Multi-scale simulations of two dimensional material based devices: the NanoTCAD ViDES suite

NanoTCAD ViDES (Versatile DEvice Simulator) is an open-source suite of computing codes aimed at assessing the operation and the performance of nanoelectronic devices. It has served the computational nanoelectronic community for almost two decades and it is freely available to researchers around the world in its website (http://vides.nanotcad.com), being employed in hundreds of works by many electronic device simulation groups worldwide. We revise the code structure and its main modules and we present the new features directed towards (i) multi-scale approaches exploiting ab-initio electron-structure calculations, aiming at the exploitation of new physics in electronic devices, (ii) the inclusion of arbitrary heterostructures of layered materials to devise original device architectures and operation, and (iii) the exploration of novel low-cost, green technologies in the mesoscopic scale, as, e.g. printed electronics.

Modeling brain dynamics and gaze behavior: Starting point bias and drift rate relate to frontal midline theta oscillations

Frontal midline theta oscillatory dynamics have been implicated as an important neural signature of inhibitory control. However, most proactive cognitive control studies rely on behavioral tasks where individual differences are inferred through button presses. We applied computational modeling to further refine our understanding of theta dynamics in a cued anti-saccade task with gaze-contingent eye tracking. Using a drift diffusion model, increased frontal midline theta power during high-conflict, relative to low-conflict, trials predicted a more conservative style of responding through the starting point (bias). During both high- and low-conflict trials, increases in frontal midline theta also predicted improvements in response efficiency (drift rate). Regression analyses provided support for the importance of the starting point bias, which was associated with frontal midline theta over the course of the task above-and-beyond both drift rate and mean reaction time. Our findings provide a more thorough understanding of proactive gaze control by linking trial-by-trial increases of frontal midline theta to a shift in starting point bias facilitating a more neutral style of responding.

Towards dynamic modeling of visual-vestibular conflict detection

Visual-vestibular mismatch is a common occurrence, with causes ranging from vehicular travel, to vestibular dysfunction, to virtual reality displays. Behavioral and physiological consequences of this mismatch include adaptation of reflexive eye movements, oscillopsia, vertigo, and nausea. Despite this significance, we still do not have a good understanding of how the nervous system evaluates visual-vestibular conflict. Here we review research that quantifies perceptual sensitivity to visual-vestibular conflict and factors that mediate this sensitivity, such as noise on visual and vestibular sensory estimates. We emphasize that dynamic modeling methods are necessary to investigate how the nervous system monitors conflict between time-varying visual and vestibular signals, and we present a simple example of a drift-diffusion model for visual-vestibular conflict detection. The model makes predictions for detection of conflict arising from changes in both visual gain and latency. We conclude with discussion of topics for future research.

Different mechanisms can account for the instruction induced proportion congruency effect

When performing a conflict task, performance is typically worse on trials with conflict between two responses (i.e., incongruent trials) compared to when there is no conflict (i.e., congruent trials), a finding known as the congruency effect. The congruency effect is reduced when the proportion of incongruent trials is high, relative to when most of the trials are congruent (i.e., the proportion congruency effect). In the current work, it was tested whether different kinds of instructions can be used to induce a proportion congruency effect, while holding the actual proportion of congruent trials constant. Participants were instructed to strategically use the (invalid) information that most of the trials would be congruent versus incongruent, or they were told to adopt a liberal versus a conservative response threshold. All strategies effectively altered the size of the congruency effect relative to baseline, although in terms of statistical significance the effect was mostly limited to the error rates. A diffusion-model analysis of the data was partially consistent with the hypothesis that both types of instructions induced a proportion congruency effect by means of different underlying mechanisms.