Switching Paradigm Research Articles

Unconventional Ferroelectric-Ferroelastic Switching Mediated by Non-Polar Phase in Fluorite Oxides.

HfO2/ZrO2-based ferroelectrics present tremendous potential for next-generation non-volatile memory due to their high scalability and compatibility with silicon technology. Unlike the continuous polar layers in perovskite ferroelectrics, HfO2/ZrO2-based ferroelectrics are composed of alternating polar layers with oxygen shifts and non-polar spacers, which leads to a distinct ferroelectric switching mechanism. However, directly observing the switching process has been a big challenge due to the polymorph feature of nanoscale fluorites and the difficulty in in situ imaging on light elements. Here, the ferroelectric-ferroelastic coupled switching process in freestanding ZrO2 thin films is directly visualized by in situ imaging on oxygen motions. A multi-step 90-degree polarization switching mechanism is uncovered that challenges the conventional one-step 180-degree switching paradigms in fluorite oxides, which is highly consistent with the interlocked nature of ferroelectricity and ferroelasticity. A non-polar tetragonal (T) phase is discovered as a crucial intermediate state, lowering the energy barrier for polarization switching by 35%. More importantly, the T phase prevents irreversible transitions to the non-polar ground state and facilitates stable ferroelectric switching. These findings are fundamental to understanding nanoscale polarization switching mechanisms in fluorite ferroelectrics, paving the way for advanced high-durability devices.

The impact of cues on language switching: do spoken questions reduce the need for bilingual language control?

Abstract The classical language switching paradigm using arbitrary cues to indicate the language to speak in has revealed switching between languages comes at a cost (i.e., switch cost) and makes one slower in the first than in the second language (i.e., reversed language dominance). However, arbitrary cues can create artificial requirements not present during everyday language interactions. Therefore, we investigated whether simulating elements of real-life conversations with question cues (‘Co?’ versus ‘What?’) facilitates language switching in comparison to the classical paradigm (Experiment 1: red versus blue outline; Experiments 2 and 3: low versus high tone). We revealed a dissociation between the two indices of language control: (1) question cues, compared to arbitrary cues, reduced switch costs but (2) did not modulate (in Experiment 1) or increase the reversed language dominance (Experiments 2 and 3). We propose that this conversational switching paradigm could be used as a conceptually more ‘true’ measure of language control.

The role of uncertain reward in voluntary task-switching as revealed by pupillometry and gaze.

Cognitive flexibility, the brain's ability to adjust to changes in the environment, is a critical component of executive functioning. Previous literature shows a robust relationship between reward dynamics and flexibility: flexibility is highest when reward changes, while flexibility decreases when reward remains stable. The purpose of this study was to examine the role of uncertain reward in a voluntary task switching paradigm on behavior, pupillometry, and eye gaze. We used pupil dilation as a neuropsychological correlate of arousal and accumulated fixations on a region (i.e. dwell time) to measure oculomotor attention capture. Results during the cue phase showed that pupil dilation under a deterministic, but not a stochastic reinforcement schedule tracked arousal from the magnitude of reward. In addition, dwell time was increased for the eventual choice and dwell-time was reduced under high reward. Taken together, results show that arousal and attentional capture by reward depends to some extent on reward certainty. Turning to reward outcome, pupil dilation was highest (and average dwell time was lowest) following Error feedback compared to correct rewarded feedback. Overall results show that uncertain reward cues may alter pupil-linked arousal and attention as compared to certain reward, highlighting the role of uncertainty as an important modulator affecting attention and reward processing in environments that demand cognitive flexibility.

Mapping common and distinct brain correlates among cognitive flexibility tasks: concordant evidence from meta-analyses.

Cognitive flexibility allows individuals to switch between different tasks, strategies, or ideas; an ability that is important for everyday life. The Wisconsin card sorting test (WCST) and task switching paradigm (TSP) are popular measures of cognitive flexibility. Although both tasks require switching, the TSP requires participants to memorize switching rules and retrieve them when they view a cue (rule-retrieval), whereas the classic WCST requires participants to discover the switching rule via trial-and-error (rule-discovery). Many functional magnetic resonance imaging studies have examined brain responses to these tasks. Extant meta-analyses show concordance in activation in a widespread set of areas including frontal, parietal, and cingulate cortices. Critically, past meta-analyses have not specifically examined brain correlates associated with rule derivation (i.e., rule-discovery vs. rule-retrieval) in cognitive flexibility tasks. We examine for the first time common and distinct concordance in brain responses to rule-discovery (i.e., WCST) and rule-retrieval (i.e., TSP), as well as TSP subtypes using quantitative meta-analyses. We analyzed data from 69 eligible articles with a total of 1617 young-adult participants. Conjunction results show concordance in common fronto-parietal areas predominantly in the left hemisphere. Contrast analyses show that rule-discovery required increased involvement in multiple cortical and subcortical regions such as frontopolar (Brodmann Area 10), parietal, insular cortex, thalamus and caudate nucleus predominantly in the right hemisphere. No significant differences in concordance were observed among the three, task switching paradigm sub-types. We propose a neuroanatomical model of cognitive flexibility and discuss theoretical and practical applications.

