QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

The Journal of Neuroscience, October 26, 2005, 25(43):10049-10060; doi:10.1523/JNEUROSCI.1661-05.2005

This Article Full Text Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (21) Citing Articles via Google Scholar Google Scholar Articles by Nover, H. Articles by DeAngelis, G. C. Search for Related Content PubMed PubMed Citation Articles by Nover, H. Articles by DeAngelis, G. C.

 Previous Article

Behavioral/Systems/Cognitive
A Logarithmic, Scale-Invariant Representation of Speed in Macaque Middle Temporal Area Accounts for Speed Discrimination Performance

Harris Nover, Charles H. Anderson, and Gregory C. DeAngelis

Washington University School of Medicine, St. Louis, Missouri 63110-1093

Human speed discrimination thresholds follow Weber's law over a large range of reference (i.e., pedestal) speeds, that is, the just-noticeable-difference in speed scales in proportion to the reference speed. We analyzed the neural representation of speed information in macaque middle temporal visual area (MT) to determine whether this representation can account for the basic form of psychophysical data. Based on theoretical considerations, we hypothesized: (1) that the speed tuning curves of MT neurons should be bell-shaped (Gaussian) as a function of the logarithm of speed, (2) that the set of speed-tuning curves should be approximately scale-invariant, (3) that the distribution of speed preferences should be approximately uniform in log speed, and (4) that response variability should be independent of speed preference. Our quantitative analysis of data from 501 MT neurons shows that the neural representation of speed approximately obeys these constraints, with modest deviations particularly at slow speeds. We then used the MT data to predict how speed discrimination thresholds should depend on pedestal speed. The shape of this prediction matches very closely to that of human psychophysical data, accounting for constant Weber fractions over a large range of intermediate speeds as well as a marked departure from Weber's law at slow speeds. Moreover, we show that deviations of the MT representation from the above constraints are important for predicting how psychophysical thresholds depart from Weber's law at slow speeds. These findings support the notion that a logarithmic, approximately scale-invariant representation of speed in area MT limits perceptual speed discrimination.

Key words: extrastriate; velocity; MT; population coding; macaque; visual motion

---

Received April 26, 2005; revised August 23, 2005; accepted September 20, 2005.

This article has been cited by other articles:

				X. Huang and S. G. Lisberger Noise Correlations in Cortical Area MT and Their Potential Impact on Trial-by-Trial Variation in the Direction and Speed of Smooth-Pursuit Eye Movements J Neurophysiol, June 1, 2009; 101(6): 3012 - 3030. [Abstract] [Full Text] [PDF]

				Y. Yang, J. Zhang, Z. Liang, G. Li, Y. Wang, Y. Ma, Y. Zhou, and A. G. Leventhal Aging Affects the Neural Representation of Speed in Macaque Area MT Cereb Cortex, November 26, 2008; (2008) bhn221v1. [Abstract] [Full Text] [PDF]

				I. Maruko, B. Zhang, X. Tao, J. Tong, E. L. Smith III, and Y. M. Chino Postnatal Development of Disparity Sensitivity in Visual Area 2 (V2) of Macaque Monkeys J Neurophysiol, November 1, 2008; 100(5): 2486 - 2495. [Abstract] [Full Text] [PDF]

				D. J. McKeefry, M. P. Burton, C. Vakrou, B. T. Barrett, and A. B. Morland Induced Deficits in Speed Perception by Transcranial Magnetic Stimulation of Human Cortical Areas V5/MT+ and V3A J. Neurosci., July 2, 2008; 28(27): 6848 - 6857. [Abstract] [Full Text] [PDF]

				N. Y. Masse and E. P. Cook The Effect of Middle Temporal Spike Phase on Sensory Encoding and Correlates with Behavior during a Motion-Detection Task J. Neurosci., February 6, 2008; 28(6): 1343 - 1355. [Abstract] [Full Text] [PDF]

				A. Schlack, B. Krekelberg, and T. D. Albright Recent History of Stimulus Speeds Affects the Speed Tuning of Neurons in Area MT J. Neurosci., October 10, 2007; 27(41): 11009 - 11018. [Abstract] [Full Text] [PDF]

				L. L. Lui, J. A. Bourne, and M. G. P. Rosa Spatial Summation, End Inhibition and Side Inhibition in the Middle Temporal Visual Area (MT) J Neurophysiol, February 1, 2007; 97(2): 1135 - 1148. [Abstract] [Full Text] [PDF]

				M. A. Hietanen, N. A. Crowder, and M. R. Ibbotson Contrast Gain Control Is Drift-Rate Dependent: An Informational Analysis J Neurophysiol, February 1, 2007; 97(2): 1078 - 1087. [Abstract] [Full Text] [PDF]

				M. S. Livingstone and B. R. Conway Contrast Affects Speed Tuning, Space-Time Slant, and Receptive-Field Organization of Simple Cells in Macaque V1 J Neurophysiol, January 1, 2007; 97(1): 849 - 857. [Abstract] [Full Text] [PDF]

				S. J. Heinen, J. Rowland, B.-T. Lee, and A. R. Wade An Oculomotor Decision Process Revealed by Functional Magnetic Resonance Imaging J. Neurosci., December 27, 2006; 26(52): 13515 - 13522. [Abstract] [Full Text] [PDF]

				B. Krekelberg, R. J. A. van Wezel, and T. D. Albright Interactions between Speed and Contrast Tuning in the Middle Temporal Area: Implications for the Neural Code for Speed. J. Neurosci., August 30, 2006; 26(35): 8988 - 8998. [Abstract] [Full Text] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help