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Aristelliger barbouri
Number of Pages: 1Integrative BiologyGeological Science
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Thecadactylus, T. rapicauda
Number of Pages: 16Integrative BiologyGeological Science
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Aristelliger georgeensis
Number of Pages: 2Integrative BiologyGeological Science
Tactile spatial attention enhances gamma-band activity in somatosensory cortex and reduces low-frequency activity in parieto-occipital areas.
We investigated the effects of spatial-selective attention on oscillatory neuronal dynamics in a tactile delayed-match-to-sample task.
Whole-head magnetoencephalography was recorded in healthy subjects while dot patterns were presented to their index fingers using Braille stimulators. The subjects’ task was to report the reoccurrence of an initially presented sample pattern in a series of up to eight test stimuli that were presented unpredictably to their right or left index finger. Attention was cued to one side (finger) at the beginning of each trial, and subjects performed the task at the attended side, ignoring the unattended side.
After stimulation, high-frequency gamma-band activity (60 –95 Hz) in presumed primary somatosensory cortex (S1) was enhanced, whereas alpha- and beta-band activity were suppressed in somatosensory and occipital areas and then rebounded. Interestingly, despite the absence of any visual stimulation, we also found time-locked activation of medial occipital, presumably visual, cortex. Most relevant,
spatial tactile attention enhanced stimulus-induced gamma-band activity in brain regions consistent with contralateral S1 and deepened and prolonged the stimulus induced suppression of beta- and alpha-band activity, maximal in parieto-occipital cortex. Additionally, the
beta rebound over contralateral sensorimotor areas was suppressed.
Wehypothesize that spatial-selective attention enhances the saliency of sensory representations by synchronizing neuronal responses in early somatosensory cortex and thereby enhancing their impact on downstream areas and facilitating interareal processing. Furthermore, processing of tactile patterns also seems to recruit visual cortex and this even more so for attended compared with unattended
stimuli
Comments on the Links between su(3) Modular Invariants, Simple Factors in the Jacobian of Fermat Curves, and Rational Triangular Billiards
We examine the proposal made recently that the su(3) modular invariant
partition functions could be related to the geometry of the complex Fermat
curves. Although a number of coincidences and similarities emerge between them
and certain algebraic curves related to triangular billiards, their meaning
remains obscure. In an attempt to go beyond the su(3) case, we show that any
rational conformal field theory determines canonically a Riemann surface.Comment: 56 pages, 4 eps figures, LaTeX, uses eps
Nonlinear dielectric response of Debye, alpha, and beta relaxation in 1-propanol
We present nonlinear dielectric measurements of glass-forming 1-propanol, a
prototypical example for the monohydroxy alcohols that are known to exhibit
unusual relaxation dynamics, namely an additional Debye relaxation, slower than
the structural alpha relaxation. Applying high ac fields of 468 kV/cm allows
for a detailed investigation of the nonlinear properties of all three
relaxation processes occurring in 1-propanol, namely the Debye, alpha, and beta
relaxation. Both the field-induced variations of dielectric constant and loss
are reported. Polarization saturation and the absorption of field energy govern
the findings in the Debye-relaxation regime, well consistent with the suggested
cluster-like nature of the relaxing entities. The behavior of the alpha
relaxation is in good accord with the expectations for a heterogeneous
relaxation scenario. Finally, the Johari-Goldstein beta-relaxation in
1-propanol seems to exhibit no or only weak field dependence, in agreement with
recent findings for the excess wing of canonical glass formers.Comment: 8 pages, 4 figure
Cooperativity and Heterogeneity in Plastic Crystals Studied by Nonlinear Dielectric Spectroscopy
The glassy dynamics of plastic-crystalline cyclo-octanol and ortho-carborane,
where only the molecular reorientational degrees of freedom freeze without
long-range order, is investigated by nonlinear dielectric spectroscopy. Marked
differences to canonical glass formers show up: While molecular cooperativity
governs the glassy freezing, it leads to a much weaker slowing down of
molecular dynamics than in supercooled liquids. Moreover, the observed
nonlinear effects cannot be explained with the same heterogeneity scenario
recently applied to canonical glass formers. This supports ideas that molecular
relaxation in plastic crystals may be intrinsically non-exponential. Finally,
no nonlinear effects were detected for the secondary processes in
cyclo-octanol.Comment: Final version as accepted for publication in Phys. Rev. Lett. 6
pages, 5 figures (including 1 page and figure in Supplemental Material
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