Neuronal domains in developing neocortex: mechanisms of coactivation

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Computational Neuroscience

Background:

• The mammalian neocortex features columnar circuits.
• Spontaneous neural activity is hypothesized to guide neocortical development.
• Previous studies identified spontaneously coactive neuronal domains in developing rat neocortex using Ca2+ imaging.

Purpose of the Study:

• To investigate the cellular mechanisms underlying the coactivation of neuronal domains in the developing neocortex.
• To determine the role of neuronal coupling in the formation of these functional circuits.

Main Methods:

• Calcium (Ca2+) imaging of neuronal activity in developing rat neocortex slices.
• Utilized tetrodotoxin to assess the role of action potentials.
• Employed gap junction blockers (halothane, octanol) to investigate intercellular communication.
• Performed simultaneous intracellular and optical recordings from dye-coupled neurons.

Main Results:

• Neuronal activation within domains initiates centrally and propagates outwards at ~100 microns/s.
• Domains persist in the presence of tetrodotoxin, indicating a non-action potential-dependent mechanism.
• Gap junction blockers abolished domain formation, implicating electrical coupling.
• Functional coupling between developing neocortical neurons was confirmed via simultaneous recordings.

Conclusions:

• Neuronal domains arise from the spontaneous excitation of trigger neurons.
• Gap junctions are critical for the spread of excitation and coactivation within these domains.
• This mechanism is essential for the development of columnar circuits in the mammalian neocortex.