Foraging Under Uncertainty Follows the Marginal Value Theorem with Bayesian Updating of Environment Representations.

Foraging theory has been a remarkably successful approach to understanding the behavior of animals in many contexts. In patch-based foraging contexts, the marginal value theorem (MVT) shows that the optimal strategy is to leave a patch when the marginal rate of return declines to the average for the environment. However, the MVT is only valid in deterministic environments whose statistics are known to the forager; naturalistic environments seldom meet these strict requirements. As a result, the strategies used by foragers in naturalistic environments must be empirically investigated. We developed a novel behavioral task and a corresponding computational framework for studying patch-leaving decisions in head-fixed and freely moving mice. We varied between-patch travel time, as well as within-patch reward depletion rate, both deterministically and stochastically. We found that mice adopt patch residence times in a manner consistent with the MVT and not explainable by simple ethologically motivated heuristic strategies. Critically, behavior was best accounted for by a modified form of the MVT wherein environment representations were updated based on local variations in reward timing, captured by a Bayesian estimator and dynamic prior. Thus, we show that mice can strategically attend to, learn from, and exploit task structure on multiple timescales simultaneously, thereby efficiently foraging in volatile environments. The results provide a foundation for applying the systems neuroscience toolkit in freely moving and head-fixed mice to understand the neural basis of foraging under uncertainty.

Anticoagulation Can Be Held in Traumatically Injured Patients on Veno-Venous Extracorporeal Membrane Oxygenation Support.

Traumatic injury is associated with several pulmonary complications, including pulmonary contusion, transfusion-related acute lung injury (TRALI), and the development of acute respiratory distress syndrome (ARDS). There is a lack of literature on these patients supported with veno-venous extracorporeal oxygenation (VV ECMO). Understanding the safety of using VV ECMO to support trauma patients and the ability to hold anticoagulation is important to broaden utilization. This is a single-center retrospective cohort study of adult trauma patients cannulated for VV ECMO during their initial admission over an 8 year period (2014-2021). We hypothesize that anticoagulation can be held in trauma patients on VV ECMO without increasing mortality or prothrombotic complications. We also describe the coagulopathy of traumatically injured patients on VV ECMO. Withholding anticoagulation was not associated with mortality in our study population, and there were no significant differences in bleeding or clotting complications between patients who did and did not receive systemic anticoagulation. Patients in the nonsurvivor group had increased coagulopathy both pre- and post-cannulation. Our study suggests anticoagulation can be safely withheld in traumatically injured VV ECMO patients without increasing mortality, complication rates, or transfusion requirements. Future, multicenter prospective studies with larger sample sizes are required to confirm our results.

Atypical symptom reporting after mild traumatic brain injury.

OBJECTIVE: Early reporting of atypical symptoms following a mild traumatic brain injury (mTBI) may be an early indicator of poor prognosis. This study aimed to determine the percentage of people reporting atypical symptoms 1-month post-mTBI and explore links to recovery 12 months later in a community-dwelling mTBI sample. METHODS: Adult participants (>16 years) who had experienced a mTBI were identified from a longitudinal incidence study (BIONIC). At 1-month post-injury, 260 participants completed the Rivermead Post-Concussion Symptoms Questionnaire (typical symptoms) plus four atypical symptom items (hemiplegia, difficulty swallowing, digestion problems and difficulties with fine motor tasks). At 12 months post-injury, 73.9% (n = 193) rated their overall recovery on a 100-point scale. An ordinal regression explored the association between atypical symptoms at 1 month and recovery at 12 months post-injury (low = 0-80, moderate = 81-99 and complete recovery = 100), whilst controlling for age, sex, rehabilitation received, ethnicity, mental and physical comorbidities and additional injuries sustained at the time of injury. RESULTS: At 1-month post-injury <1% of participants reported hemiplegia, 5.4% difficulty swallowing, 10% digestion problems and 15.4% difficulties with fine motor tasks. The ordinal regression model revealed atypical symptoms were not significant predictors of self-rated recovery at 12 months. Older age at injury and higher typical symptoms at 1 month were independently associated with poorer recovery at 12 months, p < 0.01. CONCLUSION: Atypical symptoms on initial presentation were not linked to global self-reported recovery at 12 months. Age at injury and typical symptoms are stronger early indicators of longer-term prognosis. Further research is needed to determine if atypical symptoms predict other outcomes following mTBI.