The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Jyrki Ahveninen - One of the best experts on this subject based on the ideXlab platform.
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auditory conflict resolution correlates with medial lateral frontal theta Alpha Phase synchrony
PLOS ONE, 2014Co-Authors: Samantha Huang, Stephanie Rossi, Matti Hamalainen, Jyrki AhveninenAbstract:When multiple persons speak simultaneously, it may be difficult for the listener to direct attention to correct sound objects among conflicting ones. This could occur, for example, in an emergency situation in which one hears conflicting instructions and the loudest, instead of the wisest, voice prevails. Here, we used cortically-constrained oscillatory MEG/EEG estimates to examine how different brain regions, including caudal anterior cingulate (cACC) and dorsolateral prefrontal cortices (DLPFC), work together to resolve these kinds of auditory conflicts. During an auditory flanker interference task, subjects were presented with sound patterns consisting of three different voices, from three different directions (45° left, straight ahead, 45° right), sounding out either the letters “A” or “O”. They were asked to discriminate which sound was presented centrally and ignore the flanking distracters that were phonetically either congruent (50%) or incongruent (50%) with the target. Our cortical MEG/EEG oscillatory estimates demonstrated a direct relationship between performance and brain activity, showing that efficient conflict resolution, as measured with reduced conflict-induced RT lags, is predicted by theta/Alpha Phase coupling between cACC and right lateral frontal cortex regions intersecting the right frontal eye fields (FEF) and DLPFC, as well as by increased pre-stimulus gamma (60–110 Hz) power in the left inferior fontal cortex. Notably, cACC connectivity patterns that correlated with behavioral conflict-resolution measures were found during both the pre-stimulus and the pre-response periods. Our data provide evidence that, instead of being only transiently activated upon conflict detection, cACC is involved in sustained engagement of attentional resources required for effective sound object selection performance.
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Auditory Conflict Resolution Correlates with Medial–Lateral Frontal Theta/Alpha Phase Synchrony
PLOS ONE, 2014Co-Authors: Samantha Huang, Stephanie Rossi, Matti Hamalainen, Jyrki AhveninenAbstract:When multiple persons speak simultaneously, it may be difficult for the listener to direct attention to correct sound objects among conflicting ones. This could occur, for example, in an emergency situation in which one hears conflicting instructions and the loudest, instead of the wisest, voice prevails. Here, we used cortically-constrained oscillatory MEG/EEG estimates to examine how different brain regions, including caudal anterior cingulate (cACC) and dorsolateral prefrontal cortices (DLPFC), work together to resolve these kinds of auditory conflicts. During an auditory flanker interference task, subjects were presented with sound patterns consisting of three different voices, from three different directions (45° left, straight ahead, 45° right), sounding out either the letters “A” or “O”. They were asked to discriminate which sound was presented centrally and ignore the flanking distracters that were phonetically either congruent (50%) or incongruent (50%) with the target. Our cortical MEG/EEG oscillatory estimates demonstrated a direct relationship between performance and brain activity, showing that efficient conflict resolution, as measured with reduced conflict-induced RT lags, is predicted by theta/Alpha Phase coupling between cACC and right lateral frontal cortex regions intersecting the right frontal eye fields (FEF) and DLPFC, as well as by increased pre-stimulus gamma (60–110 Hz) power in the left inferior fontal cortex. Notably, cACC connectivity patterns that correlated with behavioral conflict-resolution measures were found during both the pre-stimulus and the pre-response periods. Our data provide evidence that, instead of being only transiently activated upon conflict detection, cACC is involved in sustained engagement of attentional resources required for effective sound object selection performance.
T. Skettrup - One of the best experts on this subject based on the ideXlab platform.
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Ion exchange model for /spl Alpha/ Phase proton exchange waveguides in LiNbO/sub 3/
Journal of Lightwave Technology, 1998Co-Authors: T. Veng, T. SkettrupAbstract:An H/sup +//Li/sup +/ exchange model is found to be applicable to describe the diffusion of protons when optical waveguides are formed in LiNbO/sub 3/ by proton exchange methods where the proton doped crystal structure stays in the pure /spl Alpha/ Phase. The H/sup +/ and Li/sup +/ self-diffusion coefficients in the ion exchange model are determined as a function of the proton exchange temperature both for x-cut and z-cut LiNbO/sub 3/. In this way a very useful tool for predicting the proton concentration profiles and hence the refractive index profiles of /spl Alpha/ Phase proton exchange LiNbO/sub 3/ waveguides is achieved.
