Do crocodiles have a zona incerta?

Area of Science:

• Neuroscience
• Comparative Anatomy
• Evolutionary Biology

Background:

• The mammalian zona incerta is implicated in various behaviors like arousal and locomotion.
• Its precise identification remains challenging due to indistinct cellular morphology.
• The entopeduncular nucleus in crocodilians is adjacent to the thalamic reticular nucleus.

Purpose of the Study:

• To investigate the cellular morphology of the entopeduncular nucleus (ep) in Alligator mississippiensis.
• To determine if the ep is a distinct neuronal aggregate compared to the thalamic reticular nucleus.
• To explore the potential homology between the crocodilian ep and the mammalian zona incerta.

Main Methods:

• Golgi staining methodology was employed to visualize neuronal morphology.
• Comparative analysis of neuronal morphology and soma size between the ep and thalamic reticular nucleus.

Main Results:

• Neurons in the entopeduncular nucleus exhibited distinct morphology and soma size compared to the thalamic reticular nucleus.
• These differences confirm the ep as a separate neuronal population.
• The anatomical relationship of the ep mirrors that of the zona incerta in mammals.

Conclusions:

• The entopeduncular nucleus in crocodilians is proposed as the structural and potentially functional counterpart of the mammalian zona incerta.
• This finding offers insights into the evolution of brain structures across vertebrates.
• Comparative neuroanatomy aids in understanding the homologous brain regions.