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  1. Article ; Online: Active reinforcement learning versus action bias and hysteresis: control with a mixture of experts and nonexperts.

    Colas, Jaron T / O'Doherty, John P / Grafton, Scott T

    PLoS computational biology

    2024  Volume 20, Issue 3, Page(s) e1011950

    Abstract: Active reinforcement learning enables dynamic prediction and control, where one should not only maximize rewards but also minimize costs such as of inference, decisions, actions, and time. For an embodied agent such as a human, decisions are also shaped ... ...

    Abstract Active reinforcement learning enables dynamic prediction and control, where one should not only maximize rewards but also minimize costs such as of inference, decisions, actions, and time. For an embodied agent such as a human, decisions are also shaped by physical aspects of actions. Beyond the effects of reward outcomes on learning processes, to what extent can modeling of behavior in a reinforcement-learning task be complicated by other sources of variance in sequential action choices? What of the effects of action bias (for actions per se) and action hysteresis determined by the history of actions chosen previously? The present study addressed these questions with incremental assembly of models for the sequential choice data from a task with hierarchical structure for additional complexity in learning. With systematic comparison and falsification of computational models, human choices were tested for signatures of parallel modules representing not only an enhanced form of generalized reinforcement learning but also action bias and hysteresis. We found evidence for substantial differences in bias and hysteresis across participants-even comparable in magnitude to the individual differences in learning. Individuals who did not learn well revealed the greatest biases, but those who did learn accurately were also significantly biased. The direction of hysteresis varied among individuals as repetition or, more commonly, alternation biases persisting from multiple previous actions. Considering that these actions were button presses with trivial motor demands, the idiosyncratic forces biasing sequences of action choices were robust enough to suggest ubiquity across individuals and across tasks requiring various actions. In light of how bias and hysteresis function as a heuristic for efficient control that adapts to uncertainty or low motivation by minimizing the cost of effort, these phenomena broaden the consilient theory of a mixture of experts to encompass a mixture of expert and nonexpert controllers of behavior.
    MeSH term(s) Humans ; Reinforcement, Psychology ; Learning ; Reward ; Problem-Based Learning ; Bias
    Language English
    Publishing date 2024-03-29
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2193340-6
    ISSN 1553-7358 ; 1553-734X
    ISSN (online) 1553-7358
    ISSN 1553-734X
    DOI 10.1371/journal.pcbi.1011950
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  2. Article ; Online: Overt and Covert Object Features Mediate Timing of Patterned Brain Activity during Motor Planning.

    Marneweck, Michelle / Grafton, Scott T

    Cerebral cortex communications

    2020  Volume 1, Issue 1, Page(s) tgaa080

    Abstract: Humans are seamless in their ability to efficiently and reliably generate fingertip forces to gracefully interact with objects. Such interactions rarely end in awkward outcomes like spilling, crushing, or tilting given advanced motor planning. Here we ... ...

    Abstract Humans are seamless in their ability to efficiently and reliably generate fingertip forces to gracefully interact with objects. Such interactions rarely end in awkward outcomes like spilling, crushing, or tilting given advanced motor planning. Here we combine multiband imaging with deconvolution- and Bayesian pattern component modeling of functional magnetic resonance imaging data and in-scanner kinematics, revealing compelling evidence that the human brain differentially represents preparatory information for skillful object interactions depending on the saliency of visual cues. Earlier patterned activity was particularly evident in ventral visual processing stream-, but also selectively in dorsal visual processing stream and cerebellum in conditions of heightened uncertainty when an object's superficial shape was incompatible rather than compatible with a key underlying object feature.
    Language English
    Publishing date 2020-10-30
    Publishing country United States
    Document type Journal Article
    ISSN 2632-7376
    ISSN (online) 2632-7376
    DOI 10.1093/texcom/tgaa080
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  3. Article ; Online: Neural substrates of anticipatory motor adaptation for object lifting.

