Weak pairwise correlations imply strongly correlated network states in a neural population

Biological networks have so many possible states that exhaustive sampling is impossible. Successful analysis thus depends on simplifying hypotheses, but experiments on many systems hint that complicated, higher order interactions among large groups of elements play an important role. In the vertebrate retina, we show that weak correlations between pairs of neurons coexist with strongly collective behavior in the responses of ten or more neurons. Surprisingly, we find that this collective behavior is described quantitatively by models that capture the observed pairwise correlations but assume no higher order interactions. These maximum entropy models are equivalent to Ising models, and predict that larger networks are completely dominated by correlation effects. This suggests that the neural code has associative or error-correcting properties, and we provide preliminary evidence for such behavior. As a first test for the generality of these ideas, we show that similar results are obtained from networks of cultured cortical neurons.Comment: Full account of work presented at the conference on Computational and Systems Neuroscience (COSYNE), 17-20 March 2005, in Salt Lake City, Utah (http://cosyne.org

Hanging Out, Messing Around, and Geeking Out

The tenth-anniversary edition of a foundational text in digital media and learning, examining new media practices that range from podcasting to online romantic breakups. Hanging Out, Messing Around, and Geeking Out, first published in 2009, has become a foundational text in the field of digital media and learning. Reporting on an ambitious three-year ethnographic investigation into how young people live and learn with new media in varied settings—at home, in after-school programs, and in online spaces—it presents a flexible and useful framework for understanding the ways that young people engage with and through online platforms: hanging out, messing around, and geeking out, otherwise known as HOMAGO. Integrating twenty-three case studies—which include Harry Potter podcasting, video-game playing, music sharing, and online romantic breakups—in a unique collaborative authorship style, Hanging Out, Messing Around, and Geeking Out combines in-depth descriptions of specific group dynamics with conceptual analysis. Since its original publication, digital learning labs in libraries and museums around the country have been designed around the HOMAGO mode and educators have created HOMAGO guidebooks and toolkits. This tenth-anniversary edition features a new introduction by Mizuko Ito and Heather Horst that discusses how digital youth culture evolved in the intervening decade, and looks at how HOMAGO has been put into practice. This book was written as a collaborative effort by members of the Digital Youth Project, a three-year research effort funded by the John D. and Catherine T. MacArthur Foundation and conducted at the University of California, Berkeley, and the University of Southern California

Spontaneous Local Gamma Oscillation Selectively Enhances Neural Network Responsiveness

Synchronized oscillation is very commonly observed in many neuronal systems and might play an important role in the response properties of the system. We have studied how the spontaneous oscillatory activity affects the responsiveness of a neuronal network, using a neural network model of the visual cortex built from Hodgkin-Huxley type excitatory (E-) and inhibitory (I-) neurons. When the isotropic local E-I and I-E synaptic connections were sufficiently strong, the network commonly generated gamma frequency oscillatory firing patterns in response to random feed-forward (FF) input spikes. This spontaneous oscillatory network activity injects a periodic local current that could amplify a weak synaptic input and enhance the network's responsiveness. When E-E connections were added, we found that the strength of oscillation can be modulated by varying the FF input strength without any changes in single neuron properties or interneuron connectivity. The response modulation is proportional to the oscillation strength, which leads to self-regulation such that the cortical network selectively amplifies various FF inputs according to its strength, without requiring any adaptation mechanism. We show that this selective cortical amplification is controlled by E-E cell interactions. We also found that this response amplification is spatially localized, which suggests that the responsiveness modulation may also be spatially selective. This suggests a generalized mechanism by which neural oscillatory activity can enhance the selectivity of a neural network to FF inputs

Share wars: Sharing, theft, and the everyday production of Web 2.0 on DeviantArt

The development of Web 2.0 led to celebratory accounts about its potential to unleash human creativity. A consensus emerged that described Web 2.0 creative production as universal, democratic, communal, non-commercial, and thoroughly revolutionary. This consensus viewed young, web-savvy media makers as Web 2.0 creativity’s avant-garde: a new generation of producers, born digital, who had upended Romantic notions of creativity, authorship, ownership and related cultural practices. In this paper I draw from a multi-year ethnographic study of young creators’ use of the web from 2007 through 2010 and examine the practice and rhetoric of theft and sharing on DeviantArt, a self-described social network and community of artists. I argue that rather than overturning traditional notions of creativity, participating in DeviantArt helped young creators reaffirm traditional notions of creativity tied to the moral rights of authors to control the distribution of their work. I also demonstrate how these young media makers in turn shaped Web 2.0 ideology and technologies in practice. Seemingly well-established features for “sharing” content were actually uneasy compromises that supported multiple interpretations rather than epitomize the new era of creativity promised by the creativity consensus. These compromises reproduced Web 2.0 in everyday practice

Copy and Paste Literacy: Literacy Practices in the Production of a MySpace Profile

In this paper, I argue that MySpace is an informal learning environment that fosters the development of new literacies. This analysis is based on a model that tries to reconcile social and technical perspectives on literacy. The expressive power found in the creation of a MySpace profile concerns a technically simple but socially complex practice: the copying and pasting of code as a way to appropriate and reuse other people’s media products. However, the importance of copying and pasting code does not easily fit in the common conventions of reading and writing, consumption and production. By integrating theories of appropriation and reuse of media with theories of literacy, a new way of thinking about this practice emerges, seeing “participation ” and “remix ” as important concepts to describe the social and technical aspects of new media literacy

Navigating multi-disciplinary spaces

We propose a roundtable discussion to report results of the first UC Information Studies Lab workshop and discuss implications with a broader audience. The workshop is conceived and organized by doctoral students for doctoral students from the three "iSchools" in the University of California system: UC Berkeley's School of Information, UC Irvine's Department of Informatics, and UCLA's Department of Information Studies in the Graduate School of Education and Information Studies. The UC Information Studies Lab will host the doctoral workshop on January 22-23, 2009. This proposal includes details about the objectives of the workshop, motivation, work-to-date, and intended audience. We hope to report and discuss the planning, results and experiences from the workshop at the iConference

Unexpected Collaborations: Kids' Appropriation of GarageBand as a Group Creative Tool

In this paper we present a case study of kids' appropriation of GarageBand digital music software to create an informal, ad hoc collaborative process. We argue that elements of the socio-spatial context of use combined with the software and the audio mode created a "safe" space for collaboration and a powerful mode for informal creative exchange and feedback. We conclude with suggestions for future study and questions to consider for the design of systems to support kids' creative collaboration