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Cerebral Cortex Advance Access published online on September 29, 2006
Cerebral Cortex, doi:10.1093/cercor/bhl084
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© 2006 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article

Activation of Area MT/V5 and the Right Inferior Parietal Cortex during the Discrimination of Transient Direction Changes in Translational Motion

Julio C. Martinez-Trujillo 1 *, Douglas Cheyne 2, William Gaetz 2, Evgueni Simine 3, and John K. Tsotsos 3

1 Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6
2 Neuromagnetic Imaging Laboratory, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
3 Centre for Vision Research and Department of Computer Science & Engineering, York University, Toronto, Canada M3J 1P3

* To whom correspondence should be addressed.
Julio C. Martinez-Trujillo, E-mail: julio.martinez{at}mcgill.ca


  Abstract

The perception of changes in the direction of objects that translate in space is an important function of our visual system. Here we investigate the brain electrical phenomena underlying such a function by using a combination of magnetoencephalography (MEG) and magnetic resonance imaging. We recorded MEG-evoked responses in 9 healthy human subjects while they discriminated the direction of a transient change in a translationally moving random dot pattern presented either to the right or to the left of a central fixation point. We found that responses reached their maximum in 2 main regions corresponding to motion processing area middle temporal (MT)/V5 contralateral to the stimulated visual field, and to the right inferior parietal lobe (rIPL). The activation latencies were very similar in both regions (~135 ms) following the direction change onset. Our findings suggest that area MT/V5 provides the strongest sensory signal in response to changes in the direction of translational motion, whereas area rIPL may be involved either in the sensory processing of transient motion signals or in the processing of signals related to orienting of attention.

Keywords: attention; direction change; inferior parietal lobe; MEG; motion detection; MT/V5.
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