Characterizing responses to optogenetic stimulation

Neuronal dynamics play a central role in the operation of neural circuits that generate flexible behaviors. To test whether neuronal dynamics play a mechanistic role in behavior, causal manipulations are needed to selectively control patterns of neural activity. Optogenetics allows precise spatial and temporal control of neural activity patterns. To understand how neuronal dynamics can be controlled by optogenetic stimulation, we measured neural activity during Poisson stimulation, parametrically varying the pulse rate and pulse width. The dynamics of driven neural activity varied with pulse width, but not pulse rate. At high gamma frequencies, the driven activity was less than predicted by a simple linear model. To test possible mechanisms of this high frequency attenuation, we built a stochastic model of the LFP and a spiking neural network model of leaky integrate-and-fire neurons. The model results suggest that the attenuation may be due to network, rather than cellular, mechanisms.