    Marneweck, Michelle / Grafton, Scott T

    Scientific reports

    2020  Volume 10, Issue 1, Page(s) 10430

    Abstract: Anticipatory force control is a fundamental means by which humans stave off slipping, spilling, and tilting disasters while manipulating objects. This control must often be adapted due to changes in an object's dynamics (e.g. a lighter than expected mug ... ...

    Abstract Anticipatory force control is a fundamental means by which humans stave off slipping, spilling, and tilting disasters while manipulating objects. This control must often be adapted due to changes in an object's dynamics (e.g. a lighter than expected mug of coffee) or its relation with involved effectors or digits (e.g. lift a mug with three vs. five digits). The neural processes guiding such anticipatory and adaptive control is understudied but presumably operates along multiple time scales, analogous to what has been identified with adaptation in other motor tasks, such as perturbations during reaching. Learning of anticipatory forces must be ultrafast to minimize tilting a visually symmetric object towards its concealed asymmetric center of mass (CoM), but slower when the CoM is explicitly and systematically switched from side to side. Studying the neural substrates of this latter slower learning process with rapid multiband brain imaging, in-scanner kinematics and Bayesian pattern component modelling, we show that CoM-specific pattern distances increase with repeated CoM switching exposures and improved learning. The cerebellum showed the most prominent effects, fitting with the idea that it forms a stored internal model that is used to build and update anticipatory control. CoM-specific pattern distances were present 24 h later, in line with the presence of consolidation effects.
    MeSH term(s) Adaptation, Physiological/physiology ; Adult ; Biomechanical Phenomena/physiology ; Brain/diagnostic imaging ; Brain/physiology ; Female ; Hand Strength/physiology ; Humans ; Lifting ; Magnetic Resonance Imaging ; Male ; Psychomotor Performance/physiology ; Young Adult
    Language English
    Publishing date 2020-06-26
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-020-67453-0
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  4. Article ; Online: Subjective value then confidence in human ventromedial prefrontal cortex.

    Shapiro, Allison D / Grafton, Scott T

    PloS one

    2020  Volume 15, Issue 2, Page(s) e0225617

    Abstract: Two fundamental goals of decision making are to select actions that maximize rewards while minimizing costs and to have strong confidence in the accuracy of a judgment. Neural signatures of these two forms of value: the subjective value (SV) of choice ... ...

    Abstract Two fundamental goals of decision making are to select actions that maximize rewards while minimizing costs and to have strong confidence in the accuracy of a judgment. Neural signatures of these two forms of value: the subjective value (SV) of choice alternatives and the value of the judgment (confidence), have both been observed in ventromedial prefrontal cortex (vmPFC). However, the relationship between these dual value signals and their relative time courses are unknown. Twenty-eight men and women underwent fMRI while performing a two-phase approach-avoidance (Ap-Av) task with mixed-outcomes of monetary rewards paired with painful shock stimuli. Neural responses were measured during offer valuation (offer phase) and choice valuation (commit phase) and analyzed with respect to observed decision outcomes, model-estimated SV and confidence. During the offer phase, vmPFC tracked SV and the decision but not confidence. During the commit phase, vmPFC tracked confidence, computed as the quadratic extension of SV, but not the offer valuation nor the decision. In fact, vmPFC responses from the commit phase were selective for confidence even for reject decisions wherein confidence and SV are inversely related. Conversely, activation of the cognitive control network, including within lateral prefrontal cortex (lPFC) and dorsal anterior cingulate cortex (dACC) was associated with ambivalence, during both the offer and commit phases. Taken together, our results reveal complementary representations in vmPFC during value-based decision making that temporally dissociate such that offer valuation (SV) emerges before decision valuation (confidence).
    MeSH term(s) Brain Mapping/methods ; Choice Behavior/physiology ; Female ; Gyrus Cinguli/physiology ; Humans ; Judgment/physiology ; Magnetic Resonance Imaging/methods ; Male ; Prefrontal Cortex/physiology ; Punishment ; Reward ; Self Concept ; Young Adult
    Language English
    Publishing date 2020-02-10
    Publishing country United States
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
    ISSN 1932-6203
    ISSN (online) 1932-6203
    DOI 10.1371/journal.pone.0225617
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Representational Neural Mapping of Dexterous Grasping Before Lifting in Humans.