Impaired cognitive flexibility in major depressive disorder: Evidences from spatial-temporal ERPs analysis

BackgroundMajor Depressive Disorder (MDD) may exhibit impairments in cognitive flexibility. This study investigated whether the cognitive flexibility deficits in MDD are evident across general stimuli or specific to emotional stimuli, while exploring the underlying neuropsychological mechanism. MethodsA total of 41 MDD patients and 42 healthy controls (HCs) were recruited. Event-related potentials (ERPs) were recorded when participants performed a non-emotional and an emotional task switching paradigm (N-ETSP and ETSP), both of which assessed cognitive flexibility. Microstate and source localization analysis were applied to reflect brain activity among different brain areas during task switching. ResultsIn the N-ETSP, MDD group showed larger P3 difference wave (Pd3) amplitudes and longer P2 difference wave (Pd2) latencies. In the ETSP, MDD group displayed smaller N2 difference wave (Nd2) amplitudes and larger Pd3 amplitudes. The comparison of sLORETA images of emotional switch task and emotional repeat task showed that MDD group had increased activation in the precentral gyrus in microstate2 of the P2 time window and had reduced activation in the middle occipital gyrus in microstate3 of the N2 time window. LimitationsThe cross-sectional design failed to capture dynamic changes in cognitive flexibility in MDD. ConclusionsMDD demonstrated impaired cognitive flexibility respond to both non-emotional and emotional stimuli, with greater impairment for negative emotional stimuli. These deficits are evident in abnormal ERPs component during the early attention stage and the later task preparation stage. Furthermore, abnormal emotional switching cost in MDD appears to be related to early abnormal perceptual control in the parietal-occipital cortex.

Bumpless transfer control for switched positive time-delay systems with linear-type dissipative inequalities

In this paper, a family of amplitude limited controllers and a hysteresis switching paradigm, for switched positive systems with time-varying delays, are simultaneously determined to achieve strict (q,r) -α-dissipativity. The concept of strictly (q,r)-α-dissipative, induced by linear-type dissipative inequalities, is introduced. The main feature of the presented method lies in two aspects. The first one is that the magnitude of controller discontinuities, at the occurrence of switching, is here restricted. The other one is that the high switching frequency is refrained commonly the appearance of in state-dependent switching schemes. Moreover, dissipativity analysis as well as feedback dissipativity are taken into account. Novel criteria are derived for the considered systems to be dissipativity by resorting to multi-linear copositive storage functionals. Eventually, the validity and superiority of the presented control strategy are demonstrated through two illustrative examples.

Impact of Joint and Independent Switching Paradigms on Switching Capacity of Contention/-Less SDM-ROADM Designs

Impact of Joint and Independent Switching Paradigms on Switching Capacity of Contention/-Less SDM-ROADM Designs

Implementation of New Predictive Control Based Volterra Model for Fast Dynamic Systems Using Microcontrollers: Real Time Application

This paper presents a new contribution in the implementation of Volterra model predictive control for fast dynamics systems. The control approaches considered results on a switch paradigm that combine an online part based on suboptimal solution and an offline part referred to an offline neural network controller. The proposed approach has an advantage in comparison with nonlinear optimization-based control schemes. A real time application on STM32 to control a boost converter is studied and the results show very remarkable performances in time computing.

The neural oscillations serving task switching are altered in cannabis users.

