The Internal Dynamics of Decisions: From rats and primates to AI
Which one is the brain?
Schematic phase portraits, drawn in neutral until you answer. What is measured, and what sets how far each one wanders, is the share of the next state that arrives from outside rather than from the population itself.
The finding, in brief
Do two systems that behave alike reach a decision the same way? Behavior can’t say: a feedforward network can copy any recurrent brain’s behavior. Six networks wired two ways, trained to one score, still differ in their dynamics.
How. A subspace state-space demix splits each next state into input drive and what the population generates itself, validated on synthetic systems with known answers before any real data. The six architectures were matched on size as well as score, and none of the 144 networks was dropped, so the signature tracks architecture, not task; by architecture, 3 of 3 on the delayed task. The estimator is N4SID (Van Overschee & De Moor 1994) and the input-aware demix is InputDSA (Huang et al. 2026), on Ostrow et al. 2023.
Bio
Nathan M. Thornhill is a complexity science researcher in Fort Wayne, Indiana, working in information theory and pattern persistence. He is self-taught, and his earlier career was in healthcare: nursing assistant, then nursing-home administration, then ICU admissions.
What he studies is whether a system holds together and how you would measure that: pattern persistence in simple discrete systems, sleep stages from EEG, task success read off a model’s internal geometry. The analysis plans get written down and frozen first, and the measures that fail are reported next to the ones that work. The results so far are out as preprints and one book. He is a student member of the Association for the Scientific Study of Consciousness (ASSC).
When he isn’t researching he’s playing guitar, gardening, or with his wife and daughter.
How this work gets madeWho pays for it
No university support and no grant funding. A web design business pays for the research, ICSAC publishes it, and a tool the research needed has since turned into a product that brings in money of its own.

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Data and pre-registrations
Every recording analyzed here is public and was collected by other laboratories. Nothing on this poster required new animal work.
- Luo TZ et al. 2025. Data from: Transitions in dynamical regime and neural mode underlie perceptual decision-making. Dryad. doi:10.5061/dryad.sj3tx96dm
- Neupane S, Fiete I, Jazayeri M. 2024. Data from: Mental navigation in the primate entorhinal cortex. DANDI Archive, dandiset 000897. dandiarchive.org/dandiset/000897
- Schiereck SS et al. 2025. Data from: The orbitofrontal cortex updates beliefs for state inference. Zenodo. doi:10.5281/zenodo.16997337
Pre-registrations. Both analysis plans were written down and frozen in advance, the six-network control before a single dynamical measure was computed and the token-level test before any of its results, and both accompany the October 2026 preprint as supplementary material: doi.org/10.20944/preprints202608.1095.v2. The measure that separates the six networks and the one that does not were both named in advance, and both are reported.
References
The sources the poster draws on. The preprint carries the full text and both pre-registrations.
Show allHide 20 references
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- Luo TZ, Kim TD, Gupta D, Bondy AG, Kopec CD, Elliott VA, DePasquale B, Brody CD. 2025. Transitions in dynamical regime and neural mode during perceptual decisions. Nature 646(8087):1156–1166. doi:10.1038/s41586-025-09528-4
- [dataset] Luo TZ et al. 2025. Data from: Transitions in dynamical regime and neural mode underlie perceptual decision-making. Dryad. doi:10.5061/dryad.sj3tx96dm
- Mante V, Sussillo D, Shenoy KV, Newsome WT. 2013. Context-dependent computation by recurrent dynamics in prefrontal cortex. Nature 503(7474):78–84. doi:10.1038/nature12742
- Mashour GA, Roelfsema P, Changeux J-P, Dehaene S. 2020. Conscious processing and the global neuronal workspace hypothesis. Neuron 105(5):776–798. doi:10.1016/j.neuron.2020.01.026
- Neupane S, Fiete I, Jazayeri M. 2024. Mental navigation in the primate entorhinal cortex. Nature 630(8017):704–711. doi:10.1038/s41586-024-07557-z
- [dataset] Neupane S, Fiete I, Jazayeri M. 2024. Data from: Mental navigation in the primate entorhinal cortex. DANDI Archive, dandiset 000897. dandiarchive.org/dandiset/000897
- Ostrow M, Eisen A, Kozachkov L, Fiete I. 2023. Beyond geometry: comparing the temporal structure of computation in neural circuits with dynamical similarity analysis. Advances in Neural Information Processing Systems 36. arXiv:2306.10168
- Schiereck SS, Pérez-Rivera DT, Mah A, DeMaegd ML, Hocker D, Ward RM, Savin C, Constantinople CM. 2026. The orbitofrontal cortex updates beliefs for state inference. Neuron 114(3):507–520.e8. doi:10.1016/j.neuron.2025.10.024
- [dataset] Schiereck SS et al. 2025. Data from: The orbitofrontal cortex updates beliefs for state inference. Zenodo. doi:10.5281/zenodo.16997337
- Soldado-Magraner J, Mante V, Sahani M. 2024. Inferring context-dependent computations through linear approximations of prefrontal cortex dynamics. Science Advances 10(51):eadl4743. doi:10.1126/sciadv.adl4743
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- Van Overschee P, De Moor B. 1994. N4SID: subspace algorithms for the identification of combined deterministic–stochastic systems. Automatica 30(1):75–93. doi:10.1016/0005-1098(94)90230-5