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Abstract:
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.
