Basic neuroscienceStrategies for optical control and simultaneous electrical readout of extended cortical circuits

- We combined optogenetics with μECoG in mouse, rat, and macaque monkey.
- Optical stimulation was targeted to inhibitory as well as to excitatory neurons.
- Photovoltaic artifacts were clearly distinguishable from evoked neural activity.
- Artifacts could be minimized using transparent indium tin oxide electrodes.
- We discuss a broad palette of applications for μECoG combined with optogenetics.

BackgroundTo dissect the intricate workings of neural circuits, it is essential to gain precise control over subsets of neurons while retaining the ability to monitor larger-scale circuit dynamics. This requires the ability to both evoke and record neural activity simultaneously with high spatial and temporal resolution.New MethodIn this paper we present approaches that address this need by combining micro-electrocorticography (μECoG) with optogenetics in ways that avoid photovoltaic artifacts.ResultsWe demonstrate that variations of this approach are broadly applicable across three commonly studied mammalian species - mouse, rat, and macaque monkey - and that the recorded μECoG signal shows complex spectral and spatio-temporal patterns in response to optical stimulation.Comparison with existing methodsWhile optogenetics provides the ability to excite or inhibit neural subpopulations in a targeted fashion, large-scale recording of resulting neural activity remains challenging. Recent advances in optical physiology, such as genetically encoded Ca2+ indicators, are promising but currently do not allow simultaneous recordings from extended cortical areas due to limitations in optical imaging hardware.ConclusionsWe demonstrate techniques for the large-scale simultaneous interrogation of cortical circuits in three commonly used mammalian species.