Network Asynchrony Underlying Increased Broadband Gamma Power.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Synchronous activity of parvalbumin (PV) interneurons generates cortical gamma rhythms.
• Paradoxically, PV inhibition deficiency is linked to increased broadband gamma power.
• Elevated broadband gamma is observed in schizophrenia and after NMDAR antagonist use.

Purpose of the Study:

• To investigate the mechanisms underlying increased broadband gamma power in deficient PV inhibition.
• To determine if enhanced broadband gamma power represents a true rhythm or asynchronous activity.
• To compare network desynchronization and gamma power increases caused by genetic PV deficiency versus ketamine.

Main Methods:

• Utilized male and female mice with NMDAR activity specifically lacking in PV neurons.
• Recorded local field potentials and neuronal firing activity.
• Administered local S(+)-ketamine to control mice to induce network desynchronization.

Main Results:

• Reduced synchronicity and spike time precision in PV-deficient mice correlated with increased prefrontal broadband gamma power.
• Increased firing rates led to spectral leakage, contributing to broadband gamma power increases.
• Ketamine induced network desynchronization and enhanced broadband gamma power, but through distinct mechanisms compared to genetic PV deficiency.

Conclusions:

• Enhanced broadband gamma power can result from asynchronous neuronal activity, not necessarily a genuine rhythm.
• Long-term deficiency in PV inhibition contributes to increased broadband gamma power via desynchronized firing.
• Distinct mechanisms underlie ketamine-induced versus genetically induced increases in broadband gamma power.