258 research outputs found
Responses of Auditory Nerve and Anteroventral Cochlear Nucleus Fibers to Broadband and Narrowband Noise: Implications for the Sensitivity to Interaural Delays
The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived from AVCN neurons were lower than those derived from AN fibers, showing that the enhanced temporal coding in the AVCN improves binaural sensitivity to ITDs. AVCN processing also increased the dynamic range of ITD sensitivity and changed the shape of the frequency dependence of ITD sensitivity. Bandwidth dependence of ITD jnds from AN as well as AVCN fibers agreed with psychophysical data. These findings demonstrate that monaural preprocessing in the AVCN improves the temporal code in a way that is beneficial for binaural processing and may be crucial in achieving the exquisite sensitivity to ITDs observed in binaural pathways
Polynomial Carleson operators along monomial curves in the plane
We prove bounds for partial polynomial Carleson operators along
monomial curves in the plane with a phase polynomial
consisting of a single monomial. These operators are "partial" in the sense
that we consider linearizing stopping-time functions that depend on only one of
the two ambient variables. A motivation for studying these partial operators is
the curious feature that, despite their apparent limitations, for certain
combinations of curve and phase, bounds for partial operators along
curves imply the full strength of the bound for a one-dimensional
Carleson operator, and for a quadratic Carleson operator. Our methods, which
can at present only treat certain combinations of curves and phases, in some
cases adapt a method to treat phases involving fractional monomials, and
in other cases use a known vector-valued variant of the Carleson-Hunt theorem.Comment: 27 page
Gravitational collapse and thermalization in the hard wall model
We study a simple example of holographic thermalization in a confining field
theory: the homogeneous injection of energy in the hard wall model. Working in
an amplitude expansion, we find black brane formation for sufficiently fast
energy injection and a scattering wave solution for sufficiently slow
injection. We comment on our expectations for more sophisticated holographic
QCD models.Comment: 33 pages, 5 figure
Cochlear implantation in patients with chronic otitis media: 7 years’ experience in Maastricht
The purpose of this paper is to propose management options for cochlear implantation in chronic
otitis media (COM) based on our 7-year experience. Thirteen patients with COM who were candidates for cochlear implantation were identified. COM was divided in an inactive and an active form based on clinical and radiological findings. One major complications and one minor complication were identified in the study group. In case of an active infection or in case of a unstable cavity we advise cochlear implantation as a staged procedure. A single stage procedure is recommended in case of patients with COM presenting with a dry perforation or a stable cavity
Assessment of serum catecholamine concentrations in patients with pheochromocytoma undergoing videolaparoscopic adrenalectomy
Response characteristics in the apex of the gerbil cochlea studied through auditory nerve recordings
In this study, we analyze the processing of low-frequency sounds in the cochlear apex through responses of auditory nerve fibers (ANFs) that innervate the apex. Single tones and irregularly spaced tone complexes were used to evoke ANF responses in Mongolian gerbil. The spike arrival times were analyzed in terms of phase locking, peripheral frequency selectivity, group delays, and the nonlinear effects of sound pressure level (SPL). Phase locking to single tones was similar to that in cat. Vector strength was maximal for stimulus frequencies around 500 Hz, decreased above 1 kHz, and became insignificant above 4 to 5 kHz. We used the responses to tone complexes to determine amplitude and phase curves of ANFs having a characteristic frequency (CF) below 5 kHz. With increasing CF, amplitude curves gradually changed from broadly tuned and asymmetric with a steep low-frequency flank to more sharply tuned and asymmetric with a steep high-frequency flank. Over the same CF range, phase curves gradually changed from a concave-upward shape to a concave-downward shape. Phase curves consisted of two or three approximately straight segments. Group delay was analyzed separately for these segments. Generally, the largest group delay was observed near CF. With increasing SPL, most amplitude curves broadened, sometimes accompanied by a downward shift of best frequency, and group delay changed along the entire range of stimulus frequencies. We observed considerable across-ANF variation in the effects of SPL on both amplitude and phase. Overall, our data suggest that mechanical responses in the apex of the cochlea are considerably nonlinear and that these nonlinearities are of a different character than those known from the base of the cochlea
The Urokinase Receptor (uPAR) Facilitates Clearance of Borrelia burgdorferi
The causative agent of Lyme borreliosis, the spirochete Borrelia
burgdorferi, has been shown to induce expression of the urokinase
receptor (uPAR); however, the role of uPAR in the immune response against
Borrelia has never been investigated. uPAR not only acts as
a proteinase receptor, but can also, dependently or independently of ligation to
uPA, directly affect leukocyte function. We here demonstrate that uPAR is
upregulated on murine and human leukocytes upon exposure to B.
burgdorferi both in vitro as well as in vivo. Notably, B.
burgdorferi-inoculated C57BL/6 uPAR knock-out mice harbored
significantly higher Borrelia numbers compared to WT controls.
This was associated with impaired phagocytotic capacity of B.
burgdorferi by uPAR knock-out leukocytes in vitro. B.
burgdorferi numbers in vivo, and phagocytotic capacity in vitro,
were unaltered in uPA, tPA (low fibrinolytic activity) and PAI-1 (high
fibrinolytic activity) knock-out mice compared to WT controls. Strikingly, in
uPAR knock-out mice partially backcrossed to a B. burgdorferi
susceptible C3H/HeN background, higher B. burgdorferi numbers
were associated with more severe carditis and increased local TLR2 and
IL-1β mRNA expression. In conclusion, in B. burgdorferi
infection, uPAR is required for phagocytosis and adequate eradication of the
spirochete from the heart by a mechanism that is independent of binding of uPAR
to uPA or its role in the fibrinolytic system
Assessment of thrombin-activatable fibrinolysis inhibitor (TAFI) activation in acquired hemostatic dysfunction: a diagnostic challenge
Menu-engineering in restaurants - adapting portion sizes on plates to enhance vegetable consumption: a real-life experiment
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