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M Besson

Publications and source records attributed to M Besson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Total energy of deoxyguanosine bonded to N-2-acetylaminofluorene by the semi-empirical modified-neglect of differential diatomic overlap method.

We have computed the total energy surface as a function of two important torsion angles of the carcinogen N-2-acetylaminofluorene (AAF) bonded to the carbon C8 of deoxyguanosine using the semi-empirical quantum mechanical method, MNDO. One global minimum and one local minimum are found separated by an appreciable barrier. The equilibrium geometries show the rearrangement of AAF and the base consistent with experimental observations of previous investigators.

2-Acetylaminofluorene↗
PubMed2001

Different brain mechanisms mediate sensitivity to sensory consonance and harmonic context: evidence from auditory event-related brain potentials.

The goal of this study was to analyze the time-course of sensory (bottom-up) and cognitive (top-down) processes that govern musical harmonic expectancy. Eight-chord sequences were presented to 12 musicians and 12 nonmusicians. Expectations for the last chord were manipulated both at the sensory level (i.e., the last chord was sensory consonant or dissonant) and at the cognitive level (the harmonic function of the target was varied by manipulating the harmonic context built up by the first six chords of the sequence). Changes in the harmonic function of the target chord mainly modulate the amplitude of a positive component peaking around 300 msec (P3) after target onset, reflecting top-down influences on the perceptual stages of processing. In contrast, changes in the acoustic structure of the target chord (sensory consonance) mainly modulate the amplitude of a late positive component that develops between 300 and 800 msec after target onset. Most importantly, the effects of sensory consonance and harmonic context on the event-related brain potentials associated with the target chords were found to be independent, thus suggesting that two separate processors contribute to the building up of musical expectancy.

Acoustic Stimulation↗
PubMed2001

Behavioral and electrophysiological study of phonological priming between bisyllabic spoken words.

Phonological priming between bisyllabic (CV.CVC) spoken items was examined using both behavioral (reaction times, RTs) and electrophysiological (event-related potentials, ERPs) measures. Word and pseudoword targets were preceded by pseudoword primes. Different types of final phonological overlap between prime and target were compared. Critical pairs shared the last syllable, the rime or the coda, while unrelated pairs were used as controls. Participants performed a target shadowing task in Experiment 1 and a delayed lexical decision task in Experiment 2. RTs were measured in the first experiment and ERPs were recorded in the second experiment. The RT experiment was carried out under two presentation conditions. In Condition 1 both primes and targets were presented auditorily, while in Condition 2 the primes were presented visually and the targets auditorily. Priming effects were found in the unimodal condition only. RTs were fastest for syllable overlap, intermediate for rime overlap, and slowest for coda overlap and controls that did not differ from one another. ERPs were recorded under unimodal auditory presentation. ERP results showed that the amplitude of the auditory N400 component was smallest for syllable overlap, intermediate for rime overlap, and largest for coda overlap and controls that did not differ from one another. In both experiments, the priming effects were larger for word than for pseudoword targets. These results are best explained by the combined influences of nonlexical and lexical processes, and a comparison of the reported effects with those found in monosyllables suggests the involvement of rime and syllable representations.

Acoustic Stimulation↗
PubMed2001

Spontaneous splenic rupture associated with CMV infection: report of a case and review.

The case of a 43-y-old healthy woman presenting with spontaneous splenic rupture is reported. The outcome was favourable after splenectomy. Although the diagnosis of CMV infection was established by serology, PCR and immunostaining, no viral inclusions were observed on spleen sections. The pathophysiology of the lesions was unclear given the multiple interactions of the virus with various cell populations, and particularly with the immune system.

Adult↗
PubMed2001

Comparison between language and music.

Similarities and differences between language and music processing are examined from an evolutionary and a cognitive perspective. Language and music cannot be considered single entities; they need to be decomposed into different component operations or levels of processing. The central question concerns one of the most important claims of the generative grammar theory, that is, the specificity of language processing: do the computations performed to process language rely on specific linguistic processes or do they rely on general cognitive principles? Evidence from brain imaging results is reviewed, noting that this field is currently in need of metanalysis of the available results to precisely evaluate this claim. A series of experiments, mainly using the event-related brain potentials method, were conducted to compare different levels of processing in language and music. Overall, results favor language specificity when certain aspects of semantic processing in language are compared with certain aspects of melodic and harmonic processing in music. By contrast, results support the view that general cognitive principles are involved when aspects of syntactic processing in language are compared with aspects of harmonic processing in music. Moreover, analysis of the temporal structure led to similar effects in language and music. These tentative conclusions must be supported by other brain imaging results to shed further light on the spatiotemporal dynamics of the brain structure-function relationship.

