Figure 4.

Targeting manipulation to functionally defined ensembles of neurons. A, A field of view showing neurons coexpressing GCaMP6s (green) and C1V1–2A-mCherry (pink) in the C2 barrel of mouse somatosensory cortex. Scale bar, 50 μm. Symbols are as shown in B. B, Groups of individually identified neurons were selected for photostimulation based on their response to dorsoventral and rostrocaudal whisker stimulation. Five neurons that responded differently or not at all to sensory stimulation (gray shading) were simultaneously photostimulated (pink line; adapted from Packer et al., 2015). C, Two-photon fluorescence image of CA1 hippocampal neurons expressing GCaMP3 (green) and C1V1(E122T/E162T)-2A-EYFP (red) in an awake mouse. Inset, Images of unmixed GCaMP3 and enhanced yellow fluorescent protein (EYFP; top panels) and a pseudocolor merge (bottom; image sizes, 25 × 65 μm). Somatic GCaMP3 appeared to be annular from nuclear exclusion, whereas EYFP was diffuse. D, Schematic and experimental examples of place cell perturbation. A trained mouse ran along a 400 cm virtual reality track (top). A neuron with a place field in this environment (gray shaded region) was stimulated while the mouse ran through a different part of the track (red shaded region). Single-trial examples of place-cell activity (ΔF/F traces) are shown below for imaging-only (black; Ctrl) and stimulation (red; Stim) traversals. Place-specific stimulation mimicked the activity observed in the place field (adapted from Rickgauer et al., 2014).