Figure 18-3. Sleep architecture, or sleep cycles. REM sleep (darkened areas) occurs cyclically throughout the night at intervals of approximately 90 min in all age groups. REM sleep shows little variation in the different age groups, whereas stage 4 sleep decreases with age. Stages 3 and 4 are now considered N3. (Redrawn by permission from Kales, Kales, and Soldatos.)
Figure 18-4. Schematic representation of the “flip-flop” mechanism of transition between sleep and waking, which is determined by the state of activity of the ventrolateral preoptic nucleus (VLPO). Arrowheads denote excitation and perpendicular line ends are inhibitory. A. During wakefulness, the monoaminergic nuclei (LC, locus ceruleus; TMN, tuberomammillary nucleus; raphe nuclei) inhibit the VLPO, thereby relieving the inhibition of the monoaminergic cells, and that of the orexin (ORX) neurons. Because the VLPO neurons do not have orexin receptors, orexin serves to reinforce the monoaminergic tone, rather than directly inhibiting the VLPO. B. During sleep, firing of VLPO neurons inhibits the monoaminergic cell groups, thereby relieving their own inhibition. This inhibits the orexin neurons, further preventing monoaminergic activation that might interrupt sleep. The mutual inhibition between the VLPO and the monoaminergic cell groups forms a flip-flop switch, which produces sharp transitions in state, but is relatively unstable. The addition of the orexin neurons stabilizes the switch. (Reproduced with permission from Saper, Scammell, and Lu.)
ABCChin EMGChin EMGR9Relatively low-voltage, mixed-frequency EEGNormally active chin EMGNormally active chin EMGC3/A2O2/A1ROC/A1LOC/A2AlphaAlphaEyes closedSlow-rolling eye movementsK-complexSleep spindleLOC/A2ROC/A1O2/A1C3/A2
Figure 18-2. (Continued)
Derangements of Intellect,
Behavior, and Language Caused by Diffuse and Focal Cerebral Disease
CHAPTER 20  Dementia, the Amnesic Syndrome, and the Neurology of Intelligence and Memory
CHAPTER 21  Neurologic Disorders Caused by Lesions in Specific Parts of the Cerebrum
CHAPTER 22  Disorders of Speech and Language
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.