Regular cannabis is known to impact higher-order cognitive processes such as attention, but far less is known regarding cognitive flexibility, a component of executive function. Moreover, whether such changes are related to aberrations in the neural oscillatory dynamics serving flexibility remains poorly understood. Quantify the neural oscillatory dynamics serving cognitive flexibility by having participants complete a task-switching paradigm during magnetoencephalography (MEG). Probe whole-brain maps to identify alterations in chronic cannabis users relative to nonusers and determine how these alterations relate to the degree of cannabis use involvement. In all, 25 chronic cannabis users and 30 demographically matched nonuser controls completed neuropsychological testing, an interview regarding their substance use, a urinalysis, and a task switch paradigm during MEG. Time-frequency windows of interest were identified using a data-driven statistical approach and these were imaged using a beamformer. Whole-brain neural switch cost maps were computed by subtracting the oscillatory maps of the no-switch condition from the switch condition per participant. These were examined for group differences. Cannabis users had weaker theta switch cost responses in the dorsolateral and dorsomedial prefrontal cortices, while nonusers showed the typical pattern of greater recruitment during switch relative to no switch trials. In addition, theta activity in the dorsomedial prefrontal cortex was significantly correlated with cannabis use involvement. Cannabis users exhibited altered theta switch cost activity compared to nonusers in prefrontal cortical regions, which are critical for cognitive flexibility. This activity scaled with cannabis use involvement, indicating a link between cannabis use and aberrant oscillatory activity underlying cognitive flexibility.

Task performance errors and rewards affect voluntary task choices.

Humans are remarkably flexible in adapting their behavior to current demands. It has been suggested that the decision which of multiple tasks to perform is based on a variety of factors pertaining to the rewards associated with each task as well as task performance (e.g., error rates associated with each task and/or error commission on the previous trial). However, further empirical investigation is needed to examine whether task performance still influences task choices if task choices are rewarded but task performance is not. Accordingly, we exposed participants to a novel reward-varying voluntary task switching paradigm where the reward for the performed task gradually decreased while the reward associated for the alternative task was unchanged. Importantly, we rewarded participants' task choices before participants performed the task to investigate the effect of rewards independent from task performance. We examined the effect of (i) reward, (ii) error rates associated with each of the two tasks, and (iii) error commission in the previous trial on voluntary task choices. As expected, we found that participants' task selection was influenced by reward differences between task choices. In addition, error rates associated with a task also influenced task selection, with participants requiring larger reward differences to switch to a task associated with relatively higher error rates, compared to switching to a task with relatively lower error rates. However, errors in n - 1 did not influence participants' probability to switch to the alternative task. These findings contribute to an ongoing discussion on the influence of task performance on task selection.

Double task switching: An investigation into the effects of similarity and task-rule congruency on cognitive flexibility.

Similarity between tasks is an understudied factor in research on cognitive flexibility. This behavioural experiment had 31 participants perform a task switch paradigm in which participants were required to switch between 4 tasks of varying similarity. The experiment was constructed in a way that simultaneously allows for investigating the impact of mental fatigue and task-rule congruency on the participants. The results indicate that similarity between tasks substantially impacts performance with different effects on RT and accuracy. While learning effects may have negated the impact of mental fatigue across the 5 experimental blocks, a significant decrease in performance was observed within blocks. Furthermore, the exploratory analysis proposes a novel interaction between task-rule incongruent trials and the task of the previous trial. These results support the notion that neither the interference view of cognitive flexibility nor the reconfiguration view are fully adequate at explaining task switch costs if similarity is added as a factor. The presented study presents strong evidence that fundamental findings in the domain of cognitive flexibility may not map linearly to more ecological settings where tasks are often more dissimilar.

Fano resonance in molecular junctions of spin crossover complexes.

In this paper, we introduce a novel molecular switch paradigm that integrates spin crossover complexes with the Fano resonance effect. Specifically, by performing density-functional theory calculations, the feasibility of achieving Fano resonance using spin crossover complexes is demonstrated in our designed molecular junctions using the complex {Fe[H2B(pz)2]2[Bp(bipy)]} [pz = 1-pyrazolyl, Bp(bipy) = bis(phenylethynyl)(2,2'-bipyridine)]. It is further revealed that the Fano resonance, particularly the Fano dip, is most prominent in the junction with cobalt tips among all the schemes, together with the spin-filtering effect. Most importantly, this junction of cobalt tips is able to exhibit three distinct conductance states, which are controlled by the modulation of Fano resonance due to the spin-state transition of the complex and the applied gate voltage. Such a molecular switch paradigm holds potential for applications in logic gates, memory units, sensors, thermoelectrics, and beyond.

