The neurological analysis of complex behavioral states associated with serious brain disease not infrequently is a difficult task. In many such cases, the signs of minor degrees of akinetic mutism were found when deliberately looked for. Recognition of this feature greatly facilitated interpretation. The ancient term abulia is suggested for the specific neurological syndrome comprising slowness, decreased responsiveness, apathy, etc. Akinetic mutism is its extreme form. A lesser degree of abulia is here termed abulia minor. The attributes of abulia minor are described, and the neurological conditions with which it had been found associated are listed. Preliminary conclusions as to the anatomical localization of the syndrome are presented. The literature on akinetic mutism is reviewed, and a few special observations are commented on--paradoxical activity, the telephone effect, and reflex attention. The application of the newer knowledge of cerebral neurotransmitters to akinetic mutism is illustrated. At the beginning of the study the focus was on abulia, but it was natural that sooner or later the contrasting state of behavioral hyperactivity or agitation would have to come under equal scrutiny. A list of conditions in which psychomotor agitation was a feature has been compiled from personal files. The localization of the disease process in hyperactive states is compared with that in abulia. A few special observations on hyperactive states are presented, along with a note on a unique syndrome termed anideation. There has gradually emerged a concept of a continuum of behavioral activity extending from abulia at one end through eukinesia to hyperactivity at the other end. Involvement of specific fundamental integrative circuits is postulated. This morning we have been enthralled by Computers in Neurosurgery, Neurobiology in Neurosurgery, and Humanism in Neurosurgery. What could be more natural for a neurologist than to talk about Neurology in Neurosurgery. And how best to pay homage to the great lady of Medicine than by offering a modest example of her handiwork. Thus, I am led to discuss a neurological theme which has recently occupied my attention. To anticipate a little, I shall be talking about two somewhat opposite states: on the one hand there is abulia--slowness, apathy, and lack of spontaneity--and on the other hand, agitation and hyperactivity. By way of explanation, this study originated during the bedside examination of patients with brain damage and serious impairment of analysis appeared not only formidable but even impossible.(ABSTRACT TRUNCATED AT 400 WORDS)