Grawlixes, frontal lobe, ganglia and automatism.

"The replacement of the complex actions programs by a well-consolidated stereotype, quite unrelated to the basic program, is the most typical feature of the disturbances of voluntary activity in this group of patients.(..)
If a lesion of the frontal lobes spreads into the deep zones of the frontal region to affect the subcortical ganglia and to disturb the inhibition of primitive automatisms, the task of drawing a simple figure is easily interrupted by the revival of elementary motor automatism; having started to perform a particular task, the patient is unable to give up, and the performance of the action is interrupted by bursts of uncontrollable automatism." (my italics)

from: Alexandr Romanovich Luria. Higher Cortical Functions in Man