Synchronized Oscillations During Cooperative Feature Linking in a Cortical Model of Visual Perception

A neural network model of synchronized oscillator activity in visual cortex is presented in order to account for recent neurophysiological findings that such synchronization may reflect global properties of the stimulus. In these recent experiments, it was reported that synchronization of oscillatory firing responses to moving bar stimuli occurred not only for nearby neurons, but also occurred between neurons separated by several cortical columns (several mm of cortex) when these neurons shared some receptive field preferences specific to the stimuli. These results were obtained not only for single bar stimuli but also across two disconnected, but colinear, bars moving in the same direction. Our model and computer simulations obtain these synchrony results across both single and double bar stimuli. For the double bar case, synchronous oscillations are induced in the region between the bars, but no oscillations are induced in the regions beyond the stimuli. These results were achieved with cellular units that exhibit limit cycle oscillations for a robust range of input values, but which approach an equilibrium state when undriven. Single and double bar synchronization of these oscillators was achieved by different, but formally related, models of preattentive visual boundary segmentation and attentive visual object recognition, as well as nearest-neighbor and randomly coupled models. In preattentive visual segmentation, synchronous oscillations may reflect the binding of local feature detectors into a globally coherent grouping. In object recognition, synchronous oscillations may occur during an attentive resonant state that triggers new learning. These modelling results support earlier theoretical predictions of synchronous visual cortical oscillations and demonstrate the robustness of the mechanisms capable of generating synchrony.Air Force Office of Scientific Research (90-0175); Army Research Office (DAAL-03-88-K0088); Defense Advanced Research Projects Agency (90-0083); National Aeronautics and Space Administration (NGT-50497

GATS and the electricity and water sectors

This paper discusses the impact of the GATS agreement of the World Trade Organisation on the electricity and water sectors

‘Putting apes (body and language) together again’, a review article of Savage-Rumbaugh, S., Taylor, T. J., and Shanker, S. G. Apes, Language, and the Human Mind (Oxford: 1999) and Clark, A. Being There: Putting Brain, Body, and World Together Again (MIT: 1997)

It is argued that the account of Savage-Rumbaugh’s ape language research in Savage-Rumbaugh, Shanker and Taylor (1998. Apes, Language and the Human Mind. Oxford University Press, Oxford) is profitably read in the terms of the theoretical perspective developed in Clark (1997. Being There, Putting Brain, Body and World Together Again. MIT Press, Cambridge, MA). The former work details some striking results concerning chimpanzee and bonobo subjects, trained to make use of keyboards containing ‘lexigram’ symbols. The authors, though, make heavy going of a critique of what they take to be standard approaches to understanding language and cognition in animals, and fail to offer a worthwhile theoretical position from which to make sense of their own data. It is suggested that the achievements of Savage-Rumbaugh’s non-human subjects suggest that language ability need not be explained by reference to specialised brain capacities. The contribution made by Clark’s work is to show the range of ways in which cognition exploits bodily and environmental resources. This model of ‘distributed’ cognition helps makes sense of the lexigram activity of Savage-Rumbaugh’s subjects, and points to a re-evaluation of the language behaviour of humans

Dynamic modelling of meat plant energy systems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology at Massey University

The objective of this study was to develop dynamic mathematical models of the major energy use and recovery operations within the New Zealand meat industry. Ordinary differential equation based models were developed for the five most common rendering systems, for hot water use, generation and storage, and for the refrigeration system. These cover about 90% of process heat use and about two-thirds of electricity demand. Each model was constructed so that ultimately it could be linked to the others to develop an integrated energy supply and demand model. Strong linkages to product flow were developed for the rendering models, but those for hot water and refrigeration are less developed, although there is no technological impediment. In developing the models for rendering it was assumed that cookers and dryers are perfectly mixed vessels and that time delays in materials transport are negligible. Model predictions could be improved by removing these assumptions, but taking into account the possible extent of data uncertainties, the present accuracy may be adequate for the overall meat plant energy model. A major consequence of the development of a hot water demand model was that areas of low efficiency were identified. By attention to equipment designs for hand tool sterilisers and cleanup systems substantial heat savings are possible. Although not tested, both the model for heat recovery and the model for hot water storage and supply are expected to be accurate as few major assumptions were required in their development. The main novel feature of the refrigeration model is that it treats the refrigeration applications in abstract terms rather than performing a room by room analysis. As a consequence data demands are lower than for refrigeration models which use a room-based approach, and the actual data needed are more easily obtainable. In spite of the lower data requirements good accuracy was demonstrated. The models developed will have major benefits to the NZ meat industry, initially as stand-alone entities, but later as an integrated package to help in reducing energy use

Synchronized Oscillations During Cooperative Feature Lining in a Cortical Model of Visual Perception

A neural network model of synchronized oscillations in visual cortex is presented to account for recent neurophysiological findings that such synchronization may reflect global properties of the stimulus. In these experiments, synchronization of oscillatory firing responses to moving bar stimuli occurred not only for nearby neurons, but also occurred between neurons separated by several cortical columns (several mm of cortex) when these neurons shared some receptive field preferences specific to the stimuli. These results were obtained for single bar stimuli and also across two disconnected, but colinear, bars moving in the same direction. Our model and computer simulations obtain these synchrony results across both single and double bar stimuli using different, but formally related, models of preattentive visual boundary segmentation and attentive visual object recognition, as well as nearest-neighbor and randomly coupled models.Air Force Office of Scientific Research (90-0175); Army Research Office (DAAL-03-88-K0088); Defense Advanced Research Projects Agency (90-0083); National Aeronautics and Space Administration (NGT-50497

The financial crisis and nuclear power

An assessment of the impact of the financial crisis on the prospects for new nuclear power plant orders worldwide

Quasi-Expressivism about Statements of Law: A Hartian Theory

Speech and thought about what the law is commonly function in practical ways, to guide or assess behavior. These functions have often been seen as problematic for legal positivism in the tradition of H.L.A. Hart. One recent response is to advance an expressivist analysis of legal statements (Toh), which faces its own, familiar problems. This paper advances a rival, positivist-friendly account of legal statements which we call “quasi-expressivist”, explicitly modeled after Finlay’s metaethical theory of moral statements. This consists in a descriptivist, “rule-relational” semantics combined with a pragmatic account of the expressive and practical functions of legal discourse. We argue that this approach is at least as well-equipped as expressivism to explain the motivational and prescriptive features of “internal” legal statements, as well as a fundamental kind of legal disagreement, while being better positioned to account for various “external” uses of the same language. We develop this theory in a Hartian framework, and in the final part of the paper argue (particularly against Toh’s expressivist interpretation) that Hart’s own views in The Concept of Law are best reconstructed along such quasi-expressivist lines