Fig 1.
Timeline of behavioral and electrophysiological procedures.
a) Different phases of social development of three natal littermates before and after tube test: Dominant (D, red), Middle-ranked (M, gray), and Subordinate (S, blue) b) Timeline of surgery, T-maze task, LFP recording in decision point (4 sec) with the correct and wrong responses, and histological confirmation of the sites of the electrodes in mPFC and vHPC (LFP: local field potential; mPFC: medial prefrontal cortex; vHPC: ventral hippocampus).
Fig 2.
Determining relative dominance using tube-test.
a) Schematic dominance relationship between triads of dominant (D), middle-ranked (M), and subordinate (S) rats. b) The mean number of wins of each social status. Values express as the mean ±SEM.,****p<.0001.
Fig 3.
Performance in T-maze task with two difficulty levels
a) T-maze spontaneous alternation test comparing b) The percentage of correct responses in easy task (30s, left panel,) and difficult task (5 min, middle panel) and comparison of two difficulty levels for each rank (right panel). c) Comparing the latency in easy task (30 sec, left panel; **p<.01,***p<.001) and difficult (5 min, middle panel) and comparison of two difficulty level for each rank (right panel). Values express as the mean ±SEM.
Fig 4.
Sample time-frequency spectrogram and raw LFP signals in mPFC in subordinates.
a) Sample time-frequency spectrogram of one correct trial and its raw signal (blue) and the wrong one (red) in mPFC in easy task (delay: 30s). b) Sample time-frequency spectrogram of one correct trial and its raw signal (blue) and the wrong one (red) in mPFC in difficult task (delay: 5 min).
Fig 5.
Mean theta rhythm power (PSDs) of mPFC in T-maze task with two difficulty levels in dominant, middle-ranked, and subordinate animals.
The mean PSDs of mPFC in correct and wrong responses during (a) easy (* p<0.05, ** p<0.01, **** p<0.0001; two-way ANOVA) and (b) difficult tasks. (c) Comparing PSDs of two difficulty levels for each social rank in correct responses (two-way ANOVA). Values are expressed as mean ± SEM. Correlation of mPFC theta rhythm power with the percentage of correct responses during (d) easy (M: r= -.4161) and (e) difficult tasks of three social ranks for 4 days. Correlation of mPFC theta rhythm power with response latency during (f) easy (M: r =.4514) and (g) difficult (S: r=.2017)tasks of three social ranks for 4 days. mPFC: medial prefrontal cortex, PSD: power spectrum density.
Fig 6.
Sample time-frequency spectrogram and raw LFP signals in vHPC in subordinates.
a) Sample time-frequency spectrogram of one correct trial and its raw signal (blue) and the wrong one (red) into vHPC in easy task (delay: 30s). b) Sample time-frequency spectrogram of one correct trial and its raw signal (blue) and the wrong one (red) in vHPC in difficult task (delay: 5 min).
Fig 7.
Mean theta rhythm power (PSDs) of vHPC in T-maze task with two difficulty levels in dominant, middle-ranked, and subordinate animals.
The mean PSDs of vHPC in correct and wrong responses during (a) easy and (b) difficult tasks (* p<.05,** p<.01,**** p<.0001; two-way ANOVA). (c) Comparing PSDs of two degrees of task difficulty in correct responses (***p<0.0001; two-way ANOVA). Values are expressed as mean ±SEM. Correlation of vHPC theta power with the percentage of correct responses during (d) easy (S:r=.4505)and (e) difficult tasks of three social ranks for 4 days. Correlation of vHPC theta rhythm power with latency of response during (f) easy (D: r=.1950, S: r=.4021)and (g) difficult (D: r=.2513, M: r=.1985) tasks in three social ranks for 4 days. vHPC: ventral hippocampus, PSD: power spectrum density.
Fig 8.
Mean theta correlation of mPFC-vHPC circuit in T-maze task with two difficulty levels in dominant, middle-ranked, and subordinate animals.
The mean theta correlation of mPFC-vHPC circuit in correct and wrong responses during (a) easy (** p<.001,*** p<.001, **** p<.0001) and (b) difficult tasks. (c) Comparing mean theta correlation of two task difficulty in correct responses. Values are expressed as mean ±SEM. Relationship between the theta correlation of mPFC-vHPC circuit with the percentage of correct responses during (d) easy and (e) difficult (M: r= -.3827)tasks of three social ranks for 4 days. Relationship between the theta correlation of mPFC-vHPC circuit with the latency of correct responses during (f) easy (M; r= -.3055)and (g) difficult (S:r =.2608) tasks in three social ranks for 4 days.
Fig 9.
Mean theta coherency of mPFC-vHPC circuit in T-maze task with two difficulty levels in dominant, middle-ranked, and subordinate animals.
The mean theta coherency of the mPFC-vHPC circuit in correct and wrong responses during (a) easy (**** p<0.0001) and (b) difficult (* p<0.05, **** p<0.0001) tasks. (c) Comparing mean theta coherency of two degrees of task difficulty in correct responses (**** P<0.0001). Values are expressed as mean ±SEM. Correlation between theta coherency of mPFC-vHPC circuit with the percentage of correct responses during (d) easy (S: r=.4329) and (e) difficult (D: r=.5030) tasks of three social ranks for 4 days. Correlation between theta coherency of mPFC-vHPC circuit with the latency of correct responses during (f) easy (M: r =.2682, S: r=.1991)and (g) difficult (M: r= -.3471)tasks in three social ranks for 4 days.