Ready ... Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations, we found little fMRI activity during the waiting period; however, a large signal appears after the “go” signal, the amplitude of which reflects learned expectations about the distribution of possible waiting times. Specifically, the amplitude of the fMRI signal appears to encode a cumulative conditional probability, also known as the cumulative hazard function. The fMRI signal loses its dependence on waiting time in a “countdown” condition in which the arrival time of the go cue is known in advance, suggesting that the signal encodes temporal probabilities rather than simply elapsed time. The dependence of the signal on temporal expectation is present in “no-go” conditions, demonstrating that the effect is not a consequence of motor output. Finally, the encoding is not dependent on modality, operating in the same manner with auditory or visual signals. This finding extends our understanding of the relationship between temporal expectancy and measurable neural signals

Neural dynamics of error processing in medial frontal cortex.

Contains fulltext : 56338.pdf (publisher's version ) (Closed access)Adaptive behavior requires an organism to evaluate the outcome of its actions, such that future behavior can be adjusted accordingly and the appropriate response selected. During associative learning, the time at which such evaluative information is available changes as learning progresses, from the delivery of performance feedback early in learning to the execution of the response itself during learned performance. Here, we report a learning-dependent shift in the timing of activation in the rostral cingulate zone of the anterior cingulate cortex from external error feedback to internal error detection. This pattern of activity is seen only in the anterior cingulate, not in the presupplementary motor area. The dynamics of these reciprocal changes are consistent with the claim that the rostral cingulate zone is involved in response selection on the basis of the expected outcome of an action. Specifically, these data illustrate how the anterior cingulate receives evaluative information, indicating that an action has not produced the desired result

DEXi-Dairy: an ex post multicriteria tool to assess the sustainability of dairy production systems in various European regions

Growing awareness of global challenges and increasing pressures on the farming sector, including the urgent requirement to rapidly cut greenhouse gases (GHG) emissions, emphasize the need for sustainable production, which is particularly relevant for dairy production systems. Comparing dairy production systems across the three sustainability dimensions is a considerable challenge, notably due to the heterogeneity of production conditions in Europe. To overcome this, we developed an ex post multicriteria assessment tool that adopts a holistic approach across the three sustainability dimensions. This tool is based on the DEXi framework, which associates a hierarchical decision model with an expert perspective and follows a tree shaped structure; thus, we called it the DEXi-Dairy tool. For each dimension of sustainability, qualitative attributes were defined and organized in themes, sub-themes, and indicators. Their choice was guided by three objectives: (i) better describe main challenges faced by European dairy production systems, (ii) point out synergies and trade-offs across sustainability dimensions, and (iii) contribute to the identification of GHG mitigation strategies at the farm level. Qualitative scales for each theme, sub-theme, and indicator were defined together with weighting factors used to aggregate each level of the tree. Based on selected indicators, a list of farm data requirements was developed to populate the sustainability tree. The model was then tested on seven case study farms distributed across Europe. DEXi-Dairy presents a qualitative method that allows for the comparison of different inputs and the evaluation of the three sustainability dimensions in an integrated manner. By assessing synergies and trade-offs across sustainability dimensions, DEXi-Dairy is able to reflect the heterogeneity of dairy production systems. Results indicate that, while trade-offs occasionally exist among respective selected sub-themes, certain farming systems tend to achieve a higher sustainability score than others and hence could serve as benchmarks for further analyses

Motor-Cortical Interaction in Gilles de la Tourette Syndrome

BACKGROUND: In Gilles de la Tourette syndrome (GTS) increased activation of the primary motor cortex (M1) before and during movement execution followed by increased inhibition after movement termination was reported. The present study aimed at investigating, whether this activation pattern is due to altered functional interaction between motor cortical areas. METHODOLOGY/PRINCIPAL FINDINGS: 10 GTS-patients and 10 control subjects performed a self-paced finger movement task while neuromagnetic brain activity was recorded using Magnetoencephalography (MEG). Cerebro-cerebral coherence as a measure of functional interaction was calculated. During movement preparation and execution coherence between contralateral M1 and supplementary motor area (SMA) was significantly increased at beta-frequency in GTS-patients. After movement termination no significant differences between groups were evident. CONCLUSIONS/SIGNIFICANCE: The present data suggest that increased M1 activation in GTS-patients might be due to increased functional interaction between SMA and M1 most likely reflecting a pathophysiological marker of GTS. The data extend previous findings of motor-cortical alterations in GTS by showing that local activation changes are associated with alterations of functional networks between premotor and primary motor areas. Interestingly enough, alterations were evident during preparation and execution of voluntary movements, which implies a general theme of increased motor-cortical interaction in GTS

