Spatio-temporal dynamics of alpha brain electric fields, and cognitive modes

Brian electric activity is viewed as sequences of momentary maps of potential distribution. Frequency-domain source modeling, estimation of the complexity of the trajectory of the mapped brain field distributions in state space, and microstate parsing were used as analysis tools. Input-presentation as well as task-free (spontaneous thought) data collection paradigms were employed. We found: Alpha EEG field strength is more affected by visualizing mentation than by abstract mentation, both input-driven as well as self-generated. There are different neuronal populations and brain locations of the electric generators for different temporal frequencies of the brain field. Different alpha frequencies execute different brain functions as revealed by canonical correlations with mentation profiles. Different modes of mentation engage the same temporal frequencies at different brain locations. The basic structure of alpha electric fields implies inhomogeneity over time — alpha consists of concatenated global microstates in the sub-second range, characterized by quasi-stable field topographies, and rapid transitions between the microstates. In general, brain activity is strongly discontinuous, indicating that parsing into field landscape-defined microstates is appropriate. Different modes of spontaneous and induced mentation are associated with different brain electric microstates; these are proposed as candidates for psychophysiological ``atoms of thought''.

Reducing CT radiation dose with iterative reconstruction algorithms: the influence of scan and reconstruction parameters on image quality and CTDIvol

OBJECTIVES In this phantom CT study, we investigated whether images reconstructed using filtered back projection (FBP) and iterative reconstruction (IR) with reduced tube voltage and current have equivalent quality. We evaluated the effects of different acquisition and reconstruction parameter settings on image quality and radiation doses. Additionally, patient CT studies were evaluated to confirm our phantom results. METHODS Helical and axial 256 multi-slice computed tomography scans of the phantom (Catphan(®)) were performed with varying tube voltages (80-140kV) and currents (30-200mAs). 198 phantom data sets were reconstructed applying FBP and IR with increasing iterations, and soft and sharp kernels. Further, 25 chest and abdomen CT scans, performed with high and low exposure per patient, were reconstructed with IR and FBP. Two independent observers evaluated image quality and radiation doses of both phantom and patient scans. RESULTS In phantom scans, noise reduction was significantly improved using IR with increasing iterations, independent from tissue, scan-mode, tube-voltage, current, and kernel. IR did not affect high-contrast resolution. Low-contrast resolution was also not negatively affected, but improved in scans with doses <5mGy, although object detectability generally decreased with the lowering of exposure. At comparable image quality levels, CTDIvol was reduced by 26-50% using IR. In patients, applying IR vs. FBP resulted in good to excellent image quality, while tube voltage and current settings could be significantly decreased. CONCLUSIONS Our phantom experiments demonstrate that image quality levels of FBP reconstructions can also be achieved at lower tube voltages and tube currents when applying IR. Our findings could be confirmed in patients revealing the potential of IR to significantly reduce CT radiation doses.

Biomechanical Role of Bone Anisotropy Estimated on Clinical CT Scans by Image Registration

Image-based modeling is a popular approach to perform patient-specific biomechanical simulations. Accurate modeling is critical for orthopedic application to evaluate implant design and surgical planning. It has been shown that bone strength can be estimated from the bone mineral density (BMD) and trabecular bone architecture. However, these findings cannot be directly and fully transferred to patient-specific modeling since only BMD can be derived from clinical CT. Therefore, the objective of this study was to propose a method to predict the trabecular bone structure using a µCT atlas and an image registration technique. The approach has been evaluated on femurs and patellae under physiological loading. The displacement and ultimate force for femurs loaded in stance position were predicted with an error of 2.5% and 3.7%, respectively, while predictions obtained with an isotropic material resulted in errors of 7.3% and 6.9%. Similar results were obtained for the patella, where the strain predicted using the registration approach resulted in an improved mean squared error compared to the isotropic model. We conclude that the registration of anisotropic information from of a single template bone enables more accurate patient-specific simulations from clinical image datasets than isotropic model.

