Motor-cortex lateralisation check using a left-vs-right button-press contrast (ses-02 only). Models a task boxcar plus separate button_1 / button_2 impulse regressors, then contrasts them to reveal contralateral motor cortex activation. Restricted to ses-02 because ses-01 has a temporal confound (button assignment blocked by run half).
Contralateral motor cortex for button 1 presses.
Contralateral motor cortex for button 2 presses.