Phase Precession Relative to Turning Angle in Theta-Modulated Head Direction Cells.

Grid and place cells typically fire at progressively earlier phases within each cycle of the theta rhythm as rodents run across their firing fields, a phenomenon known as theta phase precession. Here, we report theta phase precession relative to turning angle in theta-modulated head direction cells within the anteroventral thalamic nucleus (AVN). As rodents turn their heads, these cells fire at progressively earlier phases as head direction sweeps over their preferred tuning direction. The degree of phase precession increases with angular head velocity. Moreover, phase precession is more pronounced in those theta-modulated head direction cells that exhibit theta skipping, with a stronger theta-skipping effect correlating with a higher degree of phase precession. These findings are consistent with a ring attractor model that integrates external theta input with internal firing rate adaptation-a phenomenon we identified in head direction cells within AVN. Our results broaden the range of information known to be subject to neural phase coding and enrich our understanding of the neural dynamics supporting spatial orientation and navigation.