Multifractal Multiscale Analysis of Human Movements during Cognitive Tasks.

Continuous adaptations of the movement system to changing environments or task demands rely on superposed fractal processes exhibiting power laws, that is, multifractality. The estimators of the multifractal spectrum potentially reflect the adaptive use of perception, cognition, and action. To observe time-specific behavior in multifractal dynamics, a multiscale multifractal analysis based on DFA (MFMS-DFA) has been recently proposed and applied to cardiovascular dynamics. Here we aimed at evaluating whether MFMS-DFA allows identifying multiscale structures in the dynamics of human movements. Thirty-six (12 females) participants pedaled freely, after a metronomic initiation of the cadence at 60 rpm, against a light workload for 10 min: in reference to cycling (C), cycling while playing "Tetris" on a computer, alone (CT) or collaboratively (CTC) with another pedaling participant. Pedal revolution periods (PRP) series were examined with MFMS-DFA and compared to linearized surrogates, which attested to a presence of multifractality at almost all scales. A marked alteration in multifractality when playing Tetris was evidenced at two scales, τ ≈ 16 and τ ≈ 64 s, yet less marked at τ ≈ 16 s when playing collaboratively. Playing Tetris in collaboration attenuated these alterations, especially in the best Tetris players. This observation suggests the high sensitivity to cognitive demand of MFMS-DFA estimators, extending to the assessment of skill/demand interplay from individual behavior. So, by identifying scale-dependent multifractal structures in movement dynamics, MFMS-DFA has obvious potential for examining brain-movement coordinative structures, likely with sufficient sensitivity to find echo in diagnosing disorders and monitoring the progress of diseases that affect cognition and movement control.

Contact tracing-induced Allee effect in disease dynamics.

Contact tracing, case isolation, quarantine, social distancing, and other non-pharmaceutical interventions (NPIs) have been a cornerstone in managing the COVID-19 pandemic. However, their effects on disease dynamics are not fully understood. Saturation of contact tracing caused by the increase of infected individuals has been recognized as a crucial variable by healthcare systems worldwide. Here, we model this saturation process with a mechanistic and a phenomenological model and show that it induces an Allee effect which could determine an infection threshold between two alternative states-containment and outbreak. This transition was considered elsewhere as a response to the strength of NPIs, but here we show that they may be also determined by the number of infected individuals. As a consequence, timing of NPIs implementation and relaxation after containment is critical to their effectiveness. Containment strategies such as vaccination or mobility restriction may interact with contact tracing-induced Allee effect. Each strategy in isolation tends to show diminishing returns, with a less than proportional effect of the intervention on disease containment. However, when combined, their suppressing potential is enhanced. Relaxation of NPIs after disease containment--e.g. because vaccination--have to be performed in attention to avoid crossing the infection threshold required to a novel outbreak. The recognition of a contact tracing-induced Allee effect, its interaction with other NPIs and vaccination, and the existence of tipping points contributes to the understanding of several features of disease dynamics and its response to containment interventions. This knowledge may be of relevance for explaining the dynamics of diseases in different regions and, more importantly, as input for guiding the use of NPIs, vaccination campaigns, and its combination for the management of epidemic outbreaks.

Adaptive Discount Factor for Deep Reinforcement Learning in Continuing Tasks with Uncertainty.

Reinforcement learning (RL) trains an agent by maximizing the sum of a discounted reward. Since the discount factor has a critical effect on the learning performance of the RL agent, it is important to choose the discount factor properly. When uncertainties are involved in the training, the learning performance with a constant discount factor can be limited. For the purpose of obtaining acceptable learning performance consistently, this paper proposes an adaptive rule for the discount factor based on the advantage function. Additionally, how to use the advantage function in both on-policy and off-policy algorithms is presented. To demonstrate the performance of the proposed adaptive rule, it is applied to PPO (Proximal Policy Optimization) for Tetris in order to validate the on-policy case, and to SAC (Soft Actor-Critic) for the motion planning of a robot manipulator to validate the off-policy case. In both cases, the proposed method results in a better or similar performance compared with cases using the best constant discount factors found by exhaustive search. Hence, the proposed adaptive discount factor automatically finds a discount factor that leads to comparable training performance, and that can be applied to representative deep reinforcement learning problems.

Distinguishing experts from novices by the Mind's Hand and Mind's Eye.

