ATTENTION, CONSCIOUSNESS, SLEEP AND WAKEFULNESS 



'3/0 



extent does the slower time constant of these systems 

 determine the speed of attentive adjustment, of per- 

 ceptual discrimination and so forth? With an alpha 

 frequency of 5 per sec. at 1 year of age, alpha blockade 

 time or latency is twice as long as it is when the alpha 

 frequency has attained 10 per sec. at 10 years or later. 



At the present time beta waves of 18 to 30 per sec. 

 and under 10 fiv. on the average, and gamma waves 

 of 30 to 50 per sec. and even smaller, hold little prom- 

 ise for use as analytical devices. Both are easily con- 

 fused with muscle potentials and other low-level ar- 

 tifacts. Neither is responsive to sensory stimulation 

 directly as is the alpha rhythm. Beta waves are more 

 easily observed over the frontal half of the head, and 

 over motor and frontal association zones where alpha 

 waves, though present, are not as prominent as pos- 

 teriorly. Beta waves are said to respond to motor 

 movement. 



Theta waves of 4 to 7 per sec. are seen mainly in 

 temporofrontal regions in children but are often asso- 

 ciated with behavior disorders or other physiopatho- 

 logical instabilities. Delta waves ranging from Less 

 than 1 to 4 per sec. are not seen in the EEG record of 

 normal subjects unless they are drowsy or asleep 

 Slow and large delta waves are usually considered in- 

 dicative of pathology or physiopathology. 



Characteristic*, of the EEG in Sleep 



The EEG undergoes striking changes in pattern in 

 the transition from wakefulness to sleep, and has be- 

 come one of the more convenient and reliable ways to 

 assess the state of wakefulness 01 sleep. Berger (22) 

 observed that alpha waves slow and are reduced in 

 amplitude and eventually disappear as sleep develops. 

 Loomis el al. (i66-i6g) studied all-night sleep records 

 and noted not only the abolition of alpha waxes as 

 light drowsiness gave way to deep drowsiness, but 

 that a series of distinct patterns emerged as various 

 stages of sleep ensued. In particular they called at- 

 tention to 12 to 15 per sec. sleep spindles and the ap- 

 pearance of random slow waxes as actual sleep began. 

 Growing out of the work of several groups of investi- 

 gators concerned with the study of stages of sleep 



( -28 . 53. 99' '44. '47. ! 4 8 > l6 9> >7°> 2I 5> came a fairly 

 consistent and systematic picture of the changing 

 patterns in the transition from wakefulness to sleep. 

 Brieflx' these stages may be described as follows. Stage . 1 

 (Awake). Alpha waves are present at the start Inn 

 diminish in xoltage and amount as the subject shows 

 slight drowsiness. Stage B {Drowsy). Alpha waxes di- 

 minish still further and vanish leaxing the base line 



relatively flat or with loxv-voltage fluctuations and 

 sporadic delta waves. Stage C (Light Sleep). Fourteen 

 per sec. spindle bursts develop on a random, low- 

 voltage, delta-wave background. Stage D (Medium 

 Sleep). Delta waves decrease in frequency but increase 

 in voltage and amount; the spindle bursts disappear. 

 Stage E {Deep Sleep). Delta waves increase in duration, 

 voltage and randomness. The transition stage between 

 B and C is one of going from fluctuating awareness or 

 deep drowsiness to complete lack of awareness or loss 

 of consciousness. During Stage C the subject makes no 

 perceptual discriminations and has no memorv for 

 exents or sensory stimulations, unless these are intense 

 enouuh (o wake him up. Each of the aboxe stages can 

 be further subdivided on the basis of certain criteria 

 in relation to the EEG pattern as Simon & Emmons 

 (215) have done. The above classification is based 

 mainly on that of Loomis et al. ( 169), Dax is et al. (53) 

 and Simon & Emmons (21 j 217), each of whom pre- 

 sents illustrations and detailed descriptions. 



The transition from sleep to wakefulness follows a 

 similar though more variable course in the reverse 

 direction. Changes ma) be more precipitous from one 

 stage to another. With the return of consciousness on 

 waking, alpha waxes are present in reduced amount 

 .Hid xulusje, and max not assume their regular form 

 and character for some time. Henry (99) found that 

 EEG patterns of individuals on waking tend to be 

 more homogeneous and alike than at any other time. 

 As a few hours intervene after waking, the EEG 

 records take on greater individuality. 



Ontogenetically, as shown in figure to, the EEG 

 sleep pattern emerges with time. These tracings taken 

 at different times from the same child indicate that in 

 light to moderately deep sleep the EEG sleep pattern 

 corresponding to these stages of sleep has not clearly 

 emerged during the first to to 15 days, although there 

 are evidences of incipient delta waves and even spindle 

 bursts in the motor region. B\ [05 days the general 

 pattern of spindle bursts and random sloxx wave ac- 

 tivity is clearly evident, as it also seems to be at about 

 30 days. The same general type of pattern is also seen 

 at 280 days and thereafter for light to moderate depth 

 of sleep. Others who have studied the EEG of new- 

 born and young infants are Smith (218), Hughes 

 et al. (121, 122), Xekhorocheff (184) and Ellingson 

 (7>). 



The Sleep-Wakefulness Continuum 



In attempting to relate the various stages of the 

 EEG pattern to corresponding psychological states 



