Schulich school of Medicine and Dentistry logo Physiology and Pharmacology Schulich School of Medicine & Dentistry

Julio Martinez-Trujillo

Julio Martinez-Trujillo

Associate Professor

M.D. University of Havana
PH.D. University of Tubinggen
M.Sc. University of Tubinggen
Office:  Robarts Research Institute, Room 7239
p. 519.931.5777 x.24383
f. 519.661.3827
e. julio.martinez@robarts.ca


Visit: Dr. Martinez-Trujillo's Homepage
See Publications by Dr. Martinez-Trujillo on PubMed

Neurophysiological bases of attention:

Attention can be defined as the selective filtering and modulation of information processing in the brain. It plays a major role in human performance. For example, we are much better at remembering particular details or scenes when we were paying attention to them relative to when we were distracted by something else – despite of the fact that the same information enters our senses in both situations.
Currently, we know that visual signals entering the different cortical areas are amplified when we are paying attention to them and attenuated when we ignore them. How the brain accomplishes this modulation of sensory information processing remains unclear. Today, our research aims at answering this question. We use a combination of behavioral measurements in normal subjects and patients and single cell recordings in non-human primates to study the mechanisms underlying the executive control of attention.

Visuomotor transformations in the gaze control system:

In order to successfully interact with our environment, the brain must transform visual signals entering the retina, in an eye-centered reference frame, into motor commands for the muscles executed relative to the body. We have previously demonstrated that the Supplementary Eye Fields (SEF), in the frontal cortex of primates, plays an important role in such reference frame transformation. Ongoing research in our laboratory aims at investigating the physiological properties of neurons within the SEF as well as the functional relationship between the SEF and other gaze control areas. We use a combination of 3D eye and head movement measurements, electrical microstimulation and single cell recordings in human and non-human primates.

Visual motion processing: 


The ability to process and perceive visual motion plays an important role in our daily life. Therefore, the primate brain is equipped with a system devoted to process motion and its attributes. Area middle temporal (MT), in the visual cortex of primates is thought to play a critical role in motion perception. We have demonstrated that neurons in area MT signals the occurrence of transient events on motion attributes, i.e., transient changes in the direction of moving stimuli. Research taking place in our laboratory is directed to investigate how area MT and other motion processing areas process such changes in different motion attributes.


Publications

Sharp emergence of feature-selective sustained activity along the dorsal visual pathway. Published in NATURE NEUROSCIENCE. 2014, 17, 1255–1262.
 Diego Mendoza-Halliday, Santiago Gomez-Torres, and Julio C. Martinez-Trujillo.
 
Prefrontal neurons of opposite spatial preference display distinct target selection dynamics. Published in THE JOURNAL OF NEUROSCIENCE. 2013, 33(22):9520-9529.
Therese Lennert and Julio C. Martinez-Trujillo.
 
Structure of spike count correlations reveals functional interactions between neurons in dorsolateral prefrontal cortex area 8a of behaving primates. Published in PLOS ONE. 2013, 8(4):e61503.
Matthew L. Leavitt, Florian Pieper, Adam Sachs, Ridha Joober, and Julio C. Martinez-Trujillo.
 
Frames of reference for eye-head gaze shifts evoked during frontal eye field stimulation. Published in the EUROPEAN JOURNAL OF NEUROSCIENCE. 2013, 10.1111/ejn.12175. Authors: Monteon JA, Wang H, Martinez-Trujillo J, Crawford JD.
 
Binocular rivalry of spirals and linear moving random dot patterns in human observers
Published in THE JOURNAL OF VISION.  2012, 12(10). . Authors: 1. Malek N, Mendoza-Halliday D, Martinez-Trujillo JC.
 
Multifocal attention filters out targets from distracters within and beyond primate MT neurons receptive field boundaries
Published in NEURON, 2011, 72(6):1067-79 (cover image). Authors: Niebergall R, Khayat P, Treue S, Martinez-Trujillo JC.

Expansion of MT neurons excitatory receptive fields during covert attentive tracking
Published in THE JOURNAL OF NEUROSCIENCE, 2011, 31(48):17622-36. Authors: Niebergall R, Khayat P, Treue S, Martinez-Trujillo JC.
 
Attentional modulation of neuromagnetic evoked responses in early human visual cortex and parietal lobe following a rank-order rule
Published in THE JOURNAL OF NEUROSCIENCE, 2011, 31(48):17622-36. Authors: Lennert T, Cipriani R, Jolicoeur P, Cheyne D, Martinez-Trujillo JC.
 
Searching for the neural mechanisms of feature-based attention in the primate brain
Published in NEURON. 2011, 70(6):1025-8. Author: Martinez-Trujillo J.