The role of social support in HIV prevention among young Latino men who have sex with men

The purpose of this formative study was to determine and prioritize the HIV-prevention needs of Latino young men who have sex with men (YMSM) in Chihuahua (Mexico), Texas, and California, based on YMSM and service provider perceptions of the factors affecting the assimilation and implementation of HIV-preventive behaviors. These factors included: perceived social support, identification of the modes of HIV transmission, perceived risk of HIV, perceived norms and attitudes of peers.^ The study, drawn from a secondary data set, was a convenience sample of providers (n=8) and clients (n=15). Participants completed face-to face interviews and a survey instrument. Interviews were analyzed to identify common themes and congruence among client groups, and among clients and providers. Providers’ understanding of theoretical constructs of interventions was also assessed. Survey data were analyzed to determine variable frequencies and their congruence to the qualitative analysis. ^ The results revealed several differences and many commonalities in the assimilation of protective messages. Client and provider perceptions were congruent across all domains. Providers demonstrated intuitive command of theoretical concepts but inconsistently verbalized their application. Both clients and providers recognized Latinos possessed high HIV-knowledge levels, despite inconsistent protective behaviors. Clients and providers consistently identified important reasons leading to inconsistent protective behaviors, such as: lack of access to targeted information and condoms, self-esteem, sexual identification, situational factors, decreased perceived HIV-risk, and concerns about homophobia, stigma, and rejection. Other factors included: poverty, failure to reach disenfranchised populations, and lack of role models/positive parental figures. The principal conclusion of the study was that there is a need for further study to understand the interrelationship between larger socioeconomic issues and consistent protective behaviors.^

Benthic cover map of Heron Reef derived from a high-spatial-resolution multi-spectral satellite image using object based image analysis

Providing accurate maps of coral reefs where the spatial scale and labels of the mapped features correspond to map units appropriate for examining biological and geomorphic structures and processes is a major challenge for remote sensing. The objective of this work is to assess the accuracy and relevance of the process used to derive geomorphic zone and benthic community zone maps for three western Pacific coral reefs produced from multi-scale, object-based image analysis (OBIA) of high-spatial-resolution multi-spectral images, guided by field survey data. Three Quickbird-2 multi-spectral data sets from reefs in Australia, Palau and Fiji and georeferenced field photographs were used in a multi-scale segmentation and object-based image classification to map geomorphic zones and benthic community zones. A per-pixel approach was also tested for mapping benthic community zones. Validation of the maps and comparison to past approaches indicated the multi-scale OBIA process enabled field data, operator field experience and a conceptual hierarchical model of the coral reef environment to be linked to provide output maps at geomorphic zone and benthic community scales on coral reefs. The OBIA mapping accuracies were comparable with previously published work using other methods; however, the classes mapped were matched to a predetermined set of features on the reef.

Limits of the Southern Ocean

The knowledge about processes concerning perception and understanding is of paramount importance for designing means of communication like maps and charts. This is especially the case, if one does not want to lose sight of the map-user and if map-design is to be orientated along the map-users needs and preferences in order to improve the cartographic product's usability. A scientific approach to visualization can help to achieve useable results. The insights achieved by such an approach can lead to modes of visualization that are superior to those, which have seemingly proved their value in praxis - so-called "bestpractices" -, concerning their utility and efficiency. This thesis shows this by using the example of visualizing the limits of bodies of waters in the Southern Ocean. After making some introductorily remarks on the chosen mode of problem-solution in chapter one, which simultaneously illustrate the flow of work while working on the problem, in chapter two the relevant information concerning the drawing of limits in the Southern Ocean is outlined. Chapter 3 builds the theoretical framework, which is a multidisciplinary approach to representation. This theoretical framework is based on "How Maps Work" by the American Cartographer MacEachren (1995/2004). His "scientific approach to visualization" is amended and adjusted by the knowledge gained from recent findings of the social sciences where necessary. So, the approach suggested in this thesis represents a synergy of psychology, sociology, semiotics, linguistics, communication theory and cartography. It follows the tradition of interdisciplinary research getting over the boundaries of a single scientific subject. The achieved holistic approach can help to improve the usability of cartographic products. It illustrates on the one hand those processes taking place while perceiving and recognizing cartographic information - so-called bottom-up-processes. On the other hand it illuminates the processes which happen during understanding this information in so-called top-down-processes. Bottom-up- and top-down-processes are interdependent and inseparably interrelated and therefore cannot be understood without each other. Regarding aspects of usability the approach suggested in this thesis strongly focuses on the map-user. This is the reason why the phenomenon of communication gains more weight than in MacEachren's map-centered approach. Because of this, in chapter 4 a holistic approach to communication is developed. This approach makes clear that only the map-user can evaluate the usability of a cartographic product. Only if he can extract the information relevant for him from the cartographical product, it is really useable. The concept of communication is well suited to conceive that. In case of the visualization of limits of bodies of water in the Southern Ocean, which is not complex enough to illustrate all results of the theoretical considerations, it is suggested to visualize the limits with red lines. This suggestion deviates from the commonly used mode of visualization. So, this thesis shows how theory is able to ameliorate praxis. Chapter 5 leads back to the task of fixing limits of the bodies of water in the area of concern. A convention by the International Hydrographic Organization (IHO) states that those limits should be drawn by using meridians, parallels, rhumb lines and bathymetric data. Based on the available bathymetric data both a representation and a process model are calculated, which should support the drawing of the limits. The quality of both models, which depends on the quality of the bathymetric data at hand, leads to the decision that the representation model is better suited to support the drawing of limits.

