A sound-sensitive source of alpha oscillations in human non-primary auditory cortex

The functional organization of human auditory cortex can be probed by characterizing responses to various classes of sound at different anatomical locations. Along with histological studies this approach has revealed a primary field in posteromedial Heschl's gyrus (HG) with pronounced induced high-frequency (70-150 Hz) activity and short-latency responses that phase-lock to rapid transient sounds. Low-frequency neural oscillations are also relevant to stimulus processing and information flow, however their distribution within auditory cortex has not been established. Alpha activity (7-14 Hz) in particular has been associated with processes that may differentially engage earlier versus later levels of the cortical hierarchy, including functional inhibition and the communication of sensory predictions. These theories derive largely from the study of occipitoparietal sources readily detectable in scalp electroencephalography. To characterize the anatomical basis and functional significance of less accessible temporal-lobe alpha activity we analyzed responses to sentences in seven human adults (four female) with epilepsy who had been implanted with electrodes in superior temporal cortex. In contrast to primary cortex in posteromedial HG, a non-primary field in anterolateral HG was characterized by high spontaneous alpha activity that was strongly suppressed during auditory stimulation. Alpha-power suppression decreased with distance from anterolateral HG throughout superior temporal cortex, and was more pronounced for clear compared to degraded speech. This suppression could not be accounted for solely by a change in the slope of the power spectrum. The differential manifestation and stimulus-sensitivity of alpha oscillations across auditory fields should be accounted for in theories of their generation and function.SIGNIFICANCE STATEMENTTo understand how auditory cortex is organized in support of perception, we recorded from patients implanted with electrodes for clinical reasons. This allowed measurement of activity in brain regions at different levels of sensory processing. Oscillations in the alpha range (7-14 Hz) have been associated with functions including sensory prediction and inhibition of regions handling irrelevant information, but their distribution within auditory cortex is not known. A key finding was that these oscillations dominated in one particular non-primary field, anterolateral Heschl's gyrus, and were suppressed when subjects listened to sentences. These results build on our knowledge of the functional organization of auditory cortex and provide anatomical constraints on theories of the generation and function of alpha oscillations

Sequence learning modulates neural responses and oscillatory coupling in human and monkey auditory cortex

Learning complex ordering relationships between sensory events in a sequence is fundamental for animal perception and human communication. While it is known that rhythmic sensory events can entrain brain oscillations at different frequencies, how learning and prior experience with sequencing relationships affect neocortical oscillations and neuronal responses is poorly understood. We used an implicit sequence learning paradigm (an “artificial grammar”) in which humans and monkeys were exposed to sequences of nonsense words with regularities in the ordering relationships between the words. We then recorded neural responses directly from the auditory cortex in both species in response to novel legal sequences or ones violating specific ordering relationships. Neural oscillations in both monkeys and humans in response to the nonsense word sequences show strikingly similar hierarchically nested low-frequency phase and high-gamma amplitude coupling, establishing this form of oscillatory coupling—previously associated with speech processing in the human auditory cortex—as an evolutionarily conserved biological process. Moreover, learned ordering relationships modulate the observed form of neural oscillatory coupling in both species, with temporally distinct neural oscillatory effects that appear to coordinate neuronal responses in the monkeys. This study identifies the conserved auditory cortical neural signatures involved in monitoring learned sequencing operations, evident as modulations of transient coupling and neuronal responses to temporally structured sensory input

Polymerization of a confined π-system : Chemical synthesis of tetrahedral amorphous carbon nanoballs from graphitic carbon nanocapsules

[[abstract]]Aziridination of graphitic carbon nanocapsules (CNCs) followed by pyrolysis at 700 °C at ambient pressure yields tetrahedral amorphous carbon nanoballs (CNBs, see Figure). Because of the pyramidal character of some of the double bonds in the derivatized CNCs, a radical chain mechanism is proposed to rationalize the transformation of C sp2 hybridization in the CNCs to C sp3 hybridization in the CNBs.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[incitationindex]]E

Fake news as a floating signifier: hegemony, antagonism and the politics of falsehood

‘Fake news’ has emerged as a global buzzword. While prominent media outlets, such as The New York Times, CNN, and CBS, have used the term to designate misleading information spread through websites, President Donald Trump has recently used the term as a negative designation of these very ‘mainstream media’. In this article, we argue that the concept of ‘fake news’ has become an important component in contemporary political struggles. We showcase how the term is utilised by different positions within the social space as a means of discrediting, attacking and delegitimising political opponents. Excavating three central moments within the construction of ‘fake news’, we argue that the term has increasingly become a ‘floating signifier’: a signifier lodged in-between different hegemonic projects seeking to provide an image of how society is and ought to be structured. By approaching ‘fake news’ from the viewpoint of discourse theory, the paper reframes the current stakes of the debate and contributes with new insights into the function and consequences of ‘fake news’ as a novel political category

Growth factor restriction impedes progression of wound healing following cataract surgery: identification of VEGF as a putative therapeutic target

