5,747 research outputs found
Dynamics from elastic neutron-scattering via direct measurement of the running time-integral of the van Hove distribution function
We present a new neutron-scattering approach to access the van Hove
distribution function directly in the time domain, I(t), which reflects the
system dynamics. Currently, I(t) is essentially determined from neutron
energy-exchange. Our method consists of the straightforward measurement of the
running time-integral of I(t), by computing the portion of scattered neutrons
corresponding to species at rest within a time t, (conceptually elastic
scattering). Previous attempts failed to recognise this connection. Starting
from a theoretical standpoint, a practical realisation is assessed via
numerical methods and an instrument simulation.Comment: 11 pages, 5 figures, new results, supplementary material (14 pages, 5
figures, 21 main equations, new results
How choice reveals and shapes expected hedonic outcome
Humans tend to modify their attitudes to align with past action. For example, after choosing between similarly valued alternatives, people rate the selected option as better than they originally did, and the rejected option as worse. However, it is unknown whether these modifications in evaluation reflect an underlying change in the physiological representation of a stimulus' expected hedonic value and our emotional response to it. Here, we addressed this question by combining participants' estimations of the pleasure they will derive from future events, with brain imaging data recorded while they imagined those events, both before, and after, choosing between them. Participants rated the selected alternatives as better after the decision stage relative to before, whereas discarded alternatives were valued less. Our functional magnetic resonance imaging findings reveal that postchoice changes in preference are tracked in caudate nucleus activity. Specifically, the difference in blood oxygenation level-dependent (BOLD) signal associated with the selected and rejected stimuli was enhanced after a decision was taken, reflecting the choice that had just been made. This finding suggests that the physiological representation of a stimulus' expected hedonic value is altered by a commitment to it. Furthermore, before any revaluation induced by the decision process, our data show that BOLD signal in this same region reflects the choices we are likely to make at a later time
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