Visual cortical LFP in relation to the hippocampal theta rhythm in track running rats.

Theta oscillations in the primary visual cortex (VC) have been observed during running tasks, but the mechanism behind their generation is not well understood. Some studies have suggested that theta in the VC is locally generated, while others have proposed that it is volume conducted from the hippocampus. The present study aimed to investigate the relationship between hippocampal and VC LFP dynamics. Analysis of power spectral density revealed that LFP in the VC was similar to that in the hippocampus, but with lower overall magnitude. As running velocity increased, both the power and frequency of theta and its harmonics increased in the VC, similarly to what is observed in the hippocampus. Current source density analysis triggered to theta did not identify distinct current sources and sinks in the VC, supporting the idea that theta in the VC is conducted from the adjacent hippocampus. Phase coupling between theta, its harmonics, and gamma is a notable feature in the hippocampus, particularly in the lacunosum moleculare. While some evidence of coupling between theta and its harmonics in the VC was found, bicoherence estimates did not reveal significant phase coupling between theta and gamma. Similar results were seen in the cross-region bicoherence analysis, where theta showed strong coupling with its harmonics with increasing velocity. Thus, theta oscillations observed in the VC during running tasks are likely due to volume conduction from the hippocampus.

Nonlinear Theta-Gamma Coupling between the Anterior Thalamus and Hippocampus Increases as a Function of Running Speed.

The hippocampal theta rhythm strongly correlates to awake behavior leading to theories that it represents a cognitive state of the brain. As theta has been observed in other regions of the Papez circuit, it has been theorized that activity propagates in a reentrant manner. These observations complement the energy cascade hypothesis in which large-amplitude, slow-frequency oscillations reflect activity propagating across a large population of neurons. Higher frequency oscillations, such as gamma, are related to the speed with which inhibitory and excitatory neurons interact and distribute activity on the local level. The energy cascade hypothesis suggests that the larger anatomic loops, maintaining theta, drive the smaller loops. As hippocampal theta increases in power with running speed, so does the power and frequency of the gamma rhythm. If theta is propagated through the circuit, it stands to reason that the local field potential (LFP) recorded in other regions would be coupled to the hippocampal theta, with the coupling increasing with running speed. We explored this hypothesis using open-source simultaneous recorded data from the CA1 region of the hippocampus and the anterior dorsal and anterior ventral thalamus. Cross-regional theta coupling increased with running speed. Although the power of the gamma rhythm was lower in the anterior thalamus, there was an increase in the coupling of hippocampal theta to anterior thalamic gamma. Broadly, the data support models of how activity moves across the nervous system, suggesting that the brain uses large-scale volleys of activity to support higher cognitive processes.

Unilateral Perforant Path Transection Does Not Alter Lateral Entorhinal Cortical or Hippocampal CA3 Arc Expression.

It is well established that degradation of perforant path fibers is associated with age-related cognitive dysfunction and CA3 hyperactivity. Whether this fiber loss triggers a cascade of other functional changes within the hippocampus circuit has not been causatively established, however. Thus, the current study evaluated the effect of perforant path fiber loss on neuronal activity in CA3 and layer II of the lateral entorhinal cortex (LEC) in relation to mnemonic similarity task performance. Expression of the immediate early gene Arc was quantified in rats that received a unilateral right hemisphere transection of the perforant path or sham surgery that cut the cortex but left the fibers intact. Behavior-related expression of Arc mRNA was measured to test the hypothesis that fiber loss leads to elevated activation of CA3 and LEC neurons, as previously observed in aged rats that were impaired on the mnemonic similarity task. Transection of perforant path fibers, which has previously been shown to lead to a decline in mnemonic similarity task performance, did not alter Arc expression. Arc expression in CA3, however, was correlated with task performance on the more difficult discrimination trials across both surgical groups. These observations further support a link between CA3 activity and mnemonic similarity task performance but suggest the reduced input from the entorhinal cortex to the hippocampus, as observed in old age, does not causatively elevate CA3 activity.

Characteristics of COVID-19 Workplace Clusters in Rhode Island.

The COVID-19 pandemic has impacted certain workplace settings disproportionately, putting some industries at a higher risk for workplace transmission than others. This study examines workplace clusters in Rhode Island between March 2020 and May 2021. There were 14,580 cases associated with 2784 clusters during this period, with the largest number of workplace clusters occurring in manufacturing, food services, and retail. A better understanding of most impacted industries can inform sector-specific COVID-19 guidance and policy changes.