Tetris is a complex task notable for the increasingly substantial demands it makes on perception, decision-making, and action as the game is played. To investigate these issues, we collected data on 39 features of Tetris play for each Tetris zoid (piece), for up to 16 levels of difficulty, as each of 240 players played an hour of Tetris under laboratory conditions. Using only early (level 1) data, we conducted a Principle Component Analysis which found intriguing differences among its three, statistically significant, principle components. Each of these components captures different combinations of perception, decision-making, and action which suggests differing higher level skills, tactics, and strategies. Each component is presented and discussed, and then used in a series of principle component regression analyses on subsets of these data (a) from different Tetris levels, as well as (b) from players of different levels of expertise. We validate these models with data collected at a locally held Tetris tournament. These components represent elements of expertise; namely, correlations among perceptual, decision-making, and motor features that represent processing stages and hierarchical control and which distinguish expert from novice Tetris players. These components provide evidence for an integrated complex of processes - the Mind's Hand and the Mind's Eye - that are the essence of expertise in the real-time, sequential-decision-making task of Tetris.

A double-blind randomized pilot trial comparing computerized cognitive exercises to Tetris in adolescents with attention-deficit/hyperactivity disorder.

BACKGROUND: The purpose of this trial was to examine the feasibility and efficacy of computerized cognitive exercises from Scientific Brain Training (SBT), compared to the computer game Tetris as an active placebo, in a pilot study of adolescents with attention-deficit/hyperactivity disorder (ADHD). METHOD: Eighteen adolescents with ADHD were randomized to treatment or control intervention for 7 weeks. Outcome measures were cognitive test, symptom, and motivation questionnaires. RESULTS: SBT and Tetris were feasible as home-based interventions, and participants' compliance was high, but participants perceived both interventions as not very interesting or helpful. There were no significant group differences on cognitive and ADHD-symptom measures after intervention. Pre-post intra-group measurement showed that the SBT had a significant beneficial effect on sustained attention, while the active placebo had significant beneficial effects on working memory, both with large effect sizes. CONCLUSION: Although no significant differences were found between groups on any measure, there were significant intra-group changes for each group.

Meta-T: TetrisⓇ as an experimental paradigm for cognitive skills research.

Studies of human performance in complex tasks using video games are an attractive prospect, but many existing games lack a comprehensive way to modify the game and track performance beyond basic levels of analysis. Meta-T provides experimenters a tool to study behavior in a dynamic task environment with time-stressed decision-making and strong perceptual-motor elements, offering a host of experimental manipulations with a robust and detailed logging system for all user events, system events, and screen objects. Its experimenter-friendly interface provides control over detailed parameters of the task environment without need for programming expertise. Support for eye-tracking and computational cognitive modeling extend the paradigm's scope.

Short-term transfer effects of Tetris on mental rotation: Review and registered report - A Bayesian approach.

The existence of transfer effects of video games on cognitive performance are controversially discussed in experimental psychology. Whereas recent meta-analyses suggest the absence of far transfer effects, empirical evidence regarding near transfer effects is more controversial. This conceptual replication investigated the short-term near transfer effect of playing Tetris on mental rotation abilities. The design of the conceptual replication was based on a comprehensive compilation of the methods used by previous literature on this topic and advanced in order to reach a high scientific state-of-the-art standard. We ran a high-powered conceptual replication study with 366 participants randomly assigned to either an experimental group playing Tetris or a control group playing Solitaire. Both groups completed three commonly used mental rotation tests in a pre- and a posttest session. Additionally, the experimental group played Tetris while the control group played Solitaire. Playing time was 10 hours in total within 4 weeks. Based on previous research, we hypothesized that this might generate a short-term transfer effect of Tetris on mental rotation. While participants showed a repeated testing effect for the mental rotation tests in both groups, we found evidence that Tetris does not produce a short-term transfer effect on mental rotation. Both gender and expected outcomes did not influence this effect. Our study suggests that playing Tetris does not improve mental rotation skills.

Real-time estimation of EEG-based engagement in different tasks.

