Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Automated Vascular Smooth Muscle Segmentation, Reconstruction, Classification and Simulation on Whole-Slide Histology

Histology of the microvasculature depicts detailed characteristics relevant to tissue perfusion. One important histologic feature is the smooth muscle component of the microvessel wall, which is responsible for controlling vessel caliber. Abnormalities can cause disease and organ failure, as seen in hypertensive retinopathy, diabetic ischemia, Alzheimer’s disease and improper cardiovascular development. However, assessments of smooth muscle cell content are conventionally performed on selected fields of view on 2D sections, which may lead to measurement bias. We have developed a software platform for automated (1) 3D vascular reconstruction, (2) detection and segmentation of muscularized microvessels, (3) classification of vascular subtypes, and (4) simulation of function through blood flow modeling. Vessels were stained for α-actin using 3,3\u27-Diaminobenzidine, assessing both normal (n=9 mice) and regenerated vasculature (n=5 at day 14, n=4 at day 28). 2D locally adaptive segmentation involved vessel detection, skeletonization, and fragment connection. 3D reconstruction was performed using our novel nucleus landmark-based registration. Arterioles and venules were categorized using supervised machine learning based on texture and morphometry. Simulation of blood flow for the normal and regenerated vasculature was performed at baseline and during demand based on the structural measures obtained from the above tools. Vessel medial area and vessel wall thickness were found to be greater in the normal vasculature as compared to the regenerated vasculature (p\u3c0.001) and a higher density of arterioles was found in the regenerated tissue (p\u3c0.05). Validation showed: a Dice coefficient of 0.88 (compared to manual) for the segmentations, a 3D reconstruction target registration error of 4 μm, and area under the receiver operator curve of 0.89 for vessel classification. We found 89% and 67% decreases in the blood flow through the network for the regenerated vasculature during increased oxygen demand as compared to the normal vasculature, respectively for 14 and 28 days post-ischemia. We developed a software platform for automated vasculature histology analysis involving 3D reconstruction, segmentation, and arteriole vs. venule classification. This advanced the knowledge of conventional histology sampling compared to whole slide analysis, the morphological and density differences in the regenerated vasculature, and the effect of the differences on blood flow and function

POLITICAL ECONOMY OF EXOTIC TRADE ON THE MISSISSIPPIAN FRONTIER: A CASE STUDY OF A FOURTEENTH CENTURY CHIEFDOM IN SOUTHWESTERN VIRGINIA

Although the Mississippian culture area has been studied for decades, the frontier of the Mississippian region is less understood. Various Mississippian frontiers appear to have been important for the obtainment of trade goods which were important symbols of chiefly power. Studying these frontiers will allow archaeologists to better understand the emergence and maintenance of power within Southeastern chiefdoms. This dissertation explores one frontier site, Carter Robinson (44LE10) in southwestern Virginia, and its role in Southern Appalachian chiefdom power through its control of trade at the border. This research identifies ceramic and non-utilitarian markers of trade and identifies changes at the frontier site over time, an accumulation of power that occurred through control of trade

