Endocardial and epicardial activation maps for three-dimensional-perimitral flutter using a three-dimensional mapping system: A case report

Background Perimitral flutter (PMF) is a macro-reentrant tachycardia, and mitral isthmus (MI) linear ablation is considered to be the preferable mode of treatment. Additionally, PMF can sometimes develop via epicardial connections, including coronary sinus and vein of Marshall. However, there are no reports of three-dimensional (3 D) atrial tachycardia (AT) via the intramural tissue. Case summary A 78-year-old man underwent catheter ablation for paroxysmal atrial fibrillation and AT, including pulmonary vein isolation, left atrial posterior wall isolation, superior vena cava isolation, and MI linear ablation in a total of four procedures. However, AT reoccurred, and he underwent a fifth procedure for AT. Although the MI block line was complete in both the endocardial and epicardial voltage maps, AT indicated PMF. The total activation time did not cover all phases of tachycardia cycle length due to the conduction pathway through the intramural muscle/bundles that could not be mapped with the addition of epicardial mapping. The tachycardia was terminated by ablation at the mitral valve annulus in the 2 o'clock position, where the bundles might have been attached. Discussion Both endocardial and epicardial activation maps indicated 3 D-PMF, whose circuit included the intramural muscle and bundles in a tachycardia circuit. It is necessary to recognise AT, which is involved via intramural tissues.

The Taxonomy of Writing Systems: How to Measure how Logographic a System is

Taxonomies of writing systems since Gelb (1952) have classified systems based on what the written symbols represent: if they represent words or morphemes, they are logographic; if syllables, syllabic; if segments, alphabetic; etc. Sproat (2000) and Rogers (2005) broke with tradition by splitting the logographic and phonographic aspects into two dimensions, with logography being graded rather than a categorical distinction. A system could be syllabic, and highly logographic; or alphabetic, and mostly non-logographic. This accords better with how writing systems actually work, but neither author proposed a method for measuring logography. In this article we propose a novel measure of the degree of logography that uses an attention based sequence-to-sequence model trained to predict the spelling of a token from its pronunciation in context. In an ideal phonographic system, the model should need to attend to only the current token in order to compute how to spell it, and this would show in the attention matrix activations. In contrast, with a logographic system, where a given pronunciation might correspond to several different spellings, the model would need to attend to a broader context. The ratio of the activation outside the token and the total activation forms the basis of our measure. We compare this with a simple lexical measure, and an entropic measure, as well as several other neural models, and argue that on balance our attention-based measure accords best with intuition about how logographic various systems are. Our work provides the first quantifiable measure of the notion of logography that accords with linguistic intuition and, we argue, provides better insight into what this notion means.

Reduction of Conduction Velocity in Patients with Atrial Fibrillation

It is unknown to what extent atrial fibrillation (AF) episodes affect intra-atrial conduction velocity (CV) and whether regional differences in local CV heterogeneities exist during sinus rhythm. This case-control study aims to compare CV assessed throughout both atria between patients with and without AF. Patients (n = 34) underwent intra-operative epicardial mapping of the right atrium (RA), Bachmann’s bundle (BB), left atrium (LA) and pulmonary vein area (PVA). CV vectors were constructed to calculate median CV in addition to total activation times (TAT) and unipolar voltages. Biatrial median CV did not differ between patients with and without AF (90 ± 8 cm/s vs. 92 ± 6 cm/s, p = 0.56); only BB showed a CV reduction in the AF group (79 ± 12 cm/s vs. 88 ± 11 cm/s, p = 0.02). In patients without AF, there was no predilection site for the lowest CV (P5) (RA: 12%; BB: 29%; LA: 29%; PVA: 29%). In patients with AF, lowest CV was most often measured at BB (53%) and ranged between 15 to 22 cm/s (median: 20 cm/s). Lowest CVs were also measured at the LA (18%) and PVA (29%), but not at the RA. AF was associated with a prolonged TAT (p = 0.03) and decreased voltages (P5) at BB (p = 0.02). BB was a predilection site for slowing of conduction in patients with AF. Prolonged TAT and decreased voltages were also found at this site. The next step will be to determine the relevance of a reduced CV at BB in relation to AF development and maintenance.

