Journal: Journal of Neurophysiology

Article Title: High-fidelity optical excitation of cortico-cortical projections at physiological frequencies

doi: 10.1152/jn.00456.2016

Figure Lengend Snippet: Pharmacological dissection of the optically evoked LFP to isolate action potentials in cortico-cortical axons. A, left: illustration of mouse primary visual cortex (V1) and adjacent higher visual areas (HVAs; gray). Center, fluorescence image of a posterior coronal section through the AAV-ChR2-tdTomato injection site in V1. Axons of ChR2-expressing V1 neurons arborize in the adjacent HVAs (arrows). SC, superior colliculus. Right, a coronal section anterior to the injection site, through 2 HVAs. B: schematic of the recording configuration overlaid on a confocal image of V1 axonal arborizations. LFP recordings (black trace) and optical stimulation (blue trace) were targeted to layer 2/3 of the HVA. C, left: LFP evoked by excitation of ChR2 (300 μs) in control ACSF (black trace) and in iGluR antagonists (10 μM NBQX, 30 μM APV; red trace) from a representative recording. Right, subtraction of the red trace from control reveals the field postsynaptic potential (fPSP). D, left: same recording as in C, in iGluR blockers and Cd2+ (150 μM; black trace) and after application of TTX (1 μM; red trace) to block action potentials and isolate the opsin potential. Right, subtraction of the red trace from the black trace reveals the fiber volley. E: summary of opsin potential (top) and fiber volley (bottom) amplitudes for a single light pulse at a range of light powers (n = 5). Insets, LFP recordings at 3 light powers from an example recording session. F, left: schematic of recording configuration and example opsin potentials for optical stimulation at multiple distances from the recording site. Right, summary of the dependence of opsin potential on stimulus location (n = 6). Error bars represent ± SE.

Article Snippet: Viruses encoding ChR2 (AAV2/1.CAGGS.flex.ChR2.tdTomato, Addgene 18917) and Chronos (AAV2/8.Syn.Chronos.tdTomato, Addgene 62726) were manufactured at the University of Pennsylvania Vector Core.

Techniques: Dissection, Fluorescence, Injection, Expressing, Control, Blocking Assay

Journal: Journal of Neurophysiology

Article Title: High-fidelity optical excitation of cortico-cortical projections at physiological frequencies

doi: 10.1152/jn.00456.2016

Figure Lengend Snippet: Repetitive stimulation of axons with ChR2 is unreliable. A: LFP evoked by ChR2 in response to light pulses 1–7 at 20 Hz in iGluR blockers and Cd2+ (black trace) and after application of TTX (red trace; opsin potential). B: overlay of fiber volleys (left) and opsin potentials (right) from the recording in A (black trace is first pulse). C: summary of the normalized amplitude of the ChR2-evoked (solid lines; n = 9) and electrically evoked (dashed lines; n = 8) fiber volleys for each pulse (PulseN). First-pulse fiber volley amplitude: −0.022 ± 0.003 mV. D: summary of the normalized latency for ChR2-evoked (solid lines) or electrically evoked (dashed lines) fiber volleys. First-pulse latency: 1.4 ± 0.08 ms. Inset, overlay of average ChR2-evoked fiber volley (40 Hz; black trace is first pulse). Each waveform was normalized by its peak-to-trough amplitude and averaged across experiments. E: summary of the normalized amplitude of the opsin potential. First-pulse opsin potential amplitude: −0.043 ± 0.008 mV. F: summary of normalized fiber volley amplitude in response to ChR2 stimulation (20 Hz) at multiple light powers (n = 5). See Fig. 1E for absolute amplitudes. G: relationship between fiber volley latency and light power during repetitive stimulation. Latency measurements for the lowest light power (6 mW/mm2) became unreliable during repetitive stimulation and are not plotted. H: relationship between opsin potential amplitude and light power. See Fig. 1E for absolute amplitudes. Error bars represent ± SE.

Article Snippet: Viruses encoding ChR2 (AAV2/1.CAGGS.flex.ChR2.tdTomato, Addgene 18917) and Chronos (AAV2/8.Syn.Chronos.tdTomato, Addgene 62726) were manufactured at the University of Pennsylvania Vector Core.

Techniques:

Journal: Journal of Neurophysiology

Article Title: High-fidelity optical excitation of cortico-cortical projections at physiological frequencies

doi: 10.1152/jn.00456.2016

Figure Lengend Snippet: oChIEF and Chronos undergo less use-dependent inactivation than ChR2. A, left: recording configuration to measure whole cell opsin currents. V-clamp, voltage clamp. Right, average normalized opsin current in response to blue light activation (300 μs) of ChR2 (blue trace; n = 6), oChIEF (red trace; n = 12), and Chronos (green trace; n = 9). B–D: summary of normalized amplitude of the opsin currents in response to repetitive stimulation of ChR2 (B), oChIEF (C), and Chronos (D). First-pulse opsin currents for weakly infected cells: ChR2, −295 ± 85 pA; Chronos, −536 ± 104 pA; oChIEF, −651 ± 103 pA. Insets, overlaid opsin currents (40 Hz; black trace is first pulse) for representative recordings. Error bars represent ± SE.

Article Snippet: Viruses encoding ChR2 (AAV2/1.CAGGS.flex.ChR2.tdTomato, Addgene 18917) and Chronos (AAV2/8.Syn.Chronos.tdTomato, Addgene 62726) were manufactured at the University of Pennsylvania Vector Core.

Techniques: Activation Assay, Infection

Journal: Journal of Neurophysiology

Article Title: High-fidelity optical excitation of cortico-cortical projections at physiological frequencies

doi: 10.1152/jn.00456.2016

Figure Lengend Snippet: Repetitive axonal stimulation with ChR2 drives artifactual short-term synaptic depression. A: summary of the normalized slope of the ChR2-evoked fPSP for each pulse (n = 9). Inset, Overlaid fPSPs (20 Hz; black trace is first pulse) from a representative recording. B: same as A for oChIEF (n = 7). C: same as A for Chronos (n = 9). Error bars represent ± SE.

Article Snippet: Viruses encoding ChR2 (AAV2/1.CAGGS.flex.ChR2.tdTomato, Addgene 18917) and Chronos (AAV2/8.Syn.Chronos.tdTomato, Addgene 62726) were manufactured at the University of Pennsylvania Vector Core.

Techniques: