What Types of Educational Practices Impact School Burnout Levels in Adolescents?

This study explores the relationship between educational practices perceived by high school students and their level of burnout, as defined by emotional exhaustion, cynicism and inadequacy. A total of 287 adolescents (146 girls) aged between 14 and 19 years old (M = 16.08, SD = 1.01) and recruited from a public high school in French-speaking Switzerland completed a questionnaire regarding perceived educational practices and school burnout. Results from path analysis showed that the three dimensions of burnout were negatively associated with certain teacher- and school-related educational practices. More precisely, support for struggling students (ß = -0.24, p < 0.001) as well as teaching time (ß = -0.16, p < 0.05) were predictors of exhaustion (R2 =0.27). Teachers' instructional behavior (ß = -0.22, p < 0.01) and teacher motivation (ß = -0.31, p < 0.001) were predictors of cynicism (R2 = 0.20) and application of rules (ß = -0.21, p < 0.01) predicted inadequacy (R2 = 0.09). These educational practices should be of particular interest when it comes to strengthening the protective role of schools and teachers against school burnout in adolescents.

Pathological reorganization of NMDA receptors subunits and postsynaptic protein PSD-95 distribution in Alzheimer's disease.

In Alzheimer's disease (AD), synaptic alterations play a major role and are often correlated with cognitive changes. In order to better understand synaptic modifications, we compared alterations in NMDA receptors and postsynaptic protein PSD-95 expression in the entorhinal cortex (EC) and frontal cortex (FC; area 9) of AD and control brains. We combined immunohistochemical and image analysis methods to quantify on consecutive sections the distribution of PSD-95 and NMDA receptors GluN1, GluN2A and GluN2B in EC and FC from 25 AD and control cases. The density of stained receptors was analyzed using multivariate statistical methods to assess the effect of neurodegeneration. In both regions, the number of neuronal profiles immunostained for GluN1 receptors subunit and PSD-95 protein was significantly increased in AD compared to controls (3-6 fold), while the number of neuronal profiles stained for GluN2A and GluN2B receptors subunits was on the contrary decreased (3-4 fold). The increase in marked neuronal profiles was more prominent in a cortical band corresponding to layers 3 to 5 with large pyramidal cells. Neurons positive for GluN1 or PSD-95 staining were often found in the same localization on consecutive sections and they were also reactive for the anti-tau antibody AD2, indicating a neurodegenerative process. Differences in the density of immunoreactive puncta representing neuropile were not statistically significant. Altogether these data indicate that GluN1 and PSD-95 accumulate in the neuronal perikarya, but this is not the case for GluN2A and GluN2B, while the neuropile compartment is less subject to modifications. Thus, important variations in the pattern of distribution of the NMDA receptors subunits and PSD-95 represent a marker in AD and by impairing the neuronal network, contribute to functional deterioration.

Auditory spatial deficits following hemispheric lesions: dissociation of explicit and implicit processing.

Auditory spatial deficits occur frequently after hemispheric damage; a previous case report suggested that the explicit awareness of sound positions, as in sound localisation, can be impaired while the implicit use of auditory cues for the segregation of sound objects in noisy environments remains preserved. By assessing systematically patients with a first hemispheric lesion, we have shown that (1) explicit and/or implicit use can be disturbed; (2) impaired explicit vs. preserved implicit use dissociations occur rather frequently; and (3) different types of sound localisation deficits can be associated with preserved implicit use. Conceptually, the dissociation between the explicit and implicit use may reflect the dual-stream dichotomy of auditory processing. Our results speak in favour of systematic assessments of auditory spatial functions in clinical settings, especially when adaptation to auditory environment is at stake. Further, systematic studies are needed to link deficits of explicit vs. implicit use to disability in everyday activities, to design appropriate rehabilitation strategies, and to ascertain how far the explicit and implicit use of spatial cues can be retrained following brain damage.

GABA receptor subunits in human auditory cortex in normal and stroke cases.

