A minimal dynamical model linking early embryonic asymmetry to hemispheric lateralization

Area of Science:

• Neuroscience
• Developmental Biology
• Dynamical Systems Theory

Background:

• Hemispheric asymmetry is fundamental to human brain function.
• The developmental trajectory from initial asymmetries to stable specialization is not fully understood.
• Existing models lack a mechanistic link between early molecular asymmetries and persistent hemispheric differences.

Purpose of the Study:

• To develop a minimal dynamical model explaining the amplification and stabilization of weak early left-right brain biases.
• To elucidate the conditions under which initial asymmetries lead to robust hemispheric specialization.
• To provide a dynamical bridge connecting embryonic asymmetry to later brain specialization.

Main Methods:

• Modeling each hemisphere with a continuous maturation variable.
• Representing interhemispheric interactions via nonlinear inhibitory coupling.
• Employing analytical stability analysis and numerical simulations.

Main Results:

• Hemispheric differentiation arises when the symmetric equilibrium becomes unstable.
• Stable hemispheric asymmetry emerges robustly once interhemispheric coupling surpasses a critical threshold.
• Initial weak biases influence the selection of asymmetric states rather than creating asymmetry itself.

Conclusions:

• The model provides a dynamical explanation for the emergence of stable hemispheric specialization from small initial asymmetries.
• Interhemispheric coupling strength is a critical factor in establishing brain asymmetry.
• Developmental processes, rather than solely explicit programming, drive hemispheric differentiation.