Dopamine firing plays a dual role in coding reward prediction errors and signaling motivation in a working memory task

Little is known about how dopamine (DA) neuron firing rates behave in cognitively demanding decision-making tasks. Here, we investigated midbrain DA activity in monkeys performing a discrimination task in which the animal had to use working memory (WM) to report which of two sequentially applied vibrotactile stimuli had the higher frequency. We found that perception was altered by an internal bias, likely generated by deterioration of the representation of the first frequency during the WM period. This bias greatly controlled the DA phasic response during the two stimulation periods, confirming that DA reward prediction errors reflected stimulus perception. In contrast, tonic dopamine activity during WM was not affected by the bias and did not encode the stored frequency. More interestingly, both delay-period activity and phasic responses before the second stimulus negatively correlated with reaction times of the animals after the trial start cue and thus represented motivated behavior on a trial-by-trial basis. During WM, this motivation signal underwent a ramp-like increase. At the same time, motivation positively correlated with accuracy, especially in difficult trials, probably by decreasing the effect of the bias. Overall, our results indicate that DA activity, in addition to encoding reward prediction errors, could at the same time be involved in motivation and WM. In particular, the ramping activity during the delay period suggests a possible DA role in stabilizing sustained cortical activity, hypothetically by increasing the gain communicated to prefrontal neurons in a motivation-dependent way.

Pushing and Pulling on OH-and H3O+ with Electric Fields Across Water’s Surface

<p>We use second harmonic generation spectroscopy, molecular dynamics simulation, and theoretical modeling to study the response of the neat liquid water-air interface to changes in the potential of an external electrode positioned above the liquid. We observe a parabolic dependence of second harmonic intensity on applied potential, indicating that water’s net interfacial dipole responds linearly. We also observe a minimum intensity when the potential is tuned to a specific positive value. Interpreting this minimum based on the macroscopic electrostatic potential profile yields misleading physical conclusions because it neglects the internal bias exerted on molecular orientations by the excess surface concentrations of OH^- or H₃O⁺. We thus find that water’s net interfacial dipole orientation is primarily responsive to the effects of these ionic species rather than the external electric field. </p>

Pushing and Pulling on OH-and H3O+ with Electric Fields Across Water’s Surface

<p>We use second harmonic generation spectroscopy, molecular dynamics simulation, and theoretical modeling to study the response of the neat liquid water-air interface to changes in the potential of an external electrode positioned above the liquid. We observe a parabolic dependence of second harmonic intensity on applied potential, indicating that water’s net interfacial dipole responds linearly. We also observe a minimum intensity when the potential is tuned to a specific positive value. Interpreting this minimum based on the macroscopic electrostatic potential profile yields misleading physical conclusions because it neglects the internal bias exerted on molecular orientations by the excess surface concentrations of OH^- or H₃O⁺. We thus find that water’s net interfacial dipole orientation is primarily responsive to the effects of these ionic species rather than the external electric field. </p>

Dielectric properties and switching processes of ferroelectric superlattices

We review dielectric properties of BaZrO3/BaTiO3 (BZ/BT) superlattices deposited on a single-crystal MgO substrate, and having a period of 13.32 nm. These superlattices have specific properties distinguishing them from BZ or BT bulk materials, and from thin films, with a ferroelectric phase transition around 393-395 °?, significantly higher than in bulk samples and thin films of BT, and appearing of second order. The polarization switching occurs in two stages and the precise analysis of experimental data demonstrates that the motion of the domain walls causes the switching processes. We conclude that the mobility of the domain walls decreases on heating. The presence of an internal bias field has been demonstrated and shown to be directed from the superlattice to the substrate, in agreement with an analysis based on the flexoelectric effect. The switching current has been shown to vary in weak fields as 1/E? with the exponent ? much smaller than in thin ferroelectric films. The appearance of the power index ?, which is significantly different from unity, may be due to a decrease in the average value of the switched polarization due to the boundaries between layers of different materials.

Hoodoo, Kentucky, Workers Adminstration Project, Poetry, Black Folklore, Ancestors and Memory

A poem about realizing freedom through transformation. The poem “ ‘Hoodoo’ Inspired by Mamie Hansberry from Christian Country Kentucky” is based on the voice of Mamie Hansberry, a formerly enslaved woman from Kentucky. Hansberry’s words were recorded by historians and archivists who worked for the Workers Project Administration (WPA). The WPA was a Depression-era program where historians and writers went around the South to collect the stories of the former enslaved. This program provided an opportunity for Black voices to be added and centralized in the archives. Despite positive intentions, the archivists were clouded by their own internal bias. Most of the collectors were white Southern males who held strong biases that influenced the topics they chose to explore. For example, Black folklore is featured heavily in the WPA narratives. To the recorder, these beliefs might have been viewed as eccentric and uncivilized. When interacting with Mamie Hansberry, they more than likely prompted her into explaining “Hoodism”. Instead of a simple introduction, however, Hansberry spun an oral rhyming poem, “A snake head an’ er lizard tail, Hoo-doo; Not close den a mile of jail, Hoo-doo.” Through her rhythmic re-telling, she showcases the beauty and power that resides in “Hoodisms”, that was probably lost by the white male listeners. The archives often offer us silence on Black voices that are women, poor, and rural. If they were recorded, they are often tainted by the bias of our racist and sexist systems, such as in the WPA narratives. Instead of looking to the archives to better tell the stories of my ancestors, I choose to do so through poetry allowing me to reimagine and explore where the archives offer me no assistance. Removing the white male gaze, I give my version of “Hoodism” based on the long line of Kentucky Black women who came before me, like Mamie Hansberry. This is my homage to their voices and stories. Their stories are not lost or forgotten.

Universal Anxiety Interventions in United States Schools: A Systematic Review

Objective: We reviewed studies pertaining to randomized controlled universal/Tier 1, teacher-led intervention trials in United States (US) schools, and their impact on anxiety in K-12 students. Methods: We searched 7 databases and one search engine. Anxiety was the main outcome measure. Studies published through July 5, 2018 were appraised using the Cochrane Collaborations tool. Results: We included 4 studies, all indicating efficacy for lowering anxiety symptoms. Internal bias was unclear for 3. Conclusion: Despite a call from the National Institute of Mental Health for population-based, upstream public health interventions, empirical evidence is scarce. Findings from this review are reflected by the absence of such studies from the Healthy People 2020 recommendations for evidence-based resources consumer page. There appears to be a need for development and testing of universal teacher-led anxiety interventions in US schools.