Dynamic and Integrative Properties of the Primary Visual Cortex

The ability to derive meaning from complex, ambiguous sensory input requires the integration of information over both space and time, as well as cognitive mechanisms to dynamically shape that integration. We have studied these processes in the primary visual cortex (V1), where neurons have been proposed to integrate visual inputs along a geometric pattern known as the association field (AF). We first used cortical reorganization as a model to investigate the role that a specific network of V1 connections, the long-range horizontal connections, might play in temporal and spatial integration across the AF. When retinal lesions ablate sensory information from portions of the visual field, V1 undergoes a process of reorganization mediated by compensatory changes in the network of horizontal collaterals. The reorganization accompanies the brain’s amazing ability to perceptually “fill-inâ€, or “seeâ€, the lost visual input. We developed a computational model to simulate cortical reorganization and perceptual fill-in mediated by a plexus of horizontal connections that encode the AF. The model reproduces the major features of the perceptual fill-in reported by human subjects with retinal lesions, and it suggests that V1 neurons, empowered by their horizontal connections, underlie both perceptual fill-in and normal integrative mechanisms that are crucial to our visual perception. These results motivated the second prong of our work, which was to experimentally study the normal integration of information in V1. Since psychophysical and physiological studies suggest that spatial interactions in V1 may be under cognitive control, we investigated the integrative properties of V1 neurons under different cognitive states. We performed extracellular recordings from single V1 neurons in macaques that were trained to perform a delayed-match-to-sample contour detection task. We found that the ability of V1 neurons to summate visual inputs from beyond the classical receptive field (cRF) imbues them with selectivity for complex contour shapes, and that neuronal shape selectivity in V1 changed dynamically according to the shapes monkeys were cued to detect. Over the population, V1 encoded subsets of the AF, predicted by the computational model, that shifted as a function of the monkeys’ expectations. These results support the major conclusions of the theoretical work; even more, they reveal a sophisticated mode of form processing, whereby the selectivity of the whole network in V1 is reshaped by cognitive state

Soil micromorphology and image analysis; a study of bronze age to recently improved soils at Lairg, Sutherland, Scotland

The applications of multispectral and morphometric image analysis to soil thin section descriptions is examined. It is shown that unsupervised classification and contrast stretching can be used to enhance and label features of interest. Morphometric measurements, allow the shape and abundance of features in thin sections to be compared and statistical relationships established. This method of analysis offers a precision beyond that which is possible using a qualitative approach. Using soil micromorphology as the main analytical technique a case study was carried out to evaluate the applicability of image analysis to an investigation of an archaeological site at Lairg in northern Scotland. The interactions of anthropogenic activity and pedogenesis since the Bronze Age is examined. The condition of the soils prior to the Bronze Age is not known because no buried soils predated this period. Evidence suggests that in freely draining situations complete podzols might have formed by this time. During the Bronze and Iron Age intensive cultivation of soils occurred with associated erosion. In areas of the site, where human activity is dated to the Post Medieval period, deepening of A horizons is apparent and the soils are maintained as Brown Podzols. In many areas where human activity stops stagnopodzols are the dominant soil type. The potential of image analysis to aid soil micromorphological descriptions is demonstrated. Contrast stretching aided a qualitative subdivision of thin section slides during the case study. Morphometric analysis confirmed a relationship between shape of voids and c/f ratios in an Iron Age buried A horizon, A PM buried A horizon and an undated deep topsoil. It is concluded that the full benefits of image analysis, when used as a routine tool to aid thin section descriptions, will only be realised when procedures become more interactive and processes can be speeded up

Cayuga Iroquois Households and Gender Relations During the Contact Period: An Investigation of the Rogers Farm Site, 1660s-1680s

The impact of the European presence in Iroquoian lands began to be strongly felt during the seventeenth century. The spread of epidemics, the participation of Iroquoian groups in the fur trade and the emerging world capitalist market, and the conversion of Natives to Christianity were among the numerous ramifications of Iroquois-European interaction during this period of nascent globalization. The goal of the dissertation is to investigate the extent to which traditional household-level patterns of social structure and economic organization changed or endured in the face of European contact, as well as how these processes impacted Iroquois gender relations and roles. The research project involved archaeological investigations of the Rogers Farm site, a Cayuga Iroquois village near Savannah, New York, dating from the 1660s to the 1680s. By the time of the site's occupation, the Iroquois had already experienced close to a century of interaction with Europeans. In addition, the village was the site of the Jesuit mission of St. René. The archaeological evidence recovered from Rogers Farm revealed both change and persistence in traditional household organization and domestic activities. Primary findings include: (1) a decrease in household size; (2) a decline in the importance of matrilineality and matrilocality in determining household membership; and (3) changes in household production and consumption of durable goods; but (4) continuity in household distribution of food resources. Although households contracted and were differently defined, they continued to operate cooperatively and carried out many of the same functions as prior to the Contact period. Members of the community took part in exchange with Europeans and incorporated new objects into their inventory of material culture, but the local-level economy remained based on reciprocal obligations. Lastly, neither the men nor the women of Rogers Farm were able to escape the consequences of the encroaching European presence in their lands. Men and women exercised different patterns in the selective adoption of European goods and in maintaining traditional technologies and productive activities. Although they experienced the effects of European interaction differently in their daily lives, they continued to play complementary roles in the newly reorganized economic endeavors of the period

