What is the dynamical regime of cerebral cortex?

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Cortical neurons exhibit a balance between excitatory and inhibitory inputs across various conditions.
• Understanding the precise nature of this balance is key to deciphering cortical dynamics.

Purpose of the Study:

• To review evidence on the nature of excitation-inhibition balance in cortical neurons.
• To explore the implications of different balance regimes (loose vs. tight) for neural function.

Main Methods:

• Review of theoretical models and experimental evidence.
• Analysis of the consequences of loose versus tight balance for neural population activity.

Main Results:

• Evidence supports a "loose" balance, where net input is comparable to canceling factors.
• Tight balance, where net input is minimal, is less supported by current data.
• Loose balance, unlike tight balance, can explain nonlinear population behaviors, correlated variability, and its modulation by stimuli.

Conclusions:

• The "loose" balance of excitation and inhibition is a critical feature of cortical processing.
• This regime is essential for generating complex neural population dynamics observed in sensory cortices.