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Physicians sooner or later discover, through clinical experience, the need for special competence in assessing the mental faculties of their patients. They must be able to observe with objectivity the patient’s attention, intelligence, memory, judgment, mood, character, and other attributes of cognitive performance, and personality in much the same fashion as they observe the patient’s movements, gait, and reflexes. The systematic examination of these intellectual and affective functions permits the physician to reach conclusions regarding the patient’s mental status and its relationship to his illness. Without such data, there are likely to be errors in the diagnosis and treatment of the patient’s neurologic, general medical, and psychiatric disease.

The content of this section will be more clearly understood if a few of the introductory remarks to the later section on psychiatric diseases are anticipated here. The main thesis of the neurologist is that mental and physical functions of the nervous system are two aspects of the same neural process. Mind and behavior both have their roots in the self-regulating, goal-seeking activities of the organism, the same ones that provide impulse to all forms of mammalian life. But the prodigious complexity of the human brain permits, to an extraordinary degree, the solving of difficult problems, the capacity for remembering past experiences, and casting them in a symbolic language that can be written and read, and the planning for events that have yet to take place. The constant but sometimes meandering internal verbal experience of this ideation during waking was aptly named “stream of thought” by William James. Somehow there emerges in the course of these complex cerebral functions, a continuous awareness of one’s self and the operation of one’s psychic processes. It is this continuous inner consciousness that might be called mind. Whether this is an emergent property of various mental functions or simply their representation as an idea in the mind cannot be answered, but any wide separation of the mental from the observable behavioral aspects of cerebral function is probably illusory. Biologists and psychologists have reached this view by placing all known activities of the nervous system (growth, development, behavior, and mental function) on a continuum and noting the inherent purposiveness and creativity common to all of them. The physician is persuaded of the truth of this view through daily clinical experience, in which every possible aberration of behavior and intellect appears at some time or other as an expression of cerebral disease. Furthermore, in many brain diseases, particularly the forms of confusion addressed in the first chapter in this section on confusional states, one witnesses parallel disorders of the patient’s behavior and a dissolution or distortion of the introspective awareness of his own mental capacities.

The reader will find that Chaps. 19 and 20 are concerned with common disturbances of the sensorium and of cognition, which stand as cardinal ...

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