Multiple H-Rearrangements in 10-Benzylthio-dithranol Radical Cations

10-Alkylthio- and 10-arylthio-derivatives of dithranol (anthralin; 1,8-dihydroxy-9-anthrone) are of interest in search for new anti-psoriatic agents2 , 3 ). By working out ms procedures for unequivocal identification of trace amounts of these compounds4 ) it was established that in case of 10-phenylthio-dithranol putative by-products, especially one giving rise to ions at m/z = 226 (dithranol), are artefacts of thermal reaction in the mass spectrometer1). In the EI-MS of those 10-substituted dithranols containing a S-CH2R chain, however, these ions (m/z = 226) arise from M + * as well. Scope and mechanism of their formation was examined by analyzing compound 1 and its D-labelled derivatives 2 and 3

Stereochemical Studies on a New Ciramadol Analogue by NMR-Spectroscopy

The absol. configuration of a Ciramadol analogue obtained from (-)-menthone is established by 'H-NMR-. simulated NMR-, COSY-90-, and NOEmeasurements. The final compound 2-(a-1 -pyrrolidino)benzy 1-4-isopropyl- 1 -methyl-cyclohexan-3-one (4b), e.g.. has 1R.2S,4S.l IS-configuration due to stereoselective Michael-type addition of pyrrolidine to the pertinent benzylidene intermediate 3. Die absol. Konfiguration einer Ciramadol-analogen Verbindung aus (-)- Menthon wurde durch 'H-NMR-. simulierte NMR-. COSY-90- und NOEUntersuchungen geklärt. Danach hat die als Beispiel untersuchte Verbindung 2-(a-1 -Pyrrolidino)benzyl-4-isopropyl-1 -methyl-cyclohexan-3-on (4b) 1R,2S.4S.l IS-Konfiguration, die durch eine stereoselektive Michael-analoge Addition des Pyrrolidins an die entspr. Benzyliden-Verbindung 3 entsteht

Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls

During vocal communication, the spectro‑temporal structure of vocalizations conveys important contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of signals in the temporal domain. We therefore hypothesized that for social communication as well, bats would excel at detecting minute distortions in the spectro‑temporal structure of calls. To test this hypothesis, we systematically introduced spectro‑temporal distortion to communication calls of Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized the phase spectrum inside each window. The overall degree of spectro‑temporal distortion in communication calls increased with window length. Modelling the bat auditory periphery revealed that cochlear mechanisms allow discrimination of fast spectro‑temporal envelopes. We evaluated model predictions with experimental psychophysical and neurophysiological data. We first assessed bats’ performance in discriminating original versions of calls from increasingly distorted versions of the same calls. We further examined cortical responses to determine additional specializations for call discrimination at the cortical level. Psychophysical and cortical responses concurred with model predictions, revealing discrimination thresholds in the range of 8–15 ms randomization‑window length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical resilience to temporal distortion in communication calls

Size constancy in bat biosonar?

Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed "size constancy". It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the 'sonar aperture', i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats

Population-based study of the durability of humoral immunity after SARS-CoV-2 infection

SARS-CoV-2 antibody quantity and quality are key markers of humoral immunity. However, there is substantial uncertainty about their durability. We investigated levels and temporal change of SARS-CoV-2 antibody quantity and quality. We analyzed sera (8 binding, 4 avidity assays for spike-(S-)protein and nucleocapsid-(N-)protein; neutralization) from 211 seropositive unvaccinated participants, from the population-based longitudinal TiKoCo study, at three time points within one year after infection with the ancestral SARS-CoV-2 virus. We found a significant decline of neutralization titers and binding antibody levels in most assays (linear mixed regression model, p<0.01). S-specific serum avidity increased markedly over time, in contrast to N-specific. Binding antibody levels were higher in older versus younger participants – a difference that disappeared for the asymptomatic-infected. We found stronger antibody decline in men versus women and lower binding and avidity levels in current versus never-smokers. Our comprehensive longitudinal analyses across 13 antibody assays suggest decreased neutralization-based protection and prolonged affinity maturation within one year after infection

Combination of Spectral and Binaurally Created Harmonics in a Common Central Pitch Processor

