Decoding order memory representations using high-frequency activity in the human neocortex

Remembering the order of events is a fundamental component of human episodic memory. We investigated neural representations of temporal order using intracranial EEG recordings from 43 participants performing a serial order reconstruction with extensive sampling of frontal and temporal regions. Prior non-human primate neurophysiology and human lesion studies implicate ventral prefrontal cortex in order processing. Building on this work, we examined which cortical regions and burst-based neural dynamics carry reliable serial-position information. We trained classifiers on duration-weighted burst-event time series spanning ripple-range, beta, and gamma frequencies. Burst dynamics in the left pars orbitalis and right frontal pole supported reliable above-chance decoding of serial position across participants. In contrast, hippocampal and parietal regions did not exhibit reliable cross-participant decoding using the same feature set. To situate these findings within broader episodic memory networks, we quantified functional connectivity using centrality metrics and Granger Causality analyses. Pars orbitalis and frontal pole exhibited higher network centrality, consistent with a central role in organizing temporal-order representations, and Granger-based directed effects were interpreted as suggestive of directional influence. By linking serial-position information to region-specific burst-event dynamics, these findings extend current accounts of temporal context coding, including models based on time-sensitive neuronal populations and representational drift. This framework provides a feature- and circuit-level characterization of temporal-order representations in humans and may guide future neuromodulation approaches.