EMOTIONAL BEHAVIOR 



'545 



an objectively quantifiable definition of the be- 

 havior in terms of changes in output during various 

 segments of the lever pressing curve (195). In many 

 respects, this rather restricted behavior sample 

 appears to be prototypical of the most primitive 

 aspects of an organism's emotional repertoire, and 

 the investigation of its vicissitudes — the conditions 

 which determine its increases and decreases in 

 strength, etc. — has already contributed significantly 

 to the differential experimental analysis of both the 

 physiological and psychological variables upon 

 which the organization of emotional behavior de- 

 pends. 



The potential implications for a neurophysio- 

 logical analysis of emotional behavior within this 

 rather broad operant conditioning framework first 

 became apparent as a consequence of a series of 

 studies on the effects of electroconvulsive shock 



(.33. 34. 49- 50, 5 2 > 54. 5». i4.> '93. '95> The 

 results of these experiments showed that ii was pos- 

 sible to separate and measure selectively the effects 



of such physiological manipulations upon the '<■ - 



tional' components of a behavior segment inde- 

 pendently of any gross effects upon the simple 

 repetitive lever-pressing habil which provided the 

 control base line. Subsequent applications of this 

 approach to the analysis ol more direct neurophysio- 

 logical participation in alfcclive processes have 

 made it possible to show, for example, thai the elab- 

 oration of even such basic aspects of emotional be- 

 havior depends heavily upon the integrit) of quite 

 specific portions of the forebrain and brain stem, 

 notably the limbic system. Although large neocor- 

 tical lesions were found to produce little or no effect 

 upon the acquisition, retention or extinction of the 

 conditioned suppression pattern, lesions in the septal 

 region and hippocampus produced significant decre- 

 ments in the maintenance of such behavior and 

 most dramatic changes in gross affective expression 

 (36, 53). In addition, lesions of the habenular com- 

 plex of the thalamus appear to reduce resistance to 

 extinction of the conditioned suppression response, 

 although cingulate lesions have no apparent effect 

 on such behavior (40, 43, 54). 



More recently, this operant conditioning approach 

 to the neurophysiological analysis of emotional 

 behavior has found most dramatic application in the 

 exploration of reinforcement or "reward' effects 

 produced by intracranial electrical self-stimulation 

 of the nervous system. Olds & Milner (301) first 

 reported that rats, electrically stimulating themselves 

 in various portions of the limbic system by pressing a 



n_._ 



^200 ' 



no. 3. Sample cumulative response curves showing acquisi- 

 tion trials for the conditioned 'anxiety' response superimposed 

 upon lever pressing for water and intracranial electrical stimu- 

 lation reward. The oblique solid arrows indicate the onset of the 

 conditioned auditory stimulus, and the oblique broken arrows 

 indicate the termination of the conditioned stimulus contigu- 

 ously with the brief unconditioned grid-shock stimulus to the 

 feet during each trial. [From Brady | ", 



bar, would maintain high lever-pressing rates over 

 long periods of time without an) other reward. 

 This same phenomenon has been systematically 

 reproduced and analyzed in the cat and monke) bj 

 Brack 144, (6) and others (246, 142), and investiga- 

 tive efforts have begun to delimit some of the critical 

 variables in this area. I In- s| critic anatomical locus 

 of the Stimulating electrodes, schedules of intra- 

 cranial electrical stimulation reinforcement, food 

 and water deprivation, stimulus intensity, temporal 

 factors, and (he like have all been shown to constitute 

 critical determinants of this effect (44, 4-,, 46, 48, 

 299, |00, 142). 



Of particular interest from the standpoint of a 

 primary concern with neurophysiological relation- 

 ships .md emotional behavior, however, would seem 

 to be the- recent demonstration of interaction effects 

 between the conditioned suppression response illus- 

 trated in figure j and this intracranial -elf-stimula- 

 tion phenomenon (40, 44, 4",, 4(1). The consequences 

 of repeated pairings of the clicker and shock accord- 

 ing to this conditioning procedure have been con- 

 sistently reported to include suppression of the lever- 

 pressing rate, crouchinij, immobility and usually 

 defecation in response to presentation of the audi- 

 tory stimulus. Although this relatively stable condi- 

 tioned 'fear' pattern was reported by Brady (40, 

 43-46) to be readily elicited by presentation of the 

 clicker when both rats and monkeys were pressing a 

 lever for food or water reward, substitution of brain 

 stimulation through chronically implanted limbic 

 system electrodes (septal region, medial forebrain 

 bundle) for the food or water on the same reinforce- 

 ment schedule resulted in failure of the auditorv 



