Disputation: Tristan Manfred Stöber

Doctoral candidate Tristan Manfred Stöber at the Department of informatics, Faculty of Mathematics and Natural Sciences, is defending the thesis Cooperate to compete — Identifying a potential role for hippocampal region CA2 in episodic memory formation for the degree of Philosophiae Doctor.

Picture of the candidate

Photo: Private

The University of Oslo is closed. The PhD defence and trial lecture will therefore be fully digital and streamed directly using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'. 

Trial lecture

Title: "Sequences and action in the motor cortex: Experiments and models"

  • Watch the trial lecture - will be updated later

Main research findings

To memorize an experience, our brain is replaying associated sequences of neuronal activity in the hippocamus and associated regions. Since we remember only a fraction of our experiences, the brain must have a way to prioritize certain neural activity sequences for replay.

This thesis outlines why and how interactions between hippocampal region CA2 and CA3 may play a decisive role in determining which sequences are reactivated. These interactions stand out for two reasons: First, synaptic plasticity at CA3 to CA2 projections is strongly regulated by neuromodulatory substances, which are likely released during emotionally arousing situations. Second, in both directions, excitatory activity in one region suppresses activity in the other region. Connecting these findings, I argue that neuromodulatory release can lead to selective pairing of co-active neural activity sequences across the two regions. Paired sequences may support each others reactivation, while suppressing competing sequences.

As shown by neural network simulations, such a pairing mechanism may be particularly beneficial for neural activity sequences comprised of few cells. As the number of recruited cells varies depending on the type of experience, the proposed CA2-CA3 sequence interaction may explain why CA2 is involved in some but not all situations.

Adjudication committee:

  • Principal Investigator Thomas McHugh, Laboratory for Circuit and Behavioral Physiology, Japan
  • Professor Henning Sprekeler, Institute of Software Engineering and Theoretical Computer Science, Technishe Unversität Berlin, Germany
  • Associate Professor Sjannie Lefevre Nilsson, Department of Biosciences, University of Oslo, Norway


  • Professor Marianne Fyhn, Department of Biosciences, UiO
  • Associate Professor Arvind Kumar, KTH Royal Institute of Technology, Stockholm
  • Associate Professor Trygve Solstad, NTNU
  • Associate Professor Jill Leutgeb, University of California San Diego

Chair of defence

  • Professor and Head of Department Stephan Oepen, Department of Informatics, UiO

Candidate contact information: tristan.stoeber@posteo.net and linkedin

Contact information to Department: Anniken R. Birkelund

Publisert 8. juni 2021 10:45 - Sist endret 8. juni 2021 12:19