Parallel executive pallio-motor loops in the pigeon brain

Area of Science:

• Neuroscience
• Comparative Cognition
• Avian Brain Research

Background:

• The nidopallium caudolaterale (NCL) is a key component of the avian pallial cognitive network, analogous to the mammalian prefrontal cortex (PFC).
• The NCL is crucial for executive functions like working memory and decision-making, situated between sensory and motor systems.
• It sends descending premotor projections to the intermediate arcopallium (AI) and medial striatum (MSt).

Purpose of the Study:

• To investigate the organization of descending NCL projections to the AI and MSt.
• To determine if NCL neurons projecting to AI and MSt constitute a single or distinct populations.
• To analyze the topographic organization and morphology of these projections and their relation to other descending pathways.

Main Methods:

• Retrograde and anterograde viral tracing experiments were employed.
• Neuronal morphology was analyzed in relation to projection targets.
• Topographic mapping of projections to AI and MSt was performed.

Main Results:

• Two distinct neuronal populations project from the NCL to the AI and MSt, each with unique morphologies.
• A weak topographic projection was observed in the striatum, while a strong topographic projection with distinct sensory termination fields was found in the AI.
• The study characterized the relationship between NCL descending pathways and those from the hyperpallium apicale.

Conclusions:

• The findings support a model of parallel pallio-motor loops carrying distinct sensory information to subpallial systems.
• The distinct projection patterns suggest specialized roles for NCL outputs.
• This research offers insights into the evolution of avian motor systems, potentially including the song system.