Matti Hamalainen - One of the best experts on this subject based on the ideXlab platform.
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auditory conflict resolution correlates with medial lateral frontal theta Alpha Phase synchrony
PLOS ONE, 2014Co-Authors: Samantha Huang, Stephanie Rossi, Matti Hamalainen, Jyrki AhveninenAbstract:When multiple persons speak simultaneously, it may be difficult for the listener to direct attention to correct sound objects among conflicting ones. This could occur, for example, in an emergency situation in which one hears conflicting instructions and the loudest, instead of the wisest, voice prevails. Here, we used cortically-constrained oscillatory MEG/EEG estimates to examine how different brain regions, including caudal anterior cingulate (cACC) and dorsolateral prefrontal cortices (DLPFC), work together to resolve these kinds of auditory conflicts. During an auditory flanker interference task, subjects were presented with sound patterns consisting of three different voices, from three different directions (45° left, straight ahead, 45° right), sounding out either the letters “A” or “O”. They were asked to discriminate which sound was presented centrally and ignore the flanking distracters that were phonetically either congruent (50%) or incongruent (50%) with the target. Our cortical MEG/EEG oscillatory estimates demonstrated a direct relationship between performance and brain activity, showing that efficient conflict resolution, as measured with reduced conflict-induced RT lags, is predicted by theta/Alpha Phase coupling between cACC and right lateral frontal cortex regions intersecting the right frontal eye fields (FEF) and DLPFC, as well as by increased pre-stimulus gamma (60–110 Hz) power in the left inferior fontal cortex. Notably, cACC connectivity patterns that correlated with behavioral conflict-resolution measures were found during both the pre-stimulus and the pre-response periods. Our data provide evidence that, instead of being only transiently activated upon conflict detection, cACC is involved in sustained engagement of attentional resources required for effective sound object selection performance.
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Auditory Conflict Resolution Correlates with Medial–Lateral Frontal Theta/Alpha Phase Synchrony
PLOS ONE, 2014Co-Authors: Samantha Huang, Stephanie Rossi, Matti Hamalainen, Jyrki AhveninenAbstract:When multiple persons speak simultaneously, it may be difficult for the listener to direct attention to correct sound objects among conflicting ones. This could occur, for example, in an emergency situation in which one hears conflicting instructions and the loudest, instead of the wisest, voice prevails. Here, we used cortically-constrained oscillatory MEG/EEG estimates to examine how different brain regions, including caudal anterior cingulate (cACC) and dorsolateral prefrontal cortices (DLPFC), work together to resolve these kinds of auditory conflicts. During an auditory flanker interference task, subjects were presented with sound patterns consisting of three different voices, from three different directions (45° left, straight ahead, 45° right), sounding out either the letters “A” or “O”. They were asked to discriminate which sound was presented centrally and ignore the flanking distracters that were phonetically either congruent (50%) or incongruent (50%) with the target. Our cortical MEG/EEG oscillatory estimates demonstrated a direct relationship between performance and brain activity, showing that efficient conflict resolution, as measured with reduced conflict-induced RT lags, is predicted by theta/Alpha Phase coupling between cACC and right lateral frontal cortex regions intersecting the right frontal eye fields (FEF) and DLPFC, as well as by increased pre-stimulus gamma (60–110 Hz) power in the left inferior fontal cortex. Notably, cACC connectivity patterns that correlated with behavioral conflict-resolution measures were found during both the pre-stimulus and the pre-response periods. Our data provide evidence that, instead of being only transiently activated upon conflict detection, cACC is involved in sustained engagement of attentional resources required for effective sound object selection performance.
S L Semiatin - One of the best experts on this subject based on the ideXlab platform.
