Différenciation hémisphérique auditive par analyse de potentiels évoqués auditifs

- Par opposition aux études subjectives adressant le problème de la spécialisation hémisphérique auditive, le but de ce travail est de proposer des mesures objectives permettant de différencier le comportement des deux hémisphères vis-à-vis des stimuli. Pour ce faire, nous disposons de signaux intracérébraux enregistrés en réponse à divers stimuli. Ce papier ne traite que des réponses aux sons verbaux voisé /ba/, non voisé /pa/ et à la voyelle /a/ et présente trois méthodes. La première calcule le coefficient de corrélation entre les réponses à deux stimuli, recueillies sur le même plot. La seconde porte sur l'évolution de la corrélation au cours du temps. Sur les valeurs de corrélation obtenues est effectuée une analyse factorielle des correspondances (AFC) suivie d'une classification hiérarchique ascendante appliquée sur les facteurs de l'AFC. Finalement, les réponses sont caractérisées selon le nombre d'extrema en fonction de l'hémisphère et du stimulus considérés. Les trois méthodes permettent de mettre en avant certains paramètres révélateurs de différence de comportement des deux hémisphères

Étude et analyse statistique de potentiels évoqués auditifs sous l'influence de radiofréquences

Ce papier traite de l'étude de l'influence des champs radioélectriques émis par les téléphones portables sur l'activité cérébrale humaine. Notre travail est réalisé sur le système auditif à partir du recueil de Potentiels Evoqués Auditifs (PEA) à la surface du scalp. Le protocole permet de comparer les PEA enregistrés avec ou sans exposition aux radiofréquences. Les stimuli sont deux sons purs et un système permet de contrôler la puissance des radiofréquences émises. Pour obtenir une référence et tenir compte de la fatigue, l'effet placebo est également considéré. Notre étude consiste à mettre en oeuvre des mesures fiables qui soient révélatrices de certains changements ou de certaines constances dans les signaux enregistrés. Elles concernent ici les corrélations calculées entre signaux moyens, les amplitudes de l'onde N100, ainsi que les corrélations entre ces amplitudes. La comparaison des corrélations calculées entre signaux recueillis avec et sans exposition aux radiofréquences fait apparaître une différence. Un point important de cette étude concerne le rôle de l'effet de fatigue dans l'analyse des PEA

Effects of Low Amyloid-β (Aβ) Concentration on Aβ1-42 Oligomers Binding and GluN2B Membrane Expression.

Numerous studies have shown that amyloid-β (Aβ) modulate intracellular metabolic cascades and an intracellular Ca2+ homeostasis and a cell surface NMDA receptor expression alteration in Alzheimer's disease (AD). However most of these findings have been obtained by using non-physiological Aβ concentrations. The present study deals with the effect of low Aβ concentrations on cellular homeostasis. We used nerve growth factor-differentiated PC12 cells and murine cortical neurons sequentially treated with low chronic monomeric or small oligomeric Aβ concentrations and high acute oligomeric Aβ concentrations to bring out a priming effect of chronic treatment on subsequently high Aβ concentrations-elicited cellular response. Both cell types indeed displayed an enhanced capacity to bind oligomeric Aβ after monomeric or small oligomeric Aβ application. Furthermore, the results show that monomeric Aβ1-42 application to the cells induces an increase of the Ca2+-response and of the membrane expression of the extrasynaptic subunit of the NMDA receptor GluN2B in PC12 cells, while the opposite effects were observed in cultured neurons. This suggests a sequential interaction of Aβ with the cellular plasma membrane involving monomers or small Aβ oligomers which would facilitate the binding of the deleterious high molecular Aβ oligomers. This mechanism would explain the slow progression of AD in the human nervous system and the deep gradient of neuronal death observed around the amyloid plaques in the nervous tissue.journal articleresearch support, non-u.s. gov't2015importe

The Caenorhabditis elegans HNF4α Homolog, NHR-31, Mediates Excretory Tube Growth and Function through Coordinate Regulation of the Vacuolar ATPase

Nuclear receptors of the Hepatocyte Nuclear Factor-4 (HNF4) subtype have been linked to a host of developmental and metabolic functions in animals ranging from worms to humans; however, the full spectrum of physiological activities carried out by this nuclear receptor subfamily is far from established. We have found that the Caenorhabditis elegans nuclear receptor NHR-31, a homolog of mammalian HNF4 receptors, is required for controlling the growth and function of the nematode excretory cell, a multi-branched tubular cell that acts as the C. elegans renal system. Larval specific RNAi knockdown of nhr-31 led to significant structural abnormalities along the length of the excretory cell canal, including numerous regions of uncontrolled growth at sites near to and distant from the cell nucleus. nhr-31 RNAi animals were sensitive to acute challenge with ionic stress, implying that the osmoregulatory function of the excretory cell was also compromised. Gene expression profiling revealed a surprisingly specific role for nhr-31 in the control of multiple genes that encode subunits of the vacuolar ATPase (vATPase). RNAi of these vATPase genes resulted in excretory cell defects similar to those observed in nhr-31 RNAi animals, demonstrating that the influence of nhr-31 on excretory cell growth is mediated, at least in part, through coordinate regulation of the vATPase. Sequence analysis revealed a stunning enrichment of HNF4α type binding sites in the promoters of both C. elegans and mouse vATPase genes, arguing that coordinate regulation of the vATPase by HNF4 receptors is likely to be conserved in mammals. Our study establishes a new pathway for regulation of excretory cell growth and reveals a novel role for HNF4-type nuclear receptors in the development and function of a renal system

