Temporal precedence of emotion over attention modulations in the lateral amygdala: Intracranial ERP evidence from a patient with temporal lobe epilepsy

Previous fMRI studies have reported mixed evidence for the influence of selective attention on amygdala responses to emotional stimuli, with some studies showing "automatic" emotional effects to threat-related stimuli without attention (or even without awareness), but other studies showing a gating of amygdala activity by selective attention with no response to unattended stimuli. We recorded intracranial local field potentials from the intact left lateral amygdala in a human patient prior to surgery for epilepsy and tested, with a millisecond time resolution, for neural responses to fearful faces appearing at either task-relevant or task-irrelevant locations. Our results revealed an early emotional effect in the amygdala arising prior to, and independently of, attentional modulation. However, at a later latency, we found a significant modulation of the differential emotional response when attention was directed toward or away from fearful faces. These results suggest separate influences of emotion and attention on amygdala activation and may help reconcile previous discrepancies concerning the relative responsiveness of the human amygdala to emotional and attentional factors

Role of the medial part of the intraparietal sulcus in implementing movement direction

The contribution of the posterior parietal cortex (PPC) to visually guided movements has been originally inferred from observations made in patients suffering from optic ataxia. Subsequent electrophysiological studies in monkeys and functional imaging data in humans have corroborated the key role played by the PPC in sensorimotor transformations underlying goal-directed movements, although the exact contribution of this structure remains debated. Here, we used transcranial magnetic stimulation (TMS) to interfere transiently with the function of the left or right medial part of the intraparietal sulcus (mIPS) in healthy volunteers performing visually guided movements with the right hand. We found that a "virtual lesion" of either mIPS increased the scattering in initial movement direction (DIR), leading to longer trajectory and prolonged movement time, but only when TMS was delivered 100-160 ms before movement onset and for movements directed toward contralateral targets. Control experiments showed that deficits in DIR consequent to mIPS virtual lesions resulted from an inappropriate implementation of the motor command underlying the forthcoming movement and not from an inaccurate computation of the target localization. The present study indicates that mIPS plays a causal role in implementing specifically the direction vector of visually guided movements toward objects situated in the contralateral hemifield

Anaerobes and short-chain fatty acids in crevicular fluid from adults with chronic periodontitis

Pathogeny of adult chronic periodontitis is still unclear. Bacteriological and chemical analysis of crevicular fluid have shown, in active sites of the disease, a simultaneous presence of anaerobes and their major by-product: short-chain fatty acids. The last can decrease «in vitro» the neutrophil intracellular pH, whenever these cells are incubated in an acid medium. Clinical investigations are scarce which hold out data useful to attempt verifying this possible physiopathological mechanism. This work shows the presence of anaerobes in the active periodontal pockets, together with the presence of short-chain fatty acids likely to reach a concentration level comparable to that used for inhibiting neutrophils «in vitro».Forthcoming studies should investigate about a possible intracellular pH drop in the neutrophils and other cells of the inflamed periodontium.La pathogénie des parodontites chroniques de l’adulte n’est pas encore bien comprise. Des analyses bactériologiques et chimiques du liquide créviculaire ont permis de mettre en évidence, dans des sites actifs de la maladie, des germes anaérobies et leurs principaux produits cataboliques: les acides gras à courte chaîne.Ceux-ci peuvent réduire «in vitro» le pH intracellulaire des neutrophiles en suspension dans un tampón acide. Peu d’études présentent des données cliniques permettant de vérifier «in vivo» cet éventuel mécanisme physiopathologique. Ce travail montre la présence simultanée, dans des poches parodontales, de germes anaérobies et d’acides gras à courte chaîne à des concentrations similaires à celles utilisées pour inhiber «in vitro» des neutrophiles. D’autres travaux devront étudier la chute éventuelle du pH intracellulaire des cellules du parodonte en état d’inflammation chronique

Influence of a hypoiodite mouth-wash on dental plaque formation in vivo

This study describes an in vivo inhibition of dental plaque growth after peroxidase-generated hypoiodite (OI-) mouth-washes. After giving up ail other usual hygiene procedures nine healthy volunteers washed their mouth using 10 ml of the mouth-wash [H2O2 (0.005%), Kl (50 mM) and lactoperoxidase (0.04%)] three times a day for 1 minute for 3 days. The initial oxidation power of this mixture represented 430 ±11 µM oxidised cysteine (n=6), dropping down to 87 ± 6 µM after the solution was spat out (n=5). A saline solution served as a negative control, and a 0.2% chlorhexidine digluconate solution as a positive control. Proximal dental plaque between mandibular canine and lateral incisor (left and right) was collected after 3 days using standardized sterile toothpicks, then analysed for ATP and protein content. ATP concentrations dropped to 49% of the control values after OI- rinsing, and to 9% after chlorhexidine rinsing while the protein content dropped to 48% for OI- versus 31 % for chlorhexidine. However, when considering the ATP content per protein µg, only the decrease to 6% of the initial value in the chlorhexidine testing was significant while the drop to 81% for the OI- testings was not significant. This study points out a negative effect of OI- on plaque growth in vivo.Cette étude décrit l’inhibition de la croissance in vivo de la plaque dentaire après traitement à l’aide d’un bain de bouche contenant de la peroxydase et produisant de l’hypoiodite (OI-). Neuf personnes ont utilisé ce rinçage pendant une minute, 3 fois par jour pendant 3 jours, cependant qu’elles cessaient toute autre pratique d’hygiène bucco-dentaire; une solution saline servant de contrôle négatif et une solution de chlorhexidine de contrôle positif. Des échantillons de plaque interproximale furent prélevés de manière standardisée à l’aide de cure-dents stériles et leur contenu en ATP et en protéines furent mesurés. Les concentrations en ATP après traitement à l’OI- ne représentaient plus que 49% des valeurs des contrôles négatifs; le traitement à la chlorhexidine 31%. Le rapport ATP/masse protéique est fortement abaissé après traitement à la chlorhexidine (6%) mais se maintient à 85% de la valeur témoin après traitement à l’OI-

