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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.

Sengupta R, Nasir SM. Redistribution of neural phase coherence reflects establishment of feedforward map in speech motor adaptation. J Neurophysiol 113: 2471-2479, 2015. First published January 28, 2015 doi:10.1152/jn.00731.2014.-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. speech motor learning; neural oscillations; feedforward map AS WE LEARN TO SPEAK, THE auditory, somatosensory and motor areas of our brain operate in parallel to perceive speech stimuli, detect feedback errors and generate the motor commands necessary to achieve speech goals (Guenther 2006;Perkell 2012;Tourville et al. 2008). While this process is believed to involve coordinated activity over several distributed brain areas (Guenther 2006;Hickok et al. 2011;Scott and Wise 2004), the neural mechanisms underlying their precise spatiotemporal coordination remain elusive. The oscillatory dynamics inherent in the brain's electrical activity provide a suitable means to study the neural communication within brain networks (Golfinopoulos et al. 2010;Varela et al. 2011) at timescales relevant for speech. In this study, we provide evidence that brain oscillation patterns change as a result of speech motor adaptation, enabling us to probe into the neural basis of learning at finer temporal resolutions.In recent years, the role of neuronal oscillations and crossfrequency phase coupling, particularly in the theta (3-8 Hz) and gamma (30 -55 Hz) bands, has been demonstrated in a variety of cognitive and sensorimotor tasks in humans involv- (Schack et al. 2002). Based on these results, it has been proposed that communication within brain networks during behavior is facilitated by synchronous neuronal o...

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...

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.