    Marneweck, Michelle / Grafton, Scott T

    The Journal of neuroscience : the official journal of the Society for Neuroscience

    2020  Volume 40, Issue 13, Page(s) 2708–2716

    Abstract: The ability of humans to reach and grasp objects in their environment has been the mainstay paradigm for characterizing the neural circuitry driving object-centric actions. Although much is known about hand shaping, a persistent question is how the brain ...

    Abstract The ability of humans to reach and grasp objects in their environment has been the mainstay paradigm for characterizing the neural circuitry driving object-centric actions. Although much is known about hand shaping, a persistent question is how the brain orchestrates and integrates the grasp with lift forces of the fingers in a coordinated manner. The objective of the current study was to investigate how the brain represents grasp configuration and lift force during a dexterous object-centric action in a large sample of male and female human subjects. BOLD activity was measured as subjects used a precision-grasp to lift an object with a center of mass (CoM) on the left or right with the goal of minimizing tilting the object. The extent to which grasp configuration and lift force varied between left and right CoM conditions was manipulated by grasping the object collinearly (requiring a non-collinear force distribution) or non-collinearly (requiring more symmetrical forces). Bayesian variational representational similarity analyses on fMRI data assessed the evidence that a set of cortical and cerebellar regions were sensitive to grasp configuration or lift force differences between CoM conditions at differing time points during a grasp to lift action. In doing so, we reveal strong evidence that grasping and lift force are not represented by spatially separate functionally specialized regions, but by the same regions at differing time points. The coordinated grasp to lift effort is shown to be under dorsolateral (PMv and AIP) more than dorsomedial control, and under SPL7, somatosensory PSC, ventral LOC and cerebellar control.
    MeSH term(s) Adolescent ; Adult ; Biomechanical Phenomena/physiology ; Brain/diagnostic imaging ; Brain Mapping ; Female ; Functional Neuroimaging ; Hand Strength/physiology ; Humans ; Lifting ; Magnetic Resonance Imaging ; Male ; Psychomotor Performance/physiology ; Young Adult
    Language English
    Publishing date 2020-02-03
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 604637-x
    ISSN 1529-2401 ; 0270-6474
    ISSN (online) 1529-2401
    ISSN 0270-6474
    DOI 10.1523/JNEUROSCI.2791-19.2020
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  6. Article ; Online: Moral foundations elicit shared and dissociable cortical activation modulated by political ideology.

    Hopp, Frederic R / Amir, Ori / Fisher, Jacob T / Grafton, Scott / Sinnott-Armstrong, Walter / Weber, René

    Nature human behaviour

    2023  Volume 7, Issue 12, Page(s) 2182–2198

    Abstract: Moral foundations theory (MFT) holds that moral judgements are driven by modular and ideologically variable moral foundations but where and how these foundations are represented in the brain and shaped by political beliefs remains an open question. Using ...

    Abstract Moral foundations theory (MFT) holds that moral judgements are driven by modular and ideologically variable moral foundations but where and how these foundations are represented in the brain and shaped by political beliefs remains an open question. Using a moral vignette judgement task (n = 64), we probed the neural (dis)unity of moral foundations. Univariate analyses revealed that moral judgement of moral foundations, versus conventional norms, reliably recruits core areas implicated in theory of mind. Yet, multivariate pattern analysis demonstrated that each moral foundation elicits dissociable neural representations distributed throughout the cortex. As predicted by MFT, individuals' liberal or conservative orientation modulated neural responses to moral foundations. Our results confirm that each moral foundation recruits domain-general mechanisms of social cognition but also has a dissociable neural signature malleable by sociomoral experience. We discuss these findings in view of unified versus dissociable accounts of morality and their neurological support for MFT.
    MeSH term(s) Humans ; Politics ; Morals ; Judgment ; Ethical Theory
    Language English
    Publishing date 2023-09-07
    Publishing country England
    Document type Journal Article
    ISSN 2397-3374
    ISSN (online) 2397-3374
    DOI 10.1038/s41562-023-01693-8
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  7. Article ; Online: Stress affects navigation strategies in immersive virtual reality.

