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HANDBOOK OF PHYSIOLOGY 



NEl'ROPHYSIOLOGY III 



Grunthal (161) to propose that the hippocampus, 

 as the virtual 'hub' of the limbic system, may repre- 

 sent a 'catalytic activator' which, although not 

 necessarily participating in specialized functions 

 itself, is nevertheless basic for the proper functioning 

 of affective and neocortical activity. 



More recently, MacLean (255) has reviewed and 

 elaborated Papcz' (302) earlier theoretical views on 

 emotional behavior and limbic system mechanisms 

 (or "visceral brain,' as is MacLean's reference), 

 suggesting the basic importance of these forebrain 

 structures not only for affective processes, but also 

 for correlating 'oral and visceral sensations' as well 

 as 'impressions from the sex organs, body wall, eye 

 and ear.' Even Pribram & Kruger (311) in their com- 

 prehensive review of the 'olfactory brain,' have 

 speculatively assigned 'olfactory-gustatory,' 'meta- 

 bolic' and "socioemotional" functions to the various 

 'limbic' components comprising their three 'systems.' 

 And Gloor's (155) recent analysis of telencephalic 

 influences upon the hypothalamus has assigned to 

 the limbic system the role of "modulator of func- 

 tional patterns integrated at the level of the hypo- 

 thalamus and the brain stem tegmentum," even 

 though in his view, "the limbic system docs not 

 fundamentally integrate the functions it is capable of 

 influencing by its activity." Indeed, the weight of 

 available anatomical, physiological and psycho- 

 logical evidence would certainly seem to support 

 at least some generally similar concept of the 'inter- 

 mediary' role of the limbic system in the integration 

 of brain-stem and neocortical participation in 

 emotional behavior. 



Neot hi tii n/ Fum tion 



Despite this icon! experimental and theoretical 

 emphasis upon limbic system relationships, however, 

 the long-enduring quest for 'localized functions' 

 at the level of the neocortex continues to exert im- 

 portant influences upon both clinical and laboratory 

 contributions to the neurophysiological analysis 

 oi emotional I >» - 1 1. 1 v i < »i F01 the mosl part, attention 

 has traditionally focused upon the frontal lubes with 

 specific reference to affective processes (83, 117, 

 126, 131, 132, 171, 200, 214, 231, 23 |, 244, -'78, 279, 

 [66, 376, 382), although some additional con- 

 (11 n with the participant role ol more exten- 

 sive neocortical regions (7, 86, 158, 212, 

 282, 293, 104, 313) has recently been in evidence. 

 1 ndei tandably, clinical observations can be seen 

 in have contributed the lion's share to the available 



literature in this area, although the laboratory analy- 

 sis of ablation consequences and selective changes 

 in electrically recorded potentials from the neocortex 

 has more recently suggested important neural- 

 behavioral relationships. Long before systematic 

 treatment of such problems was fashionable ob- 

 servations on the behavioral consequences of the 

 'sacred disease' — epilepsy — included both literary 

 and professional descriptions of affective changes 

 presumably related to neocortical involvement. 

 And as early as 1875, David Ferrier (120) provided 

 a provocative description of behavioral changes 

 closely related to emotional phenomena in monkeys 

 following experimental frontal ablations. Somewhat 

 later, Bianchi (25) made similar observations, and the 

 story of the classic report by Fulton & Jacobsen 

 (136) before the London meetings of the Second 

 International Neurological Congress in 1935 and 

 the subsequent adoption of frontal ablations as a 

 therapeutic procedure by Moniz & Lima (2871 is 

 now too well known to require detailed repetition. 

 Significantly, the presumed therapeutic emotional 

 changes observed to follow such prefrontal lesions 

 have frequently been rationalized in terms of the 

 intimate anatomical and functional relationship of 

 these more or less specific portions of the cerebral 

 mantle with the affective integrative mechanisms 

 of the diencephalon (via principally the dorsomedial 

 thalamus). It has now become abundantly clear, 

 however, that extensive limbic system influences 

 doubtless exert important mediating effects on such 

 diencephaliconeocortical interactions, and thai the 

 assessment of emotional changes consequent upon 

 neocortical involvement must be considered within 

 this integrative relational framework. Indeed, the 

 wide variety of behavioral changes which have 

 been observed to follow such frontal neocorlie.il 

 ablations would appear comprehensible nnlv within 

 the broad framework of such an integrative analysis. 

 For the most part, the consequences of frontal lobe 

 lesions appear to involve changes in the direction of 

 diminished 'emotional responsiveness.' Both clinical 

 and laboratory reports, however, have also con- 

 firmed the frequent appearance of increased 'emo- 

 tional lability' in man and animal following at least 

 some therapeutic and investigative efforts to alter 

 affective behavior patterns with frontal neocortical 



ablation. Clearl) we are a considerable distance 

 from a satisfactory understanding of the participant 

 role of such specific neoeortie.il regions in the elab- 

 oration oi emotional processes, although the evi- 

 dence for such involvement seems unequivocal. 



