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HANDBOOK OF PHVSIOLOGV 



NEUROPHYSIOLOGY II 



finding and clinical observation (■2'], 32, 101, 103, 



127). 



SUMMARY AND CONCLUSION 



Evidence has been presented to support the con- 

 ception that the posterior and the frontal intrinsic 

 systems serve different aspects of the problem-solving 

 process. The argument has been forwarded that two 

 major classes of behavior can be distinguished, differ- 

 entiative and intentional. The multiple object experi- 

 ment detailed above provides a paradigm of the 

 relation between each of these classes in problem solu- 

 tion. Posterior intrinsic .sector resection interferes with 

 differentiative behavior during .search; such lesions 

 affect the delineation of a problem. Frontal intrinsic 

 sector resection interferes with intentional behavior 

 after search is completed; such lesions affect the 

 economic solution of a problem. 



Furthermore, the experiment presented shows that 

 the delineation and economic solution of a problem 

 can occur more or less haphazardly. Haphazard prob- 

 lem-solving behavior is described by the relatively 

 wide range of systems of transformations of the input 

 and outcome under which behavior remains invari- 

 ant. Strategic problem solution, on the other hand, 

 occurs with restriction of the range of such systems 

 of transformations. The experiment is interpreted to 

 indicate that restriction in this instance results from 

 the operation of a mechanism (the intrinsic) that 

 partitions the neural events (in the extrinsic and 

 mediobasal forebrain systems) determined by input 

 and outcome. By providing both a referent and units, 

 partitioning defines the range of possibilities to which 

 an input or outcome is assigned by the organism. 



The distinction between neural mechanisms that 

 serve differentiation and those that subserve inten- 

 tion is not a new one. Sherrington makes this dis- 

 tinction in his description of the coordination of 

 reflexes (129) : The "singleness of action from moment 

 is the keystone in the construction of the individual." 

 This singleness of action comes about in two ways — 

 'interference' between and 'allied combinations' of 

 reflexes. In his analysis of 'interference' (or an- 

 tagonism) between reflexes, Sherrington forwards 

 concepts such as inhibition, induction and spinal 

 contrast — concepts which have relevance to dis- 

 criminative behavior [for example, as already noted, 

 the use of the concept 'induction' l)y Skinner (130) 

 for the occurrence of the 'hump" in the graphical 

 representation of complex discrimination learning]. 



Sherrington uses these concepts to provide an under- 

 standing of the differences between reflex behaviors 

 to different inputs. On the other hand, Sherrington's 

 discussions of 'allied combinations' of reflexes are 

 an attempt to understand behavior regulated by out- 

 comes: "the new reflex breaks in upon a condition of 

 equilibrium, which latter is itself a reflex," a notion 

 which has been enlarged upon by Cannon (g) and 

 more recently by Wiener (151). In discussing allied 

 combinations of reflexes, concepts such as reinforce- 

 ment, convergence, summation and facilitation are 

 used by Sherrington — concepts which ha\e rclexance 

 to intentional behavior. 



More recently, Denny-Brown (i 7) has distinguished 

 between cortical resections that affect patterns of 

 approaching (grasping, hopping, placing) and those 

 that affect patterns of avoiding (withdrawing). Al- 

 though the cortical resections made by Denny-Brown 

 and those described here are only roughly com- 

 parable, enough correspondence exists to permit the 

 suggestion that the patterns of approaching and the 

 sampling of inputs as described here may reflect 

 some common mechanism, that the patterns of avoid- 

 ing may be manifestations (in untamed animals sub- 

 jected to laboratory routines) of the behavior de- 

 scribed here as guided by outcomes. 



The neural mechanism here propo.sed is similar 

 in some respects to others already formulated. The 

 neurobehavioral data presented, and tlieir formal 

 analysis, suggest that the events in the extrinsic and 

 mediobasal forebrain systems are indeed the im- 

 portant determinants of moment-to-moment behavior 

 as in Lashley's (72) and in Kohler's formulations 

 (63-65), among others. However, these events are 

 acted upon by others which provide the contextual 

 matrix that sets limits on the moment-to-moment 

 beha\ ior, as propo.sed by Freud (33) and more 

 recenih b\ Forgus (29-31). The resultant of the 

 interaction of these two classes of neural events is 

 described more formally, though less picturesquely, 

 by the mechanism, 'partitioning of sets,' than this 

 resultant is described by Lashley's largely nativistic 

 or Hebb's largely empiricistic conceptions: redupli- 

 cated neural loops (69) or phase sequences (53). Yet 

 all three share the essential characteristic that, in 

 continued problem-solving behavior, increasingly 

 complex patterns of neural events occur, patterns that 

 allow more and more precise differentiations and 

 intentions to be made. 



Nor is the distinction Ijetween the delineativc and 

 the economic aspects of prol^lem solution a new one 

 in the behavioral sciences. The contributions of the 



