Article Figures & Data
Figures
- Figure 1.
Electrode placement in the tubercle. Coronal stereotaxic panels showing the approximate location of electrode tips (black dots) from 18 mice in the olfactory tubercle (Tu). Coronal sections span from 2.0 to 0.5 mm anterior of bregma, in 0.5 mm intervals. The region outlined in bold black is Tu. The panels are adapted from the work by Paxinos and Franklin (2000).
- Figure 2.
In vivo spontaneous multiunit tubercle activity in anesthetized mice. a, Representative traces showing multiunit activity, LFP (100 Hz low-pass filter), and respiration over the course of 2 s. Inhalation in respiratory trace is an upward deflection. The hash marks represent unit responses (spikes). b, Waveform plots for two units (unit 1, top; unit 2, bottom) indicated in a by purple and green hash marks, respectively. c, Interspike interval distributions for units displayed in a and b. Note for each unit there were no spikes with intervals ≤2 ms.
- Figure 3.
Odorant presentation evokes neural responses in the tubercle. a, Histogram (bars) and cumulative probability plot (dashed line) showing spontaneous firing rate distributions (in hertz) of 62 tubercle units. Spontaneous firing rate, Average instantaneous firing rate during the 5 s before all stimulus presentations for each unit. b, “Unit” trace showing multiunit activity, LFPs filtered from 0–100, 30–75 (gamma), and 10–35 Hz (beta) (second-order bandpass) and respiration. Inhalation in respiratory trace is an upward deflection. Odor presentation (1,7-octadiene; gray shaded region) evoked high-frequency LFP oscillations and action potentials. Note that action potentials and LFP oscillations were generally phasic and closely follow respiratory peaks. c, Power spectrograms of LFP activity before (preodor; 2 s before odor) and during (odor; 2 s during odor) odor presentation. Data are an average from four mice, four odors each, and two trials per odor. Odor presentation evoked changes in theta (0–10 Hz; p < 0.0001, two-tailed t test), beta (10–35 Hz; p < 0.0001, two-tailed t test), and gamma (30–75 Hz; p < 0.0001, two-tailed t test) oscillations compared with preodor. Error bars indicate SEM.
- Figure 4.
Odorant responsivity of tubercle units. a, Spike raster plots and peristimulus time histograms from two units (2 separate mice) throughout multiple presentations with five different odorants (gray-shaded regions). The top halves of each panel shows spike activity as raster plots (dots) of single units in response to each of the five odorants across multiple trials (y-axis; each row is a single trial). Summarizing each raster plot is a peristimulus time histogram with average firing rate (in hertz) on the y-axis. Odorants are as follows (from left to right): 1,7-octadiene, ethyl proprionate, heptanal, isoamyl acetate, and 4-methyl-3-penten-2-one. Histograms, 100 ms time bins. b, Statistical summary of odor selectivity of 17 tubercle units in response to the five odorants outlined in a and three odorant mixtures (right matrix) (see Materials and Methods). The red cells indicate significant responses across all trials (p < 0.05, two-tailed t test, 2 s prestim vs 2 s during stim). Units 6 and 2, Same data as in a. Whereas some units (e.g., 1 and 3) responded to all but one or two odorants, other units (e.g., 11) responded to only one odorant.
- Figure 5.
Tubercle units respond to an auditory stimulus. a, Representative traces showing multiunit activity, LFP (0–100 Hz second-order low-pass filter), and respiration over the course of 4 s. Inhalation in respiratory trace is an upward deflection. Time of tone presentation is indicated by the shaded gray box. b, Spike raster plot and peristimulus time histogram from a single unit throughout multiple presentations of an auditory tone. The top halves of each panel show spike activity as raster plots (dots) of the unit in response to the tone across multiple trials (y-axis; each row is a single trial). Summarizing the raster plot is a peristimulus time histogram with average firing rate (in hertz) on the y-axis. Histogram, 100 ms time bins. c, Bar graph and scatter plot showing average “pre” (2 s prestim) and tone evoked (tone icon; 2 s during stim) responses of five tubercle units that all showed significant spike rate increases in response to tone. *p < 0.05, two-tailed t test. d, LFP power spectrograms of pretone (2 s prestim) and tone (2 s during tone) LFP activity. Data are from four mice, five tone trials each.
- Figure 6.
Olfactory–auditory interactions in olfactory tubercle single units. a, Representative traces showing multiunit activity, LFP (0–100 Hz second-order low-pass filter), and respiration over the course of 4 s relative to stimulus onset. Inhalation in respiratory trace is an upward deflection. Time of stimulus presentation is indicated by the shaded gray box. Data shown are from a single electrode location (same mouse) and reflect events in response to an odor (“ODOR”; top panel), auditory tone (tone icon; middle panel), and simultaneous tone and odor presentation (tone icon and “odor”; bottom panel). Histograms, 100 ms time bins. b, Average evoked response (2 s stim to 2 s prestim), for each tone, odor, and odor-plus-tone stimulus (n = 17 units, 173–184 trials/stimulus). *p < 0.01, tone versus odor; **p < 0.005, tone versus odor plus tone, two-tailed t test. c, LFP power spectrograms of prestim (2 s prestim) and odor-plus-tone (2 s during odor plus tone) LFP activity. Data are from four mice, four trials each. Error bars indicate SEM.
- Figure 7.
Subpopulations of tubercle single units show olfactory–auditory cross-modal modulation. Bar graphs of average evoked responses across 17 units (different from those in Fig. 4), in response to tone (left), odor (middle) (for odor, see Materials and Methods), and simultaneous tone and odor presentations (right column). The red bars indicate significant responses of that unit across all trials (p < 0.05, two-tailed t test, 2 s prestim vs 2 s during stim). The blue bars are insignificant (p > 0.05). The green background color behind bars indicates that response of that unit is significantly different from responses of that unit to tone alone (p < 0.05, two-tailed t test). The blue background color behind bars indicate that response of that unit is significantly different from responses of that unit to odor alone (p < 0.05, two-tailed t test). Whereas some units (e.g., indicated with “*”) showed supraadditive responses to both stimuli simultaneously, others (e.g., indicated with “#”) showed suppressive responses. Error bars indicate SEM.
- Figure 8.
Olfactory–auditory convergence is not detected upstream of the olfactory tubercle. a, Spike raster plots and peristimulus time histograms from a single OB unit throughout 15 presentations of a tone, odor, and odor plus tone (same stimuli as in Figs. 6 and 7). The top halves of each panel shows spike activity as raster plots (dots) of the unit in response to the stimuli across multiple trials (y-axis; each row is a single trial). Summarizing the raster plot is a peristimulus time histogram with average firing rate (in hertz) on the y-axis. Histogram, 100 ms time bins. Gray-shaded area, Stimulus window. b, Average evoked response (2 s stim to 2 s prestim), for each tone, odor, and odor-plus-tone stimulus (n = 20 units, ≥108 trials/stimulus). *p < 0.0001, tone versus odor and tone versus odor plus tone, two-tailed t test. Error bars indicate SEM.
