Article Figures & Data
Figures
- Figure 1.
In vivo identification and basic firing pattern of hippocampal pyramidal neuron subtypes. A, Two recording setups used in our experiment. Left, Home cage. Right, U-shape running track. B, Eight putative pyramidal neurons sorted from a single tetrode. Each color denotes one single unit. Corresponding tetrode waveforms were illustrated at the bottom. The orange cluster in the upper right corner represents one CB+ neuron. Scale bar: 0.2 mV. C, Neuronal firing sequence of 30 simultaneously recorded pyramidal neurons for a 1000-s recording period in home cage. Vertical bar on the right denotes eight neurons recorded from one single tetrode, as illustrated in B. Each dot represents one action potential. The firing of CB+ PNs were largely inhibited on optogenetic stimulation (yellow shaded areas). Bottom, Average firing rate of these neurons showing population responses of PNs to laser stimulation. Blue, CB− PNs; orange, CB+ PNs. D, Top, Ratio of CB− PNs recorded from each tetrode in running track as a function of that in home cage. Each dot represents result from one tetrode, while each color denotes individual animal (n = 6 mice). Bottom, Ratio of active CB+ and CB− PNs recorded from two recording setups. Note the significant decrease of the ratio of CB+ neurons recorded during running (**p = 6.6e-3, χ2 test).
- Figure 2.
In vivo identification and basic firing pattern of hippocampal pyramidal neuron subtypes. A, Spectrogram of hippocampal CA1 local field potential during a 30-min home cage recording session. Different behavior states are indicated by different colors at the top. Note the high oscillation power in ripple band during SWS and the absence of ripple power during theta states (i.e., RUN and REM sleep). B, Average firing rate of CB+ and CB− PNs during three behavior states: RUN, REM, and SWS. CB− PNs showed higher firing rate than CB+ PNs during RUN state (n = 66 for CB+ PNs and 261 for CB− PNs, p = 6e-3, Mann–Whitney test), but not during REM and SWS states (n = 116 for CB+ PNs and 257 for CB− PNs, REM, p = 0.173; SWS, p = 0.114, Mann–Whitney test). C, Burst index of CB+ PNs were significantly higher than that of CB− PNs under all three behavior states (neuron number is same as in B; RUN, ***p = 5e-4; REM, *p = 0.02; SWS, *p = 0.031, Mann–Whitney test). D, Burst firing parameters of both PN subtypes under different behavior states, including burst frequency, duration, number of spikes and interspike interval within bursts (neuron number is same as in B, n.s., not significant; *p = 0.029, Mann–Whitney test).
- Figure 3.
CB+ place cells represent spatial information more efficiently than CB− place cells. A, Two example place cell firings along the linearized U-shape track. Left, CB+ place cell. Right, CB− place cell. Gray lines depict animal running trajectory. Colored triangles are spikes from each place cell. Place-selective firing of CB+ neuron is suppressed on optogenetic inhibition (yellow shaded box). B, Population activities of both CB+ and CB− place cells distributed along the running track on both directions. Neuronal firings are normalized and sorted by their relative peak firing position along the track (n = 27 for CB+ and 163 for CB− place cells). C, Example place cells recorded from one mouse. Clockwise and counter-clockwise runnings are separated and indicated by a circular arrow at the top. Gray lines are overlapped animal running trajectories. Colored dots represent firing rate of each place cell. Number of place fields and peak firing rate are shown in the middle of each figure. D, Place cell ratio of CB+ PNs is significantly lower than that of CB− PNs (CB+: n = 27 place cells and 39 nonplace cells, CB−: n = 163 place cells and 98 nonplace cells, **p = 2e-3, χ2 test). E, Number of place fields formed by CB+ and CB− place cells (n.s., not significant, p = 0.359, Mann–Whitney test). F, Distribution of varying number of place fields of CB+ and CB− place cells, with one, two, or more than three place fields (*p = 0.029, χ2 test). G, Place field size of both CB+ and CB− place cells (n.s., not significant, p = 0.798, Mann–Whitney test). H, Average firing rate (aFR) and peak firing rate (pFR) within place fields (n.s., not significant, p = 0.615 for aFR, 0.606 for pFR, Mann–Whitney test). I, Firing rate ratio inside and outside place fields. CB+ place cells fire significantly more spikes inside than outside the place fields than that of CB− place cells (***p = 1e-3, Mann–Whitney test). J, Neuronal firing sparsity and selectivity of place cells (**p = 9e-3; n.s., not significant, p = 0.379, Mann–Whitney test). K, Spatial information calculated by every spike or second of both place cell subtypes. CB+ place cells carry more information per spike than CB− place cells (**p = 5e-3; n.s., not significant, p = 0.203, Mann–Whitney test). L, Example phase precession of both place cell subtypes during one place field traverse. Two normalized theta cycles are shown for clarity. M, Phase precession of CB+ and CB− place cells. Two theta cycles are shown. N, No significant difference found in phase precession parameters, including slope, onset, and range (p = 0.934, p = 0.823, p = 0.778, Mann–Whitney test).
