ATTENTION, CONSCIOUSNESS, SLEEP AND WAKEFULNESS 



'5 8 5 



systems makes possible the various degrees of aware- 

 ness that may be distinguished by physiological and 

 psychological criteria. Gellhorn (86) has demonstrated 

 that nociceptive stimuli in lightly anesthetized cats, 

 by interaction with acoustic and optic stimuli, lead 

 to increased reactivity in the projection areas of 

 each of these modalities. A similar interaction between 

 sense modalities has been demonstrated at the reticu- 

 lar formation by Hernandez-Peon & Hagbarth (104). 

 These investigators have also shown that afferent and 

 corticifugal influences interact at the reticular forma- 

 tion and result in either interference or facilitation. 

 Both 'occlusion' and "subliminal fringe' phenomena 

 have been demonstrated. They believe it likely that 

 reticular unresponsiveness, attributable to interaction 

 upon reticular neurons from two or more sources, 

 may well influence sensory perception and conscious- 

 ness. 



Presumably moderate interaction could lead to 

 facilitation, whereas excessive bombardment could 

 result in complete blocking of reticular activation of 

 the cortex causing disturbance in attention and 

 awareness, and even complete loss of consciousness as 

 observed in some seizure states. The kind of sudden 

 and intense barrage from afferent and corticifugal 

 sources in strong emotions could be responsible for 

 the confusion and immobilization often attendant 

 upon such circumstances. The EEG in these condi- 

 tions (see fig. 11; table 1) usually shows a picture of 

 complete and prolonged flattening or increased 

 high-frequency activity. Such records have been 

 observed in acute and chronic anxiety patients by 

 Cohn (50) and Lindsley (158). 



temporal course of consciousness. Fessard (74) has 

 written a very challenging paper on nervous integra- 

 tion and conscious experience. He takes from Cobb 

 (49) the notion: "It is the integration itself, the 

 relationship of one functioning part to another, 

 which is mind and which causes the phenomenon of 

 consciousness." Fessard calls this phenomenon of 

 consciousness an "experienced integration' or EL 

 With regard to the temporal organization of con- 

 sciousness he makes three points: a) "each new EI 

 involves a process of reorganization that cannot be 

 instantaneous"; b) time and EI are intimately related 

 in that states of consciousness succeed one another; 

 and c) in order to know the nature of the integrative 

 processes resulting in EI we must attempt to deter- 

 mine the neural mechanisms corresponding to 

 memory. 



In relation to Fessard's first point, it can be shown 



as in figure 7 that two brief flashes of light 50 msec, 

 apart register as one evoked potential in the visual 

 cortex of the cat, until the reticular formation has 

 been stimulated, and then for a short time afterwards 

 the pair of flashes elicit a pair of evoked potentials. 

 The same two flashes, as Lindsley (162) has found, 

 would be seen by a human subject as one when 50 

 msec, apart, but as two when 100 msec, separate 

 them. Thus in this instance, as well as in the case of 

 fusion of repetitive flashes above flicker level, succes- 

 sive El's require time for reorganization and integra- 

 tion. The second point emphasizes Lashley's (155) 

 concept of "serial order of behavior' and stresses the 

 importance of coherence of temporal sequences, for 

 meaning depends upon order. 



Travis (226) has made an attempt to investigate 

 the temporal course of consciousness by recording the 

 EEG from subjects while they were asked to rest 

 and let their minds wander, without attempting to 

 direct the stream of consciousness. Periodically the 

 experimenter said, 'Now,' and the subject reported 

 whatever conscious state w.i^ interrupted. A variety 

 ol types of imager) was revealed, but mainly visual, 

 auditor) and kinesthetic. Reports classified as abstract 

 thinking or mental blankness also were encountered. 

 Alpha blocking or an activation pattern tended to be 

 associated with visual images, kinesthetic sensations 

 and mental effort, while mental blankness and 

 abstract thinking appeared to be accompanied by 

 Strong or well-developed alpha waves. Travis con- 

 cluded that large and regular alpha waves are indica- 

 tive of a state of cortical equilibrium and represent a 

 generalized psychic activity, whereas the breaking 

 up of this collective action into more rapid and ir- 

 regular oscillations of much smaller amplitude 

 represents a relatively high degree of specificity in 

 psychic activity. In present-day terms this would be 

 equivalent to saying cortical activation is associated 

 with attention. 



Penfield (192-194) has developed an interesting 

 collection of unique observations and subjective 

 reports by the artificial induction of awareness 

 through stimulation of the brain of conscious patients 

 at time of operation. He stresses that sensation cannot 

 be located in the cortex but instead the sensory 

 material is reorganized in a higher center which he 

 identifies as the "centrencephalon" or "higher brain 

 stem.' He states that the centrencephalon '"must be 

 in certain portions of the diencephalon, mid-brain 

 and pons." Elsewhere (193) he includes "those parts 

 of the higher brain stem, which have symmetrical 

 connections with both hemispheres," pointing out 



