Dialysis, COVID-19, Poverty, and Race in Greater Chicago: An Ecological Analysis.

RATIONALE & OBJECTIVE: Persons with end-stage kidney disease receiving in-center maintenance hemodialysis may be at high risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure and severe outcomes with coronavirus disease 2019 (COVID-19). The objective of this study was to examine the correlation of SARS-CoV-2 positivity rate per capita and COVID-19-associated deaths with number of dialysis stations and demographics of residents within zip codes in Cook County, IL. STUDY DESIGN: Ecological analysis. SETTING & PARTICIPANTS: Data for SARS-CoV-2 test results and COVID-19-associated deaths during January 21 to June 15, 2020, among the 5,232,412 residents living within the 163 zip codes in Cook County, IL, were merged with demographic and income data from the US Census Bureau. The total number of positive test results in this population was 84,353 and total number of deaths was 4,007. ASSESSMENTS: Number of dialysis stations and stations per capita within a zip code were calculated. SARS-CoV-2-positive test results per capita were calculated as number of positive test results divided by the zip code population. COVID-19-associated deaths per capita were calculated as COVID-19 deaths among residents for a given zip code divided by the zip code population. ANALYTIC APPROACH: Spearman rank correlation coefficients were calculated to examine the correlation of SARS-CoV-2-positive tests per capita and COVID-19-associated deaths per capita with dialysis stations, demographics, and household poverty. To account for multiple testing, statistical significance was considered as P < 0.005. RESULTS: Among the 163 Cook County zip codes, there were 2,501 dialysis stations. Positive test results per capita were significantly associated with number of dialysis stations (r = 0.25; 95% CI, 0.19 to 0.29; P < 0.005) but not with dialysis stations per capita (r = 0.02; 95% CI, -0.03 to 0.08; P = 0.7). Positive test results per capita also correlated significantly with number of households living in poverty (r = 0.57; 95% CI, 0.53-0.6; P < 0.005) and percentage of residents reporting Black race (r = 0.28; 95% CI, 0.23-0.33; P < 0.005) and Hispanic ethnicity (r = 0.68; 95% CI, 0.65-0.7; P < 0.001;). COVID-19-associated deaths per capita correlated significantly with the percentage of residents reporting Black race (r = 0.24; 95% CI, 0.19-0.29; P < 0.005) and with percentage of households living in poverty (r = 0.34; 95% CI, 0.29-0.38; P < 0.005). The association between the number of COVID-19-associated deaths per capita and total number of dialysis stations (r = 0.20; 95% CI, 0.14-0.25; P = 0.01) did not achieve a priori significance, whereas the association with dialysis stations per capita (r = 0.12; 95% CI, 0.07-0.17; P = 0.01) was not significant. LIMITATIONS: Analysis is at the zip code level and not at the person level. CONCLUSIONS: The number of dialysis stations within a zip code correlates with the SARS-CoV-2 positivity rate per capita in Cook County, IL, and this correlation may be driven by population density and the demographics of the residents. These findings highlight the high risk of SARS-CoV-2 exposure for patients with end-stage kidney disease living in poor urban areas.

Theta Modulated Neural Phase Coherence Facilitates Speech Fluency in Adults Who Stutter.

Adults who stutter (AWS) display altered patterns of neural phase coherence within the speech motor system preceding disfluencies. These altered patterns may distinguish fluent speech episodes from disfluent ones. Phase coherence is relevant to the study of stuttering because it reflects neural communication within brain networks. In this follow-up study, the oscillatory cortical dynamics preceding fluent speech in AWS and adults who do not stutter (AWNS) were examined during a single-word delayed reading task using electroencephalographic (EEG) techniques. Compared to AWNS, fluent speech preparation in AWS was characterized by a decrease in theta-gamma phase coherence and a corresponding increase in theta-beta coherence level. Higher spectral powers in the beta and gamma bands were also observed preceding fluent utterances by AWS. Overall, there was altered neural communication during speech planning in AWS that provides novel evidence for atypical allocation of feedforward control by AWS even before fluent utterances.

Dissociable sensitivity and bias mechanisms mediate behavioral effects of exogenous attention.

Attention can be directed endogenously, based on task-relevant goals, or captured exogenously, by salient stimuli. While recent studies have shown that endogenous attention can facilitate behavior through dissociable sensitivity (sensory) and choice bias (decisional) mechanisms, it is unknown if exogenous attention also operates through dissociable sensitivity and bias mechanisms. We tested human participants on a multialternative change detection task with exogenous attention cues, which preceded or followed change events in close temporal proximity. Analyzing participants' behavior with a multidimensional signal detection model revealed clear dissociations between exogenous cueing effects on sensitivity and bias. While sensitivity was, overall, lower at the cued location compared to other locations, bias was highest at the cued location. With an appropriately designed post-cue control condition, we discovered that the attentional effect of exogenous pre-cueing was to enhance sensitivity proximal to the cue. In contrast, exogenous attention enhanced bias even for distal stimuli in the cued hemifield. Reaction time effects of exogenous cueing could be parsimoniously explained with a diffusion-decision model, in which drift rate was determined by independent contributions from sensitivity and bias at each location. The results suggest a mechanistic schema of how exogenous attention engages dissociable sensitivity and bias mechanisms to shape behavior.