GABA receptors are ubiquitous in the cerebral cortex and play a major role in shaping responses of cortical neurons. GABA(A) and GABA(B) receptor subunit expression was visualized by immunohistochemistry in human auditory areas from both hemispheres in 9 normal subjects (aged 43-85 years; time between death and fixation 6-24 hours) and in 4 stroke patients (aged 59-87 years; time between death and fixation 7-24 hours) and analyzed qualitatively for GABA(A) and semiquantitatively for GABA(B) receptor subunits. In normal brains, the primary auditory area (TC) and the surrounding areas TB and TA displayed distinct GABA(A) receptor subunit labeling with differences among cortical layers and areas. In postacute and chronic stroke we found a layer-selective downregulation of the alpha-2 subunit in the anatomically intact cerebral cortex of the intact and of the lesioned hemisphere, whereas the alpha-1, alpha-3 and beta-2/3 subunits maintained normal levels of expression. The GABA(B) receptors had a distinct laminar pattern in auditory areas and minor differences among areas. Unlike in other pathologies, there is no modulation of the GABA(B) receptor expression in subacute or chronic stroke.

Right hemispheric dominance for echo suppression.

When two sounds are presented sequentially within a short delay ( approximately 10ms), the listener perceives a single auditory event, the location of which is dominated by the directional information conveyed by the leading sound (the precedence effect, PE). The PE is not always instantaneous, but has been shown to build-up across repetitions of lead-lag pairs. Here, we investigated the contributions of lateralization cue (interaural time and intensity differences; ITD and IID, respectively) and the side of lateralization of the leading sound on the spatio-temporal activity associated with the PE. We applied electrical neuroimaging analyses to compare auditory evoked potentials (AEPs) in response to physically identical click pairs presented early and late within a stimulus train and perceived as two segregated events or as one fused auditory event. Significant topographic AEP modulations associated with the PE were observed over the 70-117ms post-stimulus period, with one topography characterizing fused perceptions and another segregated perceptions. The specific pattern of effects varied as a function of lateralization cue and the lateralization of the leading sound. The PE for ITD stimuli built-up during the stimulus train irrespective of the lateralization of the leading sound. The PE for IID stimuli did not exhibit build-up over the course of the stimulus train, but instead was generally affected by the lateralization of the leading sound. Source estimations further suggested that bilateral temporal networks were engaged when perceptions were segregated, whereas fused perceptions resulted in decreased activity in left temporal and increased activity in right temporo-parietal cortices.

Differential changes in synaptic proteins in the Alzheimer frontal cortex with marked increase in PSD-95 postsynaptic protein.

We investigated how synaptic plasticity is related to the neurodegeneration process in the human dorsolateral prefrontal cortex. Pre- and postsynaptic proteins of Brodmann's area 9 from patients with Alzheimer's disease (AD) and age-matched controls were quantified by immunohistochemical methods and Western blots. The main finding was a significant increase in the expression of postsynaptic density protein PSD-95 in AD brains, revealed on both sections and immunoblots, while the expression of spinophilin, associated to spines, remained quantitatively unchanged despite qualitative changes with age and disease. Presynaptic protein alpha-synuclein indicated an increased immunohistochemical level, while synaptophysin remained unchanged. MAP2, a somatodendritic microtubule protein, as well as AD markers such as amyloid-beta protein and phosphorylated protein tau showed an increased expression on immunosections in AD. Altogether these changes suggest neuritic and synaptic reorganization in the process of AD. In particular, the significant increase in PSD-95 expression suggests a change in NMDA receptors trafficking and may represent a novel marker of functional significance for the disease.

The path to success in auditory spatial discrimination: electrical neuroimaging responses within the supratemporal plane predict performance outcome.

Auditory scene analysis requires the accurate encoding and comparison of the perceived spatial positions of sound sources. The electrophysiological correlates of auditory spatial discrimination and their relationship to performance accuracy were studied in humans by applying electrical neuroimaging analyses to auditory evoked potentials (AEPs) that were recorded during the completion of a near-threshold S1-S2 paradigm within the right hemispace. Data were sorted as a function of performance accuracy, and AEP responses 75-117 ms after the presentation of the first sound differed topographically between trials leading to correct and incorrect spatial discrimination. Distributed source estimations revealed that this followed from significantly stronger activity within the left (i.e. contralateral) supratemporal plane (STP) and the left inferior parietal lobule prior to correct versus incorrect discrimination performance. Successful spatial discrimination thus depends on the activity of distinct configurations of active brain networks within the contralateral temporo-parietal cortex over a time period when the first sound position is being encoded. Furthermore, significant positive correlations were observed between performance accuracy and the intracranial activity estimated within the left STP. The efficacy of S1 processing within the STP is thus predictive of behavioral performance outcome during auditory spatial discrimination. Our data support a model wherein refinement of spatial representations occurs within the STP and that interactions with parietal structures allow for transformations into coordinate frames that are required for higher-order computations including absolute localization of sound sources.