    Varshney, Apurv / Munns, Mitchell E / Kasowski, Justin / Zhou, Mantong / He, Chuanxiuyue / Grafton, Scott T / Giesbrecht, Barry / Hegarty, Mary / Beyeler, Michael

    Scientific reports

    2024  Volume 14, Issue 1, Page(s) 5949

    Abstract: There are known individual differences in both the ability to learn the layout of novel environments and the flexibility of strategies for navigating known environments. However, it is unclear how navigational abilities are impacted by high-stress ... ...

    Abstract There are known individual differences in both the ability to learn the layout of novel environments and the flexibility of strategies for navigating known environments. However, it is unclear how navigational abilities are impacted by high-stress scenarios. Here we used immersive virtual reality (VR) to develop a novel behavioral paradigm to examine navigation under dynamically changing situations. We recruited 48 participants (24 female; ages 17-32) to navigate a virtual maze (7.5 m × 7.5 m). Participants learned the maze by moving along a fixed path past the maze's landmarks (paintings). Subsequently, participants experienced either a non-stress condition, or a high-stress condition tasking them with navigating the maze. In the high-stress condition, their initial path was blocked, the environment was darkened, threatening music was played, fog obstructed more distal views of the environment, and participants were given a time limit of 20 s with a countdown timer displayed at the top of their screen. On trials where the path was blocked, we found self-reported stress levels and distance traveled increased while trial completion rate decreased (as compared to non-stressed control trials). On unblocked stress trials, participants were less likely to take a shortcut and consequently navigated less efficiently compared to control trials. Participants with more trait spatial anxiety reported more stress and navigated less efficiently. Overall, our results suggest that navigational abilities change considerably under high-stress conditions.
    MeSH term(s) Female ; Humans ; Individuality ; Maze Learning ; Spatial Navigation ; Virtual Reality ; Male ; Adolescent ; Young Adult ; Adult ; Stress, Physiological
    Language English
    Publishing date 2024-03-11
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-024-56048-8
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  8. Article ; Online: ReeBundle: A Method for Topological Modeling of White Matter Pathways Using Diffusion MRI.

    Shailja, S / Bhagavatula, Vikram / Cieslak, Matthew / Vettel, Jean M / Grafton, Scott T / Manjunath, B S

    IEEE transactions on medical imaging

    2023  Volume 42, Issue 12, Page(s) 3725–3737

    Abstract: Tractography can generate millions of complex curvilinear fibers (streamlines) in 3D that exhibit the geometry of white matter pathways in the brain. Common approaches to analyzing white matter connectivity are based on adjacency matrices that quantify ... ...