Cortical dynamics of disfluency in adults who stutter.

Stuttering is a disorder of speech production whose origins have been traced to the central nervous system. One of the factors that may underlie stuttering is aberrant neural miscommunication within the speech motor network. It is thus argued that disfluency (any interruption in the forward flow of speech) in adults who stutter (AWS) could be associated with anomalous cortical dynamics. Aberrant brain activity has been demonstrated in AWS in the absence of overt disfluency, but recording neural activity during disfluency is more challenging. The paradigm adopted here took an important step that involved overt reading of long and complex speech tokens under continuous EEG recording. Anomalies in cortical dynamics preceding disfluency were assessed by subtracting out neural activity for fluent utterances from their disfluent counterparts. Differences in EEG spectral power involving alpha, beta, and gamma bands, as well as anomalies in phase-coherence involving the gamma band, were observed prior to the production of the disfluent utterances. These findings provide novel evidence for compromised cortical dynamics that directly precede disfluency in AWS.

Anomaly in neural phase coherence accompanies reduced sensorimotor integration in adults who stutter.

Despite advances in our understanding of the human speech system, the neurophysiological basis of stuttering remains largely unknown. Here, it is hypothesized that the speech of adults who stutter (AWS) is susceptible to disruptions in sensorimotor integration caused by neural miscommunication within the speech motor system. Human speech unfolds over rapid timescales and relies on a distributed system of brain regions working in a parallel and synchronized manner, and a breakdown in neural communication between the putative brain regions could increase susceptibility to dysfluency. Using a speech motor adaptation paradigm under altered auditory feedback with simultaneous recording of EEG, the oscillatory cortical dynamics was investigated in stuttering and fluent adults (FA). Auditory feedback perturbation involved the shifting of the formant frequencies of the target vowel sound. Reduced adaptation in response to the feedback error was observed in AWS and was accompanied by differences in EEG spectral powers and anomalies in phase coherence evolving over the course of speech motor training. It is understood that phase coherence possibly captures neural communication within speech motor networks. Thus, the phase coherence network of the two groups exhibited differences involving the EEG frequency bands. These findings in anomalous neural synchrony provide novel evidence for compromised neuronal communication at short time scales within the speech motor network of AWS.

The predictive roles of neural oscillations in speech motor adaptability.

The human speech system exhibits a remarkable flexibility by adapting to alterations in speaking environments. While it is believed that speech motor adaptation under altered sensory feedback involves rapid reorganization of speech motor networks, the mechanisms by which different brain regions communicate and coordinate their activity to mediate adaptation remain unknown, and explanations of outcome differences in adaption remain largely elusive. In this study, under the paradigm of altered auditory feedback with continuous EEG recordings, the differential roles of oscillatory neural processes in motor speech adaptability were investigated. The predictive capacities of different EEG frequency bands were assessed, and it was found that theta-, beta-, and gamma-band activities during speech planning and production contained significant and reliable information about motor speech adaptability. It was further observed that these bands do not work independently but interact with each other suggesting an underlying brain network operating across hierarchically organized frequency bands to support motor speech adaptation. These results provide novel insights into both learning and disorders of speech using time frequency analysis of neural oscillations.

Redistribution of neural phase coherence reflects establishment of feedforward map in speech motor adaptation.

Despite recent progress in our understanding of sensorimotor integration in speech learning, a comprehensive framework to investigate its neural basis is lacking at behaviorally relevant timescales. Structural and functional imaging studies in humans have helped us identify brain networks that support speech but fail to capture the precise spatiotemporal coordination within the networks that takes place during speech learning. Here we use neuronal oscillations to investigate interactions within speech motor networks in a paradigm of speech motor adaptation under altered feedback with continuous recording of EEG in which subjects adapted to the real-time auditory perturbation of a target vowel sound. As subjects adapted to the task, concurrent changes were observed in the theta-gamma phase coherence during speech planning at several distinct scalp regions that is consistent with the establishment of a feedforward map. In particular, there was an increase in coherence over the central region and a decrease over the fronto-temporal regions, revealing a redistribution of coherence over an interacting network of brain regions that could be a general feature of error-based motor learning in general. Our findings have implications for understanding the neural basis of speech motor learning and could elucidate how transient breakdown of neuronal communication within speech networks relates to speech disorders.