I 564 HANDBOOK OF PHYSIOLOGY v^i NEUROPHYSIOLOGY III 



SITE BEFORE DURING 



A RAS (75) 



AFTER 



I 





rJS* _T»* Jg* 



TEMP POLE (74) 

 ASLEEP 



d 



*& *& 



TEMP POLE (74) 

 AWAKE 



A J - J* Jn ..£ tfi 



FRONTAL 

 POLE (74) 



1 



jfit 



in. 5. Behavioral arousal of a sleeping monkey by electrical stimulation through implanted 

 electrodes ill the reticular formation (A) and on the temporal pole of the cortex {B). Stimulation 

 of the temporal pole of a waking monkey alerts it to attention (C), but stimulation of the frontal 

 pole is iii« IN 1 rive 1 D). 



reacts to stimulation in each of these regions. In 

 picture-series .1, while the monkey is asleep, the 

 reticular formation (RAS) was stimulated. Note 

 progressive arousal from a sleep posture before stimu- 

 lation to an alert ,m<l uprighi posture with an in- 

 quiring appearance after the stimulation ceased. 

 flu- same behavior occurred (li\ when the temporal 

 pole was stimulated during sleep. Stimulation of the 

 temporal pole while the monke) was awake (C) 

 caused the monkey to look more alert and to scan 

 the environment for the source of the alerting stimulus, 

 Im.ilK fixing attention in a given direction. Stimula- 

 tion of the frontal pole (/>), an area less able ap- 

 parent!) to activate the ARAN or 10 mobilize atten- 

 tion through the DTPS, although receiving projections 

 limn certain portions of the DTPS, results in no 

 apparent 1 hange in behavior. 



h has been pointed out b) Walker (231 1 and others 

 thai there is considerable confusion and disagreement 

 about tin- interconnections of thalamic nuclei and 



particularly the pathways by which unspecific nuclei 

 reach or influence the cortex. Some agreement ap- 

 pears to be emerging gradually from the results of 

 several neurophysiological studies bearing on this 

 problem. In particular those structures in the thala- 

 mus which, when stimulated electrically, produce 

 recruiting responses, activation or both in widespread 

 areas are known. Destruction of certain areas elimi- 

 nates recruiting, natural sleep spindle bursts, and 

 unilateral synchronization of spindle bursts in thala- 

 mus and cortex. Some lesions appear to produce dis- 

 tractihilitv and loss of attention. In the following 

 studies the nucleus ventralis anterior, or at least 

 certain anterior ventral regions, appear to be im- 

 portanl as a possible pathwav of egress of DTPS 

 influences. 



Lindsle) ti al. (163) demonstrated in acute cat 

 preparations thai transection of the neuraxis at suc- 

 cessivel) higher levels in the brain stem produced 

 increasing amounts of electrocortical ^v nc 1 1 ionization, 



