Functional MRI investigations of cortical mechanisms of auditory spatial attention

In everyday settings, spatial attention helps listeners isolate and understand individual sound sources. However, the neural mechanisms of auditory spatial attention (ASpA) are only partially understood. This thesis uses within-subject analysis of functional magnetic resonance imaging (fMRI) data to address fundamental questions regarding cortical mechanisms supporting ASpA by applying novel multi-voxel pattern analysis (MVPA) and resting-state functional connectivity (rsFC) approaches. A series of fMRI studies of ASpA were conducted in which subjects performed a one-back task in which they attended to one of two spatially separated streams. Attention modulated blood oxygenation level-dependent (BOLD) activity in multiple areas in the prefrontal, temporal, and parietal cortex, including non-visuotopic intraparietal sulcus (IPS), but not the visuotopic maps in IPS. No spatial bias was detected in any cortical area using standard univariate analysis; however, MVPA revealed that activation patterns in a number of areas, including the auditory cortex, predicted the attended direction. Furthermore, we explored how cognitive task demands and the sensory modality of the inputs influenced activity with a visual one-back task and a visual multiple object tracking (MOT) task. Activity from the visual and auditory one-back tasks overlapped along the fundus of IPS and lateral prefrontal cortex (lPFC). However, there was minimal overlap of activity in the lPFC between the visual MOT task and the two one-back tasks. Finally, we endeavored to identify visual and auditory networks using rsFC. We identified a dorsal visual attention network reliably within individual subjects using visuotopic seeds. Using auditory seeds, we found a prefrontal area nested between segments of the dorsal visual attention network. These findings mark fundamental progress towards elucidating the cortical network controlling ASpA. Our results suggest that similar lPFC structures support both ASpA and its visual counterpart during a spatial one-back task, but that ASpA does not drive visuotopic IPS in the parietal cortex. Furthermore, rsFC reveals that visual and auditory seed regions are functionally connected with non-overlapping lPFC regions, possibly reflecting spatial and temporal cognitive processing biases, respectively. While we find no evidence for a spatiotopic map, the auditory cortex is sensitive to direction of attention in its patterns of activation

Spatiotemporal Patterns and Cause Analysis of PM 2.5

According to the monthly comprehensive air index ranking in China in 2016, Beijing ranked in the bottom tenth three times, indicating that the air pollution situation is very serious compared to other cities in China. In this study, we chose 23 urban environmental assessment points, which covered all districts and counties in Beijing. We used ArcGIS software to analyze atmospheric concentrations of particulate matter with a diameter < 2.5 μm (PM2.5) for each month of 2016 in each district/county of Beijing. Our results showed that PM2.5 concentrations in winter and spring were generally higher than those in summer and autumn. The higher monthly average PM2.5 concentrations were primarily in the southwest and southeast areas. The higher annual average values were distributed in Fangshan, Daxing, and Tongzhou, which were closely related to the high terrain in the northwest and the low-lying terrain in the southeast, the “Beijing Bay” terrain, and local climatic conditions. The temporal and spatial distributions of PM2.5 constitute a warning signal for human life and production during different seasons and regions

Short-Term Memory for Space and Time Flexibly Recruit Complementary Sensory-Biased Frontal Lobe Attention Networks

The frontal lobes control wide-ranging cognitive functions; however, functional subdivisions of human frontal cortex are only coarsely mapped. Here, functional magnetic resonance imaging reveals two distinct visual-biased attention regions in lateral frontal cortex, superior precentral sulcus (sPCS) and inferior precentral sulcus (iPCS), anatomically interdigitated with two auditory-biased attention regions, transverse gyrus intersecting precentral sulcus (tgPCS) and caudal inferior frontal sulcus (cIFS). Intrinsic functional connectivity analysis demonstrates that sPCS and iPCS fall within a broad visual-attention network, while tgPCS and cIFS fall within a broad auditory-attention network. Interestingly, we observe that spatial and temporal short-term memory (STM), respectively, recruit visual and auditory attention networks in the frontal lobe, independent of sensory modality. These findings not only demonstrate that both sensory modality and information domain influence frontal lobe functional organization, they also demonstrate that spatial processing co-localizes with visual processing and that temporal processing co-localizes with auditory processing in lateral frontal cortex. Michalka et al. report four interleaved vision-biased and auditory-biased attention regions bilaterally in human lateral frontal cortex. Short-term memory for space and for time recruits the frontal visual and auditory networks, respectively across sensory modalities

