Learned motor responses.

Subject is asked to raise his left hand to one tap, and his right hand to 2 taps, or to raise his hand to one tap and to refrain from raising his hand to 2 taps. 

More complicated version: patient is asked to respond to a fist with a finger, or to a finger with a fist.  Or, he is asked to responnd to two taps with one tap, and to one tap with 2 taps. 

More complicated yet.  the subject is asked to respond to a weak tap with a powerful hand movement, and to a powerful tap with a weak hand movement.  Or, to respond to a short acoustic stimulus with a slow movement, and a long stimulus with a prolonged movement. (cf  Marushevskii M, Disturbance of the simplest forms of voluntary action in local lesions of the frontal lobes.  in Luria AR, Khomskaya ED (eds), The frontal lobes and the regulation of psychological processes. Moscow, MGU Press, 1966.

Luria's adaptation:  He would give one task, and when mastered give a second, then without repeating instructions, go back to the first, and then the second task.  Normals had little trouble either learning the task or switching.  Neither empty or filled paused had much effect, (except occipital lesions for visual tasks and temporal lesions for auditory tasks).  Massive tumors had problems with task. 

Patients with thalamic lesions could learn the task, but not do it verbally.  These patients learned the task, were not affected by interference, but could not talk about it.