Dharmendra S. Modha

My Work and Thoughts.

Bilateral visual field maps in a patient with only one hemisphere

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A paper in PNAS by Lars Muckli, Marcus J. Naumerd and Wolf Singer provides remarkable evidence of plasticity in the brain.

Abstract: In mammals smooth retinotopic maps of the visual field are formed along the visual processing pathway whereby the left visual field is represented in the right hemisphere and vice versa. The reorganization of retinotopic maps in the lateral geniculate nucleus (LGN) of the thalamus and early visual areas (V1–V3) is studied in a patient who was born with only one cerebral hemisphere. Before the seventh week of embryonic gestation, the development of the patient’s right cerebral hemisphere terminated. Despite the complete loss of her right hemisphere (di- and telencephalon) at birth, the patient’s remaining hemisphere has not only developed maps of the contralateral (right) visual hemifield but, surprisingly, also maps of the ipsilateral (left) visual hemifield. Retinal ganglion-cells changed their predetermined crossing pattern in the optic chiasm and grew to the ipsilateral LGN. In the visual cortex, islands of ipsilateral visual field representations were located along the representations of the vertical meridian. In V1, smooth and continuous maps from contra- and ipsilateral hemifield overlap each other, whereas in ventral V2 and V3 ipsilateral quarter field representations invaded small distinct cortical patches. This reveals a surprising flexibility of the self-organizing developmental mechanisms responsible for map formation.

SciFoo: A Conference Without an Agenda

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Over the weekend, I was invited at SciFoo Camp, where Foo = Friend’s of O’Reilly, organized by Google, Nature, and O’Reilly.

I had a chance to converse with Brian Arthur (PARC), Stewart Brand (Santa Fe), John Brockman (Edge), Phillip Campbell (Editor-in-chief, Nature), Walter Fontana (Harvard), Christof Koch (CalTech, Consciousness), Marvin Minsky (MIT, AI), Larry Page (Google), Ani Patel (Neurosciences Institute), George Smoot (Nobelist), Alfred Spector (Google, Director of Research), Dmitri Tymoczko (Priceton), Geoffrey West (President, Santa Fe), and Pete Worden (NASA).

Nikola Kasabov

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Today, I had the honor and pleasure of spending some time with Professor Nikola Kasabov.

Professor Nikola Kasabov is the Founding Director and the Chief Scientist of the Knowledge Engineering and Discovery Research Institute (KEDRI), Auckland (www.kedri.info/). He holds a Chair of Knowledge Engineering at the School of Computing and Mathematical Sciences at Auckland University of Technology. He is a Fellow of the Royal Society of New Zealand, Fellow of the New Zealand Computer Society and a Senior Member of IEEE. He is the President of the International Neural Network Society (INNS) and a Past President of the Asia Pacific Neural Network Assembly (APNNA). He is a member of several technical committees of the IEEE Computational Intelligence Society and of the IFIP AI TC12. Kasabov is Associate Editor of several international journals, that include Neural Networks, IEEE TrNN, IEEE TrFS, Information Science, J. Theoretical and Computational Nanosciences. He chairs a series of int. conferences ANNES/NCEI in New Zealand. Kasabov holds MSc and PhD from the Technical University of Sofia. His main research interests are in the areas of intelligent information systems, soft computing, neuro-computing, bioinformatics, brain study, speech and image processing, novel methods for data mining and knowledge discovery. He has published more than 400 publications that include 15 books, 120 journal papers, 60 book chapters, 32 patents and numerous conference papers. He has extensive academic experience at various academic and research organisations: University of Otago, New Zealand; University of Essex, UK; University of Trento, Italy; Technical University of Sofia, Bulgaria; University of California at Berkeley; RIKEN and KIT, Japan; TUniversity Kaiserslautern, Germany, and others. More information of Prof. Kasabov can be found on the KEDRI web site: http://www.kedri.info/

A Conceptual Cortical Surface Atlas

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Today, the journal PLoS ONE published a paper entitled “A Conceptual Cortical Surface Atlas” that I authored. The paper should be useful to neuro-anatomically-challenged lay people (“dummies”) seeking a bird’s eye view of cortical surface atlas. The key contribution is encapsulated in Figure S1. You can download the atlas in excel format here.

Abstract:

Volumetric, slice-based, 3-D atlases are invaluable tools for understanding complex cortical convolutions. We present a simple scheme to convert a slice-based atlas to a conceptual surface atlas that is easier to visualize and understand. The key idea is to unfold each slice into a one-dimensional vector, and concatenate a succession of these vectors – while maintaining as much spatial contiguity as possible – into a 2-D matrix. We illustrate our methodology using a coronal slice-based atlas of the Rhesus Monkey cortex. The conceptual surface-based atlases provide a useful complement to slice-based atlases for the purposes of indexing and browsing.

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The key idea is to take slices in a stereotaxic atlas (for example, Paxinos G, Huang XF, Petrides M, Toga AW (2009) The Rhesus Monkey Brain in Stereotaxic Coordinates. Elsevier Science & Technology) and then convert each slice into a one-dimensional vector. The 1D vectors are then concatenated together to create a 2D representation.

The process of creating 1D vectors is hown below for Slices 23 and 22, respectively.

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