Cortical simple cells can extract achromatic information from the multiplexed chromatic and achromatic signals in the parvocellular pathway

AbstractP cells, which carry both achromatic and chromatic information, are largely responsible for achromatic acuity and contrast sensitivity. The P cell achromatic information must be separated from the chromatic information to be useful. Cortical simple cells are well suited to the extraction of achromatic information by spatial bandpass filtering. Bandpass filtering of Type I P cells by cortical simple cells yields an achromatic signal with a residual chromatic response. The bandpass model makes predictions in accord with existing physiological data and explains the role of a heretofore puzzling class of cortical cells, which have bandpass tuning for both achromatic and chromatic modulations. The model is shown to be related to a previously postulated class of ideal detectors. Finally, the model is used to make a number of physiological and psychophysical predictions

Zipline-Related Injuries Treated in US EDs, 1997-2012

Purpose To investigate the epidemiology of zipline-related injuries in the United States. Basic Procedures The National Electronic Injury Surveillance System database was used to examine non-fatal zipline-related injuries treated in US emergency departments (EDs) from 1997 through 2012. Sample weights were applied to calculate national estimates. Main Findings From 1997 through 2012, an estimated 16850 (95% CI, 13188-20512) zipline-related injuries were treated in US EDs. The annual injury rate per 1 million population increased by 52.3% from 7.64 (95% CI, 4.86-10.42) injuries in 2009 (the first year with a stable annual estimate) to 11.64 (95% CI, 7.83-15.45) injuries in 2012. Patients aged 0-9 years accounted for 45.0% of injuries, females made up 53.1% of injuries, and 11.7% of patients required hospitalization. Fractures accounted for the largest proportion of injuries (46.7%), and the upper extremities were the most commonly injured body region (44.1%). Falls were the most common mechanism of injury, accounting for 77.3% of injuries. Among cases where the location of the injury event was known, 30.8% of injuries occurred in a residential setting and 69.2% occurred in a public place. Principal Conclusions This study is the first to characterize the epidemiology of zipline-related injuries using a nationally representative database. The rapid increase in zipline-related injuries in recent years suggests the need for additional safety guidelines and regulations. Commercial ziplines and publicly accessible non-commercial ziplines should be subject to uniform safety standards in all states and jurisdictions across the US, and homemade ziplines should not be used

Spatiotemporal discrimination thresholds for dynamic random fractal (1/f) textures

Natural scenes are fractal in space (ie they have 1/f B spatial frequency spectra) and time (1/f A temporal spectra), and can be compellingly mimicked by fractal textures. If dynamic fractal texture statistics are used to describe natural scenes, then data on discriminability of such textures are required. The smallest detectable change was measured separately for 10 spatial (0.4 to 2.2) and 8 temporal exponents (static, and 0.2 to 1.4) with an adaptive staircase. Computational constraints limited each fractal to 64 frames (~ 2 s) of 64 × 64 pixel images. Spatial discriminations were easiest when the spatial exponent B was ~ 1.6 and were similar across all temporal exponents. Temporal discriminations were easiest when the temporal exponent A was ~ 0.8, and increased in difficulty as the spatial exponent increased. This similarity in spatial discrimination thresholds for static and dynamic fractals suggests that the spatial and temporal dimensions are independent in dynamic fractals (at least for spatial judgments), as is often assumed. The dependence of temporal judgments on the coarseness of the texture (ie on the spatial exponent) is understandable, as a 1 mm change in position is more noticeable for a 1 mm object than for a 100 m object

Harnessing HIV and Syphilis Networks to Reduce HIV Transmission in North Carolina

Sexual contact networks containing persons diagnosed with HIV and/or syphilis are efficient platforms for delivery of enhanced HIV treatment support to persons living with HIV (PLWH) and prevention resources to HIV-negative persons. We conducted three inter-related studies among men who have sex with men (MSM) in North Carolina (NC) to assess the potential for network-based interventions to reduce HIV transmission. We first generated independent and combined HIV and syphilis networks using contact tracing data for all MSM diagnosed with HIV or syphilis 2015-2017 in NC. We identified network communities, or clusters of densely connected nodes, in the combined network and evaluated interconnectivity between the syphilis and HIV networks by community. Heightened interconnectivity was associated with younger median age; higher proportions of persons self-identifying as Black, non-Hispanic; and higher proportions of syphilis cases diagnosed at sexually transmitted disease clinics. Next, we used NC surveillance data to identify two types of qualifying “network events” among MSM in NC 01/2013-06/2017: being diagnosed with early syphilis or being named as a recent sexual contact of a person diagnosed with HIV or early syphilis. We estimated prevalent and incident viral suppression among previously diagnosed PLWH at and after network events (52.6% and 35.4%, respectively) and assessed the effect of contact tracing services on incident viral suppression. The six-month cumulative incidence of reported viral suppression was 13.1 (95% CI: 8.9, 17.4) percentage points higher after events among persons reached vs. not reached by these services. Using linked insurance claims data, we also evaluated prevalent and incident pre-exposure prophylaxis (PrEP) use among HIV-negative network members (5.4% and 4.1%, respectively). Finally, we generated static contact networks with community structure drawn from the combined HIV/syphilis network described above and varied endemic HIV prevalence across network communities. We applied a stochastic transmission model to simulate HIV spread, evaluated community-level HIV incidence rates by endemic community-level HIV prevalence, and modeled the efficiency of community-prevalence-based vs. randomly allocated interventions. PrEP interventions were most efficient when preferentially deployed to susceptible persons in communities with higher endemic HIV prevalences, while viral suppression intervention efficiency did not vary significantly by intervention allocation scheme.Doctor of Philosoph

