Yuko Munakata - US grants

This research addresses two distinct types of knowledge representations- -active and latent--and their potential role in infants' task-dependent behavior with hidden objects. Infants can appear precocious or limited in almost any ability depending on the task administered to them. For example, infants as young as 3.5 months show an apparent sensitivity to the continued existence of hidden objects in visual habituation studies, yet infants fail to manually retrieve hidden objects until around 9 months, independent of any motor or problem-solving deficits. This research explores the possibility that infants use latent representations to recognize unusual events in visual habituation studies, but require later developing active representations to retrieve occluded objects. Active representations take the form of sustained neuronal firing, while latent representations take the form of changes in firing thresholds or neuronal connections that affect neuronal activity only in subsequent processing. The proposed studies are adapted from tasks used with non-human primates, in which the neural mechanisms and behavioral manifestations of active and latent representations are relatively well understood. The studies have two specific aims. First, they investigate infants' biases and capacities for forming active and latent representations. Second, they attempt to identify the potential contributions from active and latent representations to infants' task-dependent behavior with hidden objects. Study 1 tests the hypothesis that infants, like non- human primates, are biased to form latent rather than active representations when either will suffice for the task at hand. Study 2 tests the hypothesis that infants, like non-human primates, possess some capacity for forming active representations that may be obscured by their bias for latent representations. Task-dependent behaviors may provide a window onto the psychological and neural bases of development, so results from these studies may inform theory and its application to both typical and special populations.

This project aims to futher our understanding of the neural representations that underlie working memory. Working memory refers to the active maintenance of information in the service of complex cognitive tasks such as problem solving and planning. The team of investigator with study how the unique demands placed on the working memory system shape its representations during learning and development, and how these representations affect the use of working memory by the cognitive system as a whole. Their primary source of insight into this process will come from a computational analysis, which will be used to integrate and explore relevant findings from neurobiology and developmental and adult cognition. The primary hypothesis is that to maintain information in an active state over delays and in the face of interference, working memory representations should be discrete. A discrete representation admits to only a finite set of possible states, rather than representing continuous states. For example, the integers from 1 to 100 form a discrete set, in contrast to the real numbers in this range. Discreteness imparts a measure of robustness to the representation because small amounts of "noise" can be overcome by interpreting an observed state as the nearest discrete stat. From the central property of discreteness, a number of other properties follow. For example, discrete representations should be more categorical, more easily verbalize, better for perceiving or performing a sequence of steps, and more accessible to awareness. All these properties have component of the proposed research is to explore the idea that they all follow from the more basic property of dicreteness. The initial goal of the project will be establish through experimental studies the validity of the hypothesis that working memory representations are indeed discrete. This will be done by exploring a key behavioral consequence of this hypothesis: working memory representations should be more categorical than other representations. This predicition will be investigated with a set of existing empirical paradigms that have elucidated variables that affect the working memory system, including developmental age, delay, dual-task demands, and brain damage. Working memory plays a central role in most accounts of complex human behavior, because working memory is required in any task that involves multiple stos ir a temporally extended focus of attention. This kinds of tasks are important and pervasive throughout society, including: economic, political, and military planning; air-traffic control; and scientific research, to name just a few. It is essential to understand the nature of the representations in the working memory system and to understand how people learn to use working memory in the service of complex behavior. This research will advance our knowledge in this important area, and may provide insight into techniques for rehabilitation of working memory following brain injury and techniques for assisting the development of working memory in children.

The primary goal of this research is to advance understanding of the representations underlying infants' task-dependent behavior with hidden objects. Infants can appear precocious or limited in almost any ability depending on the task administered to them. For example, infants as young as 3.5 months show an apparent sensitivity to the continued existence of hidden objects in visual habituation studies, yet infants fail to manually search for objects hidden by occluders through around 9 months. And, infants as young as 5 months reach for objects in the dark. Such task-dependent behaviors can be interpreted in many ways, resulting in numerous contradictory claims about what infants know, from very young infants possessing a concept of object permanence to much older infants representing nothing about hidden objects. This project addresses this debate by focusing on the following questions: 1. How do inherent and incidental task factors contribute to infants' task- dependent behavior? 2. How do distinct types of representations contribute to infants' task- dependent behavior? 3. How do graded representations contribute to infants' task-dependent behavior? The primary methodology for this project is the detailed analysis of infants' response to objects that are presented and then hidden from view, across three paradigms: visual habituation, reaching in the dark, and searching under visible occluders. Findings from these studies will illuminate the influence of a variety of factors in the representations infants use across different tasks. In this way, the proposed work provides a coherent program for advancing our understanding of the factors contributing to infants' task-dependent behavior--an essential step toward characterizing the nature of infants' representations, and in turn informing theory and its application to both typical and special populations.

