Article Figures & Data
Figures
- Figure 1.
Recording session schedule and definition of the four phases. The experiment was conducted sequentially from Phase 1 to Phase 4. Phase 1: a male rat was placed alone in one of the two compartments of a recording chamber for 5 min. Phase 2: a female was placed in the other compartment for 5 min, but the male could not access the female because of a double mesh wall. Phase 3: the wall was removed, and the male could freely interact with the female until the male ejaculated. Phase 4: 1 min after ejaculation. The session comprising the four phases was repeated three times for each recording experiment.
- Figure 2.
Definition of the behavioral periods used for statistical analysis of neuronal responses to sexual behavior. A, Definition of the periods for the three copulatory behaviors (mount + thrust, intromission + thrust, ejaculation + intromission + thrust). A baseline period was defined as the 3.0 s period from −3.5 s to −0.5 s before onset of chasing. Periods 1 and 2 were defined as the 0.5 s periods before and after onset of chasing, respectively. Period 4 was defined as the 0.5 s period before onset of thrusting. Period 3 was defined as the period between Periods 2 and 4. Period 5 was defined as the thrust period. Period 6 was defined as the 0.25 s period after offset of thrusting. B, Definition of the periods for genital grooming. The same baseline period as in A was used because genital grooming was induced after thrusting, intromission, or ejaculation. Periods 1 and 2 were defined as the 0.5 s periods before and after onset of genital grooming, respectively. Periods 4 and 5 were defined as the 0.5 s periods before and after offset of genital grooming, respectively. Period 3 was defined as the period between Periods 2 and 4. C, Definition of the periods for sniffing inaccessible females. Periods 1–5 were similarly defined as those in B. A baseline period was defined as the period from −3.5 s to −0.5 s before onset of sniffing.
- Figure 3.
Example waveforms of four NAcS neurons isolated by offline cluster analysis. A, Superimposed waveforms recorded from four electrodes (tetrodes) (EL 1–4). The waveforms indicated by a–d correspond to the four neurons (a–d) identified by offline cluster analysis in B, respectively. B, Results of offline cluster analysis. Each dot represents one neuronal spike. The horizontal axis represents the principle component of EL 1 and the vertical axis represents the principle component of EL 3. Four colored clusters (a–d) are recognized.
- Figure 4.
Neurophysiological classification of NAcS neurons. A, Postspike suppression histogram of NAcS neurons. Ordinate and abscissa indicate the number of NAcS neurons and the postspike suppression period in 10 ms steps, respectively. Neurons with firing rates <2 Hz were not analyzed. The cluster of pTANs with a long postspike suppression period is identified. B, Scatter plot of NAcS neurons based on mean firing rates and waveform properties (ISVD and HDT). The clusters of pMSNs and pFSIs are identified. C, Examples of superimposed waveforms of a pMSN (left) and a pFSI (right).
- Figure 5.
Neuronal responses to pelvic thrusting with intromission. A, B, Perievent rasters and histograms (bin width = 0.2 s) of pMSN responses (A) and pFSI responses (B). Top, middle, and bottom histograms represent neuronal firings and frequency of chasing and genital grooming per bin, respectively. Time 0 indicates offset of thrusting with intromission. Triangles: onset of chasing, circles: onset of thrusting, underlines: duration of genital grooming. C, D, Mean firing rates of the pMSN shown in A (C) and the pFSI shown in B (D) at baseline and in Periods 1–6. *Significant difference from the baseline (Bonferroni correction, p < 0.05). E, Response patterns of all neurons that responded to intromission and thrusting. Each horizontal line comprising six squares represents responses of each neuron in Periods 1–6 (P1–6). Gray and black squares indicate excitatory and inhibitory responses. F, Number of neurons with excitatory (gray) or inhibitory (black) responses in each period in all recorded neurons (left), pMSNs (middle), and pFSIs (right).
- Figure 6.