Brain↗
PubMed2001

Divided attention between lyrics and tunes of operatic songs: evidence for independent processing.

Excerpts from French operatic songs were used to evaluate the extent to which language and music compete for processing resources. Do these two dimensions conflict? Are they integrated into a single percept? Or are they independent? The final word of each excerpt was either semantically congruous or incongruous relative to the prior linguistic context and was sung either in or out of key. Participants were asked to detect either the semantic or the melodic incongruity (single task) or both (dual task). We predicted a dual-task deficit if these tasks conflicted and no deficit if they were either independent or integrated. In order to distinguish between these last two outcomes, trial-by-trial contingency analyses were also computed, predicting no correlation if the tasks were conflicting or independent, a positive correlation under the assumption of integration and a negative correlation if dividing attention is impossible. Our results show similar levels of performance in single and dual tasks and no correlation between dual-task judgments, thus suggesting that semantic and melodic aspects of language are processed by independent systems. In addition, a comparison between musicians and nonmusicians shows that these conclusions are independent of musical expertise.

Adolescent↗
PubMed2000

Asymmetric synthesis of 2-methyl cyclohexane carboxylic acids by heterogeneous catalysis: mechanistic aspects

The catalytic hydrogenation of (S)-alkyl-N-(2-methylbenzoyl)pyroglutamates was studied over supported rhodium and ruthenium catalysts at room temperature and a pressure of 5 MPa. The reaction was diastereoselective with the predominant formation of (1S,2R)-2-methylcyclohexane carboxylic acid with a diastereomeric excess (de) of up to 96%. The most stable conformation was determined by means of a combination of modelling calculations, NMR spectroscopy and X-ray structural determination. In this conformation, the carbonyl group of the pyroglutamate auxiliary shields one face of the aromatic ring. The observed selectivity may thus be explained by a preferential adsorption at the unshielded face which avoids steric repulsion by the C=O group to result in a cis hydrogenation. The addition of an amine, the nature of the support (alumina or active carbon) or of the metal (Rh or Ru) were shown to give additional stabilisation of the adsorption at the unshielded face to increase the diastereoisomeric excess.

Journal Article↗
PubMed1999

From print to meaning: an electrophysiological investigation of the role of phonology in accessing word meaning.

This study investigated the role and time-course of phonology in accessing meaning during silent reading. In Experiment 1, the homophone effect was replicated in a semantic categorization task in French. When deciding whether a stimulus belonged to a semantic category (FOOD), subjects made more errors to homophones (MEET) than to orthographic controls (MELT). In Experiment 2, event-related brain potentials (ERPs) were used to study the online development of this effect. If access to meaning was mediated by phonology, smaller N400 components should be obtained to homophones than to orthographic controls. The ERP data exhibited a full-blown N400 component to homophones that did not differ from the N400 to controls. No differences between homophones and controls were found before the N400. After the N400, however, homophones differed from controls, with ERPs to homophones being similar to those of correct category exemplars. The results suggest that the final selection of a word's meaning does not depend on its phonological form. This result is incompatible with a strong phonological view according to which the only way to meaning is via a word's phonology.

Adult↗
PubMed1998

Semantic, repetition and rime priming between spoken words: behavioral and electrophysiological evidence.

Semantic, phonological and repetition priming for auditorily presented words were examined, using both behavioral reaction times (RTs) and electrophysiological event-related potentials (ERPs) measures. On critical trials, a word prime was followed by a word target that was semantically or phonologically related (rime) or not related (control) to the prime. Pairs of word-pseudoword items served as fillers. Participants were asked to respond to word targets in the RT experiment and to pseudowords in the ERP experiment. In each experiment stimuli were presented once and then repeated in the very same way. RTs were found to be fastest for semantic, intermediate for rime and slowest for control targets; large repetition effects occurred for all targets. ERPs results showed that both semantic and phonological priming influenced the same component, namely the N400, whose amplitude was smallest to semantic, intermediate to rime and largest to control targets; repetition effects were only found for semantic trials.

Acoustic Stimulation↗
PubMed1998

Processing syntactic relations in language and music: an event-related potential study.

In order to test the language-specificity of a known neural correlate of syntactic processing [the P600 event-related brain potential (ERP) component], this study directly compared ERPs elicited by syntactic incongruities in language and music. Using principles of phrase structure for language and principles of harmony and key-relatedness for music, sequences were constructed in which an element was either congruous, moderately incongruous, or highly incongruous with the preceding structural context. A within-subjects design using 15 musically educated adults revealed that linguistic and musical structural incongruities elicited positivities that were statistically indistinguishable in a specified latency range. In contrast, a music-specific ERP component was observed that showed antero-temporal right-hemisphere lateralization. The results argue against the language-specificity of the P600 and suggest that language and music can be studied in parallel to address questions of neural specificity in cognitive processing.

