Reference: Schneider, K. N. et al. (2020) ‘Anterior Cingulate Cortex Signals Attention in a Social Paradigm that Manipulates Reward and Shock’, Current Biology. Elsevier Ltd., pp. 1–12. doi: 10.1016/j.cub.2020.07.039.
https://www.sciencedirect.com/science/article/pii/S0960982220310319
Species: Rat
Key Questions:
- Are ACC neurons modulated by valence of reward or shocks delivered to self or others?
- Or does ACC play a role in driving attention toward arousing social and non-social cues?
Task Design:
- Pavlovian Task that predicted reward, shock, or nothing would be delivered to rate being recorded from or conspecific in opposite chamber Critically, this paradigm manipulates both appetitive and aversive stimuli within the same paradigm.
- It can help dissociate between whether activity reflects attention (both reward and shock) or outcoming identity (reward or shock)
- 3 auditory stimuli (5s) predicted delivery of 3 corresponding outcomes (sucrose pellet, foot-shock, or nothing)
- at time of cue, either rat had 50% chance of receiving following outcome
Key Results:
- ACC neurons modulated by aversive stimuli delivered to recording rate and conspecific Some neurons reflect outcome identity, but population as a whole responded similarly for reward and shock
- ACC main output function in paradigm is to increase attention in social contexts
- Rats increased food-cup entries for reward-self vs reward-others, and decreased for shock-shelf vs shock-other, suggesting rats were more concerned about self than other
- Rats froze more in shock-shelf and shock-other trials compared to neutral counterparts, and froze more on shock-self compared to shock-other trial types during directional light and outcome epochs
- When rats did not anticipate first-hand harm, they did not express behavioral reactions associated with conspecific distress (supported by observation that freezing on shock-other trials was high during trial blocks where recording rock, but not conspecific, received shock)
- Rats approached conspecific when being shocked in trial blocked when there was no first-hand threat. Increases in conspecific approach were present in blocks where rats received shock but conspecifics did not.
- Reward and shock trials have opposite valence, but are both arousing and drive behavior (shock: freezing, conspecific approach; reward: food cup entries)
- ACC firing strong during threat of first-hand shock and other-shock relative to neutral (primarily driven by first-hand threat)
- ACC may reflect attention, not valence, bolstered by evidence that ACC neurons fire similarly for reward and shock.
Bottom Line:
- At a population level, ACC is signalting attention in social context when there is threat of personal harm (although it should be noted that there is heterogeneity in the ACC neurons that are outcome-specific)
Additional Comments:
- conspecific = animal or plants belonging to the same species
- It is interesting that prior work has shown that ACC firing is modulated by rewards or shock outcomes to conspecifics located nearby
- I am less convinced that the neuronal firing of conspecifics is related to emotion per se, but it more convincing that it may reflect arousal/affective responses
- Since the cue is 50% predictive of whether they are receiving the outcome, maybe ACC is also firing because of uncertainty? It looks like they tried to rule out uncertainty as a confound by varying the reinforcement schedule, but if the same cues are being re-used its unclear whether the stimuli are unlearned?
- Interesting that there is inconsistency with primate ACC work
- Further understanding of what in encoded in the rostral/ventral ACC versus caudal/dorsal ACC is merited
- Rat are highly self-interested? (dare I even say, selfish!?!?)
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