Visual Input Modulates Audiomotor Function via Hypothalamic Dopaminergic Neurons through a Cooperative Mechanism

Visual cues often modulate auditory signal processing, leading to improved sound detection. However, the synaptic and circuit mechanism underlying this cross-modal modulation remains poorly understood. Using larval zebrafish, we first established a cross-modal behavioral paradigm in which a preceding flash enhances sound-evoked escape behavior, which is known to be executed through auditory afferents (VIIIth nerves) and command-like neurons (Mauthner cells). In vivo recording revealed that the visual enhancement of auditory escape is achieved by increasing sound-evoked Mauthner cell responses. This increase in Mauthner cell responses is accounted for by the increase in the signal-to-noise ratio of sound-evoked VIIIth nerve spiking and efficacy of VIIIth nerve-Mauthner cell synapses. Furthermore, the visual enhancement of Mauthner cell response and escape behavior requires light-responsive dopaminergic neurons in the caudal hypothalamus and D1 dopamine receptor activation. Our findings illustrate a cooperative neural mechanism for visual modulation of audiomotor processing that involves dopaminergic neuromodulation. ► Visual input improves audiomotor behavior via enhancing command neuron responses ► The modulation is achieved by decreasing neural noise and increasing synaptic gain ► Hypothalamic dopaminergic neurons mediate this cross-modal modulation ► D1 dopamine receptor activation is required for this cross-modal modulation Mu et al. provide a mechanism for visual cross-modal modulation of zebrafish audiomotor behavior, finding that hypothalamic dopaminergic neurons modulate both the signal-to-noise ratio of auditory nerves and transmission efficacy of downstream synapses.