The effects of time horizon and guided choices on explore-exploit decisions in rodents.

Humans and animals have to balance the need for exploring new options with exploiting known options that yield good outcomes. This tradeoff is known as the explore-exploit dilemma. To better understand the neural mechanisms underlying how humans and animals address the explore-exploit dilemma, a good animal behavioral model is critical. Most previous rodents explore-exploit studies used ethologically unrealistic operant boxes and reversal learning paradigms in which the decision to abandon a bad option is confounded by the need for exploring a novel option for information collection, making it difficult to separate different drives and heuristics for exploration. In this study, we investigated how rodents make explore-exploit decisions using a spatial navigation horizon task (Wilson et al., 2014) adapted to rats to address the above limitations. We compared the rats' performance to that of humans using identical measures. We showed that rats use prior information to effectively guide exploration. In addition, rats use information-driven directed exploration like humans, but the extent to which they explore has the opposite dependance on time horizon than humans. Moreover, we found that free choices and guided choices have different influences on exploration in rodents, a finding that has not yet been tested in humans. This study reveals that the explore-exploit spatial behavior of rats is more complex than previously thought. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Thyroid Disorders and Dementia Risk: A Nationwide Population-Based Case-Control Study.

BACKGROUND AND OBJECTIVES: Dementia has been gaining attention in aging societies and is estimated to affect 50 million adults globally in 2020, and 12% of the US population may develop a thyroid disorder in their lifetime. There have been limited studies investigating the correlation between thyroid disorder and dementia in the Asian population. METHODS: Our large nationwide population-based case-control study used the Taiwanese National Health Insurance Research Database. A total of 7,843 adults with newly diagnosed dementia without a history of dementia or neurodegenerative disease between 2006 and 2013 were identified and included in our study. In addition, 7,843 adults without dementia diagnosis before the index date were age and sex-matched as controls. Diagnosis of hyperthyroidism or hypothyroidism before the diagnosis of dementia or the same index date was identified. Results were obtained from logistic regression models and adjusted for sex, age, history of hypertension, diabetes, coronary artery disease, depression, hyperlipidemia, alcohol dependence syndrome, tinnitus, hearing loss, and radioactive iodine treatment. RESULTS: A total of 15,686 patients were included in the study. Both case and control groups were slightly predominantly female (4,066 [51.8%]). The mean (SD) age for those with dementia was 74.9 (11.3) years and for those without dementia was 74.5 (11.3) years. Among patients aged 65 years or older, a history of hypothyroidism was associated with an increased risk of being diagnosed with dementia (adjusted odds ratio [aOR] 1.81; 95% CI 1.14-2.87; p = 0.011), which was an association not present in patients older than 50 years but younger than 65 years. We found that this association was most significant among patients aged 65 years or older with a history of hypothyroidism who received hypothyroidism medication (aOR 3.17; 95% CI 1.04-9.69; p = 0.043). DISCUSSION: Our large-scale case-control study found that among people aged 65 years or older, those with a history of hypothyroidism were associated with an 81% increased risk of having dementia and among those, there was a more than 3-fold increased dementia risk with thyroid conditions that required thyroid hormone replacement treatment. Future well-controlled prospective longitudinal studies should be conducted to elucidate these potential mechanisms and relationships. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that among patients aged 65 years or older, a history of hypothyroidism was associated with an increased risk of being diagnosed with dementia.