The inevitable inequality of cortical columns

Area of Science:

• Neuroscience
• Comparative Anatomy
• Developmental Biology

Background:

• Classical cortical organization concepts centered on 'columns' derived from sensory system physiology.
• Connectional studies and molecular markers revealed modular organization, necessitating a revision of the classical column concept.
• Cortical organization principles are rooted in systematic variations of laminar structure.

Purpose of the Study:

• To revise the classical concept of cortical columns based on new evidence.
• To explore the evolutionary and developmental basis of cortical organization.
• To propose a framework for understanding brain architecture and its relation to disease.

Main Methods:

• Physiologic studies in sensory systems.
• Connectional mapping.
• Analysis of molecular markers.
• Comparative analysis across phylogenetically diverse cortices (limbic to eulaminate).

Main Results:

• Cortical organization is characterized by systematic laminar variation, not solely columns.
• Modular organization with vertical connections (feedforward) appears evolutionarily newer than laminar-based feedback connections.
• Both modular and laminar communication patterns are established during development.
• The interplay between laminar and modular patterns creates diverse connectional arrangements.

Conclusions:

• The brain's architecture features a graded variation of cortices with intersecting laminar and modular communication patterns.
• This framework aids in understanding how brain areas are recruited for behavior.
• Altered patterns in this architecture are implicated in developmental diseases.