- Figure 5.
CB− PNs are more actively engaged in hippocampal ripple oscillations during SWS. A, Top, Neuronal firing sequence of ten CB+ (blue dots) and ten CB− (orange dots) PNs along with hippocampal LFP (black trace) and bandpass filtered ripple oscillation (gray trace with ripple events highlighted in dark blue) during SWS. Scale bar: 0.2 mV, 0.5 s. B, Normalized neuronal firing of both PN subtypes during ripple oscillations (n = 3888 ripple events), sorted by peak firing time (n = 116 CB+ PNs, and 257 CB− PNs). Time zero represents ripple peak (white broken line). Note that CB− PNs exhibited higher firing rate before ripple peak, while CB+ PNs showed lower firing rate after LFP ripple peak. C, Normalized firing rate of each PN subtype population during hippocampal ripple oscillations. Time zero denotes ripple peak. Note that population activity of CB+ PNs are briefly suppressed after ripple peak. Bin size: 10 ms. D, Ripple participation of both PN subtypes. CB− PNs are more actively engaged in ripple oscillations (****p = 4.2e-9, Mann–Whitney test). E, Average firing rate of both neuron subtypes during ripple oscillations (****p = 1.4e-9, Mann–Whitney test). F, Firing rate ratio inside and outside ripple oscillations of both CB+ and CB− PNs (****p = 3.8e-15, Mann–Whitney test). G, Normalized firing rate dynamics of both PN subtypes during ripples. Shown here is 0.1-s data around ripple peak. Bin size: 10 ms. H, Time and peak firing rate of both PN subtypes relative to LFP ripple peak. CB+ PNs participated earlier in ripples than CB− PNs (***p = 1.3e-3, ****p = 1.2e-5, Mann–Whitney test). I, Left, Postripple firing rate of both PN subtypes. The activity of CB+ PNs decreased after ripple, and also significantly lower than CB− PNs (****p = 5.9e-6, Mann–Whitney test). Right, Ripple inhibition index of both PN subtypes. CB+ PNs were more strongly inhibited after ripple peak than their CB− peers (****p = 1.5e-11, Mann–Whitney test).
- Figure 4.
A subset of CB+ PNs shifted their theta firing phase during REM sleep. A, Example theta firing phase distribution of both PN subtypes during RUN state (theta peak = 0°, 360°, theta trough = 180°; bin size: 30°). B, Same as in A, but for preferred theta firing phase during REM sleep theta oscillations. C, Left, Distribution of preferred theta phase of both PN subtypes during RUN state (CB+ PNs, n = 43; CB− PNs, n = 199; p = 2.2e-4, Watson’s U2 test; bin size: 30°). Top trace indicates idealized reference theta cycle. Right, Theta modulation depth of CB+ and CB− PNs during RUN (**p = 8.6e-3 Mann–Whitney test). D, Same as in C, but for population distribution of preferred theta firing phase during REM sleep. Note the bimodal distribution of theta phase preference of CB+ PNs (p = 0.099, Watson’s U2 test; bin size: 30°). Right, Theta modulation depth of both PN subtypes during REM sleep (**p = 1.4e-3, Mann–Whitney test). E, Left, Comparison of preferred theta firing phase of CB+ PNs during RUN and REM states. The preferred theta firing phase shifted significantly between the two states (p = 9.1e-3, Watson’s U2 test, bin size: 30°). Right, Modulation depth of CB+ PNs during REM sleep theta is significantly deeper than RUN theta states (****p = 2.3e-8, Mann–Whitney test). F, Same as in E, but for comparison of preferred theta firing phase of CB− PNs during RUN and REM states. No significant theta phase shift was observed between the two theta states (p = 0.446, Watson’s U2 test, bin size: 30°). Right, Theta modulation depth of CB− PNs during RUN and REM states (****p = 1.7e-26, Mann–Whitney test).
