The representation of abstract task rules in the human prefrontal cortex

We have previously reported sustained activation in the ventral prefrontal cortex while participants prepared to perform 1 of 2 tasks as instructed. But there are studies that have reported activation reflecting task rules elsewhere in prefrontal cortex, and this is true in particular when it was left to the participants to decide which rule to obey. The aim of the present experiment was to use functional magnetic resonance imaging (fMRI) to find whether there was activation in common, irrespective of the way that the task rules were established. On each trial, we presented a word after a variable delay, and participants had to decide either whether the word was abstract or concrete or whether it had 2 syllables. The participants either decided before the delay which task they would perform or were instructed by written cues. Comparing the self-generated with the instructed trials, there was early task set activation during the delay in the middle frontal gyrus. On the other hand, a conjunction analysis revealed sustained activation in the ventral prefrontal and polar cortex for both conditions. We argue that the ventral prefrontal cortex is specialized for handling conditional rules regardless of how the task rules were established

Optical Properties of Crystals with Spatial Dispersion: Josephson Plasma Resonance in Layered Superconductors

We derive the transmission coefficient, $T(\omega)$, for grazing incidence of crystals with spatial dispersion accounting for the excitation of multiple modes with different wave vectors ${\bf k}$ for a given frequency $\omega$. The generalization of the Fresnel formulas contains the refraction indices of these modes as determined by the dielectric function $\epsilon(\omega,{\bf k})$. Near frequencies $\omega_e$, where the group velocity vanishes, $T(\omega)$ depends also on an additional parameter determined by the crystal microstructure. The transmission $T$ is significantly suppressed, if one of the excited modes is decaying into the crystal. We derive these features microscopically for the Josephson plasma resonance in layered superconductors.Comment: 4 pages, 2 figures, epl.cls style file, minor change

Under pressure: Response urgency modulates striatal and insula activity during decision-making under risk

When deciding whether to bet in situations that involve potential monetary loss or gain (mixed gambles), a subjective sense of pressure can influence the evaluation of the expected utility associated with each choice option. Here, we explored how gambling decisions, their psychophysiological and neural counterparts are modulated by an induced sense of urgency to respond. Urgency influenced decision times and evoked heart rate responses, interacting with the expected value of each gamble. Using functional MRI, we observed that this interaction was associated with changes in the activity of the striatum, a critical region for both reward and choice selection, and within the insula, a region implicated as the substrate of affective feelings arising from interoceptive signals which influence motivational behavior. Our findings bridge current psychophysiological and neurobiological models of value representation and action-programming, identifying the striatum and insular cortex as the key substrates of decision-making under risk and urgency

Surface Screening in the Casimir Force

We calculate the corrections to the Casimir force between two metals due to the spatial dispersion of their response functions. We employ model-independent expressions for the force in terms of the optical coefficients. We express the non-local corrections to the Fresnel coefficients employing the surface $d_\perp$ parameter, which accounts for the distribution of the surface screening charge. Within a self-consistent jellium calculation, spatial dispersion increases the Casimir force significatively for small separations. The nonlocal correction has the opposite sign than previously predicted employing hydrodynamic models and assuming abruptly terminated surfaces.Comment: 5 pages, 2 figure

Anxious and egocentric: How specific emotions influence perspective taking

People frequently feel anxious. Although prior research has extensively studied how feeling anxious shapes intrapsychic aspects of cognition, much less is known about how anxiety affects interpersonal aspects of cognition. Here, we examine the influence of incidental experiences of anxiety on perceptual and conceptual forms of perspective taking. Compared with participants experiencing other negative, high-arousal emotions (i.e., anger or disgust) or neutral feelings, anxious participants displayed greater egocentrism in their mental-state reasoning: They were more likely to describe an object using their own spatial perspective, had more difficulty resisting egocentric interference when identifying an object from others’ spatial perspectives, and relied more heavily on privileged knowledge when inferring others’ beliefs. Using both experimental-causal-chain and measurement-of-mediation approaches, we found that these effects were explained, in part, by uncertainty appraisal tendencies. Further supporting the role of uncertainty, a positive emotion associated with uncertainty (i.e., surprise) produced increases in egocentrism that were similar to anxiety. Collectively, the results suggest that incidentally experiencing emotions associated with uncertainty increase reliance on one’s own egocentric perspective when reasoning about the mental states of others

Revisiting the Evidence for Collapsing Boundaries and Urgency Signals in Perceptual Decision-Making

For nearly 50 years, the dominant account of decision-making holds that noisy information is accumulated until a fixed threshold is crossed. This account has been tested extensively against behavioral and neurophysiological data for decisions about consumer goods, perceptual stimuli, eyewitness testimony, memories, and dozens of other paradigms, with no systematic misfit between model and data. Recently, the standard model has been challenged by alternative accounts that assume that less evidence is required to trigger a decision as time passes. Such "collapsing boundaries" or "urgency signals" have gained popularity in some theoretical accounts of neurophysiology. Nevertheless, evidence in favor of these models is mixed, with support coming from only a narrow range of decision paradigms compared with a long history of support from dozens of paradigms for the standard theory. We conducted the first large-scale analysis of data from humans and nonhuman primates across three distinct paradigms using powerful model-selection methods to compare evidence for fixed versus collapsing bounds. Overall, we identified evidence in favor of the standard model with fixed decision boundaries. We further found that evidence for static or dynamic response boundaries may depend on specific paradigms or procedures, such as the extent of task practice. We conclude that the difficulty of selecting between collapsing and fixed bounds models has received insufficient attention in previous research, calling into question some previous results