Summary of the 2003 Moriond Workshop on Electroweak Interactions and Unified Theories

We recount some of the highlights of the 2003 Moriond Workshop on Electroweak Interactions and Unified Theories.Comment: LaTeX, 15 pages, 8 figures (some color), uses moriond.st

Pre-stimulus influences on auditory perception arising from sensory representations and decision processes

The qualities of perception depend not only on the sensory inputs but also on the brain state before stimulus presentation. Although the collective evidence from neuroimaging studies for a relation between prestimulus state and perception is strong, the interpretation in the context of sensory computations or decision processes has remained difficult. In the auditory system, for example, previous studies have reported a wide range of effects in terms of the perceptually relevant frequency bands and state parameters (phase/power). To dissociate influences of state on earlier sensory representations and higher-level decision processes, we collected behavioral and EEG data in human participants performing two auditory discrimination tasks relying on distinct acoustic features. Using single-trial decoding, we quantified the relation between prestimulus activity, relevant sensory evidence, and choice in different task-relevant EEG components. Within auditory networks, we found that phase had no direct influence on choice, whereas power in task-specific frequency bands affected the encoding of sensory evidence. Within later-activated frontoparietal regions, theta and alpha phase had a direct influence on choice, without involving sensory evidence. These results delineate two consistent mechanisms by which prestimulus activity shapes perception. However, the timescales of the relevant neural activity depend on the specific brain regions engaged by the respective task

Neutrino Mass, Mixing, and Oscillation

Do neutrinos have nonzero masses? If they do, then these masses are very tiny, and can be sought only in very sensitive experiments. The most sensitive of these search for neutrino oscillation, a quantum interference effect which requires neutrino mass and leptonic mixing. In these lectures, we explain what leptonic mixing is, and then develop the physics of neutrino oscillation, including the general formalism and its application to special cases of practical interest. We also see how neutrino oscillation is affected by the passage of the oscillating neutrinos through matter.Comment: LaTeX; 26 pages with 6 PostScript figure