Article Figures & Data
Figures
- Figure 1.
Opsin expression. A, eYFP expresion 3 weeks after virus injection in somatosensory cortex of a P40 mouse. Scale bar, 500 μm. Location of cortical layers and white matter (WM) is indicated. B, Overlapping eYFP and parvalbumin expression demonstrates correct targeting of the viral construct to PV cells. Scale bar, 100 μm. C, Direct eNpHR3.0 current in a PV cell. The yellow bar indicates illumination. D, eNpHR3.0 activation decreases spike output in response to depolarizing current injections (yellow shading, yellow light is turned on). E, Direct ChETA current in a PV cell. The blue bar indicates illumination. F, Current-clamp response showing that PV cells can be driven by ChETA at 100 Hz (5 ms pulse width). The blue bar indicates illumination. G, Stimulation grid surrounding a recorded PV cell (yellow star represents soma location). Red grid points indicate where action potentials were generated in the recorded cell. H, Example traces from a PYR recording showing success and failure in evoking an IPSC in successive trials, demonstrating the all-or-nothing nature of the evoked synaptic response.
- Figure 2.
PV-to-PYR connectivity maps. A, Representative grid for recording focal optogenetically evoked IPSCs in a PYR (yellow triangle indicates soma location). Location of cortical layers and white matter is indicated. B, Example traces from the grid in A, at indicated locations. The blue bar indicates the time of stimulus. C, All traces with IPSC responses from the cell in A and B. The blue horizontal line indicates stimulus time, the blue vertical line indicates 10 ms poststimulus. Note that nearly all IPSCs have a latency of <10 ms. D, Peristimulus time histogram for IPSCs in all recorded PYRs. E, IPSC map from example cell. F, Averaged IPSC map from all recorded PYRs (n = 6).
- Figure 3.
LSPS combined with eNphR-mediated PV cell silencing. A, Diagram depicting setup for LSPS and full-field yellow illumination. The yellow light is reflected by short-pass dichroic filter that transmits UV light. B, Cell-attached recording of an opsin-expressing PV cell that is activated by LSPS only in the absence of eNphR-activating yellow illumination. C, Representative grid for recording LSPS-evoked IPSCs (outward PSCs) in a PYR (orange triangle indicates soma location). Location of cortical layers and white matter is indicated. D, Example traces from the grid in C, at indicated locations. Black traces are without yellow illumination; orange traces are with yellow illumination. Inward responses, largest in perisomatic regions, mainly reflect the direct activation of postsynaptic ionotropic GluRs. The yellow bar indicates illumination. The purple line indicates stimulus onset; vertical lines indicate 10 and 50 ms, the detection times for short- and regular-latency IPSCs. E, Short-latency IPSC maps for the example PYR without (left) and with (right) yellow illumination to silence PV cells. F, Same as E, but for regular-latency ISPCs.
- Figure 4.
IPSC maps obtained via LSPS with and without PV cell silencing. A, Summary maps for short-latency IPSC maps in PYRs (triangle indicates soma location) recorded without (left) and with (right) yellow illumination. N = 6. B, Cumulative IPSC amplitudes (in pA) relative to the horizontal distance from soma without (black) and with (yellow) yellow illumination. C, Cumulative IPSC amplitude per hotspot for all six recorded maps, showing a significant decrease with PV cell silencing. D–F, Same as A–C, but for regular-latency IPSCs. No significant decrease in cumulative amplitude/hotspot with PV cell silencing (F). * indicates statistical significance at p < 0.05. n.s. = non significant.
- Figure 5.
PV cell silencing affects EPSCs in PYRs. A, PSC in a PYR cell in response to electrical stimulation without (black trace) and with (orange trace) PV cell silencing. Note the absence of an IPSC with yellow illumination. B, Response to trains of five electrical stimuli (50 Hz) in a PYR in current clamp without, with, and again without yellow illumination (top to bottom). Note two successes vs. one success of five stimuli with PV cell silencing. C, Quantification of PYR disinhibition due to PV cell silencing, measured as the fraction of successes (action potentials) for five-pulse stimuli, as shown in B.
- Figure 6.
PV cell silencing unmasks excitatory connectivity. A, Representative grid for recording LSPS-evoked EPSCs in a PYR (yellow triangle indicates soma location). Location of cortical layers and white matter is indicated. B, Example traces from the grid in A, at indicated locations. Black traces are without yellow illumination, and red traces are with yellow illumination. Yellow bar indicates yellow illumination; purple line indicates UV stimulus; black line indicates 25 ms post-UV stimulus (end of EPSC detection window). C, EPSC maps for the example PYR without (left) and with (right) yellow illumination to silence PV cells. D, Peristimulus time histogram for EPSCs recorded in 11 pyramidal cells. All detected EPSCs (spontaneous and LSPS evoked) during all sweeps from all 11 cells were sorted into 1 ms bins relative to LSPS stimulus and normalized to the average EPSC rate in controls (100 ms preceding LSPS stimulus). Black, Control (no yellow illumination); red, with PV cell silencing. EPSC rates are elevated following LSPS stimulus but return to baseline within ∼10 ms, indicating that evoked EPSCs are predominantly monosynaptic. Bottom, Zoomed-in view of the 25 ms following LSPS stimulus, which were used as a detection window for evoked EPSCs. E, Summary EPSC maps in PYRs recorded without (left) and with (right) yellow illumination. N = 11. F, Cumulative EPSC amplitudes relative to the horizontal distance from soma in 100 μm bins (left) and for each neocortical layer (right). * indicates statistical significance at p < 0.05.
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