title: Dissection of cortical microcircuits by single-neuron stimulation in vivo.
abstract: BACKGROUND
  A fundamental process underlying all brain functions is the propagation of spiking activity in networks of excitatory and inhibitory neurons. In the neocortex, although functional connections between pairs of neurons have been studied extensively in brain slices, they remain poorly characterized in vivo, where the high background activity, global brain states, and neuromodulation can powerfully influence synaptic transmission. To understand how spikes are transmitted in cortical circuits in vivo, we used two-photon calcium imaging to monitor ensemble activity and targeted patching to stimulate a single neuron in mouse visual cortex.
  
  
  RESULTS
  Burst spiking of a single pyramidal neuron can drive spiking activity in both excitatory and inhibitory neurons within a ∼100 μm radius. For inhibitory neurons, ∼30% of the somatostatin interneurons fire reliably in response to a presynaptic burst of ≥5 spikes. In contrast, parvalbumin interneurons showed no detectable responses to single-neuron stimulation, but their spiking is highly correlated with the local network activity.
  
  
  CONCLUSIONS
  Our results demonstrate the feasibility of mapping functional connectivity at cellular resolution in vivo and reveal distinct operations of two major inhibitory circuits, one detecting single-neuron spike bursts and the other reflecting distributed network activity.
authors: Division of Neurobiology, Department of Molecular Cell Biology, Helen Wills Neuroscience Institute, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
authors: Alex C
authors: AC
authors: Kwan
authors: Yang
authors: Y
authors: Dan
mesh_terms: D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling; D004558:Electric Stimulation; D007395:Interneurons / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009415:Nerve Net; D017966:Pyramidal Cells / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*