The role of the cerebellum in adaptation: ALE meta‐analyses on sensory feedback error

It is widely accepted that unexpected sensory consequences of self‐action engage the cerebellum. However, we currently lack consensus on where in the cerebellum, we find fine‐grained differentiation to unexpected sensory feedback. This may result from methodological diversity in task‐based human neuroimaging studies that experimentally alter the quality of self‐generated sensory feedback. We gathered existing studies that manipulated sensory feedback using a variety of methodological approaches and performed activation likelihood estimation (ALE) meta‐analyses. Only half of these studies reported cerebellar activation with considerable variation in spatial location. Consequently, ALE analyses did not reveal significantly increased likelihood of activation in the cerebellum despite the broad scientific consensus of the cerebellum's involvement. In light of the high degree of methodological variability in published studies, we tested for statistical dependence between methodological factors that varied across the published studies. Experiments that elicited an adaptive response to continuously altered sensory feedback more frequently reported activation in the cerebellum than those experiments that did not induce adaptation. These findings may explain the surprisingly low rate of significant cerebellar activation across brain imaging studies investigating unexpected sensory feedback. Furthermore, limitations of functional magnetic resonance imaging to probe the cerebellum could play a role as climbing fiber activity associated with feedback error processing may not be captured by it. We provide methodological recommendations that may guide future studies

Study and characterization of the structures Au/Al2O3/Si and Au/Al0/Al2O3/Si

International audienc

Study of the surface state density and potential in MIS diode Schottky using the surface photovoltage method

International audienc

Електричне дослідження структур Au/GaN/GaAs (100) як функції частоти

Різні дослідження показують, що нітрування поверхні GaAs покращує електричну якість діодів Шотткі на основі арсеніду галію. Для того, щоб спостерігати це покращення, були досліджені характеристики ємність/провідність-напруга на трьох частотах (50, 100 та 500 кГц). Ці характеристики були кореговані шляхом усунення ефекту послідовного опору. Спочатку визначали значення послідовного опору та будували графік його залежності від напруги на різних частотах. Отримані криві показують значні значення послідовного опору з піками, які спостерігаються при близько – 0,5 В для частот 50 і 100 кГц і при 0,25 В для 500 кГц. Ці піки пов'язані з омічним зворотним контактом і щільністю поверхневих станів. Потім були розраховані електричні властивості виготовленого діода Шотткі та оцінена щільність поверхневих станів діода Шотткі з ефектом послідовного опору та без нього. Щільність поверхневих станів значно зменшилася після усунення ефекту послідовного опору. Електричні параметри демонструють покращення електричної якості виготовленого діода Шотткі Au/GaN/GaAs.Various studies show that the nitridation of the GaAs surface improves the electrical quality of the Schottky diodes based on gallium arsenide. In order to observe this improvement, capacitance/conductance – voltage characteristics were investigated at three frequencies (50, 100 and 500 kHz). These characteristics were corrected by eliminating the effect of the series resistance. First, values of the series resistance were determined and plotted against voltage at different frequencies. The obtained curves show significant values of the series resistance with peaks observed at about – 0.5 V for 50 and 100 kHz frequencies and at 0.25 V for 500 kHz. These peaks are attributed to the ohmic back contact and the surface state density. The electrical properties of the fabricated Schottky diode were then calculated and the surface state density of the Schottky diode was estimated with and without the effect of the series resistance. Surface state density was significantly reduced after the elimination of the series resistance effect. Electrical parameters demonstrate an improvement of the electrical quality of the fabricated Au/GaN/GaAs Schottky diode