Analisando alguns aspectos das posições de dois filósofos cujas abordagens são reconhecidamente divergentes, W. O. Quine e M. Dummett, pretendemos sustentar um contundente ponto de acordo entre eles: a ideia de que nossos princípios lógicos constituem nossos princípios sobre o que há, e portanto, que lógica é metafísica. DOI: 10.5007/1808-1711.2011v15n1p3.
In this paper, I start with the opposition between the Husserlian project of a phenomenology of the experience of time, started in 1905, and the mathematical and physical theory of time as it comes out of Einstein’s special theory of relativity in the same year. Although the contrast between the two approaches is apparent, my aim is to show that the original program of Husserl’s time theory is the constitution of an objective time and a time of the world, starting (...) from the intuitive giveness of time, i.e., from time as it appears. To show this, I stress the structural similarity between Husserl’s original question of time and the problem of a phenomenology of space constitution as it was first developed in the his manuscripts from the nineteenth century, in which we find the threefold question of the origin of our representation of space, of the geometrization of intuitive space, and of the constitution of transcendent world space. Finally, I reconsider some of Husserl’s main theses about the phenomenological constitution of objective time in light of the main results of special relativity time-theory, introducing several corrections to central assumptions that underlie Husserl’s theory of time. (shrink)
The object of this paper is to show how one is able to construct a paraconsistent theory of models that reflects much of the classical one. In other words the aim is to demonstrate that there is a very smooth and natural transition from the model theory of classical logic to that of certain categories of paraconsistent logic. To this end we take an extension of da Costa''sC 1 = (obtained by adding the axiom A A) and prove for it (...) results which correspond to many major classical model theories, taken from Shoenfield [5]. In particular we prove counterparts of the theorems of o-Tarski and Chang-o-Suszko, Craig-Robinson and the Beth definability theorem. (shrink)
In this note we present a three-valued intensional logic, which is an extension of both Montague's intensional logic and ukasiewicz three-valued logic. Our system is obtained by adapting Gallin's version of intensional logic (see Gallin, D., Intensional and Higher-order Modal Logic). Here we give only the necessary modifications to the latter. An acquaintance with Gallin's work is pressuposed.
Epistemic naturalism holds that the results or methodologies from the cognitive sciences are relevant to epistemology, and some have maintained that scientific methods are more compatible with externalist theories of justification than with internalist theories. But practically all discussions about naturalized epistemology are framed exclusively in terms of cognitive psychology, which is only one of the cognitive sciences. The question addressed in this essay is whether a commitment to naturalism really does favor externalism over internalism, and we offer reasons for (...) thinking that naturalism in epistemology is compatible with both internalist and externalist conceptions of justification. We also argue that there are some distinctively internalist aims that are currently being studied scientifically and these notions, and others, should be studied by scientific methods. (shrink)
We present a new method for characterizing the interpretive possibilities generated by elliptical constructions in natural language. Unlike previous analyses, which postulate ambiguity of interpretation or derivation in the full clause source of the ellipsis, our analysis requires no such hidden ambiguity. Further, the analysis follows relatively directly from an abstract statement of the ellipsis interpretation problem. It predicts correctly a wide range of interactions between ellipsis and other semantic phenomena such as quantifier scope and bound anaphora. Finally, although the (...) analysis itself is stated nonprocedurally, it admits of a direct computational method for generating interpretations. (shrink)