Auditory Spatial Attention Representations in the Human Cerebral Cortex

Auditory spatial attention serves important functions in auditory source separation and selection. Although auditory spatial attention mechanisms have been generally investigated, the neural substrates encoding spatial information acted on by attention have not been identified in the human neocortex. We performed functional magnetic resonance imaging experiments to identify cortical regions that support auditory spatial attention and to test 2 hypotheses regarding the coding of auditory spatial attention: 1) auditory spatial attention might recruit the visuospatial maps of the intraparietal sulcus (IPS) to create multimodal spatial attention maps; 2) auditory spatial information might be encoded without explicit cortical maps. We mapped visuotopic IPS regions in individual subjects and measured auditory spatial attention effects within these regions of interest. Contrary to the multimodal map hypothesis, we observed that auditory spatial attentional modulations spared the visuotopic maps of IPS; the parietal regions activated by auditory attention lacked map structure. However, multivoxel pattern analysis revealed that the superior temporal gyrus and the supramarginal gyrus contained significant information about the direction of spatial attention. These findings support the hypothesis that auditory spatial information is coded without a cortical map representation. Our findings suggest that audiospatial and visuospatial attention utilize distinctly different spatial coding schemes. © 2012 The Author

SIFT Feature-Based Video Camera Boundary Detection Algorithm

Aiming at the problem of low accuracy of edge detection of the film and television lens, a new SIFT feature-based camera detection algorithm was proposed. Firstly, multiple frames of images are read in time sequence and converted into grayscale images. The frame image is further divided into blocks, and the average gradient of each block is calculated to construct the film dynamic texture. The correlation of the dynamic texture of adjacent frames and the matching degree of SIFT features of two frames were compared, and the predetection results were obtained according to the matching results. Next, compared with the next frame of the dynamic texture and SIFT feature whose step size is lower than the human eye refresh frequency, the final result is obtained. Through experiments on multiple groups of different types of film and television data, high recall rate and accuracy rate can be obtained. The algorithm in this paper can detect the gradual change lens with the complex structure and obtain high detection accuracy and recall rate. A lens boundary detection algorithm based on fuzzy clustering is realized. The algorithm can detect sudden changes/gradual changes of the lens at the same time without setting a threshold. It can effectively reduce the factors that affect lens detection, such as flash, movies, TV, and advertisements, and can reduce the influence of camera movement on the boundaries of movies and TVs. However, due to the complexity of film and television, there are still some missing and false detections in this algorithm, which need further study

Investigation of the Phenolic Component Bioavailability Using the In Vitro Digestion/Caco-2 Cell Model, as well as the Antioxidant Activity in Chinese Red Wine

Red wine is a well-known alcoholic beverage, and is known to have phenolic compounds (PCs), which contribute to its antioxidant activity and have other beneficial advantages for human health. The aim of this study was to evaluate the effect of the simulated gastro-intestinal digestion and the Caco-2 transepithelial transport assay on the PCs, bioavailability, and the antioxidant capacity of red wines. The contents of PCs in red wine were significantly reduced during most of the digestion phases. Phenolic acid had the greatest permeability, while the flavonols had the weakest. The bioavailability of PCs ranged from 2.08 to 24.01%. The result of the partial least squares structural equation model showed that the three phenols were positively correlated with the antioxidant activity of red wine. The contribution of anthocyanins was the largest (0.8667)

