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Episode 6 08.03.2010
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Why is the ability to hold something in mind, even briefly, the gateway to flexible cognition? Xiao-Jing Wang explains how attractor dynamics and slow synaptic reverberation in prefrontal cortex give rise to both working memory and decision-making. Subscribe for more from the Convergent Science Network podcast series. Xiao-Jing Wang begins with a deceptively simple argument: without the capacity to maintain information in the absence of direct sensory input, an organism is enslaved to its environment, reduced to reflexive responses. Working memory , sustained neural activity that bridges the gap between stimulus and action , is therefore the foundation of cognitive flexibility. Drawing on decades of lesion studies, single-neuron recordings, and computational modeling, Wang makes the case that prefrontal cortex is uniquely equipped for this role, thanks to its dense recurrent excitatory connections and distinctive neuromodulatory environment. The interview dives deep into the mechanics of attractor networks, which Wang uses as the theoretical framework for understanding prefrontal dynamics. He is careful to demystify the concept: attractor states are simply relatively stable states, not rigid black holes. What makes prefrontal cortex special is not persistence per se, even oculomotor circuits show persistent activity, but the capacity to maintain multiple stable states simultaneously and switch between them with brief inputs. This multiplicity is what a working memory system requires, and it emerges naturally from the nonlinear dynamics of strongly recurrent circuits. A key surprise from Wang’s modeling work is that the reverberation sustaining working memory must be slow, mediated primarily by NMDA receptors rather than fast AMPA transmission. This was not a design choice but a computational necessity: fast positive feedback makes the network explosively unstable, while slow reverberation provides both stable memory states and the gradual ramping activity observed during decision-making. The same circuit architecture that holds items in working memory also integrates evidence over time, producing the reaction-time signatures seen in prefrontal recordings during perceptual decision tasks. Wang also addresses the frontier challenges: extending local circuit models to large-scale brain systems, understanding how mixed selectivity in prefrontal neurons supports combinatorial coding of sensory, rule, and motor information, and reconciling the role of neural oscillations and correlations with the stochastic firing of individual neurons. His vision is one of building blocks , elementary computational mechanisms that can be composed into increasingly realistic models of cognition.
Tagged as:
Capacity Maintain Memory prefrontal cortex Stable States working memory
About the author call_made
Both the triumphs of humanity and its most evil deeds have resulted from collaboration. In a time where humanity is required to aspire to the former and minimize the latter, the question arises of how collaboration arises and why it fails. Surprisingly, this phenomenon, so central to who we are, is not well understood. Hence, a collaborative effort is required to understand collaboration in its full biological, psychological, sociological, cultural, and economic complexity and to translate this understanding into operational impact. This series of podcasts is one step toward achieving these complementary goals. The Collaboration Podcast presents interviews with people who are central orchestrators of collaboration in various domains including business, government, science, art, health, sustainability, and the military. The discussions were conducted by Prof. Dr. Paul F.M.J. Verschure and members of the Program Advisory Committee of the Ernst Strungmann Forum on Collaboration (https://www.esforum.de/forums/ESF32_Collaboration.html) during 2021 and had the goal to sketch a map of opportunities, challenges, and obstacles in human collaboration. The forum took place in May 2022, and now we would like to share this series of interviews with a broader audience. The full report of the Forum will be published in 2023 by MIT Press. The podcast was produced by the Convergent Science Network (https://www.convergentsciencenetwork.org/). Context: The stability of social systems depends critically on realizing sustainable methods of “collaboration,” yet how and by which means collaboration is achieved is not clearly understood; neither are the conditions or processes that lead to its breakdown or failure. Collaboration can be understood as cooperation between agents toward mutually constructed goals. Part of the reason for our lack of understanding is that the phenomenon of collaboration is, by nature, a highly multidisciplinary problem, and effective research into its complexities has been difficult to achieve across the broad range of scientific and technical disciplines involved. The need for a fundamental understanding of collaboration, however, has become increasingly important. Not only does humankind demand answers as it attempts to address critical challenges at multiple scales (e.g., climate change, migration, enhanced automation, social and economic inequality), but ever-increasing technological and economic means of interconnecting people and societies are disrupting long-established, familiar patterns of how we interact. Radical technological changes that are ongoing have the potential to reshape collaboration in ways that are currently hard to predict or influence (e.g., by altering configurations in interaction, information creation, and modes of communication). On one hand, such changes could disrupt hitherto stable forms of collaboration by affecting critical communication channels and traditional roles, as can be observed in the rapidly changing patterns in governance, commerce, and social interaction. Conversely, technology could lead to the emergence of novel, successful forms of collaboration that deviate from traditional “hierarchical” architectures. Evidence of this can be seen in areas as diverse as highly automated manufacturing plants, the open science movement, collaborative software repositories, user-centered services, and the sharing of economy-based modes of organization. Without a fundamental understanding of the mechanisms, processes, and boundary conditions of collaboration, it is not possible to evaluate or predict which of these possible scenarios are sustainable or even plausible. The Forum “How Collaboration Arises and Why it Fails” (May 8–13, 2022, Location: Frankfurt am Main, Germany) Chairs: Andreas Roepstorff and Paul Verschure Program Advisory Committee: Jenna Bednar, Julia R. Lupp, Bhavani R. Rao , Andreas Roepstorff, Ferdinand von Siemens, and Paul Verschure
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