Obviously, such complex psychologic activity must implicate many parts of the cerebrum and will suffer to some extent from a lesion in any of the parts that contribute to the functional system. Luria found that when the frontal lobes are injured, there was not only a general psychomotor slowing and easy distractibility but also an erroneous analysis of the above-listed conditions of the problem. “The plan of action that is selected quickly loses its regulating influence on behavior as a whole and is replaced by a perseveration of one particular link of the motor act or by the influence of some connection established during the patient’s past experience.” Furthermore, there was a failure to distinguish the essential sequences in the analysis and to compare the final solution with the original conception of the problem. Plausible as this scheme appears, like Goldstein’s “loss of the abstract attitude” (the patient thinks concretely, that is, he reacts directly to the stimulus situation), such psychophysiologic analyses of the mental processes are highly theoretical, and the factors to which they refer are not easily measured.
Finally, a lesion that includes the frontal eye field may, in addition to a gaze paralysis, engender a type of reduced attention to the contralateral visual environment. This probably is the result of a defect in visually guided attention and it is seen only irregularly in clinical practice. The degree of neglect seen with a nondominant parietal lobe lesion is not observed with frontal lobe lesions, and it is difficult to differentiate the frontal defect from the simple impediment of being unable to direct gaze in one direction.
In modern parlance, the frontal lobe, particularly its prefrontal components, is said to exert an executive function, referring here to the overall control and sequencing of other cognitive functions. This allows for a type of self-monitoring that guides the selection of strategies to solve problems, the inhibition of incorrect responses, the ability to deal with change in focus and novelty in tasks, and probably to be able to generalize from experience. Indeed, all ability to adapt to changes in circumstance and to learn from experience requires this executive function. Unlike some of the psychic properties mentioned above, these are subject to measurement by testing and they are observable during the clinical examination as deterioration in problem solving, by stereotypy, and by ineptitude in managing simple social situations. Probably, the trouble all individuals experience in maintaining a stream of thought when interrupted, a type of loss of attention, tests this function.
Other Alterations of Behavior and Personality
A lack of initiative and spontaneity is the most common effect of frontal lobe disease, and it is much easier to observe than to quantitate. With relatively mild forms of this disorder, patients exhibit an idleness of thought, speech, and action, and they lapse into this state without complaint. They are tolerant of most conditions in which they are placed, although they may act unreasonably for brief periods if irritated, seemingly unable to think through the consequences of their actions. They let members of the family answer questions and “do the talking,” interjecting a remark only rarely and unpredictably. Questions directed to such patients may evoke only brief, unqualified answers. Once started on a task, they may persist in it (“stimulus bound”); that is, they tend to perseverate. Fuster, in his studies of the prefrontal cortex, emphasizes the failure over time to maintain events in serial order (impairment of temporal grading) and to integrate new events and information with previously learned data. Placidity is a notable feature of the behavior. Worry, anxiety, self-concern, hypochondriasis, complaints of chronic pain, and depression are all reduced by frontal lobe disease, as they were to some extent by frontal lobotomy.