1948 



1IWDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



impulses (54, 105). The reserve must decrease when 

 reverberation continues until serious channelization 

 develops, as in maintained tension and anxiety and, 

 probably, in the neuroses (108, 109, 114). (iastaut & 

 I is, her-Williams note a similar double basis for 

 convulsive activity lowered threshold, as with 

 pentylenetetrazol, or excess stimulation, as in photic 

 driving and the absence of consciousness with 

 either too little or too much cortical activity (see also 

 Bartley, Gloor). Increased thresholds, produced l>\ 

 hypnotic drugs directly or by inactivating the diffuse 

 system, would also drastically decrease the reserve; 

 and it is tempting to guess that the unconsciousness 

 of deep sleep or anesthesia is simply the consequence 

 of too few active neurons. 



It is probable that the phenomena described by 

 psychiatrists with the unfortunate term 'psychic 

 energy' sec Colby (46)] can more reasonably be 

 accounted for in terms of the size of the physiological 

 neuron reserve. When this is diminished, temporarily 

 or permanently, there is an accompanying con- 

 striction or stenosis of behavior with greater stereotypy 

 and repetitiveness, decreased exploration and in- 

 vention, and a lowered intensity of consciousness. A 

 moderate degree of stress and unresolved problems 

 posited by the environment would bring more and 

 more neurons into action, first by summation and 

 irradiation and later by chemical reinforcement 

 through release of epinephrine or a comparable 

 substance, and through facilitating or alerting im- 

 pulses from vigilance centers. This evokes, first, 

 awareness; then, more patterned consciousness; then, 

 focused attention or alertness or vigilance, associated 

 with increasing tension and anxiety. 



Beyond an optimal level of emergency marshalling 

 of the resources of the brain, as well .is those of the 

 body, more intense continued input overload leads to 

 .1 breakdown <>! functioning ui 1 ). [Tachistoscopic 

 performance is enhanced b) mild stimulation of the 

 reticular formation, disrupted by strong stimulation 

 (Bartley).] Reverberation presumably now occupies.! 

 larger fraction of the neurons, rendering them in- 

 accessible 10 the play of shifting activity patterns; 

 vigilance progresses to mania, tension becomes 

 unstructured anxiety, perform. nice shifts from flexible 

 exploration to unadaptive and rigid repetition, and 

 psychic energ) is dissipated (116). Marrazzi (194) 

 suggests .1 reverse mechanism for such psychotii 

 phenomena as hallucinations. I \\\- assumes decreased 

 ica] control "l lowei centers and theii consequent 

 reli ise, the whole related loan inhibitor) action of 

 epinephrine Fatigue, hypoxia, drugs and various 



other means of disturbing the normal metabolic 

 activity of neurons can similarly bring about tem- 

 porary or enduring stenosis of behavior. A promising 

 simple test of flexibility and creativeness is to have .i 

 subject tap two keys in random fashion (Kornblum, 

 S., unpublished observations). With fatigue, random- 

 ness degenerates into repetitive patterns, with runs of 

 simple alternation — suggesting the lapse into autistic 

 behavior. Similarly, one would expect that, with 

 moderate tension, decision time per bit (normally 

 .125 sec.) would decrease, but th.it with severe 

 tension the time would prolong or the response would 

 become stereotyped and errors increase. These views 

 have been extended elsewhere (113, 1 1 4 1 to the 

 manifestations of schizophrenia and of old aye the 

 limited capacity decreases the possible conceptual 

 classification and so leads to the regression of schizo- 

 phrenia to predicate reasoning, personification, loss 

 of self boundary and the like [compare Arieti 111)]; 

 as well as to narrowed attention [see Callawa) & 

 Dembro (40)]. The greater loss of word usage in 

 aphasias with greater random loss of neurons (Howes, 

 D. H., Ill, Geschwind, N., personal communication) 

 is quite comparable. 



Physiological Parana /> 1 1 



The relation between brain structure and behavior 

 has been studied for centuries and much is known 

 concerning the contribution of various brain regions 

 and nuclei to all aspects of functioning. Comparable 

 efforts to relate performance differences to physi- 

 ological properties of the nervous system are almost 

 nonexistent. Yet it seems highly probable that the 

 liner nuances of perception and performance, of 

 personality and ability, will depend more on physi- 

 ological parameters than on anatomical ones. The 

 physiological neuron reserve, in contrast to the 

 .in.iiomic.il neuron population, accounts for man) 

 properties of consciousness and behavior. It can 

 hardly be questioned that physiological differences in 

 single neurons or synapses or interaction patterns — 

 quite aside from the momentary discharge or no 

 discharge of impulses will important!) influence the 

 individuality or personality of the organism. 



Kev variables lor the neuron would be: its met- 

 abolic rate and qualitv and consequent drug sensi 

 tivitv (such differences in neurons and synaptic 

 mechanisms must underlv the specificity and the 

 variance of drug action), the existence and properties 

 . .1 a spontaneous electrical rhythm; the normal 

 threshold level anil the spontaneous plav in threshold; 



