SENSORY GENERALIZATION IN INSTRUMENTAL DEFENSIVE REFLEXES IN DOGS

Transcription

1 ACTA NEUROBIOL. EXP. 1974, Lecture delivered a1 Symposium "Brain and behavior" held in Jablonna near Warszawa July 1972 SENSORY GENERALIZATION IN INSTRUMENTAL DEFENSIVE REFLEXES IN DOGS N. G. IVANOVA Institute of Higher Nervous Activity and Neurophysiology, Academy of Science of the USSR, Moscow, USSR Abstract. Five dogs were preliminarily trained in the situation of classical defensive conditioned reflexes. The training sharply impeded the subsequent instrumental avoidance conditioning (with the stimulus applied to one leg and the avoidance movement accomplished by another leg). However, following the elaboration of the instrumental avoidance to one of the signals previously used i,n the classical situation, the other signals of the classical conditioned reflex evoked the instrumental avoidance reaction at once, without any preliminary training. When the animals which had been trained under "instrumental" conditions were brought back to classical situation they revealed an extreme inertness of manifestation of the instrumental avoidