Adaptation in Sound Localization Processing Induced by Interaural Time Difference in Amplitude Envelope at High Frequencies

<div><h3>Background</h3><p>When a second sound follows a long first sound, its location appears to be perceived away from the first one (the localization/lateralization aftereffect). This aftereffect has often been considered to reflect an efficient neural coding of sound locations in the auditory system. To understand determinants of the localization aftereffect, the current study examined whether it is induced by an interaural temporal difference (ITD) in the amplitude envelope of high frequency transposed tones (over 2 kHz), which is known to function as a sound localization cue.</p> <h3>Methodology/Principal Findings</h3><p>In <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041328#s2">Experiment 1</a>, participants were required to adjust the position of a pointer to the perceived location of test stimuli before and after adaptation. Test and adapter stimuli were amplitude modulated (AM) sounds presented at high frequencies and their positional differences were manipulated solely by the envelope ITD. Results showed that the adapter's ITD systematically affected the perceived position of test sounds to the directions expected from the localization/lateralization aftereffect when the adapter was presented at ±600 µs ITD; a corresponding significant effect was not observed for a 0 µs ITD adapter. In <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041328#s3">Experiment 2</a>, the observed adapter effect was confirmed using a forced-choice task. It was also found that adaptation to the AM sounds at high frequencies did not significantly change the perceived position of pure-tone test stimuli in the low frequency region (128 and 256 Hz).</p> <h3>Conclusions/Significance</h3><p>The findings in the current study indicate that ITD in the envelope at high frequencies induces the localization aftereffect. This suggests that ITD in the high frequency region is involved in adaptive plasticity of auditory localization processing.</p> </div

Proportion of “right” responses as a function of the ITD of the test stimuli of one participant (S3).

<p>The left panels show the results in AM adapter condition (128-Hz modulation frequency), and the right panels show those in tone adapter condition (128 Hz). Each row displays results in each test condition: The abbreviations P128 and P256 refer to the 128- and 256-Hz tone respectively. AM128 and AM256 refer to the AM sounds that were modulated with 128 and 256 Hz. Unfilled circles indicate the results in the no-adapter condition. Filled and unfilled triangles indicate the results in the −937 and 937 µs ITD conditions respectively. There is a relatively larger aftereffect when both the adapting and test stimuli are AM tones.</p

The average magnitude of the aftereffect in each adapter condition as a function of the type of test stimuli.

<p>See the caption of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041328#pone-0041328-g002" target="_blank">Figure 2</a> for explanation of abbreviations such as P128. There are relatively large aftereffects when the adapter and test stimuli are of the same type. Error bars show SEs.</p

Average normalized responses as a function of the ITD of the test stimulus.

<p>Error bars represent standard errors. After the adaptation at ±600 µs, the subjective midline shifted towards the position of the adapter. Error bars show SEs.</p

Development of a Sila-Friedel−Crafts Reaction and Its Application to the Synthesis of Dibenzosilole Derivatives

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Thermolysis of a pentacoordinate 1λ6,2-thiazetidine, which was synthesized for the first time and characterized by X-ray crystallographic analysis, gave the corresponding aziridine and a cyclic sulfinate almost quantitatively. The potential intermediacy of a 1λ6,2-thiazetidine was suggested in the aza-Corey−Chaykovsky reaction

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Hydrazobenzenes 3−5 bearing a chalcogenophosphoryl group were synthesized by palladium-catalyzed cross-coupling reactions. Their X-ray crystallographic analyses and NMR and IR spectra showed the presence of intramolecular hydrogen bonds between the N−H protons and the chalcogenophosphoryl groups. The intermolecular hydrogen bonds in phosphine oxide 3 and selenide 5 were observed in the solid state. Phosphine oxide 3, sulfide 4, and selenide 5 constructed a dimeric structure, a discrete monomeric structure, and a chain structure, respectively. As the chalcogen atom changed, the crystalline structures of the 2-chalcogenophosphorylhydrazobenzenes also changed. The hydrogen bonds affected the oxidation reactions of the hydrazobenzenes, and oxidation of hydrazobenzenes bearing a lighter chalcogen atom was more difficult. For azobenzenes bearing a chalcogenophosphoryl group, X-ray crystallographic analyses and NMR spectra showed little interaction between the azo group and the chalcogenophosphoryl groups. However, in the UV−vis spectra, the red shifts of the absorption maxima due to the n → π* transitions indicated intramolecular interactions in the excited state, in contrast to the corresponding 4-substituted azobenzenes. In addition, photoirradiation of phosphine oxide (E)-7 gave (Z)-7, whereas that of phosphine sulfide (E)-8 and phosphine selenide (E)-9 did not give (Z)-8 and (Z)-9, suggesting that heavy chalcogen atoms quench excited states by through-space interactions. Introduction of a chalcogenophosphoryl group at the 2-position had a significant effect on the structure, spectral properties, and reactivity of hydrazobenzenes and azobenzenes. Although azobenzene (E)-10 bearing a hydroxyphosphoryl group at the 2-position did not show hydrogen bonding in the crystalline state, its optical properties and photoisomerization ratio were different from those of (E)-7

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Thermal and Photocontrol of the Equilibrium between a 2-Phosphinoazobenzene and an Inner Phosphonium Salt

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