Behavioral Evidence for Contextual Decision Hierarchies In the Hermit Crab, Pagurus samuelis

In this dissertation, I examined how motivation and sensory cue perception influence the behavioral choices of hermit crabs. I began by reviewing behavioral experiments that have demonstrated the underlying sensory processing of visual, chemical, and tactile information in crustaceans and propose a novel behavior model entitled Contextual Decision Hierarchies in which sensory modalities vary in relative influence on behavior depending on context. This behavioral model was tested in a series of four experiments. In the first experiment, I tested whether the hermit crab, Pa gurus samuelis, deprived of food, shells, or both will respond differently from control hermit crabs when presented with food and shells concurrently. Differences in the number of contacts with each resource and the time elapsed before choosing a resource confirmed that deprivation increased motivation to acquire either food or shells. Results further indicated that being shell-less is a stronger motivation than being starved, such that finding shelter takes priority over finding food when both are needed. Next, I examined the relative influence of sensory information on shell acquisition behavior of hermit crabs by presenting visual, chemical, and tactile cues of shell availability in a factorial manner to hermit crabs removed from their shells. During shell acquisition, tactile cues were primary while visual and chemical information was secondary. In the third experiment I tested the relative influence of the same sensory modalities on foraging behavior. In contrast to shell-seeking, chemical cues were primary in food acquisition while visual and tactile cues were secondary. In both of these experiments, even though primary cues elicited the shortest decision times, in the absence of the primary cue, secondary cues could still be used to make appropriate decisions, albeit with significantly longer decision times. In the final experiment, I investigated the relative influence of visual, chemical, and tactile cues of the predator, Pachygrapsus crassipes, on anti-predatory behavior of the hermit crab, Pa gurus samuelis. Results indicated that visual cues are primary in detecting and avoiding predators, while chemical and tactile cues are secondary. These experiments suggest that for the hermit crab, Pa gurus samuelis, information is arranged in Contextual Decision Hierarchies

Confronting Systemic Racism in Occupational Therapy: A Mixed Methods Study

This study aimed to examine how occupational therapists and students perceive systemic racism in occupational therapy practice and the effectiveness and impact of the delivery of a keynote address on confronting systemic racism in practice delivered to occupational therapists and students. The study aimed to help inform future efforts in creating a more diverse and inclusive profession at the practice, policy, and education level by providing input into the challenges and opportunities that occupational therapists and students face when reckoning with issues of racism in practice. A mixed methodology research design was used with Likert-style scale and open-ended questions delivered via online survey. Eighty-nine occupational therapists and students completed the online survey. Most of the respondents reported responding favorably to the keynote address and shared sentiment that it could be a difficult and uncomfortable topic, yet it was important to discuss because of its impact on the profession and the clients occupational therapists serve

Repeat Human Immunodeficiency Virus Testing by Transmission Risk Group and Rurality of Residence in North Carolina

Background Understanding of repeat human immunodeficiency virus (HIV) testing (RHT) is limited and the impact of rural residence as a potential barrier to RHT is unknown. Rural populations are of particular interest in the Southeastern United States because of their disproportionate HIV burden. Methods We used HIV surveillance data from publicly funded HIV testing sites in North Carolina to assess repeat testing by transmission risk group and residential rurality in a retrospective cohort study. Linear binomial regression models were used to estimate adjusted, 1-year cumulative incidences and cumulative incidence differences comparing RHT within transmission risk populations by level of rurality. Results In our total study population of 600,613 persons, 19,275 (3.2%) and 9567 (1.6%) self-identified as men who have sex with men (MSM) and persons who inject drugs (PWID), respectively. A small minority, 13,723 (2.3%) resided in rural ZIP codes. Men who have sex with men were most likely to repeat test (unadjusted, 1-year cumulative incidence after an initial negative test, 16.4%) compared with PWID (13.2%) and persons who did not identify as either MSM or PWID (13.6%). The greatest effect of rurality was within PWID; the adjusted, 1-year cumulative incidence of RHT was 6.4 (95% confidence interval, 1.4-11.4) percentage points higher among metropolitan versus rural PWID. Conclusions One-year cumulative incidence of RHT was low among all clients of publicly funded HIV testing sites in North Carolina, including MSM and PWID for whom annual testing is recommended. Our findings suggest a need for public health efforts to increase access to and support for RHT, particularly among rural PWID