A fundamental attribute of human hearing is the ability to extract a residue pitch from harmonic complex sounds such as those produced by musical instruments and the human voice. However, the neural mechanisms that underlie this processing are unclear, as are the locations of these mechanisms in the auditory pathway. The ability to extract a residue pitch corresponding to the fundamental frequency from individual harmonics, even when the fundamental component is absent, has been demonstrated separately for conventional pitches and for Huggins pitch (HP), a stimulus without monaural pitch information. HP is created by presenting the same wideband noise to both ears, except for a narrowband frequency region where the noise is decorrelated across the two ears. The present study investigated whether residue pitch can be derived by combining a component derived solely from binaural interaction (HP) with a spectral component for which no binaural processing is required. Fifteen listeners indicated which of two sequentially presented sounds was higher in pitch. Each sound consisted of two “harmonics,” which independently could be either a spectral or a HP component. Component frequencies were chosen such that the relative pitch judgement revealed whether a residue pitch was heard or not. The results showed that listeners were equally likely to perceive a residue pitch when one component was dichotic and the other was spectral as when the components were both spectral or both dichotic. This suggests that there exists a single mechanism for the derivation of residue pitch from binaurally created components and from spectral components, and that this mechanism operates at or after the level of the dorsal nucleus of the lateral lemniscus (brainstem) or the inferior colliculus (midbrain), which receive inputs from the medial superior olive where temporal information from the two ears is first combined

What a Plant Sounds Like: The Statistics of Vegetation Echoes as Received by Echolocating Bats

A critical step on the way to understanding a sensory system is the analysis of the input it receives. In this work we examine the statistics of natural complex echoes, focusing on vegetation echoes. Vegetation echoes constitute a major part of the sensory world of more than 800 species of echolocating bats and play an important role in several of their daily tasks. Our statistical analysis is based on a large collection of plant echoes acquired by a biomimetic sonar system. We explore the relation between the physical world (the structure of the plant) and the characteristics of its echo. Finally, we complete the story by analyzing the effect of the sensory processing of both the echolocation and the auditory systems on the echoes and interpret them in the light of information maximization. The echoes of all different plant species we examined share a surprisingly robust pattern that was also reproduced by a simple Poisson model of the spatial reflector arrangement. The fine differences observed between the echoes of different plant species can be explained by the spatial characteristics of the plants. The bat's emitted signal enhances the most informative spatial frequency range where the species-specific information is large. The auditory system filtering affects the echoes in a similar way, thus enhancing the most informative spatial frequency range even more. These findings suggest how the bat's sensory system could have evolved to deal with complex natural echoes

Selective Attention Increases Both Gain and Feature Selectivity of the Human Auditory Cortex

Background. An experienced car mechanic can often deduce what’s wrong with a car by carefully listening to the sound of the ailing engine, despite the presence of multiple sources of noise. Indeed, the ability to select task-relevant sounds for awareness, whilst ignoring irrelevant ones, constitutes one of the most fundamental of human faculties, but the underlying neural mechanisms have remained elusive. While most of the literature explains the neural basis of selective attention by means of an increase in neural gain, a number of papers propose enhancement in neural selectivity as an alternative or a complementary mechanism. Methodology/Principal Findings. Here, to address the question whether pure gain increase alone can explain auditory selective attention in humans, we quantified the auditory cortex frequency selectivity in 20 healthy subjects by masking 1000-Hz tones by continuous noise masker with parametrically varying frequency notches around the tone frequency (i.e., a notched-noise masker). The task of the subjects was, in different conditions, to selectively attend to either occasionally occurring slight increments in tone frequency (1020 Hz), tones of slightly longer duration, or ignore the sounds. In line with previous studies, in the ignore condition, the global field power (GFP) of event-related brain responses at 100 ms from the stimulus onset to the 1000-Hz tones was suppressed as a function of the narrowing of the notch width. During the selective attention conditions, the suppressant effect of the noise notch width on GFP was decreased, but as a function significantly different from a multiplicative one expected on the basis of simple gain model of selective attention. Conclusions/Significance. Our results suggest that auditory selective attention in humans cannot be explained by a gai