Creativity Is Optimal Novelty and Maximal Positive Affect: A New Definition Based on the Spreading Activation Model

Creativity is commonly defined as a process that leads to a novel and useful outcome (an idea, product, or expression). However, two dilemmas about this definition remain unresolved: (1) A strict application of usefulness is difficult to apply to artistic works: who decides what artwork is useful, and how it is useful? (2) The implied boundary conditions of novelty are problematic: The default perspective is that novelty has a monotonic increasing relationship with creativity, or it is categorical—i.e., novel or not. To address these dilemmas, this paper proposes a spreading activation model of creativity (SAMOC), a model built on a brain-architecture-inspired vast interconnected network of nodes, each node representing information, and assigned meanings through interaction with the environment. Nodes are linked to each other according to principles of temporal contiguity (linking objects/events in time) and similarity (linking objects/events by shared features). A node activated by attention spreads through the network through previously linked nodes. Nodes that are well connected activate each other easily, while those that are weakly connected do not. Net total activation corresponds to positive affect (e.g., pleasure), and this is proposed as an essential criteria for a creative work of art, instead of usefulness. SAMOC also predicts that creativity will be optimized at an intermediate, not extreme, level of novelty. Too much activation will occur with the activation of preexisting ideas (hence reproduction rather than creativity), and too much novelty will not produce spread of activation. The two functions (spreading activation and the novelty curve) are superposed to demonstrate this optimal novelty hypothesis. Early evidence of the hypothesis comes from the data that some great works of art were critically rejected at premiers (suggesting excessive novelty), but after sufficient repetition (and therefore linking) became suitably associated and commenced generating activation. The hypothesis has important implications for future empirical research programs on creativity, and for the definition of creativity itself.

RETRO-MAPPING: A New Approach to Activation Mapping in Persistent Atrial Fibrillation Reveals Evidence of Spatiotemporal Stability

Background - The mechanisms underlying AF remain controversial. We developed RETRO-Mapping to characterize activation wavefronts by direction and uniformity, accumulating data as an orbital plot and analyzed as frequency histograms. We applied this technique to patients undergoing AF ablation to determine if AF activation is random. Methods - Patients undergoing persistent AF ablation were recruited and an AFocusII was positioned at multiple left atrial locations and kept steady for 1min to collect electrograms. The AFocusII was returned to the original site and position after >10mins for a repeat 1min data collection. Data was exported to custom RETRO-Mapping software, and 30sec consecutive time windows at each location were studied using frequency histograms of wavefronts. R50 (the range in degrees containing 50% of the total activation) was used as a method to enable statistical comparisons of activation patterns. Electrogram characterization into categories of complex fractionated atrial electrograms (CFAEs) by Ensite Precision was subjected to similar analysis. Results - Consecutive 30secs segments were studied at 161 locations in 18pts. Mean overlap between frequency histograms was 79.5%±7.7 (95%CI 78.3 to 80.7). 9 patients underwent delayed mapping at the same location, and mean overlap between the first 30sec and >10min interval was 73%±11.8 and 71.9%±13.6 for consecutive 30sec segments. Stability was confirmed using R50 (Bland-Altman mean difference: 0.87; LOA: -34.0 to 36.0; r=0.005; P=0.95). A greater variance in R50 was observed between different locations within a patient than the variance within the same locations (ICC=0.765; p<0.0001), and similarly for both CFAE and bipolar voltage (P<0.0001). A larger area containing CFAE (80-120ms) showed weak positive correlation with increasing R50 (r = 0.36, P<0.001) suggesting a relationship between activation pattern and electrogram characteristics. Conclusions - There appears to be preferential activation patterns during persistent AF indicating spatiotemporal stability. This has important implication to our mechanistic understanding of persistent AF.

Production cross–section and reaction yield calculations for 123-126I isotopes on 123Sb(α,xn) reactions

Most of the radioisotopes used in the medical fields, like examination and treatment studies, were produced by employing nuclear reactions. Within the process of a nuclear reaction, one of the most important parameters is the cross-section data, which help reveal the reaction phenomenon's mechanisms. The main intention of this study is to investigate the efficiencies of producing iodine isotopes via 123Sb(α,xn) reactions. For this, optical and level density models of TALYS 1.8 code have been used. Production cross-section, the alpha beam energy, reaction yields, and total activation of radioisotopes have been computed. It has been figured out that a 45 MeV cyclotron could be enough for producing 123-126I radioisotopes with reaction yields of 39.3372, 5.5685, 0.2410, and 0.0796 GBq/mAh, respectively.