Objective.Recent trends in brain-computer interface (BCI) research concern the passive monitoring of brain activity, which aim to monitor a wide variety of cognitive states. Engagement is such a cognitive state, which is of interest in contexts such as learning, entertainment or rehabilitation. This study proposes a novel approach for real-time estimation of engagement during different tasks using electroencephalography (EEG).Approach.Twenty-three healthy subjects participated in the BCI experiment. A modified version of the d2 test was used to elicit engagement. Within-subject classification models which discriminate between engaging and resting states were trained based on EEG recorded during a d2 test based paradigm. The EEG was recorded using eight electrodes and the classification model was based on filter-bank common spatial patterns and a linear discriminant analysis. The classification models were evaluated in cross-task applications, namely when playing Tetris at different speeds (i.e. slow, medium, fast) and when watching two videos (i.e. advertisement and landscape video). Additionally, subjects' perceived engagement was quantified using a questionnaire.Main results.The models achieved a classification accuracy of 90% on average when tested on an independent d2 test paradigm recording. Subjects' perceived and estimated engagement were found to be greater during the advertisement compared to the landscape video (p= 0.025 andp<0.001, respectively); greater during medium and fast compared to slow Tetris speed (p<0.001, respectively); not different between medium and fast Tetris speeds. Additionally, a common linear relationship was observed for perceived and estimated engagement (rrm= 0.44,p<0.001). Finally, theta and alpha band powers were investigated, which respectively increased and decreased during more engaging states.Significance.This study proposes a task-specific EEG engagement estimation model with cross-task capabilities, offering a framework for real-world applications.

The effectiveness of two novel approaches to prevent intrusions: A pilot study comparing Tetris_dualtask and imagery rescripting to control.

BACKGROUND AND OBJECTIVES: Post-traumatic stress disorder (PTSD) is a global health problem. Although effective treatments for it exist, early interventions that prevent PTSD from developing are lacking. The aim of this pilot analogue trauma study was to compare the effects of two potential early intervention strategies, namely Tetris_dualtask and imagery rescripting (IR) to a no-intervention control group on intrusion frequency and the vividness and emotionality of aversive film memory. METHODS: Sixty healthy students were subjected to the trauma film paradigm and randomly allocated to either: Tetris_dualtask, IR or no-intervention. Main outcomes were the number of film-related intrusions at one week and vividness and emotionality ratings of the most aversive film memory. Secondary outcomes were PTSD-like symptoms, intrusion intensity, and explicit film memory. RESULTS: The Tetris_dualtask group reported significant fewer intrusions compared to the no-intervention group; whereas the IR group did not. No effect was found on vividness and emotionality ratings, PTSD-like symptoms, intrusion intensity, and explicit memory. LIMITATIONS: The sample size was small, and analogue trauma in healthy individuals was examined, thus generalizability may be limited. Also, to increase comparability between interventions, the duration of Tetris_dualtask and IR was standardized. As a result, the IR intervention was shorter compared to other studies, which might have decreased its efficacy. CONCLUSIONS: The results of this pilot study suggest that playing Tetris during retrieval of traumatic images, might hold potential as an early intervention strategy to reduce intrusions in the early aftermath of trauma and adversity. However, future large-scale replication research is needed.

Dorsal Preservation Versus Structural Techniques and Their Application.

Structure rhinoplasty and preservation rhinoplasty are 2 popular philosophies that can be used alone or in combination to provide a hybrid approach. Structure rhinoplasty is the leading option for revision rhinoplasty and utilizes cartilage grafting techniques to support and reconstruct the nose. Preservation rhinoplasty spares bone, cartilage, ligaments, and soft tissues to minimize the need for grafting and preserves the favorable features of the nose. Structural preservation rhinoplasty uses dorsal preservation in the upper two-thirds of the nose and structure rhinoplasty in the lower third. This hybrid approach has great utility in primary, revision, and reconstructive rhinoplasty.

Precision Segmental Preservation Rhinoplasty: Avoiding Widening, Defining New Dorsal Esthetic Lines in Dorsal Preservation Rhinoplasty.

Experiencing great worldwide scientific excitement, the number of nose preservation surgeries has increased rapidly, promoting a considerable percentage of drawbacks and complications, causing many surgeons to recoil and return to classic resective techniques. In this study, we develop concepts that allow us to operate noses with preservation rhinoplasty that were previously considered to be among the absolute contraindications. Redefining new dorsal aesthetic lines, controlling the nasal lateral wall and the naso-facial groove surfaces, avoiding mid-vault widening and being precise in the design of bony and cartilaginous nasal profile, avoiding any type of irregularity, are strategies that will be presented.

