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How does the human brain work?”

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‘Nature’ journals are synonymous with the very best in research. Earlier this year, an article by University of Leicester bioengineer Professor Rodrigo Quian Quiroga not only appeared in Nature Reviews Neuroscience, but also featured on the magazine cover. In the article, Prof. Quian Quiroga and co-author Dr. Stefano Panzeri discuss new methodologies that are enabling scientists to better understand how our brain processes information.

The human brain is perhaps the most complex of organs, boasting between 50-100 billion nerve cells or neurons that constantly interact with each other. These neurons ‘carry’ messages through electrochemical processes; meaning, chemicals in our body (charged sodium, potassium and chloride ions) move in and out of these cells and establish an electrical current.

Scientists have, for a long time now, stimulated with different types of inputs individual neurons that have been isolated for study. To have enough statistical power, these experiments typically involved stimulating a single neuron over and over again, to get a general idea of how it responds to different signals. Although these studies have yielded a lot of information, they have their own limitations.

Prof. Quian Quiroga explains, “The human brain typically makes decisions based on a single stimulus, by evaluating the activity of a large number of neurons. I don’t get in front of a tiger 100 times to make an average of my neuronal responses and decide if I should run or not. If I see a tiger once, I run”. Traditional studies thus undermine this complexity by only accounting for the responses single neurons.

Moreover, these studies take into account an “average response” obtained by stimulating the neuron numerous times. The brain, on the other hand, acts based on single stimulus presentations. Therefore, the information given by an averaged response can often be insufficient.

Prof. Quian Quiroga and Dr. Panzeri stress, on account of these factors “it is important to shift from a single-neuron, multiple-trial framework to multiple-neuron, single-trial methodologies”. In other words, it is more beneficial to study responses of numerous neurons to a single stimulus.

Prof. Quian Quiroga says, “A major challenge of our days is (thus) to develop the methodologies to record and process the data from hundreds of neurons and developing these is by no means a trivial task”.

He adds, “Our brains are able to create very complex processes – just imagine the perfect harmony with which we move different muscles for normal walking – thousands of neurons are involved in this and to determine the role of each is complicated”.

In his recent review paper, Prof. Quian Quiroga and Dr. Panzeri discuss two complementary approaches that can be used to resolve this, namely ‘decoding’ and ‘information theory’.

‘Decoding’ essentially helps determine what must have caused a particular response (much like “working backwards”). Thus, the response of a neuronal population is used to reconstruct the stimulus or behaviour that caused it in the first place. ‘Information theory’, on the other hand, literally quantifies how much information a number of neurons carry about the stimulus.

Prof. Quian Quiroga explains, “together, the two approaches not only allow scientists to extract more information on how the brain works, but information that is ambiguous at the level of single neurons, can be clearly evaluated when the whole ‘population’ is considered”. The review is an asset for anyone involved in the field, as it carefully considers and evaluates the two statistical approaches, as well as describes potential applications.

As part of his own research, Prof. Quian Quiroga (in collaboration with Prof. Richard Andersen at Caltech) has been studying the ‘decoding’ of movement plans using activity of certain neuronal populations. This ability to predict movement intentions from activity of neurons has application in brain-machine interfaces, especially for development of neural prostheses (electronic and/or mechanical devices that connect to the nervous system and replace functions lost as a result of disease or injury) for paralysed patients.

Rodrigo Quian Quiroga is a Professor in Bioengineering at the University of Leicester. His several research interests include visual perception (how the brain apprehends what our eyes see), memory and neural coding (how information is represented in the brain by neurons). He is actively involved in developing methods that analyse functioning of various neurons. He has published articles in several high-impact journals, including Nature, Nature Reviews Neuroscience, Neuron and the Proceedings of the National Academy of Sciences.

NOTE TO NEWSDESK:
Rodrigo Quian Quiroga – Short Biography
Rodrigo Quian Quiroga graduated in Physics at the University of Buenos Aires, Argentina, in 1993. After 2 years working at the Department of Physiology in the Institute for Neurological Investigations – FLENI, Argentina, and one further year at the Department of Epilepsy of the same institute, he moved to Germany and obtained his PhD in applied mathematics at the University of Luebeck in 1998. He was a post-doctoral fellow at the Research Center Juelich, Germany, from 1998 to 2001 and from 2001 to 2004 he was a Sloan fellow at the California Institute of Technology, USA. He was appointed as a Lecturer in Bioengineering at the Department of Engineering of the University of Leicester in 2004, was promoted to Reader in 2006 and to a personal chair in 2008.
Prof. Quian Quiroga main research focus is on Neuroscience and the analysis of electrophysiological data. This research involves the use and development of advanced methods of signal processing. In particular, he developed an automatic method for processing the neural data that is currently used by several neurophysiology laboratories. The use of this method allowed the finding of a new type of ‘abstract’ (e.g. Jennifer Aniston) neurons in the human brain that was published in Nature, obtained the first prize at an international meeting in 2005 in Madrid and received world-wide media attention, including articles in the New York Times, Scientific American, Daily Mail, New Scientist, The Independent, etc. It has also been selected as one of the top 100 scientific stories of 2005 by Discover Magazine. In 2008, his follow-up work in this line of research was selected as one of the “Breaking news in Neuroscience” by the european Federation of Neuroscience Societies (fENS).

Prof. Quian Quiroga is a member of the editorial board of 3 international journals. He acts as reviewer for several international journals in the fields of Applied Mathematics, Physics, Signal Analysis, Clinical Neurophysiology and Neuroscience. He has given more than 30 invited lectures in the last 3 years, had published more than 50 refereed journal papers and currently holds 2 EPSRC grants, 1 MRC grant and 1 grant from the Royal Society. He is the head of the Bioengineering Research Group, at the Department of Engineering of the University of Leicester.

Contact:
Rodrigo Quian Quiroga
Department of Engineering, University of Leicester, LE1 7RH Leicester, United Kingdom
email rqqg1@le.ac.uk

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