Julio Martinez-Trujillo, MD, PhD


Julio Martinez-Trujillo, Scientist

Why I Became a Scientist

I always have had an incredible appetite for knowledge. It is part of my personality to find out how things work and to answer fundamental questions about human nature. I became interested in the brain after going to medical school and becoming a clinical neurophysiologist. I used to “read” recordings of the brain electrical activity (electroencephalograms) of children with ADHD, Autism, and Epilepsy. I also used to treat them with the medications and methods I had available. It was very frustrating for me how little I could do for these children, and how little we knew about what was happening to them. I realized that the fundamental problem is that we simply do not know enough about how the brain works, and that this is essential for finding efficient methods to treat brain disease. So, I left my clinical practice and went to a research lab in Tuebingen, Germany, to investigate how the brain electrical activity produces complex behavior. After 20 years of initiating that journey I am here at Robarts. Now I have an arsenal of knowledge and techniques that I will use to my best to answer fundamental questions in basic and clinical sciences. For me, being a scientist is the best job on earth.

Research Summary

My research aims at investigating the role of the primate prefrontal cortex and associated brain regions in intelligent behavior (cognition). I use a series of techniques, such as electrophysiology, behavioral measurements, imaging, and molecular biology, to measure and manipulate brain activity during complex cognitive tasks.

We are particularly interested in isolating the brain mechanisms underlying selective attention and working memory. These two functions are largely responsible for our performance in most tasks. Attention allows us to concentrate and give priority of processing to information that is behaviourally relevant while discarding the irrelevant. It protects the brain from information processing overload.

Working memory is the ability to maintain information in an “active state” when it is no longer available to the senses. It allows us to search for a person’s face in a crowd or remember a telephone number for a few seconds while we dial it. These two functions are highly compromised in most mental disorders. We have so far found that both attention and working memory result from the activity of neurons in a network of brain areas that extend from the frontal to the occipital lobe. Our current goal is to manipulate the activity of neurons in a specific node of this network, the prefrontal cortex, to test specific hypotheses regarding the role of this brain area in these two basic functions.
 

Research Questions and Disease Implications

The prefrontal cortex is the brain region that has expanded the most in primates. Most scientists agree that this expansion is what makes us the most intelligent and behaviorally complex animals in the planet. However, many of us also agree on that the same expansion has made us vulnerable to mental disease.

Autism, ADHD, and schizophrenia are amongst the most pervasive mental disorders that affect Canadians, impacting the quality of life of individuals and families, and costing millions of dollars to our economy and health care system. It has been a longstanding hypothesis that alterations in the microcircuit of the prefrontal cortex and/or in its connectivity with the rest of the brain may be at the core of many of these disorders.

Currently, we do not know what those alterations are. Moreover, we lack understanding of prefrontal cortex microcircuitry structure and function in primates. Although non-invasive methods to explore brain function in humans such as functional imaging and EEG/MEG have been informative regarding the potential role of a given brain area in a particular cognitive function, they lack the necessary temporal and spatial resolution to study brain microcircuits.

My research program targets this complex and fundamental issue. My main goals are: a) to unravel the functional and anatomical connectivity of the primate prefrontal cortex circuitry within the framework of complex cognitive tasks, b) to generate tools and techniques that allow manipulating prefrontal cortex function and therefore generate symptoms of mental disorders in behaving non-human primates, and c) to produce interventions (e.g., deep brain stimulation or local/systemic drug delivery) that allow rescuing the generated disease phenotypes.

Education

M.D., University of Havana, Cuba, 1991

M.Sc. Neurobiology, University of Tübingen, Germany, 1998

Ph.D Neurobiology, University of Tübingen, Germany, 2000

Training

Postdoctoral Fellow, Centre for Vision Research, York University, 2004

Residency in Clinical Neurophysiology, Cuban Neuroscience Center, 1994

Residency in Internal Medicine, Hospital Manuel Fajardo, 1992

Awards

Canada Research Chair (2010)

EJLB Foundation Scholar Research Program for Research in schizophrenia and mental disorders

Ann Weschler Teaching Award (Faculty of Medicine, McGill University, 2008)

Fellowship Graduiertenkollege Neurobiologie. University of Tübingen (1998-2000)

Publications

Recent Peer Reviewed Articles

Sébastien Tremblay, Florian Pieper, Adam Sachs. Julio C. Martinez-Trujillo. Attentional filtering of visual information by neuronal ensembles in the primate lateral prefrontal cortex. Neuron (2014, in press).

Mendoza-Halliday D, Torres S, Martinez-Trujillo JC. Sharp emergence of feature-selective sustained activity along the dorsal visual pathway. Nat Neurosci. 17(9):1255-62, 2014.
Therese Lennert and Julio C. Martinez-Trujillo. Prefrontal neurons of opposite spatial preference display distinct target selection dynamics. The Journal of Neuroscience. 33(22):9520-9, 2013.

Matthew L. Leavitt, Florian Pieper, Adam Sachs, Ridha Joober, and Julio C. Martinez-Trujillo. Structure of spike count correlations reveals functional interactions between neurons in dorsolateral prefrontal cortex area 8a of behaving primates. Plos One. 8(4): e61503, 2013.

Ascencio-Monteon J, Martinez-Trujillo JC, Crawford J. Frames of reference for eye-head gaze shifts evoked during frontal eye field stimulation. European Journal of Neuroscience. 10.1111/ejn.12175, 2013.

Book Chapters

Mechanisms of Sensory Working memory. Attention and Performance XXV. Edited by Pierre Jolicouer and Julio Martinez-Trujillo (in press). Elsevier.

Feature-based attention. Neural mechanisms. The New Visual Neurosciences. By Paul Khayat and Julio Martinez-Trujillo. MIT Press by Leon M. Chalupa and John S. Werner (2013).

The feature similarity gain model of Attention: Unifying multiplicative effects of spatial and feature-based attention. 49:300-304. J Martinez-Trujillo & S Treue, The Neurobiology of Attention. Edited by Itti, Rees and Tsotsos, Elsevier Academic Press, 2005.

Attentional modulation of apparent stimulus contrast. 70:428-429. By J Martinez-Trujillo & S Treue, published in The Neurobiology of Attention. Edited by Itti, Rees and Tsotsos, Elsevier Academic Press, 2005.

Contact Information

Robarts Research Institute
100 Perth Drive, London, ON N6A 5K8, Canada
Room 7239

Email: julio.martinez@robarts.ca
Telephone: (519) 663-5777 ext. 24383