Bleeding risk by intensity of anticoagulation in critically ill patients with COVID-19: A retrospective cohort study.

BACKGROUND: Studies report hypercoagulability in coronavirus disease 2019 (COVID-19), leading many institutions to escalate anticoagulation intensity for thrombosis prophylaxis. OBJECTIVE: To determine the bleeding risk with various intensities of anticoagulation in critically ill patients with COVID-19 compared with other respiratory viral illnesses (ORVI). PATIENTS/METHODS: This retrospective cohort study compared the incidence of major bleeding in patients admitted to an intensive care unit (ICU) within a single health system with COVID-19 versus ORVI. In the COVID-19 cohort, we assessed the effect of anticoagulation intensity received on ICU admission on bleeding risk. We performed a secondary analysis with anticoagulation intensity as a time-varying covariate to reflect dose changes after ICU admission. RESULTS: Four hundred and forty-three and 387 patients were included in the COVID-19 and ORVI cohorts, respectively. The hazard ratio of major bleeding for the COVID-19 cohort relative to the ORVI cohort was 1.26 (95% confidence interval [CI]: 0.86-1.86). In COVID-19 patients, an inverse-probability treatment weighted model found therapeutic-intensity anticoagulation on ICU admission had an adjusted hazard ratio of bleeding of 1.55 (95% CI: 0.88-2.73) compared with standard prophylactic-intensity anticoagulation. However, when anticoagulation was assessed as a time-varying covariate and adjusted for other risk factors for bleeding, the adjusted hazard ratio for bleeding on therapeutic-intensity anticoagulation compared with standard thromboprophylaxis was 2.59 (95% CI: 1.20-5.57). CONCLUSIONS: Critically ill patients with COVID-19 had a similar bleeding risk as ORVI patients. When accounting for changes in anticoagulation that occurred in COVID-19 patients, therapeutic-intensity anticoagulation was associated with a greater risk of major bleeding compared with standard thromboprophylaxis.

Health of Caregivers in Rhode Island.

[Full article available at http://rimed.org/rimedicaljournal-2019-02.asp].

Disparities in Health Risk Behaviors and Health Conditions Among Rhode Island Sexual Minority and Unsure High School Students.

BACKGROUND: Sexual minority students have higher risk for health-related behaviors. We examined 5 domains including 34 health risk behaviors and health conditions among sexual minorities and unsure students in Rhode Island. We also included sexual contact of heterosexually identified students to capture heterosexually identified students who may be considered sexual minorities by their behavior. METHODS: We used the 2007-2015 Rhode Island Youth Risk Behavior Survey data (N = 14,264). We categorized students into 4 groups: students self-identified as heterosexual and reported no sexual contact with same sex only or both sexes (group 1); self-identified as heterosexual and reported sexual contact with same sex only or both sexes (group 2); self-identified as lesbian, gay, bisexual (group 3); and responded as unsure (group 4). We used multivariable adjusted logistic regression analyses to evaluate associations of sexual minority and unsure students with 34 health risk behaviors and health conditions accounting for complex sampling design. RESULTS: Students in groups 2-4 were more likely to engage in health-risk behaviors including violent behaviors, attempted suicide, substance use, and no physical activity than their peers. CONCLUSIONS: As sexual minority youth continue to report higher rates of health-related risk behaviors, targeted evidence-based prevention approaches must focus on reducing these risk behaviors among those youth.

Calculating State-Level Estimates of Upcoming Older Adult Health Needs.

OBJECTIVES: Census demographers have provided projections of the increased numbers of older adults in upcoming decades, but it is less clear whether they will also be any more or less healthy than current seniors. This is critical information for state planners, as the majority of older adults will need assistance with activities of daily living to remain in their homes. Previous longitudinal and cohort studies have yielded national estimates, but those more costly sources are generally beyond the resources of state public health agencies. We provide a more practicable model for assessing state-level changes in health-related quality of life (HRQOL) among middle-aged versus older adults as a guide to probable upcoming home- and community-based service needs. METHODS: We used 2 sets of state Behavioral Risk Factor Surveillance System data 15 years apart to calculate and compare adjusted odds ratios of 8 poor HRQOL measures for middle-aged and older adults. RESULTS: Compared with their peers only 15 years earlier, recent middle-aged adults had higher odds of poor outcomes across all HRQOL measures, whereas adults 65-74 years had higher odds of poor outcomes for far fewer of the measures. Among adults 75 years and older, odds were higher compared with 15 years ago for only 1 measure (multiple days of poor mental health). CONCLUSIONS: Compared with older adults, the health profile of middle-aged adults in this state appears to have worsened much more rapidly in the past 15 years, indicating that these adults will have many more health-related needs when they become seniors. While this model is less sophisticated than others using longitudinal data, it provides the state-level data that are often more compelling to state policy makers.