Decoding sequence learning from single-trial intracranial EEG in humans.

We propose and validate a multivariate classification algorithm for characterizing changes in human intracranial electroencephalographic data (iEEG) after learning motor sequences. The algorithm is based on a Hidden Markov Model (HMM) that captures spatio-temporal properties of the iEEG at the level of single trials. Continuous intracranial iEEG was acquired during two sessions (one before and one after a night of sleep) in two patients with depth electrodes implanted in several brain areas. They performed a visuomotor sequence (serial reaction time task, SRTT) using the fingers of their non-dominant hand. Our results show that the decoding algorithm correctly classified single iEEG trials from the trained sequence as belonging to either the initial training phase (day 1, before sleep) or a later consolidated phase (day 2, after sleep), whereas it failed to do so for trials belonging to a control condition (pseudo-random sequence). Accurate single-trial classification was achieved by taking advantage of the distributed pattern of neural activity. However, across all the contacts the hippocampus contributed most significantly to the classification accuracy for both patients, and one fronto-striatal contact for one patient. Together, these human intracranial findings demonstrate that a multivariate decoding approach can detect learning-related changes at the level of single-trial iEEG. Because it allows an unbiased identification of brain sites contributing to a behavioral effect (or experimental condition) at the level of single subject, this approach could be usefully applied to assess the neural correlates of other complex cognitive functions in patients implanted with multiple electrodes

Errors recruit both cognitive and emotional monitoring systems: Simultaneous intracranial recordings in the dorsal anterior cingulate gyrus and amygdala combined with fMRI

We studied error monitoring in a human patient with unique implantation of depth electrodes in both the left dorsal cingulate gyrus and medial temporal lobe prior to surgery. The patient performed a speeded go/nogo task and made a substantial number of commission errors (false alarms). As predicted, intracranial Local Field Potentials (iLFPs) in dorsal anterior cingulate indexed the detection of errors, showing an early differential activity around motor execution for false alarms, relative to correct responses (either hits or correct inhibitions). More surprisingly, we found that the left amygdala also participated to error monitoring (although no emotional stimuli were used), but with a very different neurophysiological profile as compared with the dorsal cingulate cortex. Amygdala iLFPs showed a precise and reproducible temporal unfolding, characterized by an early monophasic response for correct hits around motor execution, which was delayed by approximately 300ms for errors (even though actual RTs were almost identical in these two conditions). Moreover, time-frequency analyses demonstrated a reliable and transient coupling in the theta band around motor execution between these two distant regions. Additional fMRI investigation in the same patient confirmed a differential involvement of the dorsal cingulate cortex vs. amygdala in error monitoring during this go/nogo task. Finally, these intracranial results for the left amygdala were replicated in a second patient with intracranial electrodes in the right amygdala. Altogether, these results suggest that the amygdala may register the motivational significance of motor actions on a trial-by-trial basis, while the dorsal anterior cingulate cortex may provide signals concerning failures of cognitive control and behavioral adjustment. More generally, these data shed new light on neural mechanisms underlying self-monitoring by showing that even "simple" motor actions recruit not only executive cognitive processes (in dorsal cingulate) but also affective processes (in amygdala)

Hole-doping induced ferromagnetism in 2D materials

Two-dimensional (2D) ferromagnetic materials are considered as promising candidates for the future generations of spintronic devices. Yet, 2D materials with intrinsic ferromagnetism are scarce. High-throughput first-principles simulations are performed in order to screen 2D materials that present a non-magnetic to a ferromagnetic transition upon hole doping. A global evolutionary search is subsequently performed, in order to identify alternative possible atomic structures of the eligible candidates, and 122 materials exhibiting a hole-doping induced ferromagnetism are identified. Their energetic and dynamic stability, as well as their magnetic properties under hole doping are investigated systematically. Half of these 2D materials are metal halides, followed by chalcogenides, oxides and nitrides, some of them having predicted Curie temperatures above 300 K. The exchange interactions responsible for the ferromagnetic order in these 2D materials are also discussed. This work not only provides theoretical insights into hole-doped 2D ferromagnetic materials, but also enriches the family of 2D magnetic materials for possible spintronic applications