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Episode 7 15.03.2015
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What if the brain organizes thought not as a continuous stream but as a series of discrete packets, timed by nested brain oscillations? Neuroscientist John Lisman explains how theta and gamma rhythms work together to chunk information into ordered sequences , a coding scheme he proposed 20 years ago that recent experimental breakthroughs have finally confirmed. Subscribe for more from the Convergent Science Network podcast series. John Lisman joins Paul Verschure and Tony Prescott at the BCBT summer school to revisit his influential theta-gamma coding hypothesis, first published with Idiart two decades earlier. The core idea is that within each cycle of the slower theta oscillation (roughly 5–15 Hz), the brain fits approximately six or seven discrete gamma cycles (30–100 Hz), and each gamma cycle carries a distinct piece of information. In the hippocampus, this means different spatial locations are represented at different gamma phases within a single theta cycle , not as a continuous signal, but as an ordered, discretized sequence. The discussion explores what recent data from Foster and colleagues has added to this picture: direct evidence that hippocampal representations jump between discrete positions in space, locked to successive gamma cycles, confirming that the phase code is genuinely discrete rather than continuous. Lisman argues this amounts to a multi-part message delivered in under 100 milliseconds , a compressed movie of a navigational path that downstream structures like the basal ganglia could evaluate for costs and benefits during decision-making. The conversation also tackles deeper questions about whether the brain operates with anything resembling a clock cycle, how pattern completion can occur within a single gamma window, and why the irregularity of gamma timing does not undermine the coding scheme. Lisman, Verschure, and Prescott debate the relationship between episodic and statistical memory, the computational parallels to digital processing, and whether oscillatory codes represent a fundamental organizational principle or just one of many strategies the brain employs. Key topics include the theta-gamma nesting hypothesis, discrete phase coding in hippocampus, working memory capacity, attractor dynamics within gamma cycles, decision-making via sequential replay, and the role of brain oscillations in structuring cognition. Part of the Convergent Science Network podcast series from the BCBT Summer School.
Tagged as:
brain oscillations Coding Scheme Gamma Cycles theta-gamma code Within
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
15.03.2015
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