ATTENTION, CONSCIOUSNESS, SLEEP AND WAKEFULNESS 



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CLONIC PHASE 



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fig. 1; EEG record of a major grand mal seizure showing the onset with hypersynchrony about 

 6 sec. before the tonic phase was ushered in with high-voltage fast activity which gradually shifted 

 to slow waves at ;{ per sec. and the clonic phase Consciousness was lost near the onset of the tonic 

 phase during fast high-voltage waves. [From l.indslev, unpublished observations.] 



but without falling or necessarily very notice. 1 lilt- 

 change in behavior. If speaking, the patient in.i\ 

 stop or continue with poor integration. A movement 

 already started may be fixed or frozen, or may be 

 continued with poor control. Our major concern 

 here is with the state of consciousness and that is 

 variable, ranging from a complete "blank-out" to 

 partial awareness and ability to continue counting, 

 or to stop counting momentarily and continue again 

 as if nothing had happened. These and other varia- 

 tions to receive, integrate and respond to stimuli and 

 commands are apparently due to the variations in 

 the magnitude and extent of the seizure discharge 

 and perhaps also bear some relationship to its origin, 

 whether in the thalamus, cortex or elsewhere. (See 

 also Chapter XIY by Gastaut & Fischer-Williams in 

 this Handbook. I 



The loss of consciousness in syncope, and especially 

 carotid sinus syncope, has been attributed to a fall in 

 arterial pressure and decreased oxygen tension of 

 blood in the brain, but Lennox et al. (156) and Ferris 



it al. (73) concluded that some other factor than 

 cerebral anoxia must produce unconsciousness in 

 carotid sinus syncope oi the central type. Forster et al. 

 (76) found unconsciousness associated with slow 

 waves in the circulatory type, but with fast waves in 

 the central type. In recent years Bonvallet et al. (29) 

 have brought forth evidence which mav have a 

 bearing upon unconsciousness and syncope. They 

 have shown that spontaneous fluctuations of electro- 

 cortical activity arc related to sympathetic tone, and 

 that visceral and nociceptive stimuli produce marked 

 activation of the cortex and parallel sympathetic 

 changes. Two mechanisms are operating, a direct 

 influx of such stimuli to the bulbar reticular forma- 

 tion with immediate cortical activation, and a delayed 

 humoral process which acts upon the pontomesen- 

 cephalic reticular activating system and then the 

 cortex. The sympathetic tone mav be just as impor- 

 tant to the maintenance of wakefulness and conscious- 

 ness as the influx of proprioceptive and exteroceptive 

 stimuli. 