Systematic semantic ambiguities result from the interaction of the two operations that are involved in resolving ellipsis in the presence of scoping elements such as quantifiers and intensional operators: scope determination for the scoping elements and resolution of the elided relation. A variety of problematic examples previously noted - by Sag, Hirschbüihler, Gawron and Peters, Harper, and others - all have to do with such interactions. In previous work, we showed how ellipsis resolution can be stated and solved in equational (...) terms. Furthermore, this equational analysis of ellipsis provides a uniform framework in which interactions between ellipsis resolution and scope determination can be captured. As a consequence, an account of the problematic examples follows directly from the equational method. The goal of this paper is merely to point out this pleasant aspect of the equational analysis, through its application to these cases. No new analytical methods or associated formalism are presented, with the exception of a straightforward extension of the equational method to intensional logic. (shrink)
Abstract Occupational stress in nursing has attracted considerable attention as a focus for research and as a consequence multiple objects of nurses' stress, or 'stressors', have been identified. This paper puts into question the dominant conceptual and methodological approach to occupational stress in nursing research by both foregrounding the notion of anxiety and juxtaposing it with the notion of 'stress'. It is argued that the notion of 'stress' and the domination of the questionnaire have produced a narrow reading of the (...) topic. Some of the literature on occupational stress/anxiety in nursing is reviewed and our analysis illustrates how the identified objects of stress have a tendency to multiply contingent on the number of studies undertaken. Thus definitive objects of nurses' stress remain elusive. We argue that a return to the notion of 'anxiety' and methodological approaches other than empirical ones can bring both depth and breadth to the consideration of occupational distress in nursing. Further, we argue that the object of 'anxiety' is unconscious, thus unknown, and given this, a more informative approach is to map nurses' response to anxiety, the discursive formations arising out of anxiety, rather than attempt to define those objects of anxiety. (shrink)
In this study I propose an epistemological discussion of multiple spatio-temporal scales in neuroscience. Are such scales merely convenient levels of description of structure and function, or do they correspond to irreducible levels of brain organization? What criteria should we employ in order to reduce one level to another, or to identify levels that are not reducible to others? Should we think of these criteria as based on empirical and/or theoretical reasons? Beginning with an empirical criterion – the necessity of (...) different experimental methodologies for the measurement of different phenomena in the same system – I summarize spatial and temporal scales currently used in neuroscience and discuss the possibility of a more general theoretical criterion. I conclude that multiscaling should be recognized as a central concept in the epistemology of neuroscience. (shrink)
The NMDA receptor (NMDAR) channel has been proposed to function as a coincidence-detection mechanism for afferent and reentrant signals, supporting conscious perception, learning, and memory formation. In this paper we discuss the genesis of distorted perceptual states induced by subanesthetic doses of ketamine, a well-known NMDA antagonist. NMDAR blockage has been suggested to perturb perceptual processing in sensory cortex, and also to decrease GABAergic inhibition in limbic areas (leading to an increase in dopamine excitability). We propose that perceptual distortions and (...) hallucinations induced by ketamine blocking of NMDARs are generated by alternative signaling pathways, which include increase of excitability in frontal areas, and glutamate binding to AMPA in sensory cortex prompting Ca ++ entry through voltage-dependent calcium channels (VDCCs). This mechanism supports the thesis that glutamate binding to AMPA and NMDARs at sensory cortex mediates most normal perception, while binding to AMPA and activating VDCCs mediates some types of altered perceptual states. We suggest that Ca ++ metabolic activity in neurons at associative and sensory cortices is an important factor in the generation of both kinds of perceptual consciousness. (shrink)
Proceedings of the Tenth Brazilian Conference on Mathematical Logic. Coleção CLE, volume 14, 1995. Centro De Lógica, Epistemologia e História da Ciência, Unicamp, Campinas, SP, Brazil.
