neurophysiology: an integration 



195' 



unresolved tensions [the awaited message, the un- 

 solved problem, the unmade decision, the unassimi- 

 lated novelty and the unbalanced emotional equation 

 (109)] would be associated with long-maintained 

 reverberation. (If reverberation is in the amygdala in 

 dreams, as suggested by Gloor, a subject with a stimu- 

 lating electrode in this structure might remember a 

 dream on being awakened just after stimulation; 

 otherwise, not.) The progressive building-up of "physi- 

 ological inflammation,' which might be hypersynchro- 

 nization or excessive reverberation, should also be 

 recalled. Gastaut & Fischer-Williams speak, com- 

 parably, of ephaptic spread of activity in the neuropil, 

 'like oil,' when bombardment is high or threshold low; 

 but they emphasize irradiation via deep centers. 



perception and attention. Reverberation is prob- 

 ably no less involved in much shorter range phe- 

 nomena. Repression (as studied, for example, by the 

 inability to recognize forbidden words tachisto- 

 scopically), subliminal perception (210), autonomic 

 responses to stimuli subliminal for consciousness, the 

 ability of a bright flash as long as 25 msec, after a 

 patterned exposure to block recognition of the latter 

 (Lindsley; 181), and like findings all surliest (105) a 

 reverberation over milliseconds or seconds even in the 

 primitive perception of a stimulus (see also Living- 

 ston). Continued neural activity may thus be involved 

 over milliseconds to years in various junctions. 



The mechanisms for directing neural activity into 

 one or another set of channels, and so focusing 

 attention on one or another input (from outside the 

 body, from within it or even from within the nervous 

 system), or selecting an output, arc but little under- 

 stood. The feed-back loops altering sensitivity of the 

 receptors and the input channels, and the role of 

 higher structures in modulating these with habit- 

 uation or vigilance, are receiving intense study 

 (French, Livingston; see also Fry on accommodation, 

 and Paillard and Eldred on the efferent side). A 

 similar diencephalic influence on the cortex, partly 

 expressed through the alpha rhythm, has also re- 

 ceived much attention. But none of these really 

 accounts for the selectivity of action, and the figure 

 of the dieneephalon directing activity as a cathode 

 t.iv gun (96) also leaves the mechanism of control 

 vague. Miller and co-workers (209) are developing 

 a model that deals with "plans' — programs — for 

 action appropriate to the external environment. 

 [Compare the 'scheme of action' of Bianco (Paillard).] 

 Their origin is unassigned; but one is selected, or 

 substituted for another, by the frontal cortex, and 



the limbic system handles its execution. One might 

 regard the hypothalamus as similarly selecting and in 

 part executing plans for handling the internal en- 

 vironment. 



Feedback 



RECIPROCAL INHIBITION IN CONSCIOUSNESS. The 



demands on attention cannot all be met; input at all 

 levels exceeds output by many fold, and the mech- 

 anisms worked out by Sherrington for control of the 

 final motor path must largely apply to the capture of 

 attention. Certainly attention, like behavior (and 

 recall), is normally shifted abruptly in an all-or-none 

 fashion towards one or another of competing; outcomes 

 rather than split between them. There is a clear 

 reciprocal inhibition of the Sherringtonian type 

 between perceptions (N'eifi, feed-back controls 

 (Strom), different emotions (as sexual arousal and 

 anger), emotions and ideas, and various direction^ ol 

 attention. The driver hears nothing of an interesting 

 conversation during .1 traffic emergency, as the 

 student finds a chunk of a lecture displaced by 

 internal ruminations. The mechanism, inhibition of 

 neighboring units l>\ recurrents from the axon, that 

 operates in a retina to emphasize an edge and in a 

 motor pool to give clean movements, Renshaw cells, 

 may well be wideh prevent to gate all central flow 

 and sharpen the selection of alternate channels The 

 widespread presence of Renshaw-type cells is now 

 an active question. [See also Milner (212).] The 

 careful studies of Broadbenl (32), mainly on auditory 

 competition lor attention and response, clearlv 

 indicate brief lapses or blinks even in attention 

 Continuously directed to the same input. His model, 

 in terms of channel capacity and other communi- 

 cation mechanisms, will be considered later. 



affect and drives. Arousal, attention and vigilance 

 are also closely related to the internally initiated 

 drives concerned with the maintenance of homeos- 

 tasis. Actually, such drives, which imply an external 

 behavioral component, also really originate outside 

 of the organism; they are part of homeostatic mech- 

 anisms involving; negative feed-back loops extending 

 into the environment. (Less directly, sex behavior and 

 curiosity may also involve these.) External cold, 

 acting through thermoreceptors on the body surface 

 or in the hypothalamus, can bring about integrated 

 internal responses for increasing heat production and 

 decreasing heat loss. In addition, the central thermo- 

 receptors activate the LEG, increase muscle tone 