- Figure 6.
Both CB+ and CB− PNs are strongly Phase-locked to hippocampal ripple oscillations. A, Phase-locked firing of both PN subtypes with hippocampal ripple oscillations, referenced at LFP ripple peak (orange, CB+ PNs, n = 116; blue, CB− PNs, n = 257). Averaged LFP ripple trace is illustrated at the top. Note that neuronal firings of both CB+ and CB− PNs are locked to LFP ripple troughs. Bin size: 1 ms. Scale bar: 0.25 mV. B, Polar plots of neuronal firing phase distribution of example CB+ and CB− PNs. Bin size: 10°. C, Population ripple phase distribution of both CB+ and CB− PNs (bin size: 30°, p = 0.124, Watson’s U2 test). Both PN subtypes are phase locked to ripple trough. D, CB+ PNs are more strongly phase locked to ripple oscillations than CB− PNs (*p = 0.027, Mann–Whitney test).
Tables
Figure Data structure Type of test Statistic report 1D, bottom χ2 test c2 (1, n = 700) = 10.79, p = 0.0066 2B Non-normal distribution Mann–Whitney test Mann–Whitney U = 6117, n1 = 62, n2 = 255, pRUN = 0.0057, two-tailed Mann–Whitney U = 137,446, n1 = 341, n2 = 849, pREM = 0.1725, two-tailed Mann–Whitney U = 930,283, n1 = 941, n2 = 2051, pSWS = 0.1136, two-tailed 2C Non-normal distribution Mann–Whitney test Mann–Whitney U = 5195, n1 = 64, n2 = 226, pRUN = 0.0005, two-tailed Mann–Whitney U = 7470, n1 = 88, n2 = 205, pREM = 0.0195, two-tailed Mann–Whitney U = 13,197, n1 = 121, n2 = 253, pSWS = 0.031, two-tailed 2D, burst frequency Non-normal distribution Mann–Whitney test Mann–Whitney U = 8071, n1 = 73, n2 = 255, pRUN = 0.0832, two-tailed Mann–Whitney U = 13,775, n1 = 122, n2 = 253, pREM = 0.0901, two-tailed Mann–Whitney U = 14,877, n1 = 122, n2 = 253, pSWS = 0.5722, two-tailed 2D, burst duration Non-normal distribution Mann–Whitney test Mann–Whitney U = 7226, n1 = 64, n2 = 226, pRUN = 0.9916, two-tailed Mann–Whitney U = 7882, n1 = 88, n2 = 205, pREM = 0.087, two-tailed Mann–Whitney U = 13,165, n1 = 121, n2 = 253, pSWS = 0.0286, two-tailed 2D, spike/burst Non-normal distribution Mann–Whitney test Mann–Whitney U = 6614, n1 = 64, n2 = 226, pRUN = 0.2972, two-tailed Mann–Whitney U = 8480, n1 = 88, n2 = 205, pREM = 0.413, two-tailed Mann–Whitney U = 14,194, n1 = 121, n2 = 253, pSWS = 0.2553, two-tailed 2D, ISI within burst Non-normal distribution Mann–Whitney test Mann–Whitney U = 6109, n1 = 64, n2 = 226, pRUN = 0.0578, two-tailed Mann–Whitney U = 7974, n1 = 88, n2 = 205, pREM = 0.1157, two-tailed Mann–Whitney U = 13,397, n1 = 121, n2 = 253, pSWS = 0.0509, two-tailed 3D χ2 test c2 (1, n = 327) = 10.04, p = 0.0015 3E Non-normal distribution Mann–Whitney test Mann–Whitney U = 1967, n1 = 27, n2 = 163, p = 0.3588, two-tailed 3F χ2 test c2 (2) = 7.102, p = 0.0287 3G Non-normal distribution Mann–Whitney test Mann–Whitney U = 6424, n1 = 54, n2 = 367, p = 0.7982, two-tailed 3H, left Non-normal distribution Mann–Whitney test Mann–Whitney U = 9489, n1 = 54, n2 = 367, p = 0.6153, two-tailed 3H, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 9478, n1 = 54, n2 = 367, p = 0.6061, two-tailed 3I Non-normal distribution Mann–Whitney test Mann–Whitney U = 7174, n1 = 54, n2 = 367, p = 0.001, two-tailed 3J, left Non-normal distribution Mann–Whitney test Mann–Whitney U = 6835, n1 = 54, n2 = 326, p = 0.0085, two-tailed 