    Abstract Tractography can generate millions of complex curvilinear fibers (streamlines) in 3D that exhibit the geometry of white matter pathways in the brain. Common approaches to analyzing white matter connectivity are based on adjacency matrices that quantify connection strength but do not account for any topological information. A critical element in neurological and developmental disorders is the topological deterioration and irregularities in streamlines. In this paper, we propose a novel Reeb graph-based method "ReeBundle" that efficiently encodes the topology and geometry of white matter fibers. Given the trajectories of neuronal fiber pathways (neuroanatomical bundle), we re-bundle the streamlines by modeling their spatial evolution to capture geometrically significant events (akin to a fingerprint). ReeBundle parameters control the granularity of the model and handle the presence of improbable streamlines commonly produced by tractography. Further, we propose a new Reeb graph-based distance metric that quantifies topological differences for automated quality control and bundle comparison. We show the practical usage of our method using two datasets: (1) For International Society for Magnetic Resonance in Medicine (ISMRM) dataset, ReeBundle handles the morphology of the white matter tract configurations due to branching and local ambiguities in complicated bundle tracts like anterior and posterior commissures; (2) For the longitudinal repeated measures in the Cognitive Resilience and Sleep History (CRASH) dataset, repeated scans of a given subject acquired weeks apart lead to provably similar Reeb graphs that differ significantly from other subjects, thus highlighting ReeBundle's potential for clinical fingerprinting of brain regions.
    MeSH term(s) Humans ; White Matter/diagnostic imaging ; Image Processing, Computer-Assisted/methods ; Diffusion Magnetic Resonance Imaging/methods ; Brain/diagnostic imaging ; Brain/anatomy & histology ; Corpus Callosum ; Neural Pathways
    Language English
    Publishing date 2023-11-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 622531-7
    ISSN 1558-254X ; 0278-0062
    ISSN (online) 1558-254X
    ISSN 0278-0062
    DOI 10.1109/TMI.2023.3306049
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  9. Article ; Online: Motor adaptation via distributional learning.

    Mitchell, Brian A / Marneweck, Michelle / Grafton, Scott T / Petzold, Linda R

    Journal of neural engineering

    2021  Volume 18, Issue 4

    Abstract: ... ...

    Abstract Objective
    MeSH term(s) Adaptation, Physiological ; Artificial Intelligence ; Hand Strength ; Humans ; Learning ; Reinforcement, Psychology
    Language English
    Publishing date 2021-05-24
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 2170901-4
    ISSN 1741-2552 ; 1741-2560
    ISSN (online) 1741-2552
    ISSN 1741-2560
    DOI 10.1088/1741-2552/aba6d9
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  10. Article: From ideas to action: The prefrontal-premotor connections that shape motor behavior.

    Grafton, Scott T / Volz, Lukas J

    Handbook of clinical neurology

    2019  Volume 163, Page(s) 237–255

    Abstract: The prefrontal cortex serves a critical role in the coordination and execution of motor actions via its involvement in goal setting, decision-making, motivation, and cognitive control. Using the macaque connectome, the anatomic pathways from prefrontal ... ...

    Abstract The prefrontal cortex serves a critical role in the coordination and execution of motor actions via its involvement in goal setting, decision-making, motivation, and cognitive control. Using the macaque connectome, the anatomic pathways from prefrontal cortex to motor circuitry are summarized, revealing a remarkably limited set of direct connections. A highly similar connectivity pattern is inferred from human neuroimaging. The results motivate the prefrontal-premotor connector hub model, which highlights both functional segregation and a limited set of connector hub regions that provide a direct linking of prefrontal cortex to the (pre-)motor network. Moreover, the macaque connectome reveals a set of motor translator regions that provide the most direct projection from premotor to prefrontal areas. The connector hub model leads to important functional implications: Neural activation or disruption in connector hubs should lead to functional deficits that undermine integration between higher cognitive action control and motor performance ranging from response selection and inhibition to perceived agency of actions. Segregation of prefrontal-premotor networks challenges hierarchical models of motor control and underscores the critical role of the indirect pathway from prefrontal to premotor areas via the parietal cortex. The model provides a predictive framework to design neurostimulation paradigms for modulating skill learning or recovery in both healthy subjects and patient cohorts.
    MeSH term(s) Brain Mapping ; Humans ; Motor Activity/physiology ; Motor Cortex/physiology ; Neural Pathways/physiology ; Prefrontal Cortex/physiology ; Psychomotor Performance/physiology
    Language English
    Publishing date 2019-10-05
    Publishing country Netherlands
    Document type Journal Article ; Review
    ISSN 0072-9752
    ISSN 0072-9752
    DOI 10.1016/B978-0-12-804281-6.00013-6
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