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Laurent Goffart, Aaron Cecala, Neeraj Gandhi; Does the saccade-related burst in the superior colliculus convey commands related to the future location of a moving target ?. Journal of Vision 2016;16(12):98. doi: 10.1167/16.12.98.
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Following the suggestion that a dynamic command encoding the expected here-and-now target location feeds the oculomotor system during interceptive saccades, we tested whether this command originates in the deep superior colliculus (SC). Three monkeys generated saccades to targets which were static or moved along the preferred axis, away from (outward) or toward the fixation point (inward). Vertical and horizontal target motions were also tested. The animals had to make a saccade to the target and track it for few hundred msec. The target speed was generally 20°/sec. Extracellular activity of 57 saccade-related neurons was recorded. The movement field parameters (boundaries, preferred amplitude and maximum firing rate) were estimated after spline fitting the relation between saccade amplitude and average firing rate during the saccade-related burst. During radial target motion, the inner MF boundary shifted in the same direction as the target motion: toward larger amplitudes for outward motion, smaller amplitudes for inward motion. During vertical target motion, both lower and upper boundaries were shifted upward during upward motion whereas the upper boundary was shifted only during downward motions. During horizontal motions, the medial boundaries were not changed. A shift in the preferred amplitude was significant only for outward motion. Regardless of the motion direction, the average firing rate was consistently reduced for interceptive saccades. These results indicate that the saccade-related burst of SC neurons participates in the guidance of interceptive saccades. Its spatiotemporal pattern depends upon the target motion direction. When it is observed, the shift of MF boundary (in the same direction as the target motion) indicates that the neuron issued a command to orient gaze toward a past target location. The absence of shift in the direction opposite to the target motion argues against an encoding of future target location by SC activity for the generation of interceptive saccades.
Meeting abstract presented at VSS 2016
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