Midbrain periaqueductal gray and vocal patterning in a teleost fish

Area of Science:

• Neuroscience
• Comparative Biology
• Bioacoustics

Background:

• The periaqueductal gray (PAG) in the midbrain is vital for motor control and complex behaviors, including vocalization in vertebrates.
• Previous research on the PAG's role in vocalization temporal patterning has been limited to mammals.
• Midshipman fish utilize vocalizations for social signaling, with midbrain involvement suggested in call production.

Purpose of the Study:

• To investigate the role of the midshipman fish PAG in the temporal patterning of vocalization.
• To compare the functional and structural organization of the teleost PAG to that of mammals.

Main Methods:

• Extracellular single-unit recordings of PAG neuronal activity during forebrain-evoked fictive vocalizations.
• Lidocaine inactivation experiments to assess the necessity of the PAG for vocalization.
• Tract-tracing studies to map PAG connectivity to vocal motor centers.

Main Results:

• PAG neuronal activity correlated with fictive call initiation, with a subset predicting vocal output duration.
• Vocalization duration is a key feature distinguishing social call types.
• PAG inactivation demonstrated its necessity for fictive vocalization; tract-tracing revealed mammalian-like connectivity.

Conclusions:

• The midbrain PAG in teleosts plays an essential role in vocalization.
• The functional and structural organization of the teleost PAG is convergent with that of mammals.
• Specific PAG neurons may directly regulate vocalization duration, a critical element in social communication.