Tracking the implicit acquisition of nonadjacent transitional probabilities by ERPs

The implicit acquisition of complex probabilistic regularities has been found to be crucial in numerous automatized cognitive abilities, including language processing and associative learning. However, the neurocognitive processes supporting the implicit extraction of 2nd order non-adjacent transitional probabilities have not been completely elucidated. Therefore, this study investigated the sensitivity of event-related brain potentials (ERPs) to these probabilistic regularities embedded in a sequence of visual stimuli without providing explicit information on the structure of the stimulus stream. Healthy young adults (N = 32) performed a perceptual-motor RT task that included an alternating sequential regularity between non-adjacent trials while RTs and ERPs were measured time-locked to the onset of the stimulus. RT effects indicated the rapid acquisition of transitional probabilities. The acquisition process was also tracked by the P3 component. Modulations of the P3 amplitude indicated that the more probable short-range relations could be integrated in the internal representations formed on the experienced stimulus environment. Meanwhile, the less probable short-range relations delivered possibly surprising information over the course of the task, by which the internal representations could have been updated. These results suggest that representations on the probabilistic regularities of the ongoing stimulus context are implicitly formed and constantly revised. Overall, this study (1) highlights the role of predictive processes during implicit memory formation, and (2) delineates a potential to gain further insight into the dynamics of implicit acquisition processes

Perceiving structure in unstructured stimuli: implicitly acquired prior knowledge impacts the processing of unpredictable transitional probabilities

It is unclear how implicit prior knowledge is involved and remains persistent in the extraction of the statistical structure underlying sensory input. Therefore, this study investigated whether the implicit knowledge of second-order transitional probabilities characterizing a stream of visual stimuli impacts the processing of unpredictable transitional probabilities embedded in a similar input stream. Young adults (N = 50) performed a four-choice reaction time (RT) task that consisted of structured and unstructured blocks. In the structured blocks, more probable and less probable short-range nonadjacent transitional probabilities were present. In the unstructured blocks, the unique combinations of the short-range transitional probabilities occurred with equal probability; therefore, they were unpredictable. All task blocks were visually identical at the surface level. While one-half of the participants completed the structured blocks first followed by the unstructured blocks, this was reversed in the other half of them. The change in the structure was not explicitly denoted, and no feedback was provided on the correctness of each response. Participants completing the structured blocks first showed faster RTs to more probable than to less probable short-range transitional probabilities in both the structured and unstructured blocks, indicating the persistent effect of prior knowledge. However, after extended exposure to the unstructured blocks, they updated this prior knowledge. Participants completing the unstructured blocks first showed the RT difference only in the structured blocks, which was not constrained by the preceding exposure to unpredictable stimuli. The results altogether suggest that implicitly acquired prior knowledge of predictable stimuli influences the processing of subsequent unpredictable stimuli. Updating this prior knowledge seems to require a longer stretch of time than its initial acquisition

Prehistoric uses of circumpolar mineral resources: Insights and emerging questions from Arctic archaeology

Background. There are little comparative data on catheter ablation of paroxysmal atrial fibrillation (AF) using the contact force radiofrequency (CF-RF) catheter versus the second-generation cryoballoon (CB2). Methods and results. This is a single center, retrospective, nonrandomized study of 98 patients with symptomatic, drug-refractory paroxysmal AF who underwent their first PVI ablation using either the CB2 (n=40) or CF-RF (n=58). The mean age was 60 years with 63% men, a mean LA size of 42 mm. The procedure duration (74±17 versus 120±49 minutes p<0.05) was shorter for CB2 group; the fluoroscopy time (14±17 versus 16±5 minutes, p=0.45) was similar. Complete PVI was achieved in 96% of patients with RF-CF and 98% with CB2. Phrenic nerve palsies (2 transient and 1 persistent) occurred exclusively in the CB2 group and 1 severe, nonlethal complication (pericardial tamponade) occurred in the CF-RF group. At 24-month follow-up, the success rate, defined as freedom from AF/atrial tachycardia (AT) after a single procedure without antiarrhythmic drug, was comparable in CF-RF group and CB2 group (65.5% versus 67%, resp., log rank p=0.54). Conclusion. Both the CB2 and the RF-CF ablation appeared safe; the success rate at 2 years was comparable between both technologies

Adaptation to recent outcomes attenuates the lasting effect of initial experience on risky decisions

Both primarily and recently encountered information have been shown to influence experience-based risky decision making. The primacy effect predicts that initial experience will influence later choices even if outcome probabilities change and reward is ultimately more or less sparse than primarily experienced. However, it has not been investigated whether extended initial experience would induce a more profound primacy effect upon risky choices than brief experience. Therefore, the present study tested in two experiments whether young adults adjusted their risk-taking behavior in the Balloon Analogue Risk Task after an unsignaled and unexpected change point. The change point separated early “good luck” or “bad luck” trials from subsequent ones. While mostly positive (more reward) or mostly negative (no reward) events characterized the early trials, subsequent trials were unbiased. In Experiment 1, the change point occurred after one-sixth or one-third of the trials (brief vs. extended experience) without intermittence, whereas in Experiment 2, it occurred between separate task phases. In Experiment 1, if negative events characterized the early trials, after the change point, risk-taking behavior increased as compared with the early trials. Conversely, if positive events characterized the early trials, risk-taking behavior decreased after the change point. Although the adjustment of risk-taking behavior occurred due to integrating recent experiences, the impact of initial experience was simultaneously observed. The length of initial experience did not reliably influence the adjustment of behavior. In Experiment 2, participants became more prone to take risks as the task progressed, indicating that the impact of initial experience could be overcome. Altogether, we suggest that initial beliefs about outcome probabilities can be updated by recent experiences to adapt to the continuously changing decision environment

Evaluation of Isolation Area, Myocardial Injury and Left Atrial Function Following High-Power Short-Duration Radiofrequency or Second-Generation Cryoballoon Ablation for Atrial Fibrillation

This randomized study aims to compare the left atrial (LA) lesion size, function, and tissue damage following pulmonary vein isolation (PVI) by high-power short-duration (HPSD) radiofrequency (RF) and second-generation cryoballoon (CB2) ablation. We enrolled 40 patients with paroxysmal atrial fibrillation who underwent PVI by HPSD RF (n = 21) or CB2 (n = 19). Every patient underwent LA CT angiography and transthoracic echocardiography (TTE) to assess the LA anatomy and function. Biomarker levels (hs-cTnT, hs-CRP, LDH) were compared pre- and post-procedurally. Pre- and post-ablation high-density mapping (HDM) was performed. The isolation area was defined under 0.2 mV bipolar voltage (low voltage area, LVA). We calculated the post-PVI LVA/LA surface ratio using LA CT-HDM merge images. At 3-month follow-up, TTE was performed to assess the changes in LA function. Post-ablation hs-cTnT level was significantly higher in the RF group (RF: 1249 ± 469 ng/L, CB2: 995 ± 280 ng/L, p = 0.024). Post-PVI hs-CRP (RF: 9.53 ± 10.30 mg/L, CB2: 12.36 ± 5.76 mg/L, p = 0.034) and LDH levels (RF: 349.9 ± 65.6 U/L, CB2: 451.6 ± 91.3 U/L, p p = 0.022). LA function did not change significantly after the PVI procedure. Our data indicate that second-generation cryoballoon ablation produces a significantly larger LA lesion size compared to “point-by-point” HPSD radiofrequency. Both techniques preserve LA function. The myocardial component of tissue loss appears to be higher using HPSD radiofrequency ablation, with less collateral damage