Schedule of Events | Symposia

Spontaneous emergence of slow ramping prior to decision states in a brain-constrained model of fronto-temporal cortical areas

Poster Session B - Sunday, March 30, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Nick Griffin¹ (nickdgriffin@gmail.com), Aaron Schurger^2,3, Max Garagnani^1,4; ¹Goldsmiths, University of London, ²Crean College of Health and Behavioral Sciences, Chapman University, ³Institute for Interdisciplinary Brain and Behavioral Sciences, Chapman University, ⁴Freie Universität Berlin

Currently an ongoing debate exists over two prevailing interpretations of the pre-movement ramping neural signal known as the readiness potential (RP): the “early-” and “late-decision” accounts. The former holds that the RP reflects planning and preparation for movement – a decision outcome. The latter holds that it is pre-decisional, emerging because a commitment is made only after activity reaches a threshold. We used a fully brain-constrained neural-network model of six human frontotemporal areas to investigate this issue and the cortical mechanisms underlying the emergence of the RP and spontaneous decisions to act. The network was trained (using neurobiologically realistic learning mechanisms) to induce formation of distributed perception-action circuits; the spontaneous ignition of such cell assembly (CA) circuits (induced by accumulation of noise-driven activity) was taken as the model correlate of a spontaneous decision to act. Specifically, the time between trial start and first spontaneous CA ignition (simulated wait-time, WT) was recorded, along with total firing activity within the six simulated areas. We found that the model successfully replicated both behavioural and brain indexes of self-paced voluntary movements as documented in human participants: the simulated WT distribution was statistically indistinguishable from the experimental one, and the simulated RP accurately reproduced corresponding neuroimaging data. Intriguingly, individual trials also revealed sub-threshold fluctuations in CA activity insufficient by themselves for full ignition. The present brain-constrained computational architecture offers a neuro-mechanistic explanation for the emergence of endogenous decisions to act in the human brain, providing further support for a late, stochastic account of the RP.

Topic Area: THINKING: Decision making