Experience-Dependent Effects of Muscimol-Induced Hippocampal Excitation on Mnemonic Discrimination.

Memory requires similar episodes with overlapping features to be represented distinctly, a process that is disrupted in many clinical conditions as well as normal aging. Data from humans have linked this ability to activity in hippocampal CA3 and dentate gyrus (DG). While animal models have shown the perirhinal cortex is critical for disambiguating similar stimuli, hippocampal activity has not been causally linked to discrimination abilities. The goal of the current study was to determine how disrupting CA3/DG activity would impact performance on a rodent mnemonic discrimination task. Rats were surgically implanted with bilateral guide cannulae targeting dorsal CA3/DG. In Experiment 1, the effect of intra-hippocampal muscimol on target-lure discrimination was assessed within subjects in randomized blocks. Muscimol initially impaired discrimination across all levels of target-lure similarity, but performance improved on subsequent test blocks irrespective of stimulus similarity and infusion condition. To clarify these results, Experiment 2 examined whether prior experience with objects influenced the effect of muscimol on target-lure discrimination. Rats that received vehicle infusions in a first test block, followed by muscimol in a second block, did not show discrimination impairments for target-lure pairs of any similarity. In contrast, rats that received muscimol infusions in the first test block were impaired across all levels of target-lure similarity. Following discrimination tests, rats from Experiment 2 were trained on a spatial alternation task. Muscimol infusions increased the number of spatial errors made, relative to vehicle infusions, confirming that muscimol remained effective in disrupting behavioral performance. At the conclusion of behavioral experiments, fluorescence in situ hybridization for the immediate-early genes Arc and Homer1a was used to determine the proportion of neurons active following muscimol infusion. Contrary to expectations, muscimol increased neural activity in DG. An additional experiment was carried out to quantify neural activity in naïve rats that received an intra-hippocampal infusion of vehicle or muscimol. Results confirmed that muscimol led to DG excitation, likely through its actions on interneuron populations in hilar and molecular layers of DG and consequent disinhibition of principal cells. Taken together, our results suggest disruption of coordinated neural activity across the hippocampus impairs mnemonic discrimination when lure stimuli are novel.

Health profile of Rhode Island healthcare workers.

[Full article available at http://rimed.org/rimedicaljournal-2017-12.asp].

State-Level Surveillance of Underinsurance and Health Care-Related Financial Burden.

BACKGROUND: The Affordable Care Act (ACA) has reduced uninsurance, but underinsurance, health care-related financial burden, and dental uninsurance may not follow suit. Underinsurance is associated with reduced access to care, household debt, and bankruptcy but has been difficult to track without economic data. METHODS: We used readily available state-level survey data to build a model that states can adopt to implement surveillance over underinsurance and health care-related financial burden, as well as assess related disparities and health profiles. RESULTS: The state prevalence of underinsurance and dental uninsurance did not change in the first year of the ACA's individual mandate. Underinsurance was associated with poorer health-related quality-of-life measures: compared with the fully insured, underinsured adults had an adjusted odds ratio of 2.40 (95% CI, 1.71-3.38) of fair or poor general health. CONCLUSION: Tracking underinsurance and medical debt can help public health and health care access stakeholders evaluate which mechanisms (deductibles, co-pays, uncovered services, or is proportionately priced health care services and products) are barriers to care and improved health outcomes.

A latent class model to identify city/town chronic disease patterns.

OBJECTIVE: Most departments of health grapple with how to most effectively allocate resources to address chronic diseases. We adapted a model created by Massachusetts to create customized city/town profiles in order to identify the patterns of chronic disease among 39 cities/towns in Rhode Island. METHODS: We used four data sources to identify 20 indicators of four domains: demographics and socioeconomic status; health behaviors and chronic diseases prevalence; no regular provider and non-emergent emergency department visits; and chronic disease-related hospitalizations. A latent class model was used to group cities/towns into distinct latent class memberships based on similar patterns of indicators. Data were analyzed in 2014. RESULTS: The latent class model differentiated three distinct classes of city/town, reflecting three levels of economic and health indicators. CONCLUSIONS: Our model was a simplified version of one constructed by Massachusetts that larger states can also use to understand chronic disease patterns among cities/towns. Chronic disease programs and policies can use the findings to direct resources toward targets not always identified by more traditional analyses.