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Motion-evoked brain activities in human and macaque MT


Ku,  S-P
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Ku, S.-P. (2005). Motion-evoked brain activities in human and macaque MT. Talk presented at 6. Neurowissenschaftliche Nachwuchskonferenz Tübingen (NeNa '05). Blaubeuren, Germany.

In 1971 people defined that an area in macaque’s brain in the depths of the superior temporal sulcus contains a large majority of neurons who are selective for the direction of motion of visual stimuli (Dubner Zeki, 1971; Zeki, 1974). This region, which is named V5/MT nowadays receives a lot of attention since then because the neurons in this region have wellcharacteristic parametric properties. For example, using stochastic random-dot patterns in which the experimenter controlled the strength of the motion signal by specifying the percentage of dots undergoing coherent rather than random motion, people found that most MT neurons respond approximately linearly to changes in the strength of the motion signal (Britten et al., 1993). Base on electrophysiological evidences, people were also able to quantify the relationship between functional properties of human-MT+ and motion strength using fMRI (Rees et al., 2000). All these results suggest that using coherent-motion patterns comparing to incoherent motion as visual stimuli one should be able to map area MT using fMRI. However, my own results and a historical publication, though PET instead of fMRI was used (Watson et al., 1993), both indicate that this is not the case. Is there any artifact involved in my experiment-design? Or this difference reveals some fundamental properties of the dynamic brain activity? In my talk I will compare the differences of the experimentdesigns between my experiment and the previous study and try to propose some possible mechanisms which might be explaining the differences between the two studies. These differences might lead to future investigations of neural mechanisms underlying the brain activities.