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HANDBOOK OF PHYSIOI < '< ,V 



NEUROPHYSIOLOGY III 



have Niimulated much new investigation and work 

 goes on apace all over the world. There remains much 

 Inn detail to fill in, and corrections and additions 

 have already been made. There is a need to develop 

 further extensions and modifications of these views 

 so as to encompass more of the higher functions of 

 which man and his near relatives in the animal king- 

 dome are capable. Perception, memory, learning, 

 emotion and motivation arc some of the psychological 

 problems currently being pursued intensively by 

 further investigation of the ARAS and the DTPS, 

 hut especially in ancillary and related systems else- 

 where in the brain stem, limbic svstcm and neocortex. 



I. ei us attempt to trace some of the earlier and 

 alternative views of sleep and wakefulness, and par- 

 ticularly provide some of the background which 

 leads to the present concepts of the ARAS and DTPS. 

 For some reason, perhaps because adult man spends 

 only about one third of his time in sleep, wakefulness 

 has been traditionally thought of as the natural condi- 

 tion and sleep a deviant, but necessary, recuperative 

 period requiring explanation. Hence the persistent 

 search for a sleep or sleep-regulating center in the 

 brain, a son of magic push button to turn on and 

 off this process. Other conceptions of sleep have em- 

 phasized .1 generalized depression or inhibition of 

 central nervous sxstetn function. 



Whether a generalized or a local sleep-regulating 

 center was envisaged, the factors responsible for 

 depression or reduction of function in sleep have 

 variouslv been noted as anemia, accumulation of 

 fatigue products and toxins, periodic change in 

 humoral and endocrine action, change in amount 

 and rate ol cerebral circulation, development of a 

 generalized or irradiated internal inhibition, and 

 retraction of dendrites at synaptic junctions. These 

 and other theories have been reviewed by Pieion 

 (195), Ebbecke (68), von Economo (230), Gillespie 

 (91 ), Kleitman (145), Kayscr ( 1 40I and Ploou ( I <)!>). 



Concise, but relatively comprehensive, overviews 

 ..1 some of the characteristics oi sleep and theories of 

 sleep have been presented bv Wiggers (233) and 

 Morgan & Stellar (1781. Kleitman's (145) book, 

 v, ;i and Wakefulness, is .1 classic in the field 



Early Neurophysiological Concepts "I Sleep and Wakefulness 



Several viewpoints have held thai there is .1 block- 

 age "I afferent impulses at some point in the brain 

 which prevents it from being maintained in an active 

 and wakeful state. These have been called stimulus 



deficiency theories, and some of them resemble in 



general notion the modern neurophysiological theory 



based on the ARAS, but do not, of course, distinguish 

 between the specific and unspecific sensory systems 

 and their respective roles 



Following an epidemic of encephalitis lethargica, 

 with sleep as a prominent sign, Mauthner (175) in 

 1890 reported clinical and neuropathological evi- 

 dence of swelling and other lesions in the periven- 

 tricular and periaqueductal grey matter of the 

 midbrain. The sleep was attributed to a compression 

 of afferent pathways, cutting off the influx of sensory 

 impulses to the brain. Mauthner generalized upon 

 this conclusion based on patients with encephalitis 

 and proposed a midbrain sleep-regulating center 

 which in some manner regulated the flow of impulses 

 to the brain and accounted for sleep in normal per- 

 sons, von Economo (229), after similar experiences 

 with encephalitis patients following World War I, 

 extended the concepts of Mauthner. Instead of a 

 specific center, he proposed that there is an area 

 reaching from the midbrain through the hypothala- 

 mus to the basal ganglia which is concerned with the 

 regulation of sleep and wakefulness. In general tin- 

 location and structures involved correspond fairly 

 well with the modern neuroanatomical description of 

 the ARAS provided in the extensive review ol the 

 reticular formation bv Rossi & Zanchetti (204). 

 However, von Economo had rather different ideas 

 about its function. He conceived of two centers of 

 control, one rostrally located in the basal ganglai 

 which was thought to be able to inhibit the activitv 

 of the thalamus and cortex and produce disturbances 

 in consciousness and what he called "brain sleep.' The 

 other he located in the midbrain. It was thought to 

 be inhibitory to vegetative and somatic centers in the 

 posterior hypothalamus and lower brain stem, thus 

 giving rise to 'body sleep.' Numerous facts ol normal 

 and patholouie.il sleep lit such a concept, as do some 

 modern concepts of disturbances of consciousness in 

 epilepsy. However, the theory, like so many others, 

 does not make explicit how inhibition or excitation of 

 the centers is effected, nor in what manner these in- 

 fluence central or perpheral functions in sleep .mil 

 wakefulness. 



Many other proposals have been made concerning 

 the so-called sleep ,md wakefulness centers, for the 

 most part the location was in the posterior hypo- 

 thalamus, midbrain or thalamus, and overlapped in 

 some degree with the ARAS and DTPS sv steins de- 

 scribed above. The details of the individual view- 

 points have been covered in Klcitm. m's lt|V com- 

 prehensive survev. Notable, because of one element 



ol similarity to modern views, namely cortical acti- 

 vation "I the ARAS, is Kov.us' (149) conception that 



