The distinctive central utricular projections in the herring

Area of Science:

• Neuroscience
• Ichthyology
• Inner ear anatomy

Background:

• The utriculus in clupeid fishes has three distinct maculae.
• Each macula is innervated by a separate nerve.
• Understanding the neural pathways is crucial for auditory processing.

Purpose of the Study:

• To trace the neural projections of the utriculus maculae in herring.
• To identify the central targets of these vestibular nerves.
• To investigate synaptic connections, including those with the Mauthner cell.

Main Methods:

• Horseradish peroxidase (HRP) labeling of the three macular nerves in herring.
• Anatomical tracing of nerve projections within the brainstem and cerebellum.
• Microscopic examination of synaptic targets.

Main Results:

• All three macular nerves project to the ipsilateral cerebellum and octavus area.
• Projections are bilateral to the lateralis zone of the brainstem.
• Anterior macular nerve targets the dorsal octavus area and anterior octavus nucleus.
• Middle and posterior macular nerves target the ventral octavus area, reticular formation, and Mauthner cell.

Conclusions:

• The utriculus of clupeid fishes exhibits complex central projections.
• Distinct topographical organization exists for the anterior versus middle/posterior macular nerves.
• The Mauthner cell receives direct input from the middle macular nerve, suggesting a role in startle responses.