The topographic pattern of the Sudetes and the tectonic message it conveys

<p>The Sudetes in Central Europe are part of an intraplate belt of highlands and mountains that extends north of the Alps, being also the highest (1602 m a.s.l.) and one of topographically most complex geomorphic units within this belt. The Sudetes consist of numerous semi-isolated mountain massifs, dissected uplands, intramontane troughs and basins, forming a seemingly disordered patchwork of high and low relief. This topographic pattern has developed upon lithologically diverse bedrock, suggesting at least some degree of superposition of different controls. Although specific areas within the Sudetes were subject to analysis focused on the recognition of tectonic imprint in the present-day topography, attempts to disentangle this landscape complexity across the entire Sudetes range were rare and largely inconclusive. Here we approach the problem from the perspective of multidimensional analysis of regional topography, using high-resolution digital elevation data as the primary background material. The building blocks used in the exercise are spatial distribution of altitude and relief, spatial pattern of erosional (dissection) hot spots, position of the main water divide and second-order divides, geometry of main mountain fronts, spatial distribution of surfaces of low relief, considered as inherited planation surfaces, selected features of the regional drainage pattern such as the position of gorges, dominant directions, geometric anomalies etc., and spatial pattern of intramontane basins. Topography is compared with lithology, following an assumption that high strength of a rock unit may also result in considerable elevation and relief, without the necessity to have active tectonics involved. An overlay of these various topographic features allows us to propose intra-regional differentiation of the Sudetes into units typified by different topographic signatures and to separate relief features, both linear and areal, primarily controlled by uplift and subsidence from those reflecting other controls. As an end-result, tectonic interpretation of the contemporary topography is offered.</p>

The imprint of glacial and periglacial erosion processes on fluvial landscape metrics

<p>The emerging Pleistocene glaciations have left a distinct topographic footprint in mountain ranges worldwide. However, it is still unclear how the formation of cirques above (including the potential destruction of peak relief) and the excavation of glacial troughs below the long-term snowline altered to the large-scale topographic pattern of mountain ranges originally conditioned by fluvial processes.</p><p>Some mountain ranges such as the Eastern Alps feature a bimodal topographic pattern characterized by a transition from increasing to decreasing slope with elevation. Bimodality might be an expression of glacial reshaping, as glacial troughs with steepened valley flanks have been formed at low elevations and low relief surfaces at high elevations. On the other hand, bimodality might represent the state of fluvial prematurity as expression of ongoing landscape adjustment to an uplift event in the recent past. Despite their completely different evolution, both hypotheses lead to a bimodal landscape with a similar slope-elevation distribution.</p><p>In this study, we explore the impact of cold climate erosional processes on the mountain range scale topographic pattern. For this, we use synthetically generated and natural mountain range landscapes conditioned by fluvial processes and apply a surface process model for cold climate conditions (iSOSIA). In regions with high glacial impact, we explore an upstream migrating glacial signature represented by two frequency maxima in the slope elevation distribution at lower elevations (i.e. below the snowline, where glacial troughs formed). This is accompanied with an increase in slope on average compared to the initial topography. Above the snow line, bimodality vanishes and mean slope is similar to the initial fluvial topography. Interestingly, in the Eastern Alps, we explore a similar pattern where the transition from increasing to decreasing slope with elevation is located at about 1800 m, which is roughly at the position of the last glacial maximum (LGM) snowline of this region.</p>

Pre-Attentive Neural Signatures of Auditory Spatial Processing in Listeners With Normal Hearing and Sensorineural Hearing Impairment: A Comparative Study

Purpose This study was carried out to understand the neural intricacies of auditory spatial processing in listeners with sensorineural hearing impairment (SNHI) and compare it with normal hearing (NH) listeners using both local and global measures of waveform analyses. Method A standard group comparison research design was adopted in this study. Participants were assigned to 2 groups. Group I consisted of 13 participants with mild–moderate flat or sloping SNHI, while Group II consisted of 13 participants with NH sensitivity. Electroencephalographic data using virtual acoustic stimuli (spatially loaded stimuli played in center, right, and left hemifields) were recorded from 64 electrode sites in passive oddball paradigm. Both local (electrode-wise waveform analysis) and global (dissimilarity index, electric field strength, and topographic pattern analyses) measures were performed on the electroencephalographic data. Results Results of local waveform analyses marked the appearance of mismatch negativity in an earlier time window, relative to those reported conventionally in both the groups. The global measures of electric field strength and topographic modulations (dissimilarity index) revealed differences between the 2 groups in different time periods, indicating multiphases (integration and consolidation) of spatial processing. Further, the topographic pattern analysis showed the emergence of different scalp maps for SNHI and NH in the time window corresponding to mismatch negativity (78–150 ms), suggestive of differential spatial processing between the groups at the cortical level. Conclusions The findings of this study highlights the differential allotment of neural generators, denoting variations in spatial processing between SNHI and NH individuals.

White matter hyperintensities: relationship to amyloid and tau burden

Although white matter hyperintensities have traditionally been viewed as a marker of vascular disease, recent pathology studies have found an association between white matter hyperintensities and Alzheimer’s disease pathologies. The objectives of this study were to investigate the topographic patterns of white matter hyperintensities associated with Alzheimer’s disease biomarkers measured using PET. From the population-based Mayo Clinic Study of Aging, 434 participants without dementia (55% male) with FLAIR and gradient recall echo MRI, tau-PET (AV-1451) and amyloid-PET scans were identified. A subset had cerebral microbleeds detected on T2* gradient recall echo scans. White matter hyperintensities were semi-automatically segmented using FLAIR MRI in participant space and normalized to a custom template. We used statistical parametric mapping 12-based, voxel-wise, multiple-regression analyses to detect white matter hyperintense regions associated with Alzheimer’s biomarkers (global amyloid from amyloid-PET and meta-regions of interest tau uptake from tau-PET) after adjusting for age, sex and hypertension. For amyloid associations, we additionally adjusted for tau and vice versa. Topographic patterns of amyloid-associated white matter hyperintensities included periventricular white matter hyperintensities (frontal and parietal lobes). White matter hyperintense volumes in the detected topographic pattern correlated strongly with lobar cerebral microbleeds (P < 0.001, age and sex adjusted Cohen’s d = 0.703). In contrast, there were no white matter hyperintense regions significantly associated with increased tau burden using voxel-based analysis or region-specific analysis. Among non-demented elderly, amyloid load correlated with a topographic pattern of white matter hyperintensities. Further, the amyloid-associated, white matter hyperintense regions strongly correlated with lobar cerebral microbleeds suggesting that cerebral amyloid angiopathy contributes to the relationship between amyloid and white matter hyperintensities. The study did not support an association between increased tau burden and white matter hyperintense burden.