Speed skills: measuring the visual speed analyzing properties of primate MT neurons
John A. Perrone1
& Alexander Thiele2, 3
1
Department of Psychology, The University of Waikato, Private Bag 3105, Hamilton, New Zealand
2
The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd., La Jolla, California 92037, USA
3
Present address: Department of Psychology, University of Newcastle upon Tyne, Ridley Building, Claremont Place, Newcastle upon Tyne, NE1 7RU, UK
Correspondence should be addressed to John A. Perrone jpnz@waikato.ac.nz
Knowing the direction and speed of moving objects is often critical for survival. However, it is poorly understood how cortical neurons process the speed of image movement. Here we tested MT neurons using moving sine-wave gratings of different spatial and temporal frequencies, and mapped out the neurons' spatiotemporal frequency response profiles. The maps typically had oriented ridges of peak sensitivity as expected for speed-tuned neurons. The preferred speed estimate, derived from the orientation of the maps, corresponded well to the preferred speed when moving bars were presented. Thus, our data demonstrate that MT neurons are truly sensitive to the object speed. These findings indicate that MT is not only a key structure in the analysis of direction of motion and depth perception, but also in the analysis of object speed.
