 146). During encoding, participants studied triplets of objects, varying on two dimensions of the mental timeline: linearity (whether objects were presented in linear succession or not) and direction (whether objects were presented from left-to-right or right-to-left). After a delay, during retrieval, participants were tested on their memory for individual objects, and either the spatial location or temporal order of the objects. We found that overall accuracy for spatial location was higher than accuracy for temporal order, and there was a parallel developmental trajectory for both these aspects of memory. Across age groups we found that memory for temporal order, but not spatial location, was influenced by linearity and direction (i.e., match to mental timeline). Thus, in both children and adults the spatiotemporal mental timeline supported memory for temporal order, converging with predictions generated within domains of language and thought and enhancing our understanding of how space and time are represented in the mind.
                    Cover page: Space and time in episodic memory: Effects of linearity and directionality on memory for spatial location and temporal order in children and adults
                    • Article
                    • Peer Reviewed
                    UC Davis Previously Published Works (2020)
                    Although individuals with autism spectrum disorder (ASD) have been often shown to display similar memory performance on semantic memory tasks compared to typically developing (TD) children, there is ongoing debate about whether and how their ability to remember specific past events (i.e., episodic memory) is impaired. We assessed a sample of 62 children with ASD and 72 TD children, ranging in age between 8 and 12 years on 2 memory tasks. Participants encoded a series of images and their association with either where they appeared on the screen (item-space association task) or with the color of an image's border (item-color association task). Children with ASD showed worse memory in the item-space association task compared to their TD peers, but comparable memory for the item-color association task. These differences persisted when age, intellectual quotient, and general item recognition memory were accounted for statistically. We interpret these results in light of evidence for specific deficits along the dorsal stream affecting processing of spatiotemporal information in ASD. Autism Res 2020, 13: 1985-1997. © 2020 International Society for Autism Research and Wiley Periodicals LLC LAY SUMMARY: Episodic memory requires the ability to bind contextual details (such as color, location, etc.) to an item or event in order to remember the past with specific detail. Here, we compared children with autism spectrum disorder (ASD) and typically developing (TD) children on tasks examining episodic memory. Children with ASD recalled more poorly previously seen items and their associated space-related details, but they performed comparably to TD children on color details. We discuss the possible mechanisms that contribute to worse spatial processing/recall in ASD.
                      Cover page: Children with ASD Show Impaired Item‐Space Recollection, But Preserved Item‐Color Recollection
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