Frontal Lobes and Regulation of Motor Activity

Luria The working Brain c. 7 p. 187
Luria considers these tertiary zones for the limbic and motor systems and crucial for regulating vigilance and goal linked activity. "expectancy waves" in the frontal lobe precede activity. Speech has an "activating role" which formulates the problem. This increase in cortical tone from the activation role of speech is deficient in patients with frontal lobe lesions (cites numerous publications on which Homskaya is listed as an author). Autonomic changes due to an orienting reflex continue until habituation, interruption or completion of the task. Autonomic components of the orienting reflect evoked by spoken instruction continue after posterior but not anterior lesions. Luria concludes p. 189 "the frontal lobes participate in the regulation of the activation processes lying at the basis of voluntary attention."



Electrophysiologically, the EEG depression of alpha rhythm occurs in response to any spoken instructions but are absent or unstable in patients with frontal lesions, but is preserved in those with posterior lesions. Analagous findings occur with evoked potentials and frontal and posterior lesions.

Luria emphasized that the apathoakineticoabulic syndrome of massive frontal dysfunction does not affect all behavior, just higher cortical function. Orienting reactions to irrelevant stimuli, not intention based, are not only undisturbed but may be intensified. Patients do not reply to questions, make requests, or complete tasks but will lok at door that squeaks to see who is coming in. They may join physician's conversation with a neighbor, even if they won't ask questions directly posed to themselves. Luria concludes that massive injuries to the frontal lobes control only the most complex forms of regulation of conscious activity and in particular, acitivity controlled by motives formulated with the aid of speech (Luria, 1966 a,b 1969 a,b).

Effect of spoken instructions is complex, patients may cease to obey gradually, or repeat and not do command. He may also replace it with an inert stereotype eg. putting a match in his mouth and attempting to smoke it. (note- comparable to apraxic content error). {atient's own speech is also not enough to regulate. If asked to tap, rhythmically, strong, weak, weak, saying is not enough to make patient do it.

Clinical tests for-- echopraxia, usually performed correctly. Different forms of contrasting programs motor task (if I make a fist, you raise your finger). (tap once if I tap twice, tap twice if I tap once). Homskaya (1966) and Maruszewski (1966) show that patients lapse into echopraxia after a short amount of time. Luria's idea, is that each attempt to follow a spoken command leads to a "flood of inert stereotypes." Drawing may be performed correctly on first attempt (circle, square, cross) but changing leads to perseveration. Patients also lose the ability to self monitor results and change if needed. In spite, they recall the task. However, they can monitor the same tasks as OTHERS perform them and notice others' mistakes. (numerous citations p 210 Working Brain)