A Gestalt account of human behavior is supported by evidence from switching between single and dual actions

The question of how behavior is represented in the mind lies at the core of psychology as the science of mind and behavior. While a long-standing research tradition has established two opposing fundamental views of perceptual representation, Structuralism and Gestalt psychology, we test both accounts with respect to action representation: Are multiple actions (characterizing human behavior in general) represented as the sum of their component actions (Structuralist view) or holistically (Gestalt view)? Using a single-/dual-response switch paradigm, we analyzed switches between dual ([A + B]) and single ([A], [B]) responses across different effector systems and revealed comparable performance in partial repetitions and full switches of behavioral requirements (e.g., in [A + B] → [A] vs. [B] → [A], or [A] → [A + B] vs. [B] → [A + B]), but only when the presence of dimensional overlap between responses allows for Gestalt formation. This evidence for a Gestalt view of behavior in our paradigm challenges some fundamental assumptions in current (tacitly Structuralist) action control theories (in particular the idea that all actions are represented compositionally with reference to their components), provides a novel explanatory angle for understanding complex, highly synchronized human behavior (e.g., dance), and delimitates the degree to which complex behavior can be analyzed in terms of its basic components.

A Vision of 6th Generation of Fixed Networks (F6G): Challenges and Proposed Directions

Humankind has entered a new era wherein a main characteristic is the convergence of various technologies providing services and exerting a major impact upon all aspects of human activity, be it social interactions with the natural environment. Fixed networks are about to play a major role in this convergence, since they form, along with mobile networks, the backbone that provides access to a broad gamut of services, accessible from any point of the globe. It is for this reason that we introduce a forward-looking approach for fixed networks, particularly focused on Fixed 6th Generation (F6G) networks. First, we adopt a novel classification scheme for the main F6G services, comprising six categories. This classification is based on the key service requirements, namely latency, capacity, and connectivity. F6G networks differ from those of previous generations (F1G–F5G) in that they concurrently support multiple key requirements. We then propose concrete steps towards transforming the main elements of fixed networks, such as optical transceivers, optical switches, etc., such that they satisfy the new F6G service requirements. Our study categorizes the main networking paradigm of optical switching into two categories, namely ultra-fast and ultra-high capacity switching, tailored to different service categories. With regard to the transceiver physical layer, we propose (a) the use of all-optical processing to mitigate performance barriers of analog-to-digital and digital-to-analog converters (ADC/DAC) and (b) the exploitation of optical multi-band transmission, space division-multiplexing, and the adoption of more efficient modulation formats.

Contextual familiarity rescues the cost of switching.

Changes in context influence the way we form and structure memories. Yet, little is known about how qualitatively different types of context switches shape memory organization. The current experiments characterize how different features of context change influence the structure and organization of free recall. Participants completed a context switching paradigm in which we manipulated the rate of switches and prior experience with the contexts participants were switching between (repeated vs. novel). We measured free-recall performance and determined the extent to which participants organized items by the order in which they were encoded or the type of context with which they were originally presented. Across two experiments, we found and replicated that rapidly switching to novel, but not repeated contexts, impaired memory recall performance and biased memory towards a greater reliance on temporal information. Critically, we observed that these differences in performance may be due to distinctions in how participants organize their recalls when rapidly switching contexts. Results indicated that participants were less likely to only cluster their responses by the same context when the contexts were repeating at a high rate, as compared to when the contexts were novel. Overall, our findings support a model in which contextual familiarity rescues the costs associated with rapidly switching to new tasks or contexts.

Inhibition during task switching is affected by the number of competing tasks.

Inhibition during task switching is assumed to be indexed by n - 2 repetition costs-that is, performance costs when the task in the current trial equals the task in trial n - 2 (sequences of type ABA) compared with two consecutive switches to another task each (sequences CBA). The present study examined effects of a short-term reduction of the number of candidate tasks on these costs. For this purpose, a variant of the task switching paradigm was used in which in half of the trials, a precue that preceded the task cue allowed for a short-term reduction of the number of candidate tasks. In Experiment 1, one out of three tasks could be excluded. In Experiment 2, one or two out of four tasks could be excluded. Experiment 3 served as control condition using the standard cueing paradigm. Significant n - 2 repetition costs were present with three candidate tasks. In contrast, no costs were visible when the number of candidate tasks was reduced to two. This result is interpreted in terms of a task selection mechanism based on antagonistic constraints among task representations, which operates on a rather superficial level when switching among only two tasks, thereby reducing the need for inhibition.

