mPFC lesion does not impair initial active place avoidance learning, but impairs cognitive flexibility in the conflict task variant

(A) Workflow to assess the impact of mPFC or sham lesions on spatial cognitive control. (B) Assessment and impact of the mPFC lesion in three representative subjects (light grey (intermediate with dorsal anterior lesion), dark grey (intermediate with ventral anterior lesion – includes medial orbital cortex), and purple (largest lesion)). The smallest lesion spanned A-P 3.24-2.52. PrL (prelimbic), IL (infralimbic), Cg (cingulate cortex), M2 (secondary motor cortex). Representative mPFC from a sham and a lesion rat (bottom). (C) Tracked room-frame positions from two example rats across active place avoidance training. The shock zone is indicated as a 60° sector, gray (shock off) and red (shock on), and arena rotation by the curved arrow. Day 1 - Pretraining: free exploration with shock off; Days 2&3 - Initial Training: Eight daily trials to avoid the shock zone. Day 4 - Retention: One trial with shock on. Days 4&5 - Conflict Training: Eight daily trials to avoid the shock zone relocated 180° from the initial location. Sham and mPFC lesion rats did not differ in (D) locomotor activity, (E) avoidance memory, or (F) place learning. (F) The left inset compares the number of entrances during the first 5 minutes of the first (D2T1) and second days of initial training (D3T9). The right inset compares the first 5 minutes of the first (D4C1) and second (D5C9) days of conflict trials. The percent difference in number of entrances between D5C9 and D4C1 of conflict training was computed as a savings index. Savings was not related to lesion size r = 0.009, p = 0.98. *p < 0.05.

Cytochrome oxidase analysis demonstrates widespread metabolic consequences of mPFC lesion.

(A) Representative cytochrome oxidase staining and locations of the optical density readings. Cytochrome oxidase activity was measured in the dysgranular and granular retrosplenial cortices (RSD and RSG, respectively), the nucleus reuniens (RE), the central nucleus of the amygdala (CEA), basomedial and basolateral amygdala (BMA, and BLA, respectively), the dorsal hippocampus CA1, CA2, CA3 and dentate gyrus areas (dCA1, dCA2, dCA3, dDG, respectively) the ventral hippocampus CA1, CA3 and dentate gyrus areas (vCA1, vCA3, vDG, respectively) and the dorsal subiculum (DS) marked as colored circle areas. (B) Interarea covariations of CO activity by graph theory analysis. Each line indicates a significant correlation (p < 0.05) between the two brain regions (“nodes”) it connects; only the red lines survived False Discovery Rate (FDR < 0.01) correction. Sham: n = 8; Lesion: n = 8.

mPFC lesion does not change basic discharge properties, but decreases hippocampus place cell overdispersion only in the absence of the cognitive control challenge.

(A) (left) Representative histology with overlaid recording traces from the Neuropixel probe. (right) Recording schedule workflow during the cognitive control task. (B) There is no difference between sham and mPFC lesion rats in firing rate (Sham: 3.29 ± 0.27, Lesion: 3.68 ± 0.33, t184 = 0.91, p = 0.36) and burst ratio in hippocampal neurons (Sham: 1.53 ± 0.25, Lesion: 2.02 ± 0.28, t174 = 1.29, p = 0.19). (C) Distribution of standardized place cell discharge (z scores) computed during every 5-second episode in which the rat passed through place cell firing fields in the data set. Different numbers of passes qualified for evaluation during the pretraining (Sham = 2777, Lesion = 3398), retention (Sham = 4039, Lesion = 3366), and conflict (Sham = 1748, Lesion = 2336) recordings. The variance of the histograms characterizes overdispersion, statistically evaluated by their ratio as an F-test (pretraining: F2776,3397 = 2.19, p = 5.8×10-4).

Sham and mPFC lesion rats do not differ in expressing cognitive control of spatial frame-specific representations of location.

(A) Individual ensemble examples during the Day 4 retention session, and (B) group statistics of spatial frame ensemble preference (SFEP), demonstrating cognitive control in both groups. During retention, SFEP is biased to the arena frame in both the sham (t4 = 4.16, #p = 0.01) and lesion rats (t4 = 6.62, #p = 0.003). *p < 0.05 post-hoc differences. (C) Group spatial probability distribution of SFEP for room frame preference during the pretraining, initial, and conflict retention sessions with no shock. (D) Summary of average probability of room-preferring SFEP discharge in half the arena near and far from the shock zone during the initial and conflict retention sessions. Two-way Group x Location ANOVA (Sham: n=3, Lesion: n=3) during retention of the initial shock zone location: Group: F1,4 = 0.17 p = 0.68, η2 = 10-3; Location: F1,4 = 54.69, p = 0.001, η2 = 0.84; Group x Location F1,4 = 2.04, p = 0.2, η2 = 10-2; during retention of the conflict shock zone location: Group: F1,4 = 0.71 p = 0.45, η2 = 0.05; Location: F1,4 = 0.42, p = 0.55, h2 = 0.056; Group x Location F1,4 = 0.67, p = 0.45, h2 = 0.08.