Neuronal responses to genital grooming. A, B, Perievent rasters and histograms (bin width = 0.2 s) of responses of a pMSN (A) and a pFSI (B). Top, middle, and bottom histograms represent neuronal firings and frequency of chasing and genital grooming per bin, respectively. Time 0 in the left and right histograms indicates onset and offset of genital grooming, respectively. Triangles: onset of chasing, circles: onset of thrusting, underlines: duration of genital grooming. C, D, Mean firing rates of the pMSN shown in A (C) and the pFSI shown in B (D) at baseline and in Periods 1–5. *Significant difference from baseline (Bonferroni correction, p < 0.05). E, Response patterns of all neurons that responded to genital grooming. Each horizontal line comprising five squares represents responses of each neuron in Periods 1–5 (P1–5). Gray and black squares indicate excitatory and inhibitory responses. F, Number of neurons with excitatory (gray) or inhibitory (black) responses in each period in all recorded neurons (left), pMSNs (middle), and pFSIs (right).
- Figure 7.
Neuronal responses to sniffing of females in Phase 2. A, B, Perievent rasters and summed histograms (bin width = 0.2 s) of responses of a pMSN (A) and a pFSI (B). Top and bottom histograms represent neuronal firings and frequency of sniffing per bin, respectively. Time 0 in the left and right histograms indicates onset and offset of sniffing, respectively. Underlines under the raster indicate duration of sniffing. C, D, Mean firing rates of the pMSN shown in A (C) and the pFSI shown in B (D) at baseline and in Periods 1–5. *Significant difference from the baseline (Bonferroni correction, p < 0.05). E, Response patterns of all neurons that responded to sniffing. Each horizontal line comprising five squares represents responses of each neuron in Periods 1–5 (P1–5). Gray and black squares indicate excitatory and inhibitory responses. F, Number of neurons with excitatory (gray) or inhibitory (black) responses in each period in all recorded neurons (left), pMSNs (middle), and pFSIs (right).
- Figure 8.
Comparison of ratios of excitatory and inhibitory neurons between pMSNs (top) and pFSIs (bottom). Pie charts represent the number of excitatory and inhibitory neurons in response to intromission, genital grooming, and sniffing of females. The numbers shown in the chart represent the actual number of neurons and the numbers in parentheses indicate the neurons exhibiting both excitatory and inhibitory responses. *Significant difference in ratios between pMSNs and pFSIs (χ2 test, p < 0.05). n.s., No significance.
- Figure 9.
Examples of NAcS neurons with differing responses to the three copulatory behaviors. A, B, Perievent raster and summed histograms (bin size = 0.25 s) of responses of a pMSN (A) and a pFSI (B) to the three types of copulatory behavior (mount + thrust, intromission + thrust, ejaculation + intromission + thrust). Rasters and summed histograms are aligned with onset of thrusts. C, D, Mean firing rates of the pMSN (C) and pFSI (D) in Periods 4 and 5 in each copulatory behavior. Responses in A, C and B, D were recorded from the same neurons. *Significant difference (unpaired t test, p < 0.05).
- Figure 10.
Phase-differential neurons in the NAcS. A, Four examples of phase-differential neurons (a, b, pMSN; c, pFSI; d, UN). Histograms indicate instantaneous firing rates throughout a recording experiment. Marks above the histograms correspond to those in Figure 1. B, Normalized firing rates of all phase-differential neurons. P1–4 corresponds to Phases 1–4. The normalized mean firing rate in each phase was calculated by the following equation, (FRPhaseX−FRmin)/(FRmax−FRmin), where FRPhaseX, FRmax, and FRmin represent firing rate in a given phase (Phase X) and the maximum and minimum firing rates in all four phases, respectively. C, Number of phase-differential neurons with a significant difference between each pair of phases in all recorded neurons (top), pMSNs (middle), and pFSIs (bottom). P1–4 corresponds to phases 1–4. Gray bars represent the number of neurons with firing rates significantly larger in the former than in the latter phases of the pair. Black bars represent the number of neurons with firing rates significantly smaller in the former than in the latter phases of the pair. Note that the periods during copulation, genital grooming, and sniffing (Figs. 3C, 4C, 5C) were excluded from this analysis.
