Social context modulates active avoidance: Contributions of the anterior cingulate cortex in male and female rats

Abstract

Actively avoiding danger is necessary for survival. Most research on active avoidance has focused on the behavioral and neurobiological processes when individuals learn to avoid alone, within a solitary context. Therefore, little is known about how social context affects active avoidance. Using a modified version of the platform-mediated avoidance task in rats, we investigated whether the presence of a social partner attenuates conditioned freezing and enhances avoidance compared to avoidance in a solitary context. Rats spent a similar amount of time avoiding during either context; however, rats trained in the social context exhibited greater freezing as well as lower rates of darting and food seeking compared to rats trained in the solitary context. In addition, we observed higher levels of avoidance in females compared to males in the solitary context, but this sex difference was not present in rats trained in the social context. To gain greater mechanistic insight, we optogenetically inactivated glutamatergic projection neurons in the anterior cingulate cortex (ACC) following avoidance training in either context. After avoidance was learned in a social context, photoinactivation of ACC reduced expression of avoidance during a test when the social partner was absent, but not when the partner was present. Our findings suggest a novel contribution of the ACC in avoidance that is learned with a social partner, which has translational implications for understanding ACC dysfunction in those suffering from trauma-related disorders.

Keywords: Fear; Optogenetics; Prefrontal cortex; Sex differences.

Fig. 1

Social Partner platform-mediated avoidance (PMA) increases freezing and decreases darting and food-seeking compared to Solitary PMA. A. Schematic of PMA within a social (left, purple, n = 42) or solitary (blue, n = 59) context. B. Percentage of time spent on the platform during the tone, C. Number of shocks avoided per day, D. Percentage of time freezing during the tone, E. Number of darting bouts during the tone, and F. Number of lever presses during the ITI. There was no significant difference in time on platform (z = −0.868, p = 0.385) or number of shocks avoided (z = −0.552, p = 0.581). There was a significant increase in freezing (z = 6.229, p < 0.001) and a significant decrease in darting (z = −4.786, p < 0.001) and ITI pressing (z = −6.034, p < 0.001) in social compared to solitary rats. Data reported are main effects of the regression models (see Supplementary Tables S1–S5). Data shown across 10 days of training (trials shown in blocks of 3) and as mean ± SEM; ∗∗∗p < 0.001.

Fig. 2

Social partner PMA reduces behavioral sex differences that are observed during solitary PMA. A. Percentage of time on platform during the tone, B. Number of shocks avoided and shock reactivity (inset), as measured by the maximum velocity of each rat during Tone 1 on the first day of training, C. Percentage of time freezing during the tone, D. Number of darting bouts during the tone, and E. Number of lever presses during the ITI in female (n = 21, salmon) and male (n = 21, teal) rats trained in Social Partner PMA. During social partner PMA training, females pressed significantly less than males (z = −3.112, p = 0.002), but there were no sex differences in time on platform (z = 1.638, p = 0.102), number of shocks avoided (z = 1.590, p = 0.112), freezing (z = −1.045, p = 0.296), or darting (z = −0.886, p = 0.375). F. Percentage of time on platform during the tone, G. Number of shocks avoided and shock reactivity (inset), H. Percentage of time freezing during the tone, I. Number of darting bouts during the tone, and J. Number of presses during the ITI in female (n = 27, salmon) and male (n = 32, teal) rats trained in solitary PMA. During solitary PMA training, females spent significantly more time on the platform (z = 2.791 p = 0.005), avoided significantly more shocks (z = 2.949, p = 0.003), and pressed significantly less (z = −3.044, p = 0.002) compared to males, but there were no sex differences in freezing (z = 1.311, p = 0.190) or darting (z = 0.401, p = 0.688). Data reported are post-hoc Tukey tests on the regression models. Data shown across 10 days of training (trials shown in blocks of 3) and as mean ± SEM; ∗∗p < 0.01.

