Auditory regulation of hippocampal locomotion circuits by a non-canonical reticulo-limbic pathway

The ability to rapidly detect and respond to unexpected auditory stimuli is critical for adaptive behavior, especially during locomotion. Since movement suppresses auditory cortical activity, it remains unclear how salient auditory information influences locomotor circuits. In this work, using in vivo calcium imaging, electrophysiology, chemo- and optogenetics, we investigate the path that relays loud broadband sounds to the dorsal hippocampus (dHPC) and modulates theta oscillations. We demonstrate that noise accelerates theta frequency and decreases its power, effects mediated by entorhinal cortex (EC) and medial septum (MS) inputs while independent of the primary auditory cortex. Activation of dorsal cochlear nucleus (DCN) neurons projecting to the pontine reticular nucleus (PRN) mimics noise-driven hippocampal responses, supporting a brainstem-limbic auditory processing route. Furthermore, noise selectively modulates CA1 pyramidal neuron and interneuron activity, reflecting diverse circuit dynamics. Finally, loud broadband noise stimulus increased theta coherence between the dHPC and the medial prefrontal cortex (mPFC), enhancing interregional synchronization. These results highlight the mechanisms in which the DCN filters behaviorally relevant sounds promoting acoustic motor integration in the hippocampus during locomotion, without direct influence of the auditory cortex.