O presente artigo se refere a uma parte integrante do projeto de pesquisa intitulado "A Cientificidade na Obra Marxiana de Maturidade" e pretende explicitar o estatuto categorial, determinativo, de dois dos principais conceitos que integram a crítica marxiana da economia política em sua versão madura: formas de ser e modos de produção. Tomados na linguagem corrente como praticamente sinônimos, as duas noções ganham no corpus científico-filosófico construído pela reflexão marxiana, cada qual, uma significação bastante precisa. Propomo-nos a esclarecer o conteúdo (...) e a função teóricos cumpridos pelas duas categorias em questão, chamando a atenção para o problema da articulação categorial pensada que, em Marx, deve reproduzir, ou seja, traduzir e transpor o real na cabeça do homem. Procurar-se-á assim delimitar o efetivo sentido dos modos, histórico-sociais concretos, como modalidades de articulação de formas de ser efetivas da sociabilidade. Modos e formas de ser de entes, relações e processos sociais são momentos da determinação categorial da realidade societária. De um lado, tem-se a multiplicidade das efetivas formas de ser de relações, atividades e produtos. De outro lado, é a articulação que preside a vigência das ditas formas como existentes atualmente e parâmetro da sociabilidade como um todo. This article refers to a part of the research project entitled "The Marxian Scientificity in Maturity Work" and aims to clarify the categorial status, determinative of the two main concepts that are part of the Marxian critique of political economy in its mature version: forms of being and modes of production. Taken in the current language as virtually synonymous, the two concepts gain in scientific and philosophical corpus built by Marxist reflection, each one, a fairly precise meaning. We propose to clarify the theoretical content and function fulfilled by the two categories in question, drawing attention to the problem of articulation categorical thought that, in Marx, to reproduce, that is, translate and transpose the real man's head. Search will thus define the actual meaning of the modes, concrete social-historical, as kinds of articulation to be effective forms of sociability. Ways and forms of being loved, relationships and social processes are moments of categorical determination of corporate reality. On one side, there is a multiplicity of ways to be effective in relationships, activities and products. On the other side, is the joint that presides over the duration of that currently existing ways and parameter of sociality as a whole. (shrink)
The relationship between Lexical-Functional Grammar (LFG) functional structures (f-structures) for sentences and their semanticinterpretations can be formalized in linear logic in a way thatcorrectly explains the observed interactions between quantifier scopeambiguity, bound anaphora and intensionality.Our linear-logic formalization of the compositional properties ofquantifying expressions in natural language obviates the need forspecial mechanisms, such as Cooper storage, in representing thescoping possibilities of quantifying expressions. Instead, thesemantic contribution of a quantifier is recorded as a linear-logicformula whose use in a proof will establish the (...) scope of thequantifier. Different proofs can lead to different scopes. In eachcomplete proof, the properties of linear logic ensure thatquantifiers are properly scoped. (shrink)
The research team measured the enterprise web accessibility levels of the Forbes 250 largest enterprises using the fully automatic accessibility evaluation tool Sortsite, and presented the compliance of the evaluated websites to WCAG 1.0, WCAG 2.0 and Section 508 accessibility levels. Given the recent attention to organizational leaders having ethical duties towards their dedicated employees, we propose that ‘societal citizenship behaviour’ concerns ethical duties of organizational leaders towards society in general and in particular to those who have less means to (...) assert their needs. In effect, we found enterprise website accessibility levels to be in need of significant improvement. An interpretation of a positive path forward to better enterprise website accessibility levels is put forth based on a focus-group interaction and using BNML—a novel Business Narrative Modelling Language. (shrink)
In our paper we aim at reflecting upon the extent to which educational theory may be used as a framework in the analysis of policy documents. As policy texts are ‘heteroglossic in character’ (Lingard and Ozga, in The Routledge Falmer reader in education policy and politics, Routledge, London and New York, 2007 , p. 2) and create “circumstances in which the range of options available in deciding what to do are narrowed or changed” (Ball in, Education policy and social class: (...) The selected works of Stephen J Ball, Routledge, London and New York, 2006 , p. 46), they need to be theoretically tackled in their underlying assumptions and implications. This proposal draws on an analysis of two sets of documents of the European Union: texts produced between 2000 and 2006, underlying the European Union programmes; and texts produced by a working group focusing on the key competences of Lifelong Learning (2003–2006). Initially, the framework for the analysis of different documents was grounded on the existing research in the field of educational policy. Now we attempt a secondary analysis of the collected data by transposing the borders of this particular and highly prolific field. We argue that what is outside the texts may reshape what is inside the texts. Educational theory allows us to define some conceptual tools in order to question the documents as political apparatus which open and constrain possibilities. Therefore, we will use educational theory as an arena where different matters, perspectives and possibilities may be explored and assembled. We have engaged in a conversation with both the data and some theoretical approaches. Central to this conversation are the concepts of “ignorant schoolmaster” (Rancière, in The ignorant schoolmaster five lessons in intellectual emancipation, Stanford University Press, Stanford, 1991 ), “learning contexts” (Edwards, in Rethinking contexts for learning and teaching, Routledge, Oxon and New York, 2009a , b ), and “experience” (Larrosa, in Revista Brasileira de Educação, 19:20–28, 2002 ). (shrink)
