lunes, 31 de mayo de 2010

The end of vitalism

The end of vitalism

Arthur Caplan

Professor of bioethics, University of Pennsylvania

Venter and his colleagues have shown that the material world can be manipulated to produce what we recognize as life. In doing so they bring to an end a debate about the nature of life that has lasted thousands of years. Their
achievement undermines a fundamental belief about the nature of life that is likely to prove as momentous to our view of ourselves and our place in the Universe as the discoveries of Galileo, Copernicus, Darwin and Einstein.

More than 100 years ago, the French philosopher Henri-Louis Bergson claimed that
life could never be explained simply mechanistically. Nor could it be artificially created by synthesizing molecules. There was, he argued, an “élan vital” — a vital force that was the ineffable current distinguishing the living from the inorganic. No manipulations of the inorganic would permit the creation of any living thing.

This ‘vitalist’ view has come in many forms over the centuries. Galen wrote of the ‘vital spirit’ in the second century; Louis Pasteur in 1862 looked to ‘vital action’ to explain how life exists; and the biologist Hans Driesch posited an ‘entelechy’ or essential force as a requisite for life as recently as 1894. The molecular-biology
revolution notwithstanding, science has continued to struggle with the reducibility of life to the material.

Meanwhile, Christianity, Islam and Judaism, among other religions, have maintained that a soul constitutes the explanatory essence of at least human life. All of these deeply entrenched metaphysical views are cast into doubt by the demonstration
that life can be created from non-living parts,albeit those harvested from a cell. Venter’s achievement would seem to extinguish the argument that life requires a special force or power to exist. In my view, this makes it one of the most important scientific achievements in the history of mankind.

source: NATURE|Vol 465|27 May 2010

viernes, 28 de mayo de 2010

"El cerebro está hecho para historias más que para enciclopedias o información digital"

"Lo importante es que se sigan contando historias. El cerebro humano está hecho para historias más que para enciclopedias o información digital", ha señalado hoy el escritor noruego Jostein Gaarder a los internautas en la inauguración de la cobertura especial que ha preparado Babelia en su blog Papeles Perdidos , con motivo de la 69ª Feria del Libro de Madrid (del 28 de mayo al 13 de junio). Aunque el autor de El mundo de Sofía (Siruela) le ha restado importancia al dilema del soporte, da igual si se lee en papel o en pantalla, lo primordial es que se siga acudiendo a la creatividad y a la narrativa. El Chat de Gaarder se incluye dentro de la programación propia con que Babelia cubre la cita literaria en el parque del Retiro en el que participarán más de 30 escritores de todo el mundo como Chuck Palahniuk, Javier Marías, Asa Larson, Laura Restrepo, Jorge Volpi y John Banville.

The Nature of Abstract Orthographic Codes: Evidence from Masked Priming and Magnetoencephalography

Liina Pylkkänen1,2*, Kana Okano3

1 Department of Linguistics, New York University, New York, New York, United States of America, 2 Department of Psychology, New York University, New York, New York, United States of America, 3 Department of Psychology, Tufts University, Medford, Massachusetts, United States of America

What kind of mental objects are letters? Research on letter perception has mainly focussed on the visual properties of letters, showing that orthographic representations are abstract and size/shape invariant. But given that letters are, by definition, mappings between symbols and sounds, what is the role of sound in orthographic representation? We present two experiments suggesting that letters are fundamentally sound-based representations. To examine the role of sound in orthographic representation, we took advantage of the multiple scripts of Japanese. We show two types of evidence that if a Japanese word is presented in a script it never appears in, this presentation immediately activates the (“actual”) visual word form of that lexical item. First, equal amounts of masked repetition priming are observed for full repetition and when the prime appears in an atypical script. Second, visual word form frequency affects neuromagnetic measures already at 100–130 ms whether the word is presented in its conventional script or in a script it never otherwise appears in. This suggests that Japanese orthographic codes are not only shape-invariant, but also script invariant. The finding that two characters belonging to different writing systems can activate the same form representation suggests that sound identity is what determines orthographic identity: as long as two symbols express the same sound, our minds represent them as part of the same character/letter.

viernes, 21 de mayo de 2010

Musical genres: beating to the rhythms of different drums

Online music databases have increased significantly as a consequence of the rapid growth of the Internet and digital audio, requiring the development of faster and more efficient tools for music content analysis. Musical genres are widely used to organize music collections. In this paper, the problem of automatic single and multi-label music genre classification is addressed by exploring rhythm-based features obtained from a respective complex network representation. A Markov model is built in order to analyse the temporal sequence of rhythmic notation events. Feature analysis is performed by using two multivariate statistical approaches: principal components analysis (unsupervised) and linear discriminant analysis (supervised). Similarly, two classifiers are applied in order to identify the category of rhythms: parametric Bayesian classifier under the Gaussian hypothesis (supervised) and agglomerative hierarchical clustering (unsupervised). Qualitative results obtained by using the kappa coefficient and the obtained clusters corroborated the effectiveness of the proposed method.

Introduction and background. The constant increase in online music databases has required the development of reliable and fast tools for automatic music content analysis. Widely used to organize music collections, music genres are interesting descriptors, since they express common characteristics in pieces of music. However, there is not a definitive and clear taxonomy of music genres. The problem of automatically classifying them is a nontrivial task because the same music piece can be associated with more than one genre. There are many studies about automatic genre classification, but only a few concerning multi-genre classification, which is particularly appropriate in this scenario.

Main results. We analysed similar and different characteristics of rhythms from four music genres in terms of the occurrence of sequences of events represented by rhythmic notation. We found that the rhythms are very complex, and that many features are required to separate them. In addition, the multi-genre classification allowed a generalization of the genre taxonomy, since new sub-genres were originated from the originals.

Wider implications. This study provided strong evidence that music genres are surprisingly complex and contain many redundancies. It is often difficult even for experts to distinguish between genres. We focused only on rhythmic analysis, which offered a substantial reduction of computational cost through a more compact representation. The viability of the proposed methodology indicates that a deeper analysis of the rhythms can be performed to enhance the effectiveness of the method.

martes, 18 de mayo de 2010

Adult Neurogenesis Conference

This meeting will be chaired by Gerd Kempermann, Center for Regenerative Therapies Dresden.

Adult neurogenesis is a particular and extraordinary example of plasticity in the adult and aging brain. "Plasticity" in general can be defined as the reciprocal relationship between structure and function. But how exactly are structure and function linked through new neurons? In contrast to synaptic plasticity which adds new connections, adult neurogenesis provides new knots in the network which in turn can make additional new connections. It thus seems that with adult neurogenesis a kind of plasticity can be achieved that is impossible with changing synapses alone. This conference brings together some of the very best researchers on adult neurogenesis to discuss structure and function in adult neurogenesis.