ATTENTION, CONSCIOUSNESS, SLEEP AND WAKEFULNESS 



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HAND-CLAP CAT OPENS EYES AND RAISES HEAD 



SLOW WAVES OUT I 1/2 win SPINDLES OUT 2 1/2 MIN 



FIG. 3. Arousal of a sleeping cat by auditory stimulus and shift of elcctrocortical activity from 

 slow waves and spindle bursts of sleep to low-voltage fast activity (ailed activation. Left and right, 

 anterior and posterior recordings all show same diffuse effect of activation. TFrom Lindslev el al. 

 (164) 



portion of the ARAS is epinephrine-sensitive and 

 gives rise to persisting tonic activation influences, 

 whereas the DTPS does not. Although the evidence 

 is not perfectly clear, due to conflicting results by 

 different workers, there arc nevertheless indications 

 that activation or behavioral arousal responses, 01 

 both, elicited from ARAS and DTPS are somewhat 

 differentially affected by mephenesin, chlorpromazine 

 and barbiturates (30, 32, 70, 143). 



ARAS and DTPS Arousal mid Alerting Effect! 



Lindslev et al. (1(141 have shown the nature "1 

 elcctrocortical 'arousal' and its association with be- 

 havioral arousal in the cat (see fig. 3). It will In- noted 

 that the sleeping cat's EEG record shows irregular 

 slow waves and periodically occurring spindle bursts 

 composed of 12 to 14 per sec. waves. An auditor) 

 stimulus, such as a sharp hand-clap, caused the EEG 

 picture to change immediately to a low -amplitude 

 fast-activity pattern, without slow waves or spindle 

 bursts. Associated with this was behavioral arousal 

 consisting of opening of the eyes and raising of the 

 head. The EEG sleep picture was not restored for at 

 least 2 or 3 min. when the cat again assumed a 

 sleeping posture. Thus the association between electro- 

 cortical 'arousal' and behavioral arousal was estab- 

 lished, and although exceptions to this have been re- 

 ported under the influence of certain drugs (31, 82, 

 234), especially atropine, repeated confirmation has 

 permitted the general use of electrocortical and be- 

 havioral arousal interchangeably. 



Figure 4 illustrates how intactness of the reticular 

 formation is essential to wakefulness and how its 

 interruption produces somnolence or sleep. Section 

 confined to the lateral afferent pathways in the mid- 

 brain region of the cat still permits behavioral (.-!) and 



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fig. 4. Cat with bilateral section ol the classical afferent path- 

 u.ivs in the midbrain, sparing the tegmentum, standing awake 

 1 with characteristic waking Mi. I Cat vmiIi mesen- 

 cephalic tegmentum interrupted, sparing the classical afferent 

 pathways, lies somnolent (B), with sleeping lit. /.' from 

 Lindsley el "I '. (164) 



electrocortical (A') wakefulness. Note that the elec- 

 trocortical activity i*- characteristic of waking in a 

 normal cat, with low-amplitude fast activity pre- 

 dominating, and that behaviorally the cat is awake. 

 In contrast to this, after a lesion of the midbrain 

 tegmentum, interrupting the ARAS, the behavior 

 (5) and the electrocortical activity (B r ) are those of 

 somnolence or sleep. In such a state the animal can 

 be aroused only momentarily by strong stimuli, and 

 the electrocortical and behavioral arousal do not 

 persist after the stimulation has ceased. 



Segundo and co-workers (212) have demonstrated 

 in the monkey how arous.il and alerting may be 

 produced by reticular stimulation. Figure 5 illustrates 

 how an otherwise normal monkey, with electrodes 

 chronically implanted in the reticular formation and 

 also over the temporal and frontal poles of the cortex, 



