A Brainstem reticulotegmental neural ensemble drives acoustic startle reflexes

The reticulotegmental nucleus (RtTg) has long been recognized as a crucial component of brainstem reticular formation (RF). However, the function of RtTg and its related circuits remain elusive. Here, we report a role of the RtTg in startle reflex, a highly conserved innate defensive behaviour. Optogenetic activation of RtTg neurons evokes robust startle responses in mice. The glutamatergic neurons in the RtTg are significantly activated during acoustic startle reflexes (ASR). Chemogenetic inhibition of the RtTg glutamatergic neurons decreases the ASR amplitudes. Viral tracing reveals an ASR neural circuit that the cochlear nucleus carrying auditory information sends direct excitatory innervations to the RtTg glutamatergic neurons, which in turn project to spinal motor neurons. Together, our findings describe a functional role of RtTg and its related neural circuit in startle reflexes, and demonstrate how the RF connects auditory system with motor functions. The function of brainstem reticulotegmental nucleus (RtTg) and its related circuits are not fully understood. Here, the authors report a cochlear nucleus-RtTg-spinal motor neuron circuit that specifically mediates acoustic startle reflexes.

Automated summary

The function of the brainstem reticulotegmental nucleus (RtTg) and its related circuits is not fully understood. This study demonstrates that a cochlear nucleus-RtTg-spinal motor neuron circuit mediates acoustic startle reflexes.