Normal 0 21 false false false MicrosoftInternetExplorer4 O presente artigo analisa a passagem da hermenêutica metodológica à experiência hermenêutica como crítica e fundamento do saber filosófico. Inicialmente, apresenta a crítica da hermenêutica à absolutizaçáo da lógica matemática como estrutura da pesquisa e produçáo de sentido na filosofia. A lógica matemática sedimenta a dinâmica da vida do homem por náo estar aberta às contingências da existência, porém a vida do homem náo se compreende sob a forma da lógica matemática. Posteriormente, demonstra (...) que compreender a dinâmica da vida do sujeito pressupõe uma hermenêutica filosófica, que interprete o verdadeiro sentido do humano. Essa compreensáo hermenêutico-filosófica se estabelece mediante uma inter-relaçáo entre o sujeito e o algo a ser interpretado. Por fim, defende que a condiçáo de possibilidade dessa inter-relaçáo é a experiência hermenêutica, o que implica uma abertura ao que esse algo tem a dizer ao sujeito, tornando-se, assim, o ponto de partida da compreensáo e fundamentaçáo do saber crítico-reflexivo. (shrink)
In this paper we show the embedding of Hybrid Probabilistic Logic Programs into the rather general framework of Residuated Logic Programs, where the main results of (definite) logic programming are validly extrapolated, namely the extension of the immediate consequences operator of van Emden and Kowalski. The importance of this result is that for the first time a framework encompassing several quite distinct logic programming semantics is described, namely Generalized Annotated Logic Programs, Fuzzy Logic Programming, Hybrid Probabilistic Logic Programs, and Possibilistic (...) Logic Programming. Moreover, the embedding provides a more general semantical structure paving the way for defining paraconsistent probabilistic reasoning with a logic programming semantics. (shrink)
This study attempts to identify differences in the perceptions of top management (defined as CEOs, directors, and presidents) and employees (defined as middle and supervisory management) regarding (a) the effects of dependent care responsibilities on job performance, and (b) the extent of a firm's responsibility in providing support for those faced with caring needs concerning eldercare, childcare, substance abuse, and mental/physical handicaps.The results indicate that these two groups have significantly different perceptions of the effect of dependent care responsibilities on job (...) performance, and on the firm's responsibility in providing support for three types of dependent care. (shrink)
No presente trabalho buscou-se realizar uma pesquisa a respeito de algumas características elementares do humanismo na tradição marxista - particularmente reveladas por Marx nas suas obras de juventude - e bem assim procurou-se efetuar um levantamento da crítica que lhe tem sido oposta por autores comprometidos com uma visão antropológica cristã.
Há uma espécie de drama de consciência no interior do pensamento iluminista em relaçáo à Revoluçáo Francesa: de um lado, aceita, de bom grado, fazer da queda do Antigo Regime um de seus mais belos e significativos frutos; de outro, recusa, por vezes enojado, os meios violentos utilizados para tanto e náo aceita, ou custa a aceitar, filiaçáo ideológica com eles. Esta violência “excessiva” seria exclusivamente obra da massa, segundo o elitismo iluminista. O percurso realizado neste artigo procura explicitar, no (...) contexto da Revoluçáo Francesa em geral e do pensamento e da açáo de Saint-Just em específico, a relaçáo entre pensamento e açáo revolucionária, de modo que se possa identificar o potencial de violência presente no próprio ideal que atravessa o pensamento revolucionário francês, sintetizado pela idéia de Virtude, e que culminará na política do Terror. (shrink)
About the Republic is the only commentary left by Averroes, the Commentator, so called on behalf of his commentaries on Aristotle’s work. Although the original in Arabic is lost, there is a medieval version in Hebrew and two later translations in Latin from the Hebrew version. Averroes’ Commentary on the ‘Republic’ – divided in three Books – can be considered an original work as only 1/3 of it corresponds to the platonic treatise. Averroes presents in it aristotelic concepts drawn from (...) the Nicomachean Ethics and also several notions from Alfarabi’s political works. He also presents his own thoughts and offers criticisms of his own society. KEY WORDS – Plato’s Republic; a commentary or an original work? Ethics. Politics. Cardinal virtues. Ideal city. Education. (shrink)
Basically the anti-infallibility position of the eighteenth and twentieth centuries is fivefold: that infallibility, especially papal, is unfounded, unverified, undesirable, unnecessary, and impossible.
