Article Figures & Data
Figures
- Figure 1.
Light evoked extracellular voltage responses in the mitral cell layer of an OB slice. a, Fluorescence image of the OB. b, Left, 200 ms of whole-field laser stimulation (473 nm) evokes robust extracellular voltage variation in the mitral cell layer caused by mitral cell spiking (data filtered from 300 to 4000 Hz). b, Middle, Light-evoked action potentials are completely blocked by application of NBQX (10 μm) and AP-5 (100 μm). b, Right, The response partially recovers after washing with Ringer's solution. Top, Extracellular voltage traces. Blue bars represent light stimulation. Bottom, Variance of the extracellular voltage.
- Figure 2.
Recording of sniffs and extracellular voltage in the mitral cell layer and light-elicited stimulation of ChR2 expressed in the axons of OSNs. a, Optotetrodes. Left, The combination of a guide glass tube and tetrodes was inserted into the mitral cell layer of the OB to allow recording of M/T cell activity and light stimulation of glomerular ChR2. Center, View of the optotetrode attached to the EIB-16 electrode interface. Right, Higher magnification view of the tip of the tetrodes and the glass guide for the optic fiber. The tip of the tetrodes is ∼0.2–0.3 mm longer than the fiber. b, Example of raw recording of extracellular potential and voltage changes recorded by the pressure sensor measuring nose pressure. Light was turned on at times shown by the trace labeled Sti. c, Two units separated from the data in b using Spike2 software. Left, Voltage variation for the two units. Right, Separation of the two units using principal component analysis. d, Three examples of the effect of light stimulation on spike firing by M/Ts. From left to right: Excitatory response, inhibitory response, and no response. Above, Raster for 60 trials; below. PSTH. Blue bars represent light stimulation (60 ms). e, Light pulses are not synchronized with the sniff. Top, Average voltage recording with the pressure sensor detecting pressure inside the nose for 681 sniffs taking place during light activation. Bottom, Bar graph showing the timing of light activation in the same time interval. A Rayleigh test for the significance of the mean direction in a histogram indicated that there was no specific distribution for this bar graph (p > 0.05).
- Figure 3.
Some M/Ts in the OB display responses with information on the duration of the stimulus (duration-informative responses). a, b, Two representative M/Ts not showing (a) or showing (b) duration-informative responses. The blue bars represent light stimulation of the glomerular OSN input in OMP-hChR2V mice. c, d, Firing rate changes in the cells displayed in a and b evoked by light stimulation with different durations shown for different time windows used to calculate an average change in the firing rate. One-way ANOVA for duration of the light stimulus: n.s, p > 0.05. One-way ANOVA for the time window F = 77 in c and 8 in d, p < 0.001. e, Percentage of responsive M/Ts (significant firing changes after light stimulation) for different light durations and different time windows for all experiments (n = 81 for each light duration/time window). Friedman two-way ANOVA yielded χ2 = 12, p = 0.02 for statistic difference between time windows (asterisk shows post hoc significant difference between time windows). Post hoc Tukey's HSD multiple-comparison test reveals significant differences (#p < 0.05). f, Duration of the response (response time) calculated as the time occupied by bars higher than average firing before light stimulation plus 3xSD plotted as a function of light pulse duration (duration). Blue, response time calculated for the data in a; red, response time calculated for the data in b. g, Duration of the response (response time) calculated as the time occupied by bars higher than average firing before light stimulation plus 3 SDs plotted as a function of light pulse duration (duration) calculated for all the data. Only units for which at least one bar was above background plus 3xSD were included (21 of 81 units). Shown is average ± SD. The correlation coefficient (r) and the p value for its difference from zero are shown in f and g. h, Mean change in firing rate for all units recorded from normalized by dividing by the firing rate before stimulation with light (n = 81).
- Figure 4.
Animal performance in go—no-go odor discrimination or optogenetic discrimination tasks. a, Schematic of cannula implant for light delivery. The cannula was implanted in the OB to stimulate a subset of ventral glomeruli. b, Time course for trials in the odor discrimination or optogenetic discrimination tasks. OV, olfactory valve; FV, final valve; RA, response area; WR, water reward. OV and FA were only used for the odor discrimination task, not for the optogenetic discrimination task. Light is applied as a train of pulses (10 pulses; interval, 250 ms; pulse duration from 10 to 200 ms). c, Percentage correct for go—no-go odor discrimination as a function of block number for six OMP-hChR2V mice. In each block the animal was exposed in 10 trails to the rewarded (S+) odor (1% phenyl acetate) and 10 trials to the unrewarded (S–) odor (1% 2-butanone). Different colors show the results for different mice. d, Percentage correct for go—no-go sessions with rewarded stimulus of optogenetic activation of glomeruli by light (S+, light pulses with 100 ms duration) and the unrewarded stimulus was no activation by light (S–). e, f, Go—no-go for odor discrimination (e) or for optogenetic light activation (f) for three C57BL/6 mice. g, Discrimination of 100 ms pulses (S+) and shorter durations (S−, 10–95 ms) for a representative mouse. h, Discrimination of 100 ms pulses (S+) and longer durations (S−, 200–105 ms) for the same mouse. Two dashed lines show 50 and 80% correct responses, respectively. i, Percentage correct response for the last two blocks of sessions with 100 ms light pulse duration for the S+ stimulus and different light durations for the S− stimulus (average ± SD, n = 6). These points (*) differ from the 95 and 105 ms points in an ANOVA followed up by a post hoc Tukey's HSD criterion (p < 0.05).