My First Twenty Rhinoplasties Using Dorsal Preservation Techniques.

Dorsal preservation involves eliminating the dorsal hump by performing reduction while preserving the patient's natural dorsal anatomy. This can involve surface manipulation or foundational techniques or a combination of both. When surgeons begin performing dorsal preservation, there are important factors to consider to avoid complications. In an effort to inform surgeons on how to avoid unfavorable outcomes, I will discuss my first 20 cases where I performed dorsal preservation. I review less than ideal outcomes and how these issues can be prevented.

Using a Brief Mental Imagery Competing Task to Reduce the Number of Intrusive Memories: Exploratory Case Series With Trauma-Exposed Women.

BACKGROUND: Novel interventions should be developed for people who have undergone psychological trauma. In a previous case study, we found that the number of intrusive memories of trauma could be reduced with a novel intervention. The intervention included a brief memory reminder, a visuospatial task and mental rotation, and targeted trauma memory hotspots one at a time in separate sessions. OBJECTIVE: This case series (N=3) extended the first case study with 3 new cases to determine whether a similar pattern of beneficial results is observed. We explored whether the brief intervention would result in reduced numbers of intrusive memories and whether it would impact symptoms of posttraumatic stress, depression and anxiety, and general functioning. Acceptability of the intervention was also explored. METHODS: A total of 3 women completed the study: 2 with posttraumatic stress disorder and other comorbidities and 1 with subthreshold posttraumatic stress disorder. The primary outcome was the change in the number of intrusive memories from the baseline phase to the intervention phase and at the 1-month follow-up, with an assessment of the intrusion frequency at 3 months. Participants monitored the number of intrusive memories in a daily diary for 1 week at baseline, for maximum of 6 weeks during the intervention phase and for 1 week at the 1-month and 3-month follow-ups. The intervention was delivered in person or digitally, with guidance from a clinical psychologist. A repeated AB design was used (A was a preintervention baseline phase and B intervention phase). Intrusions were targeted individually, creating repetitions of an AB design. RESULTS: The total number of intrusive memories was reduced from the baseline to the intervention phase for all participants. The total number for participant 3 (P3) reduced from 38.8 per week during the baseline phase to 18.0 per week in the intervention phase. It was 13 at the 3-month follow-up. The total number for P4 reduced from 10.8 per week at baseline to 4.7 per week in the intervention phase. It was 0 at the 3-month follow-up. The total number for P5 was reduced from 33.7 at baseline to 20.7 per week in the intervention phase. It was 8 at the 3-month follow-up. All participants reported reduction in posttraumatic stress symptoms in the postintervention phase. Depression and anxiety symptoms reduced in 2 of the 3 participants in the postintervention phase. Acceptability was favorable. CONCLUSIONS: We observed good compliance with the intervention and intrusive memory diary in all 3 cases. The number of intrusive memories was reduced for all participants during the intervention phase and at the 1-month follow-up, with some improvement in other symptoms and functioning. Further research should explore the remote delivery of the intervention and whether nonspecialists can deliver the intervention effectively.

A Segmental Approach in Dorsal Preservation Rhinoplasty: The Tetris Concept.

Rhinoplasty has become a detail-dependent surgery. With precise techniques better results have been achieved. We are continually searching for the ideal technique to offer predictable, accurate, and desired long-term results. Conservative rhinoplasty techniques have been described for more than 100 years as an alternative to dorsal resective surgeries and have reemerged as the new fashion among rhinoplasty surgeons. This article presents our philosophy when approaching the nasal dorsum regarding its segments and their specific anatomic aspects and surgical demands. We describe our intermediate septal strip approach, the intermediate split and the Tetris concept, and discuss their advantages and limitations.

Reducing Intrusive Memories of Childhood Trauma Using a Visuospatial Intervention: Case Study in Iceland.