HIV Viral Suppression and Pre-exposure Prophylaxis in HIV and Syphilis Contact Tracing Networks: An Analysis of Disease Surveillance and Prescription Claims Data

Background: HIV and syphilis contact tracing networks offer efficient platforms for HIV treatment and prevention interventions, but intervention coverage within these networks has not been characterized. Setting: HIV and syphilis sexual contact tracing networks among men who have sex with men (MSM) in North Carolina (NC). Methods: Using surveillance data, we identified 2 types of "network events" that occurred between January 2013 and June 2017 among MSM in NC: being diagnosed with early syphilis or being named as a recent sexual contact of a person diagnosed with HIV or early syphilis. We estimated prevalent and incident HIV viral suppression among persons diagnosed with HIV before the network event, and we assessed the effect of contact tracing services on a 6-month cumulative incidence of viral suppression among previously HIV-diagnosed, virally unsuppressed persons. Using linked prescription claims data, we also evaluated prevalent and incident pre-exposure prophylaxis (PrEP) use in an insured subset of HIV-negative network members. Results: Viral suppression prevalence among previously HIV-diagnosed persons was 52.6%. The 6-month cumulative incidence of viral suppression was 35.4% overall and 13.1 (95% confidence interval: 8.8 to 17.4) percentage points higher among persons reached than among those not reached by contact tracing services. Few HIV-negative persons had prevalent (5.4%) or incident (4.1%) PrEP use in the 6 months before or after network events, respectively. Conclusions: Suboptimal viral suppression and PrEP use among MSM in NC in HIV/syphilis contact tracing networks indicate a need for intensified intervention efforts. In particular, expanded services for previously HIV-diagnosed persons could improve viral suppression and reduce HIV transmission within these networks

Pretreatment integrase strand transfer inhibitor resistance in North Carolina from 2010-2016

Objective: We sought to define the prevalence of pretreatment integrase strand transfer inhibitor (INSTI) resistance and assess the transmission networks of those with pretreatment INSTI resistance. Design: A retrospective cohort study of HIV-positive patients with genotypic resistance testing sent to a single referral laboratory in North Carolina between 2010 and 2016. Methods: We linked genotype and public health data for in-care HIV-positive individuals to determine the prevalence of INSTI resistance among treatment-naive (defined as those with a first genotype ≤3 months after diagnosis) and treatment-experienced (defined as those with a first genotype >3 months after diagnosis) patients. We performed molecular and phylogenetic analyses to assess whether pretreatment INSTI resistance mutations represented clustered HIV transmission. Results: Of 8825 individuals who contributed sequences for protease, reverse transcriptase, or INSTI genotypic resistance testing during the study period, 2784 (31%) contributed at least one sequence for INSTI resistance testing. Of these, 840 were treatment-naive individuals and 20 [2.4%, 95% confidence interval (CI): 1.5, 3.6%] had INSTI mutations; only two (0.2%, 95% CI: 0.02, 0.9%) had major mutations. Of 1944 treatment-experienced individuals, 9.6% (95% CI: 8.3, 11.0%) had any INSTI mutation and 7.0% (95% CI: 5.9, 8.3%) had major mutations; the prevalence of INSTI mutations among treatment-experienced patients decreased overtime (P<0.001). In total 12 of 20 individuals with pretreatment INSTI mutations were part of 10 molecular transmission clusters; only one cluster shared identical minor mutations. Conclusion: The prevalence of major pretreatment INSTI resistance is very low. Pretreatment INSTI mutations do not appear to represent clustered HIV transmission

Prediction of HIV transmission cluster growth with statewide surveillance data

Background:Prediction of HIV transmission cluster growth may help guide public health action. We developed a predictive model for cluster growth in North Carolina (NC) using routine HIV surveillance data.Methods:We identified putative transmission clusters with ≥2 members through pairwise genetic distances ≤1.5% from HIV-1 pol sequences sampled November 2010-December 2017 in NC. Clusters established by a baseline of January 2015 with any sequences sampled within 2 years before baseline were assessed for growth (new diagnoses) over 18 months. We developed a predictive model for cluster growth incorporating demographic, clinical, temporal, and contact tracing characteristics of baseline cluster members. We internally and temporally externally validated the final model in the periods January 2015-June 2016 and July 2016-December 2017.Results:Cluster growth was predicted by larger baseline cluster size, shorter time between diagnosis and HIV care entry, younger age, shorter time since the most recent HIV diagnosis, higher proportion with no named contacts, and higher proportion with HIV viremia. The model showed areas under the receiver-operating characteristic curves of 0.82 and 0.83 in the internal and temporal external validation samples.Conclusions:The predictive model developed and validated here is a novel means of identifying HIV transmission clusters that may benefit from targeted HIV control resources. © 2018 Wolters Kluwer Health, Inc. All rights reserved