Adolescent↗
PubMed1997

What's in a pause: event-related potential analysis of temporal disruptions in written and spoken sentences.

Two experiments examined the effects of disrupting the temporal patterns that develop during sentence reading and listening. Sentences were presented either visually, one word at a time (Experiment 1) or as natural speech (Experiment 2). Half of the sentences were familiar (proverbs or idioms) while the other half were constructed anew for these experiments. Within half the sentences, there was an unexpected 600-ms delay between the final two words. In both modalities, the amplitude of the N400 component of the event-related brain potential (ERP) to sentence final words was larger for unfamiliar than familiar sentences. The results in the two modalities differed, however, in that a Contingent Negative Variation (CNV) developed during the delay interval in the visual modality, whereas in the auditory modality the delay was marked by an emitted potential. The present results show that temporal patterns are processed differently in natural speech and in reading words presented one at a time in the center of a computer screen.

Acoustic Stimulation↗
PubMed1997

Finding the locus of semantic satiation: an electrophysiological attempt.

The present study examined the effect of massed repetition of an initial category name upon the subsequent semantic categorization of a target word by means of an electrophysiological measure of semantic processing: the N400. Results showed the classic N400 effect, whereby evoked potentials were more negative for targets that were not members of the repeated category than for member targets. Moreover, repetition of the category name led to an increased and sustained positivity. The N400 effect was not modified, however, by repetition. Hence, insomuch as the N400 reflects meaning integration processes, these results do not support the hypothesis that massed repetition exerts its influence at the level of meaning integration.

Adult↗
PubMed1996

The time-course of metaphor comprehension: an event-related potential study.

ERPs were recorded while subjects were reading short familiar metaphors (e.g., Those fighters are lions), unfamiliar metaphors (Those apprentices are lions), or literal control sentences (Those animals are lions) presented in isolation or preceded by either an irrelevant or relevant context (e.g., They are not idiotic: ...." vs. "They are not cowardly: Those fighters are lions"). The terminal word of metaphors elicited larger N400 components than did the terminal word of literal sentences (Experiment 1) suggesting that the (incongruous) literal meaning of metaphors was indeed accessed at some point during comprehension. The analysis of the 600-1000 and 1000-1400 latency bands (Late Positive Components) revealed no significant difference between metaphors and literal sentences. The manipulation of metaphor difficulty (Experiments 2 and 3) also failed to reveal any late effect specifically linked to metaphorical processing. Finally, an effect of the preceding sentence context was found in Experiments 3 and 4, as early as 300 ms following the terminal word onset. Overall, these results support a context-dependent account of metaphor comprehension stating that when contextually relevant, the metaphorical meaning is the only one accessed.

Adolescent↗
PubMed1994

Brain waves associated with musical incongruities differ for musicians and non-musicians.

Musicians and non-musicians were presented with short musical phrases that were either selected from the classical musical repertoire or composed for the experiment. The phrases terminated either in a congruous or a 'harmonically', 'melodically', or 'rhythmically' incongruous note. The brain waves produced by the end-notes differed greatly between musicians and non-musicians, and as a function of the subject's familiarity with the melodies and the type of incongruity. The timing of these brain waves revealed that musicians are faster than non-musicians in detecting incongruities. This study provides further neurophysiological evidence concerning the mechanisms underlying music perception and the differences between musical and linguistic processing.

Brain↗
PubMed1994

Selection of a gyrA mutant of Mycobacterium tuberculosis resistant to fluoroquinolones during treatment with ofloxacin.

A strain of Mycobacterium tuberculosis resistant to ofloxacin was selected in a patient with a long history of multidrug-resistant tuberculosis eventually treated by ofloxacin combined with other second-line drugs. A mutation in the gyrA gene was hypothesized to be the mechanism of acquired resistance to ofloxacin in this strain. Chromosomal DNA of strains MTB1, isolated before treatment and susceptible to ofloxacin (MIC, 1 microgram/mL), and MTB2, isolated during treatment and resistant to ofloxacin (MIC, 32 micrograms/mL), was amplified by polymerase chain reaction (PCR) using two oligonucleotide primers highly homologous to DNA sequences flanking the quinolone resistance-determining region in gyrA of mycobacteria. Comparison of the nucleotide sequences of the 150-bp fragments obtained by PCR revealed a point mutation in MTB2 leading to the substitution of histidine for aspartic acid at a position corresponding to residues involved in quinolone resistance in Escherichia coli (Asp87), Staphylococcus aureus (Glu88), and Campylobacter jejuni (Asp90).

Adult↗