BACKGROUND: Additional interventions are needed for survivors of psychological trauma because of several barriers to and limitations of existing treatment options (eg, need to talk about the trauma in detail). Case studies are an important step in exploring the development of novel interventions, allowing detailed examination of individual responses to treatment over time. Here, we present a case study that aims to test a novel intervention designed to disrupt memory reconsolidation, taking a single-symptom approach by focusing on intrusive memories of a traumatic event. OBJECTIVE: This study aims to examine a novel brief cognitive intervention to reduce the number of intrusive memories of trauma in an Icelandic setting and to extend previous studies by examining long-term effects for up to 3 months. The intervention was guided by a clinical psychologist and comprised a brief memory reminder, followed by Tetris gameplay with mental rotation, targeting one memory at a time in each session. METHODS: This was a single case study in Iceland with a woman in her 50s (drawn from an epidemiological study of trauma) with subthreshold posttraumatic stress disorder and a diagnosis of obsessive-compulsive disorder and social anxiety disorder. The participant had four different intrusive memories from a traumatic event that happened in her childhood. The primary outcome was the change in the number of intrusive memories from baseline to intervention phase and to follow-ups. The number of intrusions was monitored in a daily diary for 4 weeks preintervention, 8 weeks during the intervention, and 1 week at 1-month and 3-month follow-ups. Intrusions were targeted one by one over six intervention sessions, creating four repetitions of an AB design (ie, length of baseline A and intervention phase B varied for each memory). We examined changes in both the total number of intrusions (summed across all four memories) and individually for each memory. In addition, we explored whether having fewer intrusive memories would have an impact on functioning, posttraumatic stress, and depression or anxiety symptoms. RESULTS: The total number of intrusions per week was 12.6 at baseline, 6.1 at the intervention phase (52% reduction from baseline), 3.0 at the 1-month follow-up (76% reduction), and 1.0 at the 3-month follow-up (92% reduction). Reductions in the symptoms of posttraumatic stress and depression were observed postintervention. Sleep, concentration, stress, and functioning improved. The participant considered the gameplay intervention acceptable and helpful in that she found that the memories disappeared while she was playing. CONCLUSIONS: This guided brief cognitive intervention reduced the number of intrusive memories over the intervention phase and follow-ups. The brief memory reminder was well tolerated, removing the need to discuss trauma in detail. The next steps require an extension to more cases and exploring remote delivery of the intervention.

Constructing Expertise: Surmounting Performance Plateaus by Tasks, by Tools, and by Techniques.

Acquiring expertise in a task is often thought of as an automatic process that follows inevitably with practice according to the log-log law (aka: power law) of learning. However, as Ericsson, Chase, and Faloon (1980) showed, this is not true for digit-span experts and, as we show, it is certainly not true for Tetris players at any level of expertise. Although some people may simply "twitch" faster than others, the limit to Tetris expertise is not raw keypress time but the techniques acquired by players that allow them to use the tools provided by the hardware and software to compensate for the game's relentlessly increasing drop speed. Unfortunately, these increases in drop speed between Tetris levels make performance plateaus very short and quickly followed by game death. Hence, a player's success at discovering, exploring, and practicing new techniques for the tasks of board preparation, board maintenance, optimal placement discovery, zoid rotation, lateral movement of zoids, and other tasks important to expertise in Tetris is limited. In this paper, we analyze data collected from 492 Tetris players to reveal the challenges they confronted while constructing expertise via the discovery of new techniques for gameplay at increasingly difficult levels of Tetris.

Investigating the frequency of intrusive memories after 24 hours using a visuospatial interference intervention: a follow-up and extension.

Background: There is a need for effective, low-cost, readily available measures for reducing trauma symptoms so that people exposed to potentially traumatic events can receive help more quickly. A previous study reported that performing an intervention including a visuospatial task shortly after a reminder of a series of unpleasant film clips seen 24 hours earlier reduced the number of intrusive memories over the following week. Objective: This study reports a follow-up and extension of the earlier promising finding. The prediction was that participants performing the visuospatial task immediately after the reminder would report fewer intrusions compared to three other groups who 1) performed no task, and novel conditions who 2) performed the task before the reminder, and 3) performed the task 90 minutes after the reminder. Method: A trauma-analogue method was used, where students (N = 200) watched a series of short films with unpleasant material. Over the following week, they were asked to write down any intrusive memories they experienced in a diary. On the second day they returned to the lab and saw static reminders of the films. They were then randomly allocated to condition, recorded intrusive memories over the following days and returned to the lab for final testing on Day 8. Results: A total of 49 participants did not report any intrusions and were excluded from the analyses. Two more participants were excluded as outliers, leaving a final sample of n = 149. Despite using largely the same materials as the original study there were no significant differences in the number of intrusive memories between the four groups post intervention. Conclusions: Possible explanations include the effect not being as robust as expected, a low number of intrusions across groups, baseline differences in attention, and minor but potentially important differences in procedure between this and the original study.