Searching for Archaic Semi-Subterranean Habitation At the Halls Swamp Site in Southern New England

Abstract Semi-subterranean habitation structures, also referred to as pithouses have been interpreted on archaeological sites across North America and over a long span of time, up to 9,000 radiocarbon years before present (RCYBP) and are still used today. Although pithouses or earth lodges may vary in their size, shape, and construction, they share the following attributes: a floor, hearth, depression, and post molds. Experimental archaeology based on ethnographic studies used to reconstruct pithouses has helped define the archaeological signatures of pre-contact pithouses. The high investment of time and labor needed for the construction of large features, such as pithouses, storage pits, and ossuaries has been documented for pre-contact period peoples. Understanding how these large features fit into the Archaic period (10,000 to 3,000 RCYBP) has been challenging for archaeologists in the Northeast, and more specifically in southern New England where soil strata and depositional events are often blurred or erased by bioturbation. By evaluating and comparing archaeological features from known pithouses in southern New England, this thesis aimed to develop a model and test the suspected pithouse features at the Halls Swamp site in Kingston, Massachusetts. The model was used to evaluate a concentration of features identified at the Halls Swamp site which confirmed a Late Archaic period pithouse at this multi-component site. The presence of this feature type suggests fall and winter occupations along wetlands often taking advantage of slopes in sandy soils. Additional spatial, depositional, and grain size analysis along with a newly acquired radiocarbon date, was used in conjunction with previously reported data to test the model and overall connect this concentration of features to one single event

Shape Processing across Lateral Occipital Cortex

There are two predominant means of identifying visual areas in the human brain; retinotopy (exploiting maps of the visual field) and localisers (exploiting functional selectivity). This thesis aimed to bridge those two approaches, assessing the roles of LO-1 and LO-2; two retinotopically-defined regions that show overlap with the functionally-defined (shape selective) Lateral Occipital Complex (LOC). More generally, we asked what is the nature of the shape representation across Lateral Occipital cortex? We first probed the functional roles of LO-1 and LO-2, finding that LO-2 is the more shape-sensitive region of the pair and will respond to second order shape stimuli, whereas LO-1 may process more local cues (perhaps orientation information). Our later work then assessed neural shape representations across visual cortex, identifying two discrete representations; ‘Shape-profile’ (essentially retinotopic responses) and ‘Shape-complexity’ (responses based upon the complexity of a shape’s contour). The latter dimension captured variance in LOC, and surprisingly LO-2. This indicates that even explicit visual field maps can respond to non‑retinotopic attributes such as curvature complexity. Intriguingly, a transition between dimensions occurred around LO-1 and LO-2. Finally, we explicitly tested whether the ‘Shape-complexity’ representation may be curvature based. Our results implied that radial shape protrusions are highly salient features for Lateral Occipital cortex, but it is not necessarily the points of maximal curvature that are being responded to. Instead, we hypothesise that it is the convergent lines comorbid with curvature that neurons may be attuned to, as such lines likely represent the most salient or characteristic features in a given shape. In sum, we argue for an evolving shape representation across visual cortex, with some degree of shape sensitivity first emerging around LO-1 and LO-2. These maps may then be acting as preliminary processing stages for more selective shape tunings in LOC