3J, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 8144, n1 = 54, n2 = 326, p = 0.3791, two-tailed 3K Non-normal distribution Mann–Whitney test Mann–Whitney U = 6709, n1 = 54, n2 = 326, pbits/spk = 0.0051, two-tailed Mann–Whitney U = 7850, n1 = 54, n2 = 326, pbits/s = 0.2031, two-tailed 3N, left Non-normal distribution Mann–Whitney test Mann–Whitney U = 2710, n1 = 32, n2 = 171, p = 0.9337, two-tailed 3N, middle Non-normal distribution Mann–Whitney test Mann–Whitney U = 2667, n1 = 32, n2 = 171, p = 0.8231, two-tailed 3N, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 2649, n1 = 32, n2 = 171, p = 0.7777, two-tailed 4C, left Watson’s U2 test p = 0.0002 4C, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 3190, n1 = 43, n2 = 199, p = 0.0086, two-tailed 4D, left Watson’s U2 test p = 0.0990 4D, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 3346, n1 = 52, n2 = 181, p = 0.0014, two-tailed 4E, left Watson’s U2 test p = 0.0091 4E, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 370, n1 = 52, n2 = 43, p = 2.28E-08, two-tailed 4F, left Watson’s U2 test p = 0.4460 4F, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 6616, n1 = 181, n2 = 199, p = 1.68E-26, two-tailed 5D Non-normal distribution Mann–Whitney test Mann–Whitney U = 9242, n1 = 116, n2 = 257, p = 4.21E-09, two-tailed 5E Non-normal distribution Mann–Whitney test Mann–Whitney U = 9071, n1 = 116, n2 = 257, p = 1.42E-09, two-tailed 5F Non-normal distribution Mann–Whitney test Mann–Whitney U = 7329, n1 = 116, n2 = 257, p = 3.84E-15, two-tailed 5H, left Non-normal distribution Mann–Whitney test Mann–Whitney U = 11,320, n1 = 116, n2 = 257, p = 0.0013, two-tailed 5H, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 10,692, n1 = 116, n2 = 257, p = 1.2E-5, two-tailed 5I, left Non-normal distribution Mann–Whitney test Mann–Whitney U = 10,538, n1 = 116, n2 = 257, p = 5.9E-6, two-tailed 5I, right Non-normal distribution Mann–Whitney test Mann–Whitney U = 8397, n1 = 116, n2 = 257, p = 1.5E-11, two-tailed 6C Watson’s U2 test p = 0.124 6D Non-normal distribution Mann–Whitney test Mann–Whitney U = 3922, n1 = 60, n2 = 162, p = 0.027, two-tailed CB+
(mean ± SEM)CB−
(mean ± SEM)Average firing rate_RUN (Hz) 0.931 ± 0.154 1.322 ± 0.092 Average firing rate_REM (Hz) 0.558 ± 0.040 0.584 ± 0.027 Average firing rate_SWS (Hz) 0.632 ± 0.018 0.674 ± 0.014 Burst index_RUN 0.337 ± 0.022 0.255 ± 0.009 Burst index_REM 0.325 ± 0.019 0.282 ± 0.011 Burst index_SWS 0.313 ± 0.015 0.28 ± 0.009 Place field size (cm) 29.81 ± 1.474 31.11 ± 0.829 In field aFR (Hz) 5.793 ± 0.623 5.344 ± 0.215 In field pFR (Hz) 9.029 ± 0.948 8.372 ± 0.332 In/out field FR 17.63 ± 1.606 13.24 ± 0.607 Sparsity 0.177 ± 0.026 0.229 ± 0.01 Selectivity 11.17 ± 0.816 10.8 ± 0.378 Spatial information (bits/spk) 2.338 ± 0.182 1.809 ± 0.064 Spatial information (bits/s) 1.253 ± 0.146 1.114 ± 0.058 aFR in ripple (Hz) 0.659 ± 0.059 1.245 ± 0.07 pFR in ripple (Hz) 1.66 ± 0.121 2.429 ± 0.119 FR in/out ripple 1.028 ± 0.058 1.707 ± 0.053 Ripple participation 0.038 ± 0.003 0.067 ± 0.003 Peak time (ms) −19.74 ± 4.149 −11.28 ± 2.062 Baseline FR (Hz) 0.643 ± 0.046 0.775 ± 0.039 Postripple FR (Hz) 0.515 ± 0.039 0.798 ± 0.042 Inhibition index 0.19 ± 0.037 −0.087 ± 0.027
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