Dynamics of Spontaneous Activity in Neocortical Slices

• Published in: Neuron (Cambridge, Mass.) Mass.), 2001-12, Vol.32 (5), p.883-898
• Main Authors: Mao, Bu-Qing, Hamzei-Sichani, Farid, Aronov, Dmitriy, Froemke, Robert C, Yuste, Rafael
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Excitatory Amino Acid Antagonists - pharmacology; In Vitro Techniques; Membrane Potentials - drug effects; Membrane Potentials - physiology; Mice; Mice, Inbred C57BL; Neocortex - drug effects; Neocortex - physiology; Neurons - drug effects; Neurons - physiology; Pyramidal Cells - drug effects; Pyramidal Cells - physiology; Visual Cortex - drug effects; Visual Cortex - physiology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/S0896-6273(01)00518-9

The flow of activity in the cortical microcircuitry is poorly understood. We use calcium imaging to reconstruct, with millisecond and single-cell resolution, the spontaneous activity of populations of neurons in unstimulated slices from mouse visual cortex. We find spontaneous activity correlated among networks of layer 5 pyramidal cells. Synchronous ensembles occupy overlapping territories, often share neurons, and are repeatedly activated. Sets of neurons are also sequentially activated numerous times. Network synchronization and sequential correlations are blocked by glutamatergic antagonists, even though spontaneous firing persists in many “autonomously active” neurons. This autonomous activity is periodic and depends on hyperpolarization-activated cationic (H) and persistent sodium (Na p) currents. We conclude that the isolated neocortical microcircuit generates spontaneous activity, mediated by a combination of intrinsic and circuit mechanisms, and that this activity can be temporally precise.