601,092 research outputs found
Individual differences in human path integration abilities correlate with gray matter volume in retrosplenial cortex, hippocampus, and medial prefrontal cortex
Humans differ in their individual navigational abilities. These individual differences may exist in part because successful navigation relies on several disparate abilities, which rely on different brain structures. One such navigational capability is path integration, the updating of position and orientation, in which navigators track distances, directions, and locations in space during movement. Although structural differences related to landmark-based navigation have been examined, gray matter volume related to path integration ability has not yet been tested. Here, we examined individual differences in two path integration paradigms: (1) a location tracking task and (2) a task tracking translational and rotational self-motion. Using voxel-based morphometry, we related differences in performance in these path integration tasks to variation in brain morphology in 26 healthy young adults. Performance in the location tracking task positively correlated with individual differences in gray matter volume in three areas critical for path integration: the hippocampus, the retrosplenial cortex, and the medial prefrontal cortex. These regions are consistent with the path integration system known from computational and animal models and provide novel evidence that morphological variability in retrosplenial and medial prefrontal cortices underlies individual differences in human path integration ability. The results for tracking rotational self-motion-but not translation or location-demonstrated that cerebellum gray matter volume correlated with individual performance. Our findings also suggest that these three aspects of path integration are largely independent. Together, the results of this study provide a link between individual abilities and the functional correlates, computational models, and animal models of path integration
Upright posture and the meaning of meronymy: A synthesis of metaphoric and analytic accounts
Cross-linguistic strategies for mapping lexical and spatial relations from body partonym systems to external object meronymies (as in English âtable legâ, âmountain faceâ) have attracted substantial research and debate over the past three decades. Due to the systematic mappings, lexical productivity and geometric complexities of body-based meronymies found in many Mesoamerican languages, the region has become focal for these discussions, prominently including contrastive accounts of the phenomenon in Zapotec and Tzeltal, leading researchers to question whether such systems should be explained as global metaphorical mappings from bodily source to target holonym or as vector mappings of shape and axis generated âalgorithmicallyâ. I propose a synthesis of these accounts in this paper by drawing on the species-specific cognitive affordances of human upright posture grounded in the reorganization of the anatomical planes, with a special emphasis on antisymmetrical relations that emerge between arm-leg and face-groin antinomies cross-culturally. Whereas Levinson argues that the internal geometry of objects âstripped of their bodily associationsâ (1994: 821) is sufficient to account for Tzeltal meronymy, making metaphorical explanations entirely unnecessary, I propose a more powerful, elegant explanation of Tzeltal meronymic mapping that affirms both the geometric-analytic and the global-metaphorical nature of Tzeltal meaning construal. I do this by demonstrating that the âalgorithmâ in question arises from the phenomenology of movement and correlative body memoriesâan experiential ground which generates a culturally selected pair of inverse contrastive paradigm sets with marked and unmarked membership emerging antithetically relative to the transverse anatomical plane. These relations are then selected diagrammatically for the classification of object orientations according to systematic geometric iconicities. Results not only serve to clarify the case in question but also point to the relatively untapped potential that upright posture holds for theorizing the emergence of human cognition, highlighting in the process the nature, origins and theoretical validity of markedness and double scope conceptual integration
The emergence of cities: complexity and urban dynamics
This paper presents an approach to urban dynamics that generalizes the traditionalrank-size model first popularized by Zipf (1949). It argues that we need to define the rate atwhich new cities emerge and old cities disappear within the apparent macro stability posed byZipf?s Law. We illustrate this with a reworking and extension of Zipf?s analysis of the USurban system, taking his analysis from 1790 to 1930 forward to the year 2000. In doing so, weintroduce a variety of devices to detect urban change based on traces through the rank-sizephase space, trajectories using a rank-time clock, and the definition of urban half-lives. We setthis analysis within the wider context of stochastic simulation that is currently dominatingdiscussion of scaling processes such as these
Semantic analysis of field sports video using a petri-net of audio-visual concepts
The most common approach to automatic summarisation and highlight detection in sports video is to train an automatic classifier to detect semantic highlights based on occurrences of low-level features such as action replays, excited commentators or changes in a scoreboard. We propose an alternative approach based on the detection of perception concepts (PCs) and the construction of Petri-Nets which can be used for both semantic description and event detection within sports videos. Low-level algorithms for the detection of perception concepts using visual, aural and motion characteristics are proposed, and a series of Petri-Nets composed of perception concepts is formally defined to describe video content. We call this a Perception Concept Network-Petri Net (PCN-PN) model. Using PCN-PNs, personalized high-level semantic descriptions of video highlights can be facilitated and queries on high-level semantics can be achieved. A particular strength of this framework is that we can easily build semantic detectors based on PCN-PNs to search within sports videos and locate interesting events. Experimental results based on recorded sports
video data across three types of sports games (soccer, basketball and rugby), and each from multiple broadcasters, are used to illustrate the potential of this framework
How young children understand electric circuits: prediction, explanation and exploration
This paper reports findings from a study of young childrenâs views about electric circuits. Twenty- eight children aged 5 and 6 were interviewed. They were shown examples of circuits and asked to predict whether they would work and explain why. They were then invited to try out some of the circuit examples or make circuits of their own choosing. Children expressed a variety of views about the connections needed in a circuit, offered different kinds of explanation and showed differing levels of competence in circuit making. The range of responses showed similarities to those of older students found in previous research. The relationship between practical competence, prediction and explanation was not straightforward. For example children with similar levels of practical competence made different predictions or offered different kinds of explanation. Analysis of the circuits children chose to construct suggested influences of existing competence and knowledge. In particular some children tested out circuit examples about which they had been unsure during the interview while others explored circuit connections more generally. Findings underline the importance of drawing on a variety of evidence in assessing young childrenâs understandings of electric circuits. They indicate that young children may offer views about electric circuits not unlike those of older children and adults with similar experience. Finally there was some suggestion that the interview procedure may have acted as an instructive stimulus in helping children to become more conscious of their own views and reflect on their thinking in the light of further evidence
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