Task Switching and Visual Search: Evidence for a Tradeoff Between Congruent and Incongruent Target Responses

In task switching studies, mapping different responses to the same physical keys creates two response categories: congruent and incongruent. Congruent and incongruent responses are distinguished by whether or not a key press is the same between different task instructions. Task switching studies often report that incongruent responses have higher error rates and RTs than congruent responses. In this study, we investigate this congruency effect by asking: Does the presence of incongruent stimuli detract from performance on congruent stimuli? If true, participants may perform worse on congruent stimuli as more incongruent stimuli are added. To test this hypothesis, we created a visual search and task switching paradigm where participants search for targets while the congruence of a target changes. Results show a tradeoff in accuracy between incongruent and congruent targets—when incongruent stimuli are added, participants are worse at finding congruent stimuli, even though congruent stimuli are targets throughout the task.

Impact of age of onset on bilinguals’ task switching performance in a nonimmigration context

It is not clear whether bilingualism leads to task switching benefits in single-language nonimmigration contexts, as in dual-language and code-switching immigration contexts. Ninety young Persian-speaking monolingual and bilingual adults reported their language proficiency and use, with the early bilinguals indicating a balanced rating for their L1 and L2, and late bilinguals reporting slightly higher ratings for L1, relative to L2. Concerning the onset age of bilingualism, the bilinguals were classified as early and late bilinguals according to whether they initiated active regular use of the two languages before or after the age of eight. A nonverbal alternating-runs task switching paradigm was used to measure global switch cost (GSC) and local switch cost (LSC). The findings revealed a slight nonsignificant GSC but a significantly lower LSC for early bilinguals, compared to monolinguals, suggesting that bilingualism effects on task switching do not transpire uniformly across different contexts.

Control dilemma: Evidence of the stability–flexibility trade-off

Cognitive control can be applied flexibly when task goals or environments change (i.e., cognitive flexibility), or stably to pursue a goal in the face of distraction (i.e., cognitive stability). Whether these seemingly contradictory characteristics have an inverse relationship has been controversial, as some studies have suggested a trade-off mechanism between cognitive flexibility and cognitive stability, while others have not found such reciprocal associations. This study investigated the possible antagonistic correlation between cognitive flexibility and stability using a novel version of the flexibility–stability paradigm and the classic cued task switching paradigm. In Experiment 1, we showed that cognitive flexibility was inversely correlated with cognitive stability, as increased distractor proportions were associated with decreased cognitive flexibility and greater cognitive stability. Moreover, cognitive flexibility and stability were regulated by a single control system instead of two independent control mechanisms, as the model selection results indicated that the reciprocally regulated model with one integration parameter outperformed all other models, and the model parameter was inversely linked to cognitive flexibility and stability. We found similar results using the classic cued task switching paradigm in Experiment 2. Therefore, a trade-off between cognitive flexibility and stability was observed from the paradigms used in this study.

Planning ahead: Predictable switching recruits task-active and resting-state networks.

Switching is a difficult cognitive process characterised by costs in task performance; specifically, slowed responses and reduced accuracy. It is associated with the recruitment of a large coalition of task-positive regions including those referred to as the multiple demand cortex (MDC). The neural correlates of switching not only include the MDC, but occasionally the default mode network (DMN), a characteristically task-negative network. To unpick the role of the DMN during switching we collected fMRI data from 24 participants playing a switching paradigm that perturbed predictability (i.e., cognitive load) across three switch dimensions-sequential, perceptual, and spatial predictability. We computed the activity maps unique to switch vs. stay trials and all switch dimensions, then evaluated functional connectivity under these switch conditions by computing the pairwise mutual information functional connectivity (miFC) between regional timeseries. Switch trials exhibited an expected cost in reaction time while sequential predictability produced a significant benefit to task accuracy. Our results showed that switch trials recruited a broader activity map than stay trials, including regions of the DMN, the MDC, and task-positive networks such as visual, somatomotor, dorsal, salience/ventral attention networks. More sequentially predictable trials recruited increased activity in the somatomotor and salience/ventral attention networks. Notably, changes in sequential and perceptual predictability, but not spatial predictability, had significant effects on miFC. Increases in perceptual predictability related to decreased miFC between control, visual, somatomotor, and DMN regions, whereas increases in sequential predictability increased miFC between regions in the same networks, as well as regions within ventral attention/ salience, dorsal attention, limbic, and temporal parietal networks. These results provide novel clues as to how DMN may contribute to executive task performance. Specifically, the improved task performance, unique activity, and increased miFC associated with increased sequential predictability suggest that the DMN may coordinate more strongly with the MDC to generate a temporal schema of upcoming task events, which may attenuate switching costs.