DESCRIPTION (provided by applicant): The primary goal of this research is to advance understanding of the representations underlying task-dependent behavior. Infants and children can appear precocious or limited in almost any ability depending on the task administered to them. For example, infants as young as 3.5 months seem to understand the continued existence of hidden objects in violation-of-expectation studies, yet infants fail to manually search for objects hidden by occluders until around 9 months. Similarly, children can answer verbal queries about how to respond flexibly in different situations, yet they fail to show such flexibility in their actual behaviors. Such task-dependent behaviors, or dissociations, raise important questions about the organization, development, and training of our cognitive systems. This project investigates these issues via the following questions: 1.) What kinds of representations lead to task-dependent behaviors, specifically: How do graded representations contribute to task-dependent behaviors? How do distinct types of representations (active and latent) contribute to task-dependent behaviors? How do graded and distinct types of representations interact to influence behavior? 2.) How general is the graded, active-latent framework proposed for understanding infants' and children's task-dependent behaviors, specifically: What revisions are required for computational models of this framework to more fully account for behavioral and biological findings? What are the potential educational implications from this framework? What is the relevance of this framework for understanding adult behavior? The proposed studies investigate these questions through the integration of behavioral testing, neural network modeling, and findings from cognitive neuroscience. The proposed work provides a coherent program for advancing our understanding of the factors contributing to task-dependent behavior -- an essential step toward characterizing the nature of representations of knowledge, and in turn informing theory and its application to both typical and special populations.

The overarching goal of the proposed research is to understand the representations supporting executive control and its development during childhood. Although mature humans show unique abilities to flexibly adapt their behavior to changing circumstances, children can show stunning failures to do so. For example, children often perseverate, repeating prior behaviors when they are no longer appropriate. Much progress has been made in studying the remarkable developments children show in executive function. However, a unified framework is still needed for understanding the cognitive processes and neural factors underlying these developments. The proposed research builds on a biologically-based computational modeling framework for understanding the development of executive control. This work investigates the hypothesis that two critical factors in the development of executive control are the emergence of increasingly abstract, rule-like representations and increasing abilities to maintain information in an active form, both of which rely on prefrontal cortical developments. These issues are investigated through behavioral studies with children, neuroimaging studies with adults, and neural network models tested at different points in development. This approach will allow us to better understand components of executive control and their development, at the cognitive, computational, and neural levels. We pursue these aims: Aim 5.1: Investigating Relations among Abstract Representations, Active Representations and Executive Control During Early Development These studies with children and developing neural network models address critical questions from preliminary work on these factors, and systematically evaluate early developing relations among these factors. Aim 5.2: Investigating Effects of Manipulating Abstraction and Active Maintenance Abilities During Early Development These studies with children and developing neural network models focus on effects on executive control of manipulations designed to enhance or interfere with components of executive control. Aim 5.3: Investigating Neural Components of Executive Control Representations These studies in adults and fully developed neural network models assess the neural substrates and signatures associated with representations supporting executive control. The proposed work provides a coherent program for advancing understanding of the relations among components of executive control, and developmental changes in these components and relations. This is an essential step in understanding our uniquely human executive function abilities and factors that lead to their enhancement or impairment, and in turn informing applications for both typical and special populations.

DESCRIPTION (provided by applicant): The primary goal of this research is to advance understanding of the development of cognitive flexibility. Children can show stunning failures to flexibly adapt their behavior to changing circumstances. For example, children often perseverate, repeating prior behaviors when they are no longer appropriate, even in the face of repeated and explicit information to change course. In contrast, mature humans show unique abilities to flexibly adapt their behavior to changing circumstances, even in the absence of explicit information about how or when to do so. Much of the work in the developmental literature has focused on one aspect of this process - children's increasing abilities to actively maintain goals that are provided for them. While this work has led to a rich understanding of the mechanisms supporting children's flexible behaviors, it has largely failed to address two critical transitions in development. First, prior to children's gradual improvements in proactive maintenance of goal representations, they show a qualitatively different, reactive, form of cognitive control, retrieving goals only as they are needed in the moment. Second, even after children excel at maintaining goals that are provided for them to guide exogenous (externally-cued) flexibility, they show continued limitations and developments in endogenous (internally-driven) flexibility, when they must select goals for themselves. The proposed research builds on a unified, biologically-based computational modeling framework to investigate developments in these diverse components of flexibility, through parallel studies with children and neural network models. This framework focuses on the role of active, abstract knowledge representations in driving transitions from reactive to proactive control, and from exogenous to endogenous control. This work will advance explicit mechanistic models of how children develop, maintain, and update representations in the service of flex- ible behavior, and will inform applications for improving flexibility - from infant search to children's rule use to increasing abilities to drive flexible behavior on one's own.