Leftward Lateralization of Auditory Cortex Underlies Holistic Sound Perception in Williams Syndrome

BACKGROUND: Individuals with the rare genetic disorder Williams-Beuren syndrome (WS) are known for their characteristic auditory phenotype including strong affinity to music and sounds. In this work we attempted to pinpoint a neural substrate for the characteristic musicality in WS individuals by studying the structure-function relationship of their auditory cortex. Since WS subjects had only minor musical training due to psychomotor constraints we hypothesized that any changes compared to the control group would reflect the contribution of genetic factors to auditory processing and musicality. METHODOLOGY/PRINCIPAL FINDINGS: Using psychoacoustics, magnetoencephalography and magnetic resonance imaging, we show that WS individuals exhibit extreme and almost exclusive holistic sound perception, which stands in marked contrast to the even distribution of this trait in the general population. Functionally, this was reflected by increased amplitudes of left auditory evoked fields. On the structural level, volume of the left auditory cortex was 2.2-fold increased in WS subjects as compared to control subjects. Equivalent volumes of the auditory cortex have been previously reported for professional musicians. CONCLUSIONS/SIGNIFICANCE: There has been an ongoing debate in the neuroscience community as to whether increased gray matter of the auditory cortex in musicians is attributable to the amount of training or innate disposition. In this study musical education of WS subjects was negligible and control subjects were carefully matched for this parameter. Therefore our results not only unravel the neural substrate for this particular auditory phenotype, but in addition propose WS as a unique genetic model for training-independent auditory system properties

Microautophagy of the Nucleus Coincides with a Vacuolar Diffusion Barrier at Nuclear–Vacuolar Junctions

Nuclear-vacuolar (NV) junctions are organelle contact sites in yeast. They exclude nuclear pores from the organelle interface. On the vacuolar side, a lipid-dependent process excludes specific membrane proteins, such as V-ATPase, from the contact site. This suggests that NV junctions establish selective diffusion barriers

Patients’ Preference and Experiences of Forced Medication and Seclusion

This study examined patients’ preferences for coercive methods and the extent to which patients’ choices were determined by previous experience, demographic, clinical and intervention-setting variables. Before discharge from closed psychiatric units, 161 adult patients completed a questionnaire. The association between patients’ preferences and the underlying variables was analyzed using logistic regression. We found that patients’ preferences were mainly defined by earlier experiences: patients without coercive experiences or who had had experienced seclusion and forced medication, favoured forced medication. Those who had been secluded preferred seclusion in future emergencies, but only if they approved its duration. This suggests that seclusion, if it does not last too long, does not have to be abandoned from psychiatric practices. In an emergency, however, most patients prefer to be medicated. Our findings show that patients’ preferences cannot guide the establishment of international uniform methods for managing violent behaviour. Therefore patients’ individual choices should be considered

Zebrafish Mutants calamity and catastrophe Define Critical Pathways of Gene–Nutrient Interactions in Developmental Copper Metabolism

Nutrient availability is an important environmental variable during development that has significant effects on the metabolism, health, and viability of an organism. To understand these interactions for the nutrient copper, we used a chemical genetic screen for zebrafish mutants sensitive to developmental copper deficiency. In this screen, we isolated two mutants that define subtleties of copper metabolism. The first contains a viable hypomorphic allele of atp7a and results in a loss of pigmentation when exposed to mild nutritional copper deficiency. This mutant displays incompletely penetrant skeletal defects affected by developmental copper availability. The second carries an inactivating mutation in the vacuolar ATPase that causes punctate melanocytes and embryonic lethality. This mutant, catastrophe, is sensitive to copper deprivation revealing overlap between ion metabolic pathways. Together, the two mutants illustrate the utility of chemical genetic screens in zebrafish to elucidate the interaction of nutrient availability and genetic polymorphisms in cellular metabolism

Individual Differences in Sound-in-Noise Perception Are Related to the Strength of Short-Latency Neural Responses to Noise

Important sounds can be easily missed or misidentified in the presence of extraneous noise. We describe an auditory illusion in which a continuous ongoing tone becomes inaudible during a brief, non-masking noise burst more than one octave away, which is unexpected given the frequency resolution of human hearing. Participants strongly susceptible to this illusory discontinuity did not perceive illusory auditory continuity (in which a sound subjectively continues during a burst of masking noise) when the noises were short, yet did so at longer noise durations. Participants who were not prone to illusory discontinuity showed robust early electroencephalographic responses at 40–66 ms after noise burst onset, whereas those prone to the illusion lacked these early responses. These data suggest that short-latency neural responses to auditory scene components reflect subsequent individual differences in the parsing of auditory scenes