Inducibility of atrial fibrillation is associated with disturbed activation pattern in bachmanns bundle

Background Electrophysiological differences in Bachmann's bundle (BB) between patients with a history of atrial fibrillation (AF) and patients without prior tachyarrhythmias have been demonstrated, including a higher proportion of conduction block (CB) and longer lines of CB. However, whether conduction abnormalities in BB influence inducibility of AF is yet unknown. Purpose To investigate which electrophysiological characteristics of BB during sinus rhythm increase susceptibility to AF in patients undergoing elective cardiac surgery, using intraoperative high density epicardial mapping data. Methods Fifty-four patients without a history of AF, admitted for correction of structural cardiac disease (coronary artery disease, heart valve regurgitation or stenosis or congenital heart disease), were examined. Epicardial mapping of Bachmann's bundle during sinus rhythm was performed using a rectangle-shaped electrode array (192 electrodes, interelectrode distance: 2mm). AF was induced using bursts of fixed rate pacing. Patients in whom sustained AF was induced (lasting throughout the mapping procedure, N=34) and patients in whom AF was non-inducible (N=20) were compared with respect to lines of conduction block (CB, defined as interelectrode conduction time &gt;12ms), total activation time of Bachmann's bundle and patterns of activation. Results AF inducibility was not related to patient characteristics. Patients in whom AF was induced showed a higher proportion of CB (3.23 (0.0–23.9)% vs 1.82 (0.048- 4.6)%, p&lt;0.05), longer maximum lines of CB (12 (0–78)mm vs 9 (2–24)mm, p&lt;0.05) and a longer total activation time (55.0 (24.0–154.5)ms vs 41.8 (23.0–73.0)ms, p&lt;0.01) compared to patients in the non-inducibility group. In addition, BB was activated by more separate waves entering the mapping area from different directions in the induced AF group; more than 1 wave entered BB in 22 (65%) of the induced AF patients versus 7 (40%) of non-inducibility patients, p&lt;0.05. Conclusion Inducibility of AF is associated with an increased proportion of CB, longer maximum continuous lines of CB, a longer total activation time of BB and more than 1 wave entering the mapping area from different directions during sinus rhythm. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Dutch Heart Foundation

What Cognitive Mechanisms Do People Reflect on When They Predict IAT Scores?

Research indicates that individuals can prospectively predict biases they will show on the implicit-association test (IAT). The present study uses the Quadruple process model to analyze data from Hahn, Judd, Hirsh, and Blair to investigate which cognitive mechanisms people reflect on when predicting their racial bias scores on the IAT. The Quadruple process model reveals that a combination of activated associations and self-regulatory control best explains what participants report when they predict their biases on the IAT. Furthermore, it appears to be specifically the total activation of positive attitudes toward Whites and negative attitudes toward minorities rather than negative attitudes toward minorities alone, that participants use to make their predictions.

What cognitive mechanisms do people reflect on when they predict IAT scores?

Research indicates that individuals can prospectively predict biases they will show on the IAT (Hahn, Judd, Hirsh, &amp; Blair, 2014). The present study uses the Quadruple process model to analyze data from Hahn et al. (2014) to investigate which cognitive mechanisms people reflect on when predicting their racial bias scores on the IAT. The Quadruple process model reveals that a combination of activated associations and self-regulatory control best explains what participants report when they predict their biases on the IAT. Further, it appears to be specifically the total activation of positive attitudes toward Whites and negative attitudes toward minorities rather than negative attitudes towards minorities alone, that participants use to make their predictions.

Correlation of Impedance and Effective Electrode Area of Iridium Oxide Neural Electrodes

Iridium oxide is routinely used for bionic applications owing to its high charge injection capacity. The electrode impedance at 1 kHz is typically reported to predict neural recording performance. In this article, the impedance of activated iridium oxide films (AIROFs) has been examined. The impedance of unactivated iridium electrodes was half that of platinum electrodes of similar geometry, indicating some iridium oxide was present on the electrode surface. A two time constant equivalent circuit was used to model the impedance of activated iridium. The impedance at low and intermediate frequencies decreased with increasing number of activation pulses and total activation charge. The impedance at 12 Hz correlated with the steady-state diffusion electroactive area. The impedance at 12 Hz also correlated with the charge density of the electrode. The high charge density and low impedance of AIROFs may provide improved neural stimulation and recording properties compared with typically used platinum electrodes.