Project Summary Children show dramatic developments in executive functioning (EF), the goal-directed processes that support flexible adaptation of behavior in response to changing circumstances. For example, children's early- developing forms of EF are reactive, or on-the-fly, based on retrieval of goal-relevant information as needed in the moment. With development, children become increasingly proactive, or planful, maintaining goal-relevant information in anticipation of needing it. Such EFs and their development are associated with benefits to cognition, emotion, and action, and their impairment has been implicated in clinical disorders, including ADHD, autism, OCD, schizophrenia, and Tourette's syndrome. Given this significance for important outcomes, much research has focused on developments in and interventions targeting core EFs such as working memory. However, EFs are diverse rather than unitary or all-purpose, each with relative costs and benefits. Proactive forms of EF bring benefits to preparedness, but also costs in terms of time and effort required prior to actually doing something. Similarly, goal-maintenance can aid staying on task, but confers costs when goal- shifting is required. Such trade-offs require people to coordinate which EFs to engage when, for example, in focusing on one task until it is completed, or switching among several tasks to make progress on each. Thus, children's dramatic improvements in EF may rely upon their self-directed, adaptive coordination of distinct forms of EF, particularly as children gain independence and must determine on their own what tasks to take on, which EFs to engage from their expanding repertoire, and when. Moreover, this adaptive coordination of EFs could explain links between performance on EF measures and significant life outcomes. To address this critical but underexplored aspect of EF, we test developments in the self-directed, adaptive coordination of forms of EF (Aim 1), the factors influencing this coordination (Aim 2), and the trajectories that children show over time (Aim 3), and their relationship to real-world measures. We investigate these processes via cross-sectional and longitudinal studies, using behavioral studies integrated with physiological measures, building on theoretical and empirical work from our lab and others. The studies test: 1) young children, who have demonstrated some capacity for adaptive coordination of EFs, but may rely more on a trial-and-error process sampling from a broad repertoire of potential approaches, 2) older children, who may learn over experience with particular tasks to be increasingly targeted in their adaptive coordination of EFs, and 3) adults, whose adaptive coordination of EFs may be more strategic at the outset across different contexts, reflecting the selection of EFs that are best suited to current demands. We also track children longitudinally as they progress through a key transition window. Together, these studies will advance a new understanding of the role of increasingly adaptive coordination of EFs in development, and provide important constraints and insights for theories and models of executive function and dysfunction more broadly.  

Project Summary Children show remarkable limitations in their ability to suppress inappropriate actions, thoughts, and emotions. Their gradual development of inhibitory control is critical in the moment, allowing children to delay gratification, behave flexibly rather than following habits, and regulate their emotions, and in the longer term, predicting a wide range of important life outcomes, including health, academic achievement, and income. Deficits in inhibitory control are implicated in numerous clinical disorders, including ADHD, autism, OCD, and schizophrenia. Studying the development of inhibitory control thus represents an opportunity, because children's protracted limitations and successes provide a window into fundamental processes that are crucial for mental health. Studying the development of inhibitory control also represents a challenge, because targeted intervention efforts to improve children's inhibitory control have met with limited success. Some broad intervention efforts have shown promise but are multifaceted and time-intensive, making it difficult to identify which components are critical in order to inform targeted interventions and theory development. Two recent advances point to a promising way forward. The first advance is a new understanding of a core component of successful inhibitory control in adults: the ability to proactively monitor the environment for signals that indicate that an action should be stopped. This advance suggests that inhibitory limitations, developments, and interventions may depend critically upon processes for proactive monitoring. The second advance is a new understanding of developmental changes in the temporal dynamics of executive function: children gradually transition from a reactive form of executive function (engaging control processes only as needed in the moment) to a proactive form (engaging control processes and maintaining them in anticipation of needing them in the future). Together, the two advances suggest that children's struggles with inhibitory control reflect their prolonged development of proactive control (which ultimately supports the proactive monitoring that is critical for inhibitory control), and their early use of reactive control (which is less efficient for inhibitory control). Interventions must be designed accordingly. This proposal builds on our work developing the components of this framework and integrating them, to test a unified framework for understanding the development of inhibitory control and effective interventions. The studies test young children who rely heavily on reactive control, and older children who have some capacity for proactive control, and tracks children longitudinally as they progress through a key transition window. We tightly integrate these behavioral studies with computational models. Our foundational neural network simulations show how proactive monitoring can develop through learning, to support inhibitory control. Our proposed models will help to distinguish alternative theories and generate testable predictions, to advance understanding of the mechanisms supporting developments in inhibitory control and effective intervention.