Synaesthetic colours do not camouflage form in visual search

One of the major issues in synaesthesia research is to identify the level of processing involved in the formation of the subjective colours experienced by synaesthetes: are they perceptual phenomena or are they due to memory and association learning? To address this question, we tested whether the colours reported by a group of grapheme-colour synaesthetes (previously studied in an functional magnetic resonance imaging experiment) influenced them in a visual search task. As well as using a condition where synaesthetic colours should have aided visual search, we introduced a condition where the colours experienced by synaesthetes would be expected to make them worse than controls. We found no evidence for differences between synaesthetes and normal controls, either when colours should have helped them or where they should have hindered. We conclude that the colours reported by our population of synaesthetes are not equivalent to perceptual signals, but arise at a cognitive level where they are unable to affect visual search

The role of salience on crowding and visual search in the context of synaesthesia

Visual crowding is a phenomenon in which the identification of visual stimuli is impaired by nearby directions. it occurs both for simple stimuli (oriented lines) and for more complex forms. The literature on crowding is reviewed, along with relevant literature on visual search and stimulus salience. Experiments are reported to test the idea that visually salient stimuli can escape, in part from crowding. The salience of stimuli was manipulated by varying their motion direction, colour, or temporal frequency relative to dis tractors. Salience was also measured independently of crowding using the pop out paradigm in visual search. Results showed that stimuli independently defined as salient did escape, in part, from crowding. A following experiment attempted to see whether the same would be true for the subjective colours experienced by synaesthetes

Performance of a deterministic source of entangled photonic qubits

We study the possible limitations and sources of decoherence in the scheme for the deterministic generation of polarization-entangled photons, recently proposed by Gheri et al. [K. M. Gheri et al., Phys. Rev. A 58, R2627 (1998)], based on an appropriately driven single atom trapped within an optical cavity. We consider in particular the effects of laser intensity fluctuations, photon losses, and atomic motion.Comment: 10 pages, 6 figure

Coupling a single atomic quantum bit to a high finesse optical cavity

The quadrupole S$_{1/2}$ -- D$_{5/2}$ optical transition of a single trapped Ca$^+$ ion, well suited for encoding a quantum bit of information, is coherently coupled to the standing wave field of a high finesse cavity. The coupling is verified by observing the ion's response to both spatial and temporal variations of the intracavity field. We also achieve deterministic coupling of the cavity mode to the ion's vibrational state by selectively exciting vibrational state-changing transitions and by controlling the position of the ion in the standing wave field with nanometer-precision

Bright squeezing from self-induced transparencies in dressed three-level atoms

We investigate two schemes for the efficient conversion of coherent input light into bright-squeezed output light. Both schemes utilize strong signal and weak probe fields, interacting with three-level ladder-configuration atoms inside optical cavities. The schemes differ in the resonance requirements of the cavities and produce noise suppression for quite different tuning regimes. Quantum-noise reduction is a consequence of the dressing of the atoms with two coherent fields. By tuning the probe light in the right fashion, spontaneous emission from the excited state can be made to counteract signal-light intensity fluctuations

High field brain proton magnetic resonance spectroscopy and volumetry in children with chronic, compensated liver disease - A pilot study.

There is increasing evidence that children or young adults having acquired liver disease in childhood display neurocognitive impairment which may become more apparent as they grow older. The molecular, cellular and morphological underpinnings of this clinical problem are incompletely understood. Therefore, we used the advantages of highly-resolved proton magnetic resonance spectroscopy at ultra-high magnetic field to analyze the neurometabolic profile and brain morphometry of children with chronic, compensated liver disease, hypothesizing that with high field spectroscopy we would identify early evidence of rising brain glutamine and decreased myoinositol, such as has been described both in animals and humans with more significant liver disease. Patients (n = 5) and age-matched controls (n = 19) underwent 7T MR scans and short echo time <sup>1</sup> H MR spectra were acquired using the semi-adiabatic SPECIAL sequence in two voxels located in gray and white matter dominated prefrontal cortex, respectively. A 3D MP2RAGE sequence was also acquired for brain volumetry and T <sub>1</sub> mapping. Liver disease had to have developed at least 6 months before entering the study. Subjects underwent routine blood analysis and neurocognitive testing using validated methods within 3 months of MRI and MRS. Five children aged 8-16 years with liver disease acquired in childhood were included. Baseline biological characteristics were similar among patients. There were no statistically significant differences between subjects and controls in brain metabolite levels or brain volumetry. Finally, there were minor neurocognitive fluctuations including attention deficit in one child, but none fell in the statistically significant range. Children with chronic, compensated liver disease did not display an abnormal neurometabolic profile, neurocognitive abnormalities, or signal intensity changes in the globus pallidus. Despite the absence of neurometabolic changes, it is an opportunity to emphasize that it is only by developing the use of <sup>1</sup> H MRS at high field in the clinical arena that we will understand the significance and generalizability of these findings in children with CLD. Healthy children displayed neurometabolic regional differences as previously reported in adult subjects