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4 results

  • Contextual influence of reinforcement learning performance of depression: evidence for a negativity bias?

  • Henri Vandendriessche, Amel Demmou, Sophie Bavard, Julien Yadak, Cédric Lemogne, Thomas Mauras, Stefano Palminteri
  • Journal:
    Psychological Medicine / Volume 53 / Issue 10 / July 2023
    Published online by Cambridge University Press:
    21 June 2022, pp. 4696-4706
    • Article
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  • Backgrounds

    Value-based decision-making impairment in depression is a complex phenomenon: while some studies did find evidence of blunted reward learning and reward-related signals in the brain, others indicate no effect. Here we test whether such reward sensitivity deficits are dependent on the overall value of the decision problem.

    Methods

    We used a two-armed bandit task with two different contexts: one ‘rich’, one ‘poor’ where both options were associated with an overall positive, negative expected value, respectively. We tested patients (N = 30) undergoing a major depressive episode and age, gender and socio-economically matched controls (N = 26). Learning performance followed by a transfer phase, without feedback, were analyzed to distangle between a decision or a value-update process mechanism. Finally, we used computational model simulation and fitting to link behavioral patterns to learning biases.

    Results

    Control subjects showed similar learning performance in the ‘rich’ and the ‘poor’ contexts, while patients displayed reduced learning in the ‘poor’ context. Analysis of the transfer phase showed that the context-dependent impairment in patients generalized, suggesting that the effect of depression has to be traced to the outcome encoding. Computational model-based results showed that patients displayed a higher learning rate for negative compared to positive outcomes (the opposite was true in controls).

    Conclusions

    Our results illustrate that reinforcement learning performances in depression depend on the value of the context. We show that depressive patients have a specific trouble in contexts with an overall negative state value, which in our task is consistent with a negativity bias at the learning rates level.

  • 1 - General Introduction

  • Francesco de Bello, University of South Bohemia, Czech Republic, Carlos P. Carmona, University of Tartu, Estonia, André T. C. Dias, Universidade Federal do Rio de Janeiro, Lars Götzenberger, Marco Moretti, Matty P. Berg, Vrije Universiteit, Amsterdam
  • Book:
    Handbook of Trait-Based Ecology
    Published online:
    08 March 2021
    Print publication:
    11 March 2021, pp 1-16

  • Summary

    Chapter 1 summarizes the main concepts representing the pillars of trait-based ecology. Key definitions from the literature, and widely used in the book, are synthetized and clarified. This includes an in-depth discussion of which traits are to be considered more functional, dissecting the relationship between species traits and species fitness and how this can change across different habitats. The classic distinction between response and effect traits is introduced, together with some broad open challenges for future research in trait-based ecology.

  • 14 - How to Evaluate Agents and Agency

  • from Part Two - Agency and the Dynamics of Earth System Governance
  • Edited by Michele M. Betsill, Colorado State University, Tabitha M. Benney, University of Utah, Andrea K. Gerlak, University of Arizona
  • Book:
    Agency in Earth System Governance
    Published online:
    04 January 2020
    Print publication:
    02 January 2020, pp 168-180

  • Summary

    − ESG–Agency scholars have embraced the notion that agent influence is complex, contingent, and context dependent, with the success of environmental governance depending considerably on propitious environmental and social conditions. − Scholars have shifted from an earlier focus on how agents influence behaviours and environmental quality in earth system governance to how they influence governance processes, with increasing focus on democracy, participation, legitimacy, transparency, and accountability. − ESG–Agency scholars employ increasingly diverse methods to integrate insights from case studies, interviews, surveys, statistical analyses, and other approaches leading to deeper and more nuanced understanding of agency in earth system governance. − Adopting more interdisciplinary, multidisciplinary, and transdisciplinary approaches to evaluating agency can foster future understandings of and contributions to earth system governance.

  • Facilitation and suppression of single striate-cell activity by spatially discrete pattern stimuli presented beyond the receptive field

  • KEIKO MIZOBE, URI POLAT, MARK W. PETTET, TAKUJI KASAMATSU
  • Journal:
    Visual Neuroscience / Volume 18 / Issue 3 / May 2001
    Published online by Cambridge University Press:
    10 September 2001, pp. 377-391

  • Visual stimulation of a region outside the receptive field of single cells in visual cortex often results in the modulation of their responses. The modulatory effects are thought to be mediated through lateral connections within visual cortex. Research on lateral interactions commonly shows suppression. There has been no systematic study of the optimal conditions for facilitation. Here we have studied the nature of the modulation using a new type of compound stimulus: contrast reversal of pattern stimuli made of three discrete grating patches. The middle patch, optimally fitted to the receptive field in orientation, size, and spatial as well as temporal frequencies, was flanked by two similar patches presented well outside the receptive field. We found that (1) both facilitation and suppression occurred often in the same cells, when orientations of the target and flankers matched the receptive-field's optimal orientation; (2) facilitation with collinear flankers occurred most frequently at target contrasts just above the cell's firing threshold and suppression prevailed at high contrasts; (3) facilitative or suppressive modulation was obtained with target-flankers separation of up to 12 deg or more; (4) collinear facilitation was lost when flankers' orientation was rotated by 90 deg, while keeping all other parameters the same; and (5) neither the modulation mode nor the proportion of modulated cells was related to the cell types (simple vs. complex cells) and cells' laminar locations. Here we have provided physiological evidence for contrast-dependent, collinear facilitation probably underlying perceptual grouping in humans.