'336 



HANDBOOK OF PHYSIOLOG'l- 



NEUROPHYSIOLOGY II 



40 

 30 

 20 

 10 



30 



20 



10 







-1 1 1 1 r 



POSTERIOR 



560-390 



I 2 3 4 5 6 

 20" PERIODS OF INTERVAL 



FIG. 13. Graph showing the change in distribution of 

 monkeys' response rate following frontal intrinsic sector ablation 

 (three monkeys). Note that the distribution of rate over the 

 interval is not aflected in the controls (four monkeys) and after 

 posterior intrinsic sector ablations (three monkeys). Also note 

 that the total rate of response (nutnkers below names of groups ) 

 did not increase; rather that rate was somewhat decreased, 

 probably due to the ad libitinn feeding period which all 

 groups were given prior to operation — approximately 1 wk. 

 before postoperative testing. (Compare with fig. 12 and see 

 legend to that figure.) 



interval of 2 min. The conditioning procedure as a 

 rule results in performance curves (.scallops) which 

 during the early portions of the interval reflect a slow 

 rate of response, and during the latter portions an 

 accelerating rate which nears maximum just prior 

 to the end of the interval. All of the monkeys used in 

 this experiment were trained every other day for 2-hr. 

 sessions until their performance curves remained 

 stable (as determined by superimposition of records 

 and visual inspection) for a least 10 consecutive hours. 

 Two experimental conditions were then imposed, 

 one at a time: a) deprivation of food for 72 and 1 10 hr., 

 and h) resection of frontal and posterior intrinsic 



cortex. Food deprivation increases the total rate of 

 response of all animals markedly but does not alter 

 the proportion of responses made during portions 

 of the interval (fig. 12). Resection of the frontal 

 intrinsic sector does not change the total number of 

 responses but does alter the distribution of responses 

 through the interval — there is a marked decrease in 

 the difference between the proportion of responses 

 made during the various portions of the interval. 

 Monkeys with lesions of the posterior intrinsic sectors 

 and unoperated controls show no such changes 

 (fig- 13)- 



Analysis of Results 



The results of the constant interval experiment sup- 

 port the contention that the effect of an outcome of 

 an action is influenced by variables which can be 

 classified separately. Deprivation influences total rate 

 of response; frontal lesions, the distribution of that 

 rate. Deprivation variables are akin to those which 

 have in the past been assigned to influence the dispo- 

 sition of the organism. The frontal intrinsic sector 

 lesion appears to influence the monkey's estimate of 

 the situation. This finding is thus in accord with that 

 obtained in the multiple-object problem. Both experi- 

 mental findings can be formally treated by the device 

 of 'mathematical expectation' (140). The distribution 

 of responses in the constant interval experiment can 

 be considered a function of the temporal 'distance' 

 from the outcome; distribution of response probabili- 

 ties in the multiple-object experiment is a function of 

 the number of objects in the situation. Frontal intrinsic 

 sector lesions interfere with those aspects of intention 

 that depend on an estimation of the effects that an 

 outcome of an action has in terms of the total set of 

 possible outcomes that are available. The effects of 

 frontal intrinsic sector lesions on behavior related to 

 outcomes thus parallels the effects of posterior intrinsic 

 sector ablations on behavior related to inputs. A 

 general model of intrinsic sector mechanisms seems 

 therefore to be possible. As a step, after a brief review 

 of available data, a model of the frontal intrinsic 

 mechanisms is proposed. 



Review of Other Data 



The effect of frontal intrinsic sector resection on the 

 distribution of responses in the multiple-object and 

 constant-interval problems is correlated with other 

 deficiencies in preferential beha\ior that follow such 

 resections. The most clear-cut deficiency is in the per- 