As a human rights activist and lawyer who believes in the mutuality of theology and legal philosophy, the author argues that Catholic philosophy can catalyse the process of global reconciliation. This is because the Church has the ability to recognise the double burden faced by Christians around the world (especially in Asia) who are struggling to disassociate themselves from an “alien” and “western” mantle, while still trying to live and preach the Christian doctrine and find common ground with other religions (...) and cultures. Catholic philosophy, therefore, must engage itself and others meaningfully at an inter-religious, interdisciplinary, and multi-cultural level. We now live at a time in Church history when the gap in education between the clergy and the laity has been dramaticallynarrowed; as a result, it is imperative—especially now—to allow competing voices within the Church to be heard so that a healthy tension might arise andthrive. This will help to increase the transparency of discourse within the Catholic community itself, while also providing adaptive tools for dialogue with other,non-Catholic communities. (shrink)
This paper develops two main themes: in the first place, one tries to make clear how, from the point of view of our contemporary philosophical ideas, a retrospective interpretation of Greek sceptic pyrrhonism allows us to read it, not only as a questioning of the theses and arguments of dogmatic philosophy, but as a questioning, too, of the very legitimity of the traditional plilosophical problems and philosophical language. But the second part of the text is a "positive" one, which proceeds (...) to an analysis of the relation between a phenomenic and a dogmatic level of language and, then, explatrins how the idea of a philosophical investigation of problems formulated in the phenomenic level is plainly compatible with (neo)pyrrhonic philosophy. And a discussion is undertaken of the relation between problems formulated in one and another levels. (shrink)
Esse trabalho apresenta uma reconstruçáo das referidas Deduçáo e Refutaçáo como argumentos contra uma forma empirista de ceticismo questionando a validade de juízos empíricos acerca de objetos externos na chamada acepçáo empírica, náo-transcendental do termo.
Resenha do livro de: ALVES NETO, Rodrigo Ribeiro. Alienações do mundo: uma interpretaçáo da obra de Hannah Arendt . Rio de Janeiro/Sáo Paulo: Editora PUC-Rio/Edições Loyola, 2009, 216 p.
No livro “As vozes da igualdade” (“Las voces de la igualdad. Bases para una teoría crítica de la justicia”. Ed. Proteus, 2010. 288 páginas – Ainda sem tradução para o português), o Prof. Dr. Gustavo Pereira, da Universidad de la Republica, Uruguai, procura analisar estas questões investigando as principais teorias de justiça contemporâneas que pretendem respondê-las e apresenta sua proposta de um caminho para a fundamentação de uma teoria crítica de justiça renovada, mais abrangente, que ofereça meios mais adequados (...) e eficazes para promover a justiça social e desenvolver as capacidades humanas necessárias para a construção de uma “eticidade democrática”. (shrink)
In his interesting, original and well organized paper "O Ceticismo Pirrônico e os Problemas Filosóficos" Oswaldo Porchat Pereira reinterprets ancient Pyrrhonism and claims a new domain for the philosophical activity, namely the "phenomenic" one. The present text examines this doctrine in order to unravel not only the similarities between the Porchatian approach and contemporary pragmatism, but also some of the main difficulties connected with that reinterpretarion of Pyrrhonism.
