Vocal-acoustic pathways in a teleost fish

Area of Science:

• Neuroscience
• Bioacoustics
• Fish Biology

Background:

• Teleost fish use vocalizations for communication via sonic muscle contractions.
• Understanding the neural basis of vocalization is crucial for bioacoustics research.

Purpose of the Study:

• To identify and characterize the complete vocal motor circuit in the brainstem of midshipman fish.
• To investigate the neural pathways linking vocal and acoustic processing centers.

Main Methods:

• Biocytin tracing was applied to the sonic nerve to label vocal motor neurons.
• Ultrastructural analysis examined synaptic connections between neurons.
• Biocytin tracing was also applied to the saccular nerve to trace auditory pathways.
• Electrical stimulation in the brainstem was used to elicit vocalizations.

Main Results:

• Eight distinct neuronal groups forming the vocal motor circuit were identified in the midshipman brainstem.
• A serial, transneuronal transport suggested at least three interconnected neuronal groups.
• A novel ventral medullary nucleus was discovered, linking caudal and rostral brainstem vocal centers.
• A medial brainstem column, including the octaval efferent nucleus, was identified as part of a vocal-acoustic network.
• This network overlaps with brain regions where electrical stimulation evokes vocalizations.

Conclusions:

• The identified vocal-acoustic network in the brainstem controls vocalization activation and likely mediates acoustically elicited vocalizations.
• This network provides a corollary discharge to acoustic nuclei, suggesting shared vocal-acoustic processing mechanisms across vertebrates.
• Direct neural links between vocal and acoustic brain regions are a conserved trait in vertebrates.