Fig. 3

Photoinactivation of ACC projection neurons during social partner PMA impairs avoidance at test when the partner is absent. A. Schematic of virus infusion, micrograph of AAV expression, followed by avoidance training and tests. At Test with partner and without partner (Days 11/12), 532 nm light was delivered to ACC during the entire 30-s tone presentation (Tone 1). B. Percentage of time on platform at final training day and Test (Day 11/12, Tone 1 with laser ON and Tone 2 with laser OFF) for ArchT-eYFP rats (n = 13, red) and eYFP control rats (n = 10, black) when the partner was present. There was a significant main effect of AAV (F_(1,21) = 6.870, p = 0.016) in the percentage of time spent on the platform between ArchT-eYFP and eYFP control rats but no significant difference between groups during Tone 1 of test (post-hoc Tukey, p = 0.209). Within the ArchT-eYFP group, there was a significant decrease in time on platform during Tone 1 and Tone 2 of test compared to the last training day (post-hoc Tukey tests, all p's < 0.001, red stars). I In the eYFP control group, there was also a significant decrease in time on platform between Tone 1 of the last training day and Tone 1 of test (post-hoc Tukey, p = 0.022). C. Percentage of time on platform in 3 s bins (Tone 1 at Test) during Test w/partner. D. Latency of avoidance for each rat during Test w/partner. E. Percentage of freezing (left), suppression of bar pressing (middle), and number of darting bouts (right) during Tone 1 at Test w/partner in all eYFP control (black) and all ArchT-eYFP (red) rats. F. Percentage time on platform at final training day and Test (Day 11/12, Tone 1 with laser ON and Tone 2 with laser OFF) for ArchT-eYFP (n = 12, red) and eYFP control rats (n = 11, black) when the partner was absent. There was a significant main effect of trial (repeated measures ANOVA, F_(2,42) = 23.220, p < 0.001), a significant main effect of AAV (F_(1,21) = 18.550, p < 0.001), and an interaction between trial and AAV (F_(2,42) = 4.877, p = 0.013) for time on platform between ArchT-eYFP and eYFP control rats. Post-hoc Tukey tests revealed a significant decrease in time on platform between the ArchT-eYFP and eYFP control groups during Tone 1 of test (Laser ON) (p = 0.0016). Within the ArchT-eYFP group, we also observed a significant decrease in time on platform during Tone 1 and Tone 2 of test compared to the last training day (post-hoc Tukey tests, all p's < 0.001) and no significant difference within the eYFP control group across trials (all p's > 0.05). G. Percentage of time on platform in 3 s bins (Tone 1 at Test) during Test w/o partner revealed a significant reduction in the timecourse of avoidance in ArchT-eYFP rats compared to eYFP controls (repeated measures ANOVA, main effect of AAV, F (_1,21) = 13.82, p = 0.0013). H. Latency of avoidance for each rat during Test w/o partner revealed a significant decrease in the latency to avoid for all ArchT-eYFP compared to eYFP control rats (t₍₂₁₎ = 2.555, p = 0.018). I. Percentage of freezing (left), suppression of bar pressing (middle), and number of darting bouts (right) during the Tone + Laser trial revealed a significant decrease in freezing in ArchT-eYFP rats (t₍₂₁₎ = 2.593, p = 0.016), a significantly lower suppression of bar pressing in ArchT-eYFP rats (t₍₂₁₎ = 4.275, p < 0.001) and a trend for increased darting in ArchT-eYFP rats (t₍₂₁₎ = 2.072, p = 0.051). All data are shown as mean ± SEM; #p < 0.05, ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.

Fig. 4

Photoinactivation of ACC projection neurons during solitary PMA has no effect on expression of avoidance. A. Schematic of virus infusion, micrograph of AAV expression, followed by avoidance training and test. At Test, 532 nm light was delivered to ACC during the entire 30-s tone presentation (Tone 1). B. Percentage of time on platform on the final training day and Test (Day 11, Tone 1 with laser ON and Tone 2 with laser OFF) for ArchT-eYFP (n = 22, red) and eYFP control rats (n = 26, black). There was no main effect of AAV (F_(1,46) = 1.500, p = 0.227) but a significant main effect of trial (F_(1,46) = 12.830, p < 0.001). Post-hoc Tukey tests showed no significant difference in time on platform between the ArchT-eYFP and eYFP control groups during Tone 1 of test (Laser ON; p = 0.783). Within the ArchT-eYFP group, there was a decrease in time on platform during Tone 1 and Tone 2 of test compared to Tone 1 of the last training day (post-hoc Tukey tests, all p's < 0.05, red star). Within the eYFP control group, there was a decrease in time on platform between Tone 1 of the last training day and Tone 1 of test (post-hoc Tukey test, p = 0.025). C. Percentage of time on platform in 3 s bins during Test. D. Latency of avoidance for each rat during Test. E. Percentage of freezing (left) suppression of bar pressing (middle), and number of darting bouts (right) during the Tone + Laser trial revealed a trend in increased darting in ArchT-eYFP rats (t₍₃₂₎ = 1.969, p = 0.058). Data shown as mean ± SEM; ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; #p > 0.05.