The Comparison and Modeling of the Driving Factors of Urban Expansion for Thirty-Five Big Cities in the Three Regions in China

This paper presents a national- and regional-scale urban growth model (NRUGM) of China based on panel data analysis. Through the panel analysis, population growth, road construction, salary increment per capita, and secondary industry product increment were proven to be the major driving factors for national-scale urban expansion. According to Seventh Five-Year Plan, China had been divided into three regions, Eastern China, Middle China, and Western China, by their geographic position and economic development. We studied the relationship between urban expansion and the driving factors for the three regions between 1990 and 2010 in China. The driving factors of urban expansion were different for the different regions and periods. Population growth and road construction were identified as the two major factors driving urban expansion for Eastern China. Secondary industry and economic development had become the major driving factors for urban expansion over the last twenty years in Middle China. Over the same period, for Western China, economic growth had become the major driving factor for urban expansion. Our results have significant policy implications for China. The macrocontrol of the central government should utilize different policies to adjust urban expansion in the different regions

Fabrication and study of micro-bubble generator

Gas bubbles have been used in various industries for many years. Applications include water purification, particle removal, and aeration. Much research has been done in an attempt to achieve smaller bubble sizes and various methods of bubble generation have been considered. The authors chose to study a particular micro orifice method in their experiments. The main focus for this theme project was to develop and fabricate a micro bubble generator. As there were four parameters to be studied, a designed experiment was used to decrease the number of experiment runs. It was shown that the orientation of the orifice and the hydrostatic head were significant parameters while pressure and orifice diameter did not have major impact at the given range. Further observations show that the pressure inputs were out of range, and a better pressure gauge was required for future experiments. It was found that there was a critical maximum pressure that will generate a distribution of bubble sizes instead of a steady stream of uniform-sized bubbles.​Master of Science (IMST

Characterization of beam quality of unstable laser beams with the multiple hyperbolas method

In this paper, the multiple hyperbolas method is proposed for characterizing the beam quality of unstable laser beams. Based on the traditional beam quality analyzer equipment, the proposed method captures multiple intensity images at every measurement positions. Afterward, three different hyperbolas are fitted according to the widths of laser intensities. With the fitted hyperbolas, three parameters, which include the average beam quality factor (Maver2) and variation factors (νpos, νneg), are determined. With the proposed method and determined parameters, the beam quality of unstable laser beams can be characterized more accurately and completely. The limitation of the traditional ISO standard-based method for characterizing unstable laser beams is also presented. In addition, the simulation and experimental results agree well with each other, indicating that the new method and determined parameters are appropriate for characterizing unstable laser beams. Keywords: Laser beam delivery and diagnostics, Laser characteristic, Laser beam quality, Unstable laser beam

Auditory Spatial Coding Flexibly Recruits Anterior, but Not Posterior, Visuotopic Parietal Cortex

Audition and vision both convey spatial information about the environment, but much less is known about mechanisms of auditory spatial cognition than visual spatial cognition. Human cortex contains >20 visuospatial map representations but no reported auditory spatial maps. The intraparietal sulcus (IPS) contains several of these visuospatial maps, which support visuospatial attention and short-term memory (STM). Neuroimaging studies also demonstrate that parietal cortex is activated during auditory spatial attention and working memory tasks, but prior work has not demonstrated that auditory activation occurs within visual spatial maps in parietal cortex. Here, we report both cognitive and anatomical distinctions in the auditory recruitment of visuotopically mapped regions within the superior parietal lobule. An auditory spatial STM task recruited anterior visuotopic maps (IPS2–4, SPL1), but an auditory temporal STM task with equivalent stimuli failed to drive these regions significantly. Behavioral and eye-tracking measures rule out task difficulty and eye movement explanations. Neither auditory task recruited posterior regions IPS0 or IPS1, which appear to be exclusively visual. These findings support the hypothesis of multisensory spatial processing in the anterior, but not posterior, superior parietal lobule and demonstrate that recruitment of these maps depends on auditory task demands