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The control of movement can be studied with the countermanding (stop signal) task

success. success. error. The control of movement can be studied with the countermanding (stop signal) task. RT distributions of non-cancelled and no stop signal trials. Inhibition function. STOP WINS! cancelled trial. GO WINS! non-cancelled trial. Race model can explain behavior.

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The control of movement can be studied with the countermanding (stop signal) task

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  1. success success error The control of movement can be studied with the countermanding (stop signal) task

  2. RT distributions of non-cancelled and no stop signal trials Inhibition function

  3. STOP WINS! cancelled trial GO WINS! non-cancelled trial Race model can explain behavior Stop Signal Reaction Time (SSRT) – time needed to cancel a previously planned movement

  4. Frontal Eye Field (as part of a network!) Controls when gaze shifts Activation 0.0 0.1 0.2 Time from stimulus (sec) Hanes, D.P. and J.D. Schall (1996) Neural control of voluntary movement initiation. Science 274:427-430.

  5. No Stop Signal Trials Stop Signal SSRT Stop Signal SSRT 200 100 100 Non-canceled Trials 0 400 200 0 0 200 400 No Stop Signal Trials Stop Signal SSRT Stop Signal SSRT 200 Sig. difference before SSRT. 100 100 0 400 200 0 Canceled Trials 0 200 400 Canceled Trials Stop Signal SSRT Stop Signal SSRT 100 100 Sig. difference before SSRT. fixation neurons 50 No Stop Signal Trials 0 0 200 400 400 200 0 No difference. FEF SC movement neurons

  6. GO process STOP process Movement Neuron Fixation Neuron

  7. Mapping the race model onto neural processes 1 - The race model of countermanding performance assumes that the GO and the STOP processes have independent finish times (Logan & Cowan, 1984). 2 – Saccades are produced by a network of interacting neurons. Paradox – How can a network of interacting neurons produce behavior that looks like the outcome of race between independent processes?

  8. Mapping the race model onto neural processes Explore properties of simple network of GO and STOP units. Constrain by the properties of countermanding behavior and by the form of activation of neurons L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An interactive race model of countermanding saccades. Program No. 72.10. 2003 Abstract Viewer/Itinerary Planner.

  9. ß STOP 1.0 G O pr oc e s s S T O P pr oc e s s G O S T O P 0.5 ß GO s m m s GO, GO STOP, STOP 0.0 0 1 0 0 2 0 0 300 Time from stimulus (ms) GO activation = (GO growth rate – STOP inhibition) + noise STOP activation = (STOP growth rate – GO inhibition) + noise

  10. G O S T O P s m m s GO, GO STOP, STOP Independent Race Model

  11. G O S T O P s m m s GO, GO STOP, STOP Independent Race Model Non-cancelled and no stop signal

  12. ß STOP G O S T O P ß GO s m m s GO, GO STOP, STOP Interactive Race Model

  13. ß STOP G O S T O P ß GO m s m s GO, GO STOP, STOP Interactive Race Model Observed Model Predictions Non-cancelled and no stop signal Cancelled and no stop signal

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