Crop row detection in maize fields inspired on the human visual perception

This paper proposes a new method, oriented to image real-time processing, for identifying crop rows in maize fields in the images. The vision system is designed to be installed onboard a mobile agricultural vehicle, that is, submitted to gyros, vibrations, and undesired movements. The images are captured under image perspective, being affected by the above undesired effects. The image processing consists of two main processes: image segmentation and crop row detection. The first one applies a threshold to separate green plants or pixels (crops and weeds) from the rest (soil, stones, and others). It is based on a fuzzy clustering process, which allows obtaining the threshold to be applied during the normal operation process. The crop row detection applies a method based on image perspective projection that searches for maximum accumulation of segmented green pixels along straight alignments. They determine the expected crop lines in the images. The method is robust enough to work under the above-mentioned undesired effects. It is favorably compared against the well-tested Hough transformation for line detection.

Interactive Atlas of habitability. Urban data management for the improvement of habitability and coexistence

In this paper we approximate to the understanding of the hybrid city as a context of changes, produced in the perception and in the modes of inhabiting and coexisting in cities through new technologies of information and communication.

The extraordinarily rapid disappearance of entoptic images.

It has been known for more than 40 years that images fade from perception when they are kept at the same position on the retina by abrogating eye movements. Although aspects of this phenomenon were described earlier, the use of close-fitting contact lenses in the 1950s made possible a series of detailed observations on eye movements and visual continuity. In the intervening decades, many investigators have studied the role of image motion on visual perception. Although several controversies remain, it is clear that images deteriorate and in some cases disappear following stabilization; eye movements are, therefore, essential to sustained exoptic vision. The time course of image degradation has generally been reported to be a few seconds to a minute or more, depending upon the conditions. Here we show that images of entoptic vascular shadows can disappear in less than 80 msec. The rapid vanishing of these images implies an active mechanism of image erasure and creation as the basis of normal visual processing.

Parameters affecting conscious versus unconscious visual discrimination with damage to the visual cortex (V1).

When the visual (striate) cortex (V1) is damaged in human subjects, cortical blindness results in the contralateral visual half field. Nevertheless, under some experimental conditions, subjects demonstrate a capacity to make visual discriminations in the blind hemifield (blindsight), even though they have no phenomenal experience of seeing. This capacity must, therefore, be mediated by parallel projections to other brain areas. It is also the case that some subjects have conscious residual vision in response to fast moving stimuli or sudden changes in light flux level presented to the blind hemifield, characterized by a contentless kind of awareness, a feeling of something happening, albeit not normal seeing. The relationship between these two modes of discrimination has never been studied systematically. We examine, in the same experiment, both the unconscious discrimination and the conscious visual awareness of moving stimuli in a subject with unilateral damage to V1. The results demonstrate an excellent capacity to discriminate motion direction and orientation in the absence of acknowledged perceptual awareness. Discrimination of the stimulus parameters for acknowledged awareness apparently follows a different functional relationship with respect to stimulus speed, displacement, and stimulus contrast. As performance in the two modes can be quantitatively matched, the findings suggest that it should be possible to image brain activity and to identify the active areas involved in the same subject performing the same discrimination task, both with and without conscious awareness, and hence to determine whether any structures contribute uniquely to conscious perception.

Análise do processo de escolha de crédito bancário: uma enquete nas pequenas empresas da indústria gráfica do Distrito Federal

O objetivo deste estudo consistiu-se em analisar os fatores influentes no comportamento de compra industrial, na situação de decisão de crédito bancário em pequenas empresas. Para tanto, foram entregues questionários a doze empresas da indústria gráfica, selecionadas pelo número de empregados (de 20 a 100 - pequenas indústrias, segundo o critério do IBGE), localizadas no Distrito Federal e associadas ao sindicato da categoria. De acordo com resultados obtidos por meio do levantamento de campo, as conclusões desta pesquisa puderam ser exploradas tendo-se como base três pontos principais: a) os resultados relativos aos fatores influentes no comportamento do consumidor industrial, tais como os referentes a importância da localização geográfica do fornecedor, dos seus recursos tecnológicos e da redução, pelos compradores, dos riscos percebidos nas decisões de compras, dentre outros que mostraram-se condizentes com as pressuposições do modelo de comportamento do mercado industrial adotado; b) a discussão relativa à situação de decisão de crédito bancário, baseado na literatura pesquisada. De acordo com os resultados, puderam-se detalhar os aspectos relativos aos atributos dos bancos e do crédito, destacando-se, dentre outros, a importância da imagem da instituição financeira, da qualidade do gerente de contas e do custo dos empréstimos e financiamentos; c) as especificidades da pequena empresa, que puderam ser visualizadas nos resultados da pesquisa de campo como, por exemplo, a estratégia intuitiva e pouco formalizada, a situação extra-organizacional incontrolável e a racionalidade político-econômico-familiar do pequeno empresário.

