Comparative organization of the claustrum: what does structure tell us about function?

Area of Science:

• Neuroscience
• Comparative Anatomy
• Evolutionary Biology

Background:

• The claustrum is a subcortical nucleus found in all placental mammals, primarily connecting with the cerebral cortex.
• Its connectivity suggests a role in amplifying or facilitating cortical information processing.
• Cortical complexity varies greatly across species, raising questions about the claustrum's evolution and function.

Purpose of the Study:

• To investigate the organization of the claustrum in animals with large brains, specifically great apes and cetaceans.
• To explore how evolutionary changes in the cerebral cortex might influence claustrum structure and function.
• To evaluate proposed theories of claustrum function, such as global roles in perception or consciousness.

Main Methods:

• Survey of claustrum organization in selected species, including primates (monkeys, gorillas) and cetaceans.
• Anatomical analysis focusing on the continuity and structure of the claustrum.
• Comparison of claustrum organization with cerebral cortex complexity across species.

Main Results:

• The claustrum is not always a continuous structure.
• Isolated cell islands within the claustrum are minimal in monkeys and gorillas but numerous in cetaceans.
• These discontinuities challenge theories requiring extensive intraclaustral integration for global functions.

Conclusions:

• The structural discontinuities in the claustrum, particularly in cetaceans, argue against proposed mechanisms for intraclaustral information processing.
• The findings support the interpretation that functional subdivisions of the claustrum are linked to specific cortical partners.
• Claustrum function is likely specialized, adapting to the specific cortical architecture of different species.