Abstract The aim of this paper is to critically review several interpretations of Kantian sensible intuition. The first interpretation is the recent construal of Kantian sensible intuition as a mental analogue of a direct referential term. The second is the old, widespread assumption that Kantian intuitions do not refer to mind-independent entities, such as bodies and their physical properties, unless they are brought under categories. The third is the assumption that, by referring to mind-independent entities, sensible intuitions represent objectively in (...) the sense that they represent in a relative, perspective-independent manner. The fourth is the construal of Kantian sensible intuitions as non-conceptual content. In this paper, I support the alternative view that Kantian sensible representation is to be seen as iconic de re presentation of objects without representational content. Content Type Journal Article Pages 1-22 DOI 10.1007/s11098-011-9851-x Authors Roberto Horácio de Sá Pereira, The Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil Journal Philosophical Studies Online ISSN 1573-0883 Print ISSN 0031-8116. (shrink)
The aim of this paper is to critically review several interpretations of Kantian sensible intuition. The first interpretation is the recent construal of Kantian sensible intuition as a mental analogue of a direct referential term. The second is the old, widespread assumption that Kantian intuitions do not refer to mind-independent entities, such as bodies and their physical properties, unless they are brought under categories. The third is the assumption that, by referring to mind-independent entities, sensible intuitions represent objectively in the (...) sense that they represent in a relative, perspective-independent manner. The fourth is the construal of Kantian sensible intuitions as non-conceptual content. In this paper, I support the alternative view that Kantian sensible representation is to be seen as iconic de re presentation of objects without representational content. (shrink)
The purpose of the present study is to examine the attitudes of Portuguese chartered accountants with respect to questions of ethical nature that can arise in their professional activity. Respondents were asked to respond to the Ethics Position Questionnaire developed by Forsyth (Journal of Personality and Social Psychology 39(1), 175–184, 1980), in order to determine their idealism and relativism levels. Subsequently, they answered questions about five scenarios related to accounting practices, with the objective of measuring their ethical judgments. Based on (...) the idealism and relativism levels of our respondents, they were classified into one of four groups, representing different ethical ideologies (absolutism, exceptionism, subjectivism, and situationism). The results indicated that age was the major determinant of relativism. Contrary to previous research, older respondents revealed themselves significantly more relativistic than younger ones. Gender seems to be the most important determinant of ethical judgments; against expectations, men evidenced significantly stricter judgments than women in two of the five scenarios. Findings also indicated that respondents’ ethical judgments did not differ significantly based on their ethical ideology, supporting the idea that ethical ideology is not an important determinant of ethical judgments. (shrink)
Everett (2005) has claimed that the grammar of Piraha˜ is exceptional in displaying ‘inexplicable gaps’, that these gaps follow from a cultural principle restricting communication to ‘immediate experience’, and that this principle has ‘severe’ consequences for work on universal grammar. We argue against each of these claims. Relying on the available documentation and descriptions of the language, especially the rich material in Everett 1986, 1987b, we argue that many of the exceptional grammatical ‘gaps’ supposedly characteristic of Piraha˜ are misanalyzed by (...) Everett (2005) and are neither gaps nor exceptional among the world’s languages. We find no evidence, for example, that Piraha˜ lacks embedded clauses, and in fact find strong syntactic and semantic evidence in favor of their existence in Piraha˜. Likewise, we find no evidence that Piraha˜ lacks quantifiers, as claimed by Everett (2005). Furthermore, most of the actual properties of the Piraha˜ constructions discussed by Everett (for example, the ban on prenominal possessor recursion and the behavior of WH-constructions) are familiar from languages whose speakers lack the cultural restrictions attributed to the Piraha˜. Finally, following mostly Gonc¸alves (1993, 2000, 2001), we also question some of the empirical claims about Piraha˜ culture advanced by Everett in primary support of the ‘immediate experience’ restriction. We conclude that there is no evidence from Piraha˜ for the particular causal relation between culture and grammatical structure suggested by Everett. (shrink)