Caesarean Birth vs. Vaginal Delivery: Effects upon Maternal Satisfaction, Maternal Confidence and Maternal Perception of the Newborn Behaviour

In order to test the hypothesis that caesarean birth has negative consequences upon newly mothers’ satisfaction and perceptions, women delivering by caesarean birth (WCB) were compared with women delivering by vaginal birth (WVB). Subjects: 180 newly mothers; 93 WCB and 87 WVB. Instruments: A Socio-Demographic Questionnaire developed for this research, the Childbirth Perceptions Questionnaire and the Mother and Baby Scales. Results: WCB had significantly lower scores in perceptions of baby as alert/responsive and nearly significant lower scores for baby as alert during feeds. WVB showed a significantly higher level of satisfaction with delivery and conduct during labour, as also had significantly lower scores for perceptions of baby as irritable during feeds and for lack of confidence in feeds. After controlling for the kind of anesthesia received in labour, three conclusions must be taken into account: 1) between WCB with regional anaesthesia and WCB with general anaesthesia there is only one significant difference, with the former having higher scores for perception of baby as alert during feeds; 2) between WVB with regional anaesthesia and WVB with no anaesthesia there are only two significant differences, with the former having higher scores for lack of confidence in feeding and having lower scores for global confidence; 3) between WCB with regional anaesthesia and WVB with regional anaesthesia four significant differences emerge, with the former having a lower level of satisfaction with delivery and conduct in labour and having lower scores for perception of baby as alert responsive, and also having higher scores of perception of baby as irritable in feeds and higher scores for lack of confidence in feeding. Data seem compatible with the hypothesis that caesarean birth has some negative consequences upon mothers’ satisfaction and perceptions and, for this reason, psychological surveys should constitute a routine procedure in maternity hospitals, especially when newly mothers pertain to families affected by risks of psychological or social nature.

The perceptual factors in reading; a quantitative study of the psychological processes involved in work perception.

Columbia contributions to philosophy and psychology, vol. XVII, no. l.

Bimanual coordination: constraints imposed by the relative timing of homologous muscle activation

It has often been supposed that patterns of rhythmic bimanual coordination in which homologous muscles are engaged simultaneously, are performed in a more stable manner than those in which the same muscles are activated in an alternating fashion. In order to assess the efficacy of this constraint, the present study investigated the effect of forearm posture (prone or supine) on bimanual abduction-adduction movements of the wrist in isodirectional and non-isodirectional modes of coordination. Irrespective of forearm posture, non-isodirectional coordination was observed to be more stable than isodirectional coordination. In the latter condition, there was a more severe deterioration of coordination accuracy/stability as a function of cycling frequency than in the former condition. With elevations in cycling frequency, the performers recruited extra mechanical degrees of freedom, principally via flexion-extension of the wrist, which gave rise to increasing motion in the vertical plane. The increases in movement amplitude in the vertical plane were accompanied by decreasing amplitude in the horizontal plane. In agreement with previous studies, the present findings confirm that the relative timing of homologous muscle activation acts as a principal constraint upon the stability of interlimb coordination. Furthermore, it is argued that the use of manipulations of limb posture to investigate the role of other classes of constraint (e.g. perceptual) should be approached with caution because such manipulations affect the mapping between muscle activation patterns, movement dynamics and kinematics.

The development of preferences for specific body shapes

Research with adults has shown a preference for average-weight female figures with waist-to-hip ratios (WHR) of 0.7, and average weight male figures with waist-to-hip ratios of 0.9. This study investigated the development of preferences for WHR sizes as well as preferences for specific body weights. Five-hundred eleven children ranging in age from 6 to 17 were presented with drawings of 12 male and 12 female silhouettes varying in weight and WHR and asked to select one they thought looked the nicest or most attractive. The youngest children showed preferences for the underweight figures, changing to consistent preferences for the average weight figures in the teenage years. The developmental curves for waist-to-hip ratio preferences were linear, changing gradually over time to become more adult-like. Potential developmental models for the development of preferences for specific body shapes are considered in relation to these data.