Dharmendra S. Modha

My Work and Thoughts.

Archives for 2009

Vitaly Feldman

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Vitaly Feldman is a theoretical computer scientist at IBM Almaden. Today, we had a great intellectual pleasure of listening to a wonderful and stimulating white-board talk from Vitaly on his upcoming paper in Neural Computation. 

Title:
Experience-Induced Neural Circuits That Achieve High Capacity

Abstract:
Over a lifetime cortex performs a vast number of di®erent cognitive actions, mostly dependent on past experience. Previously it has not been known how such capabilities can be reconciled, even in principle, with the known resource constraints on cortex, such as low connectivity and low average synaptic strength. Here we describe neural circuits and associated algorithms that respect the brain’s most basic resource constraints and support the execution of high numbers of cognitive actions when presented with natural inputs. Our circuits simultaneously support a suite of four basic kinds of task that each require some circuit modi¯cation: hierarchical memory formation, pairwise association, supervised memorization, and inductive learning of threshold functions. The capacity of our circuits is established via experiments in which sequences of several thousands of such actions are simulated by computer and the circuits created tested for subsequent e±cacy. Our underlying theory is apparently the only biologically plausible systems-level theory of learning and memory in cortex for which such a demonstration has been performed, and we argue that no general theory of information processing in the brain can be considered viable without such a demonstration.

Connectomics aims to map the atlas of the brain

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This week’s Economist carried a story on the wiring diagram of the brain.  It is worth reading.

"The result of all this effort, it is hoped, will be precise circuit-diagrams of brains. The first brains to be mapped will probably have belonged to mice. Besides being cheap and disposable, a mouse brain weighs half a gram and packs a mere 16m neurons. Human brains (1.4kg and 100 billion neurons) will come later, when all the wrinkles have been ironed out in rodents, and proper methods devised to analyse the results. But come they will. And when they do, the most complicated object in the known universe will begin to give up the secrets of how it really works."

A Proposal for a Coordinated Effort for the Determination of Brainwide Neuroanatomical Connectivity in Model Organisms at a Mesoscopic Scale

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A very interesting proposal was published in PLoS computational Biology.

Abstract:

In this era of complete genomes, our knowledge of neuroanatomical circuitry remains surprisingly sparse. Such knowledge is critical, however, for both basic and clinical research into brain function. Here we advocate for a concerted effort to fill this gap, through systematic, experimental mapping of neural circuits at a mesoscopic scale of resolution suitable for comprehensive, brainwide coverage, using injections of tracers or viral vectors. We detail the scientific and medical rationale and briefly review existing knowledge and experimental techniques. We define a set of desiderata, including brainwide coverage; validated and extensible experimental techniques suitable for standardization and automation; centralized, open-access data repository; compatibility with existing resources; and tractability with current informatics technology. We discuss a hypothetical but tractable plan for mouse, additional efforts for the macaque, and technique development for human. We estimate that the mouse connectivity project could be completed within five years with a comparatively modest budget.

IEEE’s 125th Anniversary

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IEEE is a great organization, and I had great honor and privilege to help kick-off IEEE’s 125th Anniversary celebration in New York on March 10, 2009. I had the opportunity to meet with countless IEEE dignitaries including IEEE’s outgoing President & CEO Dr. Lewis M. Terman.

Other speakers included:

Miguel Nicolelis, professor and co-director, Center for Neuroengineering, Duke University Medical Center

Roy Want, senior principal engineer, Intel Corporation

Krishna Palem, professor, George Brown School of Engineering, Rice University

Katie Hall, chief technology officer, WiTricity

Rangachar Kasturi, professor, University of South Florida

K.J. Ray Liu, professor, University of Maryland, College Park

The panel was moderated by Steve Lohr of New York Times and by Susan Hassler who is Editor-in-chief of IEEE Spectrum.

Here is IEEE’s newswire and related story in Scientific American.