Assistant Professor - Department of Neuroscience Ph.D., Massachusetts Institute of Techology, 2000 One Baylor Plaza Baylor College of Medicine Houston TX, 77030 Telephone: 713-798-4071 - Fax: 713-798-2874 Email: astolias@bcm.edu Web:toliaslab.wordpress.com

Question: How Does the Neocortex Work?
Our aim is to understand the rules by which networks of nerves cells in the neocortex orchestrate their activity to process information; to decipher the neural code.

The outermost part of our brain – the neocortex – houses our mental functions like perception, cognition and action. Over the last few decades important steps have been made in understanding the small-scale organization of the neocortex. For example, there is a plethora of knowledge about the properties of single neurons and the molecular mechanisms of sub-cellular processes such as synaptic plasticity. Also, we know a lot about the large-scale organization of the neocortex such as the fact that it is split into numerous distinct areas that serve different functions.

Yet, despite this progress, we still do not know how the neocortex processes information. The essence of the problem lies in understanding how the billions of neurons communicating through trillions of connections coordinate their activities to give rise to our mental faculties. Obviously, we are faced with a problem of immense complexity. However, if there are underlying principles and rules that govern this complexity, discovering them provides a powerful strategy to make progress towards understanding how the neocortex works.

The goal of our research team is to unravel the elementary principles that underlie cortical computations in our quest to discover the canonical algorithm(s) implemented by cortical microcircuits. We study cortical function in vivo in behaving animals at the circuit level by following a multidisciplinary approach: we combine electrophysiological and two-photon imaging methods for multi-neuronal recording with molecular techniques for circuit tracing and manipulation.  We use computational and theoretical methods for data analysis and for modeling cortical circuit function. Currently, our work focuses on the visual system of mice and non-human primates. Our goal is to follow a cross-species and cross-cortical area comparison in order to identify similarities and differences between the algorithms of the necortex. We hope that this approach will provide a unique window to study the evolution of the neocortex. Numerous neuropsychiatric illnesses such as autism spectrum disorders, stroke, Alzheimer’s disease and schizophrenia are associated with cortical malfunction, underscoring the importance of understanding how the neocortex works.

Novel Methods for Circuit Analysis
Our research team has also a strong focus in developing new methods to study the functional organization of cortical circuits in vivo. For example in collaboration with Dr. Peter Saggau we have developed a fast in vivo 3D two-photon microscope based on 3D random-access multi-photon excitation. This microscope employs a series of acousto-optical deflectors that enable us to generate arbitrary 3D scanning paths at frame rates two orders of magnitude faster than current state-of-the-art two-photon imaging systems. We are also working on developing novel chronic high-density multi-electrode recording methods.

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Ku S. P., A. S. Tolias, N. K. Logothetis, J. Goense: FMRI of the face-processing network in the ventral temporal lobe of awake and anesthetized macaques. Neuron. 70(2):352-62.

Berens, P., A. S. Ecker, S. Gerwinn, A. S. Tolias and M. Bethge: Reassessing optimal neural population codes with neurometric functions. Proceedings of the National Academy of Sciences 108(11), 4423-4428

Ecker AS, Berens P, Keliris GA, Bethge M, Logothetis NK, Tolias AS. Decorrelated neuronal firing in cortical microcircuits. Science. 2010 Jan 29;327(5965):584-7.

Tehovnik EJ, Slocum WM, Smirnakis SM, Tolias AS. Microstimulation of visual cortex to restore vision. Prog Brain Res. 2009;175:347-75. Review.

Macke JH, Berens P, Ecker AS, Tolias AS, Bethge M. Generating spike trains with specified correlation coefficients. Neural Comput. 2009 Feb;21(2):397-423.

Berens P, Keliris GA, Ecker AS, Logothetis NK, Tolias AS. Feature selectivity of the gamma-band of the local field potential in primate primary visual cortex. Front Neurosci. 2008 Dec;2(2):199-207. Epub 2008 Dec 15.

Berens P, Keliris GA, Ecker AS, Logothetis NK and Tolias AS (2008). Comparing the feature selectivity of the gamma-band of the local field potential and the underlying spiking activity in primate visual cortex. Front. Syst. Neurosci.

Tolias, A. S., A. S. Ecker, A. G. Siapas, A. Hoenselaar, G. A. Keliris and N. K. Logothetis (2007). Recording Chronically from the same Neurons in Awake, Behaving Primates. Journal of Neurophysiology 98(6), 3780-3790.

Tolias A.S., Sultan F, Augath M, Oeltermann A, Tehovnik E.J., Schiller PH, Logothetis N.K. (2005) Mapping cortical activity elicited by electrical microstimulation using fMRI in the macaque. Neuron, 48, 901-11.

Tolias A.S., Keliris G., Smirnakis S.M., Logothetis N.K. (2005). Neurons in macaque area V4 acquire directional tuning after adaptation to motion stimuli. Nature Neuroscience, 8(5), 591-3.

Smirnakis S.M, Brewer A.A, Schmid M.C, Tolias A.S., Sch Augath M., Inhoffen W., Wandell B.A., Logothetis N.K. (2005). Adult macaque V1 fails to reorganize in the months following homonymous retinal lesions. Nature, 435(7040), 288-9.

Schiller P.H., Slocum W., Carvey C., Tolias A.S. (2004) Are express saccades generated under natural viewing conditions? European J. of Neuroscience, 20(9), 2467-73.

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• James Cotton (Neuroscience)
• George Denfield (Neuroscience)
• Cathryn Hughes (Neuroscience)
• Shan Shen (Neuroscience)
• Manivannan Subramaniyan (Neuroscience)
• Dimitri Yatsenko (Neuroscience)

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