Hearing hippocampal ripples: Event-faithful, reproducible sonification of multineuronal spiking with hierarchy-guided orchestration

Abstract

Among the human senses, hearing is distinguished by its high frequency resolution and sensitivity to spatiotemporal patterns. Accordingly, sonification—the rendering of neural activity as sound for direct perception—has a long history in neuroscience. Although sonification can facilitate exploration of the temporal structure of population activity, dense spike trains are often difficult to track by ear. Here, I present HERO (Hierarchy-guided Event-faithful Reproducible Orchestration), a pipeline that assigns stable musical voices to recorded units while preserving spike onsets in a MIDI event representation. Each spike within a selected interval produces a single Note On message whose timing is determined by a global temporal dilation followed by bounded clock rounding. A separate analysis pathway uses multiscale correlations and block-bootstrap co-association to organize units into a hierarchy. This hierarchy guides instrument assignment, whereas each unit is assigned a fixed key, tuning offset, velocity, and stereo position. A derived SoundFont stores tuning and pan parameters independently for units that share a MIDI channel. Rate-dependent velocity and channel-volume settings are intended to reduce the dominance of frequently firing units. An online audio example illustrating the audibility of individual activity during large-scale firing is available at: https://www.youtube.com/watch?v=zOYGXcp727A. HERO provides a reproducible auditory representation of population activity that may help direct attention toward features warranting subsequent quantitative analysis.