Interactions between auditory 'what' and 'where' pathways revealed by enhanced near-threshold discrimination of frequency and position.

Partially segregated neuronal pathways ("what" and "where" pathways, respectively) are thought to mediate sound recognition and localization. Less studied are interactions between these pathways. In two experiments, we investigated whether near-threshold pitch discrimination sensitivity (d') is altered by supra-threshold task-irrelevant position differences and likewise whether near-threshold position discrimination sensitivity is altered by supra-threshold task-irrelevant pitch differences. Each experiment followed a 2 x 2 within-subjects design regarding changes/no change in the task-relevant and task-irrelevant stimulus dimensions. In Experiment 1, subjects discriminated between 750 Hz and 752 Hz pure tones, and d' for this near-threshold pitch change significantly increased by a factor of 1.09 when accompanied by a task-irrelevant position change of 65 micros interaural time difference (ITD). No response bias was induced by the task-irrelevant position change. In Experiment 2, subjects discriminated between 385 micros and 431 micros ITDs, and d' for this near-threshold position change significantly increased by a factor of 0.73 when accompanied by task-irrelevant pitch changes (6 Hz). In contrast to Experiment 1, task-irrelevant pitch changes induced a response criterion bias toward responding that the two stimuli differed. The collective results are indicative of facilitative interactions between "what" and "where" pathways. By demonstrating how these pathways may cooperate under impoverished listening conditions, our results bear implications for possible neuro-rehabilitation strategies. We discuss our results in terms of the dual-pathway model of auditory processing.

Learning-induced plasticity in auditory spatial representations revealed by electrical neuroimaging.

Auditory spatial representations are likely encoded at a population level within human auditory cortices. We investigated learning-induced plasticity of spatial discrimination in healthy subjects using auditory-evoked potentials (AEPs) and electrical neuroimaging analyses. Stimuli were 100 ms white-noise bursts lateralized with varying interaural time differences. In three experiments, plasticity was induced with 40 min of discrimination training. During training, accuracy significantly improved from near-chance levels to approximately 75%. Before and after training, AEPs were recorded to stimuli presented passively with a more medial sound lateralization outnumbering a more lateral one (7:1). In experiment 1, the same lateralizations were used for training and AEP sessions. Significant AEP modulations to the different lateralizations were evident only after training, indicative of a learning-induced mismatch negativity (MMN). More precisely, this MMN at 195-250 ms after stimulus onset followed from differences in the AEP topography to each stimulus position, indicative of changes in the underlying brain network. In experiment 2, mirror-symmetric locations were used for training and AEP sessions; no training-related AEP modulations or MMN were observed. In experiment 3, the discrimination of trained plus equidistant untrained separations was tested psychophysically before and 0, 6, 24, and 48 h after training. Learning-induced plasticity lasted <6 h, did not generalize to untrained lateralizations, and was not the simple result of strengthening the representation of the trained lateralizations. Thus, learning-induced plasticity of auditory spatial discrimination relies on spatial comparisons, rather than a spatial anchor or a general comparator. Furthermore, cortical auditory representations of space are dynamic and subject to rapid reorganization.

Laminar specificity of intrinsic connections in Broca's area.

Broca's area and its right hemisphere homologue comprise 2 cytoarchitectonic subdivisions, FDgamma and FCBm of von Economo C and Koskinas GN (1925, Die Cytoarchitektonik der Hirnrinde des erwachsenen Menschen. Vienna/Berlin [Germany]: Springer). We report here on intrinsic connections within these areas, as revealed with biotinylated dextran amine and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate tracing in postmortem human brains. Injections limited to supragranular layers revealed a complex intrinsic network of horizontal connections within layers II and III spreading over several millimeters and to a lesser extent within layers IV, V, and VI. Ninety percent of the retrogradely labeled neurons (n = 734) were in supragranular layers, 4% in layer IV, and 6% in infragranular layers; most were pyramids and tended to be grouped into clusters of approximately 500 microm in diameter. Injections involving layer IV revealed extended horizontal connections within layers I-IV (up to 3.7 mm) and to a lesser extent in layers V and VI. Injections limited to the infragranular layers revealed horizontal connections mainly limited to these layers. Thus, intrinsic connections within Broca's area display a strong laminar specificity. This pattern is very similar in areas FDgamma and FCBm and in the 2 hemispheres.

