Michel Schmitt

Interactions between exogenous auditory and visual spatial attention

Six experiments were carried out to investigate the issue of cross-modality between exogenous auditory and visual spatial attention employing Posners cueing paradigm in detection, localization, and discrimination tasks. Results indicated cueing in detection tasks with visual or auditory cues and visual targets but not with auditory targets (Experiment 1). In the localization tasks, cueing was found with both visual and auditory targets. Inhibition of return was apparent only in the within-modality conditions (Experiment 2). This suggests that it is important whether the attention system is activated directly (within a modality) or indirectly (between modalities). Increasing the cue validity from 50% to 80% influenced performance only in the localization task (Experiment 4). These findings are interpreted as being indicative for modality-specific but interacting attention mechanisms. The results of Experiments 5 and 6 (up/down discrimination tasks) also show cross-modal cueing but not with visual cues and auditory targets. Furthermore, there was no inhibition of return in any condition. This suggests that some cueing effects might be task dependent.

Early modulation of visual input: A study of attentional strategies

Despite agreement among many attentional theories that processing resources are limited and allocated according to task demands, controversy continues about the locus of selectivity. Studies of spatial orientation of attention suggest an early effect. These results, however, can be explained instead by effects of decision processes. The present study avoids this difficulty by directly manipulating attention in a dual-task paradigm and by using SDT to dissociate sensory tuning from criterion shifts. Ten subjects judged whether two lines to the left of fixation were the same or different in length; they also judged two lines presented simultaneously to the right. In a given block of 64 trials, the subject was to allocate 80%, 50%, or 20% of attention to one pair of lines and the rest to the other. On every trial, the subject judged both pairs. Results showed that d′ increased from 0.77 with 20% allocation to 1.69 with 80%, indicating that sensitivity is modulated by attentional instructions. These results are predicted quantitatively by Luces sample-size model.

Cross-modal exogenous attention and distance effects in vision and hearing

In the present study we investigated cross-modal orienting in vision and hearing by using a cueing task with four different horizontal locations. Our main interest concerned cue–target distance effects, which might further our insight in the characteristics of cross-modal spatial attention mechanisms. A very consistent pattern was observed for both the unimodal (cue and target were both visual or auditory) and the cross-modal conditions (cue and target from different modalities). RTs to valid trials were faster than for invalid trials, and, most interestingly, there was a distance effect: RTs increased with greater cue–target distance. This applied to detection of visual targets and to localisation of both visual and auditory targets. The time interval between cue and target was also varied. Surprisingly, there was no indication of inhibition of return even with the longest cue–target intervals. In order to assess the role of endogenous (strategic) factors in exogenous spatial attention we increased in two additional experiments the cue validity from 25% to 80%. This appeared to have no large influence on the cueing pattern in both the detection and localisation tasks. Currently, it is assumed that spatial attention is organised in multiple strongly linked modality-specific systems. The foregoing results are discussed with respect to this supposed organisation.

Axial structure of oxathiane benzyl sulfonium perchlorate

Abstract It is shown that the S-benzyl substituent, in the S-benzyl sulfonium perchlorate 2 derived from Eliels oxathiane, has an axial position in the solid state (X Ray analysis of a single crystal) as well as in solution (2D 1H NMR), probably due to 1-3-anomeric effect between the lone-pairs of oxygen and sulfur.

Stereodifferentiation in a Chiral 1,4-Oxazin-2-one Derived from 2-Hydroxy-2-methyl-1-tetralone − A Reagent for Deracemization of Amino Acids

Non-activated iodides (MeI, EtI, iPrI) provide moderate to good levels of conversion (55−100%) of 1,4-oxazin-2-one (1) into monoalkylated 3-alkyl-1,4-oxazin-2-ones 5, with satisfactory diastereoselectivities (89:11 to 92:8) and reasonably low amounts of dialkylation (0 to 36%). Alkylation of 3-methyl-1,4-oxazin-2-one (5a) occurs with high levels of conversion (82 to 100%), total diastereoselectivity, and only a small amount of O-alkylation, thus providing a three-step synthesis of enantiopure quaternary amino acids. Enantiopure (R)- or (S)-2-hydroxy-2-methyl-1-tetralone (4) can be efficiently used to epimerize/deracemize amino acids (with recovery of the excess amino acid used and also of 4, which can be reused). (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

TMSO-triflate-assisted addition of enols to heteroaromatic imines or hydroxyaminal intermediates

Abstract TMSOTf-promoted reaction of heteroaromatic imines or hydroxyaminal intermediates with various enolic ketones are reported. This reaction constitutes an original and regioselective mode of alkylation of exocyclic amines of heterocyclic amidines.

Proton/deuterium exchange in cinchonidine and deuteration of ethyl pyruvate using platinum/Al2O3 catalysts

A study of deuteration of cinchonidine (CD) under conditions (pressure (40 bar), temperature (25°C) and reaction times (2 h)) used for usual hydrogenation of ethyl pyruvate showed that the vinyl group is totally transformed into an ethyl (deuterated) and that H for D exchanges occur on the quinoline ring and at C9. Deuteration of ethyl pyruvate under the same conditions showed that no deuteration occurs at the chain-methyl, neither in toluene nor in AcOH, indicating that the enol is not the reacting species.

(E)-ethyl β-formylacrylate dimethylhydrazone methiodide : A reactive and convenient precursor of (E)-ethylβ-formylacrylate

Abstract The methiodide of (E)-Ethyl-β-formylacrylate dimethylhydrazone is readily prepared in two steps. It gives rise to regioselective 1,4-additions and is a stable and convenient precursor of (E)-Ethyl-β-formylacrylate.