Secondary visual loss occurs in millions of patients due to a wound-healing response, known as posterior capsule opacification (PCO), following cataract surgery. An intraocular lens (IOL) is implanted into residual lens tissue, known as the capsular bag, following cataract removal. Standard IOLs allow the anterior and posterior capsules to become physically connected. This places pressure on the IOL and improves contact with the underlying posterior capsule. New open bag IOL designs separate the anterior capsule and posterior capsules and further reduce PCO incidence. It is hypothesised that this results from reduced cytokine availability due to greater irrigation of the bag. We therefore explored the role of growth factor restriction on PCO using human lens cell and tissue culture models. We demonstrate that cytokine dilution, by increasing medium volume, significantly reduced cell coverage in both closed and open capsular bag models. This coincided with reduced cell density and myofibroblast formation. A screen of 27 cytokines identified nine candidates whose expression profile correlated with growth. In particular, VEGF was found to regulate cell survival, growth and myofibroblast formation. VEGF provides a therapeutic target to further manage PCO development and will yield best results when used in conjunction with open bag IOL designs

Supercoiling of an excised genomic island represses effector gene expression to prevent activation of host resistance

The plant pathogen Pseudomonas syringae pv. phaseolicola, which causes halo blight disease of beans, contains a 106kb genomic island PPHGI-1. PPHGI-1 carries a gene, avrPphB, which encodes an effector protein that triggers a resistance response in certain bean cultivars. Previous studies have shown that when PPHGI-1 is excised from the bacterial chromosome avrPphB is down regulated and therefore the pathogen avoids triggering the host’s defence mechanism. Here we investigate whether the down regulation of avrPphB is caused by supercoiling of PPHGI-1. We also investigate the effect of a PPHGI-1 encoded type 1A topoisomerase, TopB3, on island stability and the bacterial pathogenicity in the plant. Supercoiling inhibitors significantly increased the expression of avrPphB but did not affect the excision of PPHGI-1. An insertional mutant of topB3 displayed an increase in avrPphB expression and an increase in PPHGI-1 excision as well as reduced population growth in resistant and susceptible cultivars of bean. These results suggest an important role for topoisomerases in the maintenance and stability of a bacterial encoded genomic island and demonstrate that supercoiling is involved in the down regulation of an effector gene once the island has been excised, allowing the pathogen to prevent further activation of the host defence response

Mapping effective connectivity in the human brain with concurrent intracranial electrical stimulation and BOLD-fMRI

BACKGROUND: Understanding brain function requires knowledge of how one brain region causally influences another. This information is difficult to obtain directly in the human brain, and is instead typically inferred from resting-state fMRI. NEW METHOD: Here, we demonstrate the safety and scientific promise of a novel and complementary approach: concurrent electrical stimulation and fMRI (es-fMRI) at 3 T in awake neurosurgical patients with implanted depth electrodes. RESULTS: We document the results of safety testing, actual experimental setup, and stimulation parameters, that safely and reliably evoke activation in distal structures through stimulation of amygdala, cingulate, or prefrontal cortex. We compare connectivity inferred from the evoked patterns of activation with that estimated from standard resting-state fMRI in the same patients: while connectivity patterns obtained with each approach are correlated, each method produces unique results. Response patterns were stable over the course of 11 min of es-fMRI runs. COMPARISON WITH EXISTING METHOD: es-fMRI in awake humans yields unique information about effective connectivity, complementing resting-state fMRI. Although our stimulations were below the level of inducing any apparent behavioral or perceptual effects, a next step would be to use es-fMRI to modulate task performances. This would reveal the acute network-level changes induced by the stimulation that mediate the behavioral and cognitive effects seen with brain stimulation. CONCLUSIONS: es-fMRI provides a novel and safe approach for mapping effective connectivity in the human brain in a clinical setting, and will inform treatments for psychiatric and neurodegenerative disorders that use deep brain stimulation

Genetic Analysis of Anti-Amoebae and Anti-Bacterial Activities of the Type VI Secretion System in Vibrio cholerae

A type VI secretion system (T6SS) was recently shown to be required for full virulence of Vibrio cholerae O37 serogroup strain V52. In this study, we systematically mutagenized each individual gene in T6SS locus and characterized their functions based on expression and secretion of the hemolysin co-regulated protein (Hcp), virulence towards amoebae of Dictyostelium discoideum and killing of Escherichia coli bacterial cells. We group the 17 proteins characterized in the T6SS locus into four categories: twelve (VipA, VipB, VCA0109–VCA0115, ClpV, VCA0119, and VasK) are essential for Hcp secretion and bacterial virulence, and thus likely function as structural components of the apparatus; two (VasH and VCA0122) are regulators that are required for T6SS gene expression and virulence; another two, VCA0121 and valine-glycine repeat protein G 3 (VgrG-3), are not essential for Hcp expression, secretion or bacterial virulence, and their functions are unknown; the last group is represented by VCA0118, which is not required for Hcp expression or secretion but still plays a role in both amoebae and bacterial killing and may therefore be an effector protein. We also showed that the clpV gene product is required for Dictyostelium virulence but is less important for killing E. coli. In addition, one vgrG gene (vgrG-2) outside of the T6SS gene cluster was required for bacterial killing but another (vgrG-1) was not. However, a bacterial killing defect was observed when vgrG-1 and vgrG-3 were both deleted. Several genes encoded in the same putative operon as vgrG-1 and vgrG-2 also contribute to virulence toward Dictyostelium but have a smaller effect on bacterial killing. Our results provide new insights into the functional requirements of V. cholerae's T6SS in the context of secretion as well as killing of bacterial and eukaryotic phagocytic cells