Show Reference: "Linear ensemble-coding in midbrain superior colliculus specifies the saccade kinematics."

Linear ensemble-coding in midbrain superior colliculus specifies the saccade kinematics. Biological Cybernetics, Vol. 98, No. 6. (June 2008), pp. 561-577, doi:10.1007/s00422-008-0219-z by John van Opstal, Jeroen Goossens
@article{obstal-and-goossens-2008,
    abstract = {Recently, we proposed an ensemble-coding scheme of the midbrain superior colliculus ({SC}) in which, during a saccade, each spike emitted by each recruited {SC} neuron contributes a fixed minivector to the gaze-control motor output. The size and direction of this 'spike vector' depend exclusively on a cell's location within the {SC} motor map (Goossens and Van Opstal, in J Neurophysiol 95: 2326-2341, 2006). According to this simple scheme, the planned saccade trajectory results from instantaneous linear summation of all spike vectors across the motor map. In our simulations with this model, the brainstem saccade generator was simplified by a linear feedback system, rendering the total model (which has only three free parameters) essentially linear. Interestingly, when this scheme was applied to actually recorded spike trains from 139 saccade-related {SC} neurons, measured during thousands of eye movements to single visual targets, straight saccades resulted with the correct velocity profiles and nonlinear kinematic relations ('main sequence properties' and 'component stretching'). Hence, we concluded that the kinematic nonlinearity of saccades resides in the spatial-temporal distribution of {SC} activity, rather than in the brainstem burst generator. The latter is generally assumed in models of the saccadic system. Here we analyze how this behaviour might emerge from this simple scheme. In addition, we will show new experimental evidence in support of the proposed mechanism.},
    author = {van Opstal, John and Goossens, Jeroen},
    doi = {10.1007/s00422-008-0219-z},
    issn = {0340-1200},
    journal = {Biological Cybernetics},
    keywords = {basal-ganglia, biology, control, eye-movements, motor, population-coding, sc, spiking},
    month = jun,
    number = {6},
    pages = {561--577},
    pmcid = {PMC2798131},
    pmid = {18491166},
    posted-at = {2012-08-29 14:57:45},
    priority = {2},
    publisher = {Springer},
    title = {Linear ensemble-coding in midbrain superior colliculus specifies the saccade kinematics.},
    url = {http://dx.doi.org/10.1007/s00422-008-0219-z},
    volume = {98},
    year = {2008}
}

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Some models assume SC output encodes saccade amplitude and direction. In other models, each spike from a burst neuron encodes a motion segment, with length and direction depending on the position of the neuron and strength of connection to brainstem areas