In this essay we advance the view that analytical epistemology and artificial intelligence are complementary disciplines. Both fields study epistemic relations, but whereas artificial intelligence approaches this subject from the perspective of understanding formal and computational properties of frameworks purporting to model some epistemic relation or other, traditional epistemology approaches the subject from the perspective of understanding the properties of epistemic relations in terms of their conceptual properties. We argue that these two practices should not be conducted in isolation. We (...) illustrate this point by discussing how to represent a class of inference forms found in standard inferential statistics. This class of inference forms is interesting because its members share two properties that are common to epistemic relations, namely defeasibility and paraconsistency. Our modeling of standard inferential statistical arguments exploits results from both logical artificial intelligence and analytical epistemology. We remark how our approach to this modeling problem may be generalized to an interdisciplinary approach to the study of epistemic relation. (shrink)
Ronan Reilly's connectionist simulation both strengthens and advances the theoretical model presented in my 1991 target article, “Language, Tools, and Brain: The Ontogeny and Phylogeny of Hierarchically Organized Sequential Behavior.” Reilly has tested the whole ontogenetic model with a single simulation study explicitly planned for this purpose. His methodology has established that the various components of the theoretical model imply and are compatible with one another. It has also indicated how learning can actualize a pre-established ontogenetic sequence of combining (...) lingusitic symbols and objects. His simulation suggests that the acquisition of linguistic speech may be facilitated by experience with object manipulation, but not vice versa. This hypothesis can and should be empirically tested through research on behavioral development in the two domains. Finally, Reilly has simulated brain architecture, as well as neural learning. His simulation therefore shows how the development of language and object manipulation can result from an interaction between preprogrammed neural architecture (analogous to network architecture) and experience (analogous to the network's training cycles). (shrink)
In her Behavioral and Brain Sciences target article, Greenfield (1991) proposed that early in a child's development Broca's area may serve the dual function of coordinating object assembly and organizing the production of structured utterances. As development progresses, the upper and lower regions of Broca's area become increasingly specialized for motor coordination and speech, respectively. This commentary presents a connectionist simulation of aspects of this proposal. The results of the simulation confirm the main thrust of Greenfield's argument and suggest that (...) an important impetus for the developmental differentiation in Broca's area may be the increasing complexity of the computational demands made upon it. (shrink)
In this study I propose an epistemological discussion of multiple spatio-temporal scales in neuroscience. Are such scales merely convenient levels of description of structure and function, or do they correspond to irreducible levels of brain organization? What criteria should we employ in order to reduce one level to another, or to identify levels that are not reducible to others? Should we think of these criteria as based on empirical and/or theoretical reasons? Beginning with an empirical criterion â the necessity of (...) different experimental methodologies for the measurement of different phenomena in the same system â I summarize spatial and temporal scales currently used in neuroscience and discuss the possibility of a more general theoretical criterion. I conclude that multiscaling should be recognized as a central concept in the epistemology of neuroscience. (shrink)
The NMDA receptor (NMDAR) channel has been proposed to function as a coincidence-detection mechanism for afferent and reentrant signals, supporting conscious perception, learning, and memory formation. In this paper we discuss the genesis of distorted perceptual states induced by subanesthetic doses of ketamine, a well-known NMDA antagonist. NMDAR blockage has been suggested to perturb perceptual processing in sensory cortex, and also to decrease GABAergic inhibition in limbic areas (leading to an increase in dopamine excitability). We propose that perceptual distortions and (...) hallucinations induced by ketamine blocking of NMDARs are generated by alternative signaling pathways, which include increase of excitability in frontal areas, and glutamate binding to AMPA in sensory cortex prompting Ca++ entry through voltage-dependent calcium channels (VDCCs). This mechanism supports the thesis that glutamate binding to AMPA and NMDARs at sensory cortex mediates most normal perception, while binding to AMPA and activating VDCCs mediates some types of altered perceptual states. We suggest that Ca++ metabolic activity in neurons at associative and sensory cortices is an important factor in the generation of both kinds of perceptual consciousness. (shrink)
