JClub: Hosking et al., 2015

Reference: Hosking, J. G., Floresco, S. B. and Winstanley, C. A. (2015) ‘Dopamine antagonism decreases willingness to expend physical, but not cognitive, effort: A comparison of two rodent cost/benefit decision-making tasks’, Neuropsychopharmacology. Nature Publishing Group, 40(4), pp. 1005–1015. doi: 10.1038/npp.2014.285.
https://www.nature.com/articles/npp2014285

Species: Rat

Key Questions:

• Does willingness to work hard in mental effort correspond to willingness to work hard in physical effort?
• What are dopaminergic and noradrenergic contributions to effort?
• Goal: to compare animals’ behavior on rCET and wettl-established physical effort task, and examine DA and NE contribution to cognitive vs. physical effort

Task Design:

• rat cognitive effort task (rCET): animals can choose to allocate greater visuospatial attention for greater reward
  • 5-hole operant chamber. animals presented 1 or 2 levers (Low reward or High reward), and following stimulus lights they had to nosepok with previously illuminated aperture for a rerward
  • Trials were unrewarded if rat 1) failed to make a lever response within 10s (choice omission), 2) nosepoked during ITI (premature), poked wrong aperture (incorrectly response), or failed to nosepke at array within 5s (response omission). behaviors were punished with 5s time-out
  • Behavioral measurement: percent choice. two groups of animals, workers (n=40) and slackers (n=15)
• physical effort-discounting task (EDT)
  • 40 free-choice trials per 32 min session, divided into 4 blocks
  • LR lever: both levers retraced and animal immediately received 2 sugar pellets
  • HR lever: LR lever retracted and animals given 25 seconds to complete a higher number of presses for 4 sugar pellets
  • Animals did not receive reward if they did not make a choice within 25s of lever insertion (choice omision), or if they fialed complete required number of lever presses for HR trial (incomplete HR response)
  • Beahvioral measurement: Percent choice
• Pharmacological challenge
  • D2 antagonist eticlopride
  • D1 antagonist SCH23390
  • adrenic receptor antagonist yohimbine
  • selective norepinephrine reuptake inhibitor atomoxetine

Key Results:

• rCET Eticlopride Admin
  • animals chose HR trials more than LR tirlas following saline injection. D2 receptor antagonist eticlopride had not effect on animals choice
  • Animals more accurate on LR vs HR trials (saline). Ectriclopride had no effect on accuracy
  • Etic increase correct response latencies, response and choice omissions, decreased number of completed trials
• rCET SCH23390 Admin
  • no effect
• rCET Yohimbine Admin
  • no effect on choice
  • yohimbine dose-dependently decreased accuracy (at highest dose)
  • at low and intermediate doses, speeding effect on all latencies, decreased response omission, increased completed trials
  • highest doest increased response and choice omissions, decreased trials
• rCET Atomoxetine
  • no effect on choice, accuracy, trending to decreased performance on LR trials
  • increased choice latency and choice omissions, decreased number of completed trials
• EDT vs rCET
  • all animals demonstrated sensitivity to physical effort costs, choice of HR decreased across blocks as costs increased
• EDT Eticlopride
  • decreased all animals choice of HR trial across blocks
  • increased latency to complete HR trials, modest increase of choice omissions
• EDT SCH23390
  • decreased choice at highest effort block
  • modestly increased choice latencies and choice omissions
• EDT Yohimbine
  • decreasing choice of HR lever during first two blocks but effect not robust
  • lengthened latency to complete HR trials for each block
• EDT Atomoxetine
  • No effects

Bottom Line:

• Dopamine is minimally involved in cost/benefit decision-making with cognitive effort costs

Additional Comments:

• It is interesting that they use 1.0s vs 0.2s stimuli for Low effort and High effort, respectively. I wonder to what extend these differences may more reflect perceptual difficulty, than cognitive effort, per se
• Observed differences may be due to differences in task design?
• reward learning and motor learning may be more functionally and anatomically integrated than previously suggested? (Kratviz et al 2012)
• mental and physical effort differ in systemic cateholamine profiles – interesting. (Fibiger et al 1984)
• sustained attention and acetycholine? (Passetti et al, 200, Dalley et al., 2001)

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JClub: Schneider et al., 2020

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!?!?)