Antecedentes: Existe la necesidad de medidas efectivas de bajo costo y fácilmente disponibles para reducir los síntomas del trauma, de modo que las personas expuestas a eventos potencialmente traumáticos puedan recibir ayuda más rápidamente. James y cols. (2015) reportaron que realizar una intervención que incluye una tarea viso-espacial poco después de un recordatorio consistente en una serie de clips de películas desagradables vistos 24 horas antes, redujo el número de recuerdos intrusivos durante la semana siguiente.Objetivo: Este estudio reporta un seguimiento y extensión del prometedor hallazgo de James y cols. La predicción fue que los participantes que realizaran la tarea viso-espacial inmediatamente después del recordatorio reportarían menos intrusiones en comparación con otros tres grupos que: 1) no realizaron ninguna tarea, y en condiciones novedosas que 2) realizaron la tarea antes del recordatorio y 3) realizaron la tarea 90 minutos después del recordatorio.Método: Se utilizó un método analógico de trauma, donde los estudiantes (N = 200) vieron una serie de cortometrajes con material desagradable. Durante la semana siguiente, se les pidió que escribieran cualquier recuerdo intrusivo que experimentaran en un diario. El segundo día regresaron al laboratorio y vieron recordatorios estáticos de las películas. Luego fueron asignados aleatoriamente a la condición, registraron recuerdos intrusivos durante los días siguientes y regresaron al laboratorio para la prueba final el día 8.Resultados: Un total de 49 participantes no reportó ninguna intrusión y fueron excluidos de los análisis. Se excluyeron dos participantes adicionales como valores atípicos, dejando una muestra final de n = 149. A pesar de utilizar en gran parte los mismos materiales que el estudio original, no hubo diferencias significativas en el número de recuerdos intrusivos entre los cuatro grupos después de la intervención.Conclusiones: Las posibles explicaciones incluyen que el efecto no es tan robusto como se esperaba, un número bajo de intrusiones entre los grupos, diferencias basales de atención y diferencias menores pero potencialmente importantes en el procedimiento entre éste y el estudio original.

Sleep disturbance and intrusive memories after presenting to the emergency department following a traumatic motor vehicle accident: an exploratory analysis.

Background: Sleep disturbances are common after traumatic events and have been hypothesized to be a risk factor in the development of psychopathology such as that associated with posttraumatic stress disorder (PTSD). Objective: To assess the association between intrusive memories, a core clinical feature of PTSD, and self-reported sleep disturbance shortly after experiencing or witnessing a motor vehicle accident, and whether a brief behavioural intervention (trauma reminder cue and Tetris gameplay) reduced sleep disturbance post-trauma. Method: The exploratory analyses included 71 participants (mean age 39.66, standard deviation 16.32; 37 women, 52.1%) enrolled in a previously published proof-of-concept randomized controlled trial. Participants were recruited from the emergency department after experiencing or witnessing a traumatic motor vehicle accident. Intrusive memories were assessed with a daily paper-and-pen diary for one week post-trauma, and sleep disturbances with three questions from the Impact of Event Scale-Revised assessing problems initiating sleep, problems maintaining sleep and dreams about the event at one week and one month post-trauma. Missing data were imputed 15 times. Results: The total number of intrusive memories during the first week post-trauma suggested weak to moderate pooled intercorrelations with problems initiating and maintaining sleep. An ordinal regression using imputed data suggested that the intervention had no effect on sleep disturbances, while completers only analyses suggested an improvement in problems maintaining sleep at one week. Conclusions: This exploratory study suggested that experiencing early intrusive memories is related to sleep disturbances. Sleep disturbance might be a particularly important construct to assess in studies involving intrusive memories post-trauma.

