An Experimental Study of the Functions of the Frontal Lobes in Man*

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Abstract
The results on a number of experiments of five patients with unilateral lesions of the frontal lobes (one with a lesion of the left lobe and four with lesions of the right lobes) were compared with those of eight normal controls of approximately the same age range and educational status. On five experiments the following differences were found between the two groups: (1) The subjects with frontal lobe lesions required a longer time and more illumination to perceive geometrical figures and words than the controls. (2) They were unable to perceive as many meaningful objects in ambiguous figures as the controls. (3) The illusory effect of the Muller-Lyer illusion measured quantitatively was exaggerated, and the illusory effects of many other visual illusions were not perceived. (4) The patients were unable to recall as many objects exposed visually as the controls. (5) They were unable to perceive reversals on many of the figures with reversible perspectives, and if reversals occurred their frequency was below average. The differences between the patients and the controls can be accounted for by postulating that following frontal lobectomies: (1) a longer time is required to perceive a stimulus, (2) the number, of situations which are perceived in a stimulus field is decreased, (3) there is an inability to shift readily from one stimulus to another, and (4) there is a distortion of normal perceptions. The results on the visual illusions suggest that when a normal reaction is affected by frontal lobectomy, a response which appeared earlier in the behavior of the individual replaces the mature adult response. Other forms of atypical behavior were noted as follows: Euphoria was present in two of the experimental subjects. The patient with a lesion of the left frontal lobe showed unmistakable symptoms of aphasia. Many of the reactions of the four patients with lesions of the right lobes were, however, similar to the symptoms which have been described as constituting part of the syndrome of aphasia. It is suggested that symptoms which have often been ascribed as belonging to the fields of emotion and aphasia are due largely to the disturbed perceptual processes. Immediate memory, as far as could be determined, was not affected in the subjects with frontal lobe lesions. It is, therefore, suggested that association, if uncomplicated by perceptual processes, is not primarily a function of the frontal lobes. One of the subjects with a lesion of the right lobe showed some restitution of behavior with the lapse of time. There is some evidence to show that a recovery of the function which was affected did not occur, but that substitute behavior produced the same end results as would have been produced by the affected function.

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