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Dissolution of the Alpha Phase in Ti-6Al-4V During Isothermal and Continuous Heat Treatment
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2019Co-Authors: S L Semiatin, Mark Obstalecki, E. J. Payton, Adam L. Pilchak, Paul A. Shade, N. C. Levkulich, J. M. Shank, Darren C. Pagan, F. Zhang, Jaimie TileyAbstract:The kinetics of the dissolution of the equiaxed Alpha Phase into the beta matrix in Ti-6Al-4V were established and modeled for both isothermal (constant temperature) and transient/continuous heating conditions. For the isothermal experiments, samples were solution treated at a subtransus temperature to equilibrate the microstructure followed by rapid, direct-resistance heating to a temperature either 25 K or 78 K (25 °C or 78 °C) above the equilibrium beta transus and held for times ranging from 1 to 32 seconds. Dissolution behavior under transient conditions was determined in-situ using an indirect-resistance furnace and X-ray (synchrotron) source; these trials comprised a similar initial subtransus solution heat treatment followed by continuous heating at a constant rate in the range between 15 and 135 K/min (15 and 135 °C/min) to a temperature lying 25 K (25 °C) above the transus. Measurements of the temporal evolution of the volume fraction of Alpha were interpreted using numerical simulations based on the Whelan dissolution model modified to treat a distribution of particle sizes and the possible interaction of the concentration gradients developed around adjacent particles; i.e., soft impingement. The isothermal dissolution measurements were bounded by predictions from simulations with and without the soft-impingement assumption. Similar trends were found for continuous-heating behavior. In particular, slow or fast heating-rate observations were replicated by simulation predictions with or without the soft-impingement constraint, respectively.
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an automated method to determine the orientation of the high temperature beta Phase from measured ebsd data for the low temperature Alpha Phase in ti 6al 4v
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: M G Glavicic, P A Kobryn, T R Bieler, S L SemiatinAbstract:A method was developed to determine the orientation of the high-temperature beta Phase from measured electron-backscatter diffraction (EBSD) data for the low-temperature Alpha Phase in Ti-6Al-4V. This technique is an improvement over existing methods because it does not require a priori knowledge of the variant selection process and can accommodate variants from adjacent beta grains being incorporated in the data set submitted for analysis. It is a general method and therefore can be used to examine texture relationships in materials other than Ti-6Al-4V which undergo a burgers-type Phase transformation.
Mathilde Bonnefond - One of the best experts on this subject based on the ideXlab platform.
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Top–Down Control of Alpha Phase Adjustment in Anticipation of Temporally Predictable Visual Stimuli
Journal of Cognitive Neuroscience, 2018Co-Authors: Rodolfo Solís-vivanco, Ole Jensen, Mathilde BonnefondAbstract:Alpha oscillations (8–14 Hz) are proposed to represent an active mechanism of functional inhibition of neuronal processing. Specifically, Alpha oscillations are associated with pulses of inhibition repeating every ∼100 msec. Whether Alpha Phase, similar to Alpha power, is under top–down control remains unclear. Moreover, the sources of such putative top–down Phase control are unknown. We designed a cross-modal (visual/auditory) attention study in which we used magnetoencephalography to record the brain activity from 34 healthy participants. In each trial, a somatosensory cue indicated whether to attend to either the visual or auditory domain. The timing of the stimulus onset was predictable across trials. We found that, when visual information was attended, anticipatory Alpha power was reduced in visual areas, whereas the Phase adjusted just before the stimulus onset. Performance in each modality was predicted by the Phase of the Alpha oscillations previous to stimulus onset. Alpha oscillations in the left pFC appeared to lead the adjustment of Alpha Phase in visual areas. Finally, Alpha Phase modulated stimulus-induced gamma activity. Our results confirm that Alpha Phase can be top–down adjusted in anticipation of predictable stimuli and improve performance. Phase adjustment of the Alpha rhythm might serve as a neurophysiological resource for optimizing visual processing when temporal predictions are possible and there is considerable competition between target and distracting stimuli.
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gamma activity coupled to Alpha Phase as a mechanism for top down controlled gating
PLOS ONE, 2015Co-Authors: Mathilde Bonnefond, Ole JensenAbstract:Coupling between neural oscillations in different frequency bands has been proposed to coordinate neural processing. In particular, gamma power coupled to Alpha Phase is proposed to reflect gating of information in the visual system but the existence of such a mechanism remains untested. Here, we recorded ongoing brain activity using magnetoencephalography in subjects who performed a modified Sternberg working memory task in which distractors were presented in the retention interval. During the anticipatory pre-distractor period, we show that the Phase of Alpha oscillations was coupled with the power of high (80-120Hz) gamma band activity, i.e. gamma power consistently was lower at the trough than at the peak of the Alpha cycle (9-12Hz). We further show that high Alpha power was associated with weaker gamma power at the trough of the Alpha cycle. This result is in line with Alpha activity in sensory region implementing a mechanism of pulsed inhibition silencing neuronal firing every ~100 ms.