L’impossible réalité brute

Élodie Perreau — Au cours de vos recherches, vous avez exploré plusieurs aspects de la création audiovisuelle et vous avez toujours tenu compte de la dimension sociale de la production des images en posant les questions du contexte d’usage et de la position du spectateur. Vous vous êtes penché sur l’analyse de différentes sortes de « textes » : les films ethnographiques, le western, le journalisme de télévision, ou encore les grandes cérémonies télévisuelles. J’aimerais connaître la façon don..

From Media Events to Expressive Events : An Interview with Daniel Dayan

In this interview, Professor Daniel Dayan provides a philosophical and theoretical reflection on the development of media event theory and its influence in media and communication studies since 1990s. He reveals the main theoretical premises and inspirations behind the theory and provides a thoughtful reflection of the historical situation in which the theory was developed. The latter part of the interview observes the present day terrorist violence in the framework of media event theory.Peer reviewe

Pour une critique des médias

Dans un entretien avec Béatrice Fleury et Jacques Walter, le chercheur Daniel Dayan explique son étonnement devant certains aspects du discours sur le Proche-Orient proposés par les médias français et européens, au moment de la seconde Intifada. Ce qui l’a amené à passer de l’indignation à la curiosité, à la rédaction d’un journal ensuite, puis à la transformation de son agenda de recherches, de façon à essayer de comprendre les phénomènes qu’il observait. Aujourd’hui, le sommet de la crise chroniquée dans le journal du chercheur est passé. Il est alors plus facile de rendre compte d’une ferveur qui a mené à bien des excès. Tout chercheur prend des risques en s’écartant des questions paradigmatiques posées par sa discipline pour en poser d’autres, en réponse à une situation historique. Une telle démarche est-elle néanmoins légitime ?In an interview with Béatrice Fleury and Jacques Walter, media scholar Daniel Dayan tells about his astonishment concerning many aspects of the coverage of the Palestinian-Israeli conflict by French media during the period that has been called the « second Intifada ». Moving from amazement, to indignation, and to curiosity, Dayan explains how he progressively transformed his research agenda in order to describe and understand the striking phenomena he was witnessing. Today, the crisis is perhaps over. This makes it easier to look back at what took place during years of almost religious enthusiasm. A scholar is always at risk when he or she tries to propose analytic tools to address a current historical situation. Sticking to the paradigmatic questions dictated by a field is certainly much more comfortable. But then, what is the point of expertise 

Mentir par les médias

Cet article prend appui sur le trouble que suscitent des situations de mensonge possible, probable ou avéré, afin d’analyser les finalités (parfois triviales, parfois respectables) du mensonge par les médias et quelques-unes des techniques mises en jeu. Trois explorations sont proposées. La première porte sur ce que l’on pourrait appeler le « casting » du mensonge par les médias. Il s’agit de savoir qui ment et s’il existe un rôle dévolu à ceux à qui l’on ment. La seconde montre combien il est aisé de mentir à l’aide d’images censées servir de preuves et tente d’identifier, au sein même des discours mensongers, des fils rouges permettant de remonter jusqu’à la vérité. La troisième questionne le relativisme désinvolte d’un certain nombre de praticiens des médias dont le discours « interprétationniste » tend à dissoudre les notions mêmes de mensonge et de vérité. L’accusation de mensonge doit-elle, tout comme l’exigence de vérité qui lui fait pendant, être rangée au catalogue des superstitions naïves 

Long Memory Lifetimes Require Complex Synapses and Limited Sparseness

Theoretical studies have shown that memories last longer if the neural representations are sparse, that is, when each neuron is selective for a small fraction of the events creating the memories. Sparseness reduces both the interference between stored memories and the number of synaptic modifications which are necessary for memory storage. Paradoxically, in cortical areas like the inferotemporal cortex, where presumably memory lifetimes are longer than in the medial temporal lobe, neural representations are less sparse. We resolve this paradox by analyzing the effects of sparseness on complex models of synaptic dynamics in which there are metaplastic states with different degrees of plasticity. For these models, memory retention in a large number of synapses across multiple neurons is significantly more efficient in case of many metaplastic states, that is, for an elevated degree of complexity. In other words, larger brain regions allow to retain memories for significantly longer times only if the synaptic complexity increases with the total number of synapses. However, the initial memory trace, the one experienced immediately after memory storage, becomes weaker both when the number of metaplastic states increases and when the neural representations become sparser. Such a memory trace must be above a given threshold in order to permit every single neuron to retrieve the information stored in its synapses. As a consequence, if the initial memory trace is reduced because of the increased synaptic complexity, then the neural representations must be less sparse. We conclude that long memory lifetimes allowed by a larger number of synapses require more complex synapses, and hence, less sparse representations, which is what is observed in the brain

Internal Representation of Task Rules by Recurrent Dynamics: The Importance of the Diversity of Neural Responses

Neural activity of behaving animals, especially in the prefrontal cortex, is highly heterogeneous, with selective responses to diverse aspects of the executed task. We propose a general model of recurrent neural networks that perform complex rule-based tasks, and we show that the diversity of neuronal responses plays a fundamental role when the behavioral responses are context-dependent. Specifically, we found that when the inner mental states encoding the task rules are represented by stable patterns of neural activity (attractors of the neural dynamics), the neurons must be selective for combinations of sensory stimuli and inner mental states. Such mixed selectivity is easily obtained by neurons that connect with random synaptic strengths both to the recurrent network and to neurons encoding sensory inputs. The number of randomly connected neurons needed to solve a task is on average only three times as large as the number of neurons needed in a network designed ad hoc. Moreover, the number of needed neurons grows only linearly with the number of task-relevant events and mental states, provided that each neuron responds to a large proportion of events (dense/distributed coding). A biologically realistic implementation of the model captures several aspects of the activity recorded from monkeys performing context-dependent tasks. Our findings explain the importance of the diversity of neural responses and provide us with simple and general principles for designing attractor neural networks that perform complex computation