The spatio-temporal brain dynamics of processing and integrating sound localization cues in humans.

Interaural intensity and time differences (IID and ITD) are two binaural auditory cues for localizing sounds in space. This study investigated the spatio-temporal brain mechanisms for processing and integrating IID and ITD cues in humans. Auditory-evoked potentials were recorded, while subjects passively listened to noise bursts lateralized with IID, ITD or both cues simultaneously, as well as a more frequent centrally presented noise. In a separate psychophysical experiment, subjects actively discriminated lateralized from centrally presented stimuli. IID and ITD cues elicited different electric field topographies starting at approximately 75 ms post-stimulus onset, indicative of the engagement of distinct cortical networks. By contrast, no performance differences were observed between IID and ITD cues during the psychophysical experiment. Subjects did, however, respond significantly faster and more accurately when both cues were presented simultaneously. This performance facilitation exceeded predictions from probability summation, suggestive of interactions in neural processing of IID and ITD cues. Supra-additive neural response interactions as well as topographic modulations were indeed observed approximately 200 ms post-stimulus for the comparison of responses to the simultaneous presentation of both cues with the mean of those to separate IID and ITD cues. Source estimations revealed differential processing of IID and ITD cues initially within superior temporal cortices and also at later stages within temporo-parietal and inferior frontal cortices. Differences were principally in terms of hemispheric lateralization. The collective psychophysical and electrophysiological results support the hypothesis that IID and ITD cues are processed by distinct, but interacting, cortical networks that can in turn facilitate auditory localization.

Intrinsic connectivity of human superior colliculus.

The superior colliculus (SC) is believed to play an important role in sensorimotor integration and orienting behavior. It is classically divided into superficial layers predominantly containing visual neurons and deep layers containing multisensory and premotor neurons. Investigations of intrinsic connectivity within the SC in non-human species initially led to controversy regarding the existence of interlaminar connections between superficial and deep layers. It now seems more likely that such connections exist in a number of species, including non-human primates. In the latter, anatomical data concerning intrinsic SC connectivity are restricted to a limited number of intracellularly labeled neurons. No studies have been conducted to investigate the existence of intrinsic connections of human SC. In the present study, DiI (1,1'-dioctadecyl-3,3,3',3'- tetramethylindocarbocyanine perchlorate) and BDA (biotinylated dextran amine) were two tracers used in post-mortem human brains to examine intrinsic SC connections. Injections into the superficial layers revealed tangential connections within superficial layers and radial superficial-layer to deep-layer connections. Within superficial layers, horizontal connections were found over the entire rostro-caudal axis and were mostly directed laterally, i.e. toward the brachium of the inferior colliculus. Superficial-layer to deep-layer connections were more prominent in sections containing the injection site or located close to it. In these sections, an axon bundle having roughly the same diameter as the injection site crossed all deep layers, and individual axons displayed en passant or terminal boutons. The present results suggest that intrinsic connections within superficial layers and radial superficial-layers to deep-layers exist in human SC. The putative roles of these connections are discussed with regard to visual receptive field organization, as well as visuomotor and multisensory integration.

Patterns of calcium-binding proteins support parallel and hierarchical organization of human auditory areas.

The human primary auditory cortex (AI) is surrounded by several other auditory areas, which can be identified by cyto-, myelo- and chemoarchitectonic criteria. We report here on the pattern of calcium-binding protein immunoreactivity within these areas. The supratemporal regions of four normal human brains (eight hemispheres) were processed histologically, and serial sections were stained for parvalbumin, calretinin or calbindin. Each calcium-binding protein yielded a specific pattern of labelling, which differed between auditory areas. In AI, defined as area TC [see C. von Economo and L. Horn (1930) Z. Ges. Neurol. Psychiatr.,130, 678-757], parvalbumin labelling was dark in layer IV; several parvalbumin-positive multipolar neurons were distributed in layers III and IV. Calbindin yielded dark labelling in layers I-III and V; it revealed numerous multipolar and pyramidal neurons in layers II and III. Calretinin labelling was lighter than that of parvalbumin or calbindin in AI; calretinin-positive bipolar and bitufted neurons were present in supragranular layers. In non-primary auditory areas, the intensity of labelling tended to become progressively lighter while moving away from AI, with qualitative differences between the cytoarchitectonically defined areas. In analogy to non-human primates, our results suggest differences in intrinsic organization between auditory areas that are compatible with parallel and hierarchical processing of auditory information.