- Figure 11.
Delta and high gamma oscillation in the NAcS. A, B, Examples of NAcS neurons that exhibited delta (A) or high gamma (B) oscillation. Histograms indicate auto-correlograms (gray) of each neuron in each phase. The fitted functions (Eq. 1 in the text) are superimposed on the auto-correlograms. *Significant oscillation in delta (A) and high gamma (B) ranges. C, D, The number of NAcS neurons with significant oscillation in delta (C) and high gamma (D) ranges in all recorded neurons (left), pMSNs (middle), and pFSIs (right). P1–P4 represents Phases 1–4. *Significant difference compared with the average number of delta (C) or high gamma (D) oscillating neurons (residual analysis, standard residual > 2.0). E, Perievent histogram of activity index (bin size = 5 s). Time 0 indicates the offset of thrusting in ejaculation. Error bars indicate SEM. F, Mean activity index during Phases 3 and 4. Error bars indicate SEM. *Significant difference found by paired t test (p < 0.001).
- Figure 12.
Relationships between behavior-related neurons and delta oscillating neurons in Phase 4. Left column: percentage of behavior-related neurons (behavior-responsive and phase-differential neurons). Middle column: percentage of neurons that significantly oscillated in the delta range in Phase 4. Right column: percentage of behavior-related neurons that significantly oscillated in the delta range in Phase 4. Gray-colored squares inside the columns indicate the neuronal types shown in the inset.
- Figure 13.
Recording sites of NAcS neurons. Circles indicate histologically identified locations of the tetrode tips, where all NAcSs (A), pMSNs (B), pFSIs (C), pTANs (D), and UNs (E) were recorded. All the neurons were recorded only from the left NAcS. Black circles indicate the locations of the tetrode tips where behavior-related neurons (behavior-responsive and phase-differential neurons) were recorded, open circles indicate locations of the tetrode tips where behavior-unrelated neurons were recorded, half-filled circles indicate locations of the tetrode tips where both the behavior-related and behavior-unrelated neurons were recorded. The area shaded with horizontal and vertical lines indicates the NAc shell and core regions, respectively. Values below each section indicate the distance (in mm) anterior from the bregma. Note that, since multiple neurons were usually recorded from each tetrode, the total number of the tetrode tips is smaller than the total number of the neurons.
Tables
- Table 1.
Number of neurons with different firing rates between two different copulatory behaviors
Mount + thrust (M) vs Intromission + thrust (I) Ejaculation + intromission + thrust (E) vs Intromission + thrust (I) Total M > I I > M N Total E > I I > E N Prethrust period Total 7 4 3 115 9 5 4 123 pMSN 5 3 2 59 0 0 0 60 pFSI 0 0 0 20 2 1 1 21 Thrust period Total 14* 10 4 115 6 5 1 123 pMSN 9* 6 3 59 3 3 0 60 pFSI 3* 3 0 20 2 2 0 21 M, Thrust after mount (mount + thrust); I, thrust with intromission (intromission + thrust); E, thrust with intromission followed by ejaculation (ejaculation + intromission + thrust); N, number of recorded neurons. Asterisks indicate that the number is significantly larger than chance level (5%, which is the type I error rate of the t test used for the comparisons) (χ2 test, p < 0.05).
- Table 2.
Pearson's correlation coefficients derived from the all NAcS neurons between the two possible phases
Phase 1 Phase 2 Phase 3 Phase 4 Phase 1 1 Phase 2 0.24 1 Phase 3 −0.42 −0.33 1 Phase 4 −0.53 −0.37 −0.13 1 - Table 3.
Pearson's correlation coefficients derived from the 44 phase-differential neurons between the two possible phases
Phase 1 Phase 2 Phase 3 Phase 4 Phase 1 1 Phase 2 0.38 1 Phase 3 −0.52 −0.36 1 Phase 4 −0.62 −0.50 0.10 1