Antecedentes: Las alteraciones del sueño son frecuentes tras eventos traumáticos y han sido planteados como un factor de riesgo para el desarrollo de psicopatología como la que está asociada con el trastorno de estrés postraumático (TEPT).Objetivo: Evaluar la asociación entre recuerdos intrusivos, característica clínica central del TEPT, y alteraciones del sueño auto-reportadas, al poco tiempo luego de experimentar o ser testigo de un accidente automovilístico, y si una intervención conductual breve (estímulos gatillantes de recuerdos traumáticos, y el juego Tetris) reduce alteraciones del sueño postrauma.Método: Los análisis exploratorios incluyeron 71 participantes (edad promedio 39.66, desviación estándar 16.32; 37 mujeres, 42.1%) incluidos en ensayo clínico randomizado previamente publicado. Los participantes fueron reclutados desde el departamento de emergencias tras experimentar o haber sido testigo de un accidente automovilístico traumático. Los recuerdos intrusivos fueron evaluados diariamente con papel y lápiz a través de un diario durante 1 semana postrauma, y las alteraciones del sueño con 3 preguntas provenientes de la Escala Revisada de Impacto del Evento evaluando problemas para conciliar el sueño, problemas para mantener el sueño, y sueños sobre el evento a la primera semana y al primer mes postrauma. Datos faltantes fueron imputados 15 veces.Resultados: El número total de recuerdos intrusivos durante la primera semana postrauma sugirieron inter-correlaciones leves a moderadas con alteraciones de conciliación y mantención del sueño. Una regresión ordinal que utilizó datos imputados sugirió que la intervención no tuvo efecto en las alteraciones del sueño, mientras que los análisis 'completers-only' sugirieron una mejoría en las alteraciones de mantención del sueño a la semana 1.Conclusiones: Este estudio exploratorio sugirió que la experimentación de recuerdos intrusivos está relacionada con alteraciones del sueño. Las alteraciones del sueño pueden ser un constructo particularmente importante, a evaluar en estudios que involucran recuerdos intrusivos postrauma.

Sigmoid-weighted linear units for neural network function approximation in reinforcement learning.

In recent years, neural networks have enjoyed a renaissance as function approximators in reinforcement learning. Two decades after Tesauro's TD-Gammon achieved near top-level human performance in backgammon, the deep reinforcement learning algorithm DQN achieved human-level performance in many Atari 2600 games. The purpose of this study is twofold. First, we propose two activation functions for neural network function approximation in reinforcement learning: the sigmoid-weighted linear unit (SiLU) and its derivative function (dSiLU). The activation of the SiLU is computed by the sigmoid function multiplied by its input. Second, we suggest that the more traditional approach of using on-policy learning with eligibility traces, instead of experience replay, and softmax action selection can be competitive with DQN, without the need for a separate target network. We validate our proposed approach by, first, achieving new state-of-the-art results in both stochastic SZ-Tetris and Tetris with a small 10 × 10 board, using TD(λ) learning and shallow dSiLU network agents, and, then, by outperforming DQN in the Atari 2600 domain by using a deep Sarsa(λ) agent with SiLU and dSiLU hidden units.

Dynamic Threshold Selection for a Biocybernetic Loop in an Adaptive Video Game Context.

Passive Brain-Computer interfaces (pBCIs) are a human-computer communication tool where the computer can detect from neurophysiological signals the current mental or emotional state of the user. The system can then adjust itself to guide the user toward a desired state. One challenge facing developers of pBCIs is that the system's parameters are generally set at the onset of the interaction and remain stable throughout, not adapting to potential changes over time such as fatigue. The goal of this paper is to investigate the improvement of pBCIs with settings adjusted according to the information provided by a second neurophysiological signal. With the use of a second signal, making the system a hybrid pBCI, those parameters can be continuously adjusted with dynamic thresholding to respond to variations such as fatigue or learning. In this experiment, we hypothesize that the adaptive system with dynamic thresholding will improve perceived game experience and objective game performance compared to two other conditions: an adaptive system with single primary signal biocybernetic loop and a control non-adaptive game. A within-subject experiment was conducted with 16 participants using three versions of the game Tetris. Each participant plays 15 min of Tetris under three experimental conditions. The control condition is the traditional game of Tetris with a progressive increase in speed. The second condition is a cognitive load only biocybernetic loop with the parameters presented in Ewing et al. (2016). The third condition is our proposed biocybernetic loop using dynamic threshold selection. Electroencephalography was used as the primary signal and automatic facial expression analysis as the secondary signal. Our results show that, contrary to our expectations, the adaptive systems did not improve the participants' experience as participants had more negative affect from the BCI conditions than in the control condition. We endeavored to develop a system that improved upon the authentic version of the Tetris game, however, our proposed adaptive system neither improved players' perceived experience, nor their objective performance. Nevertheless, this experience can inform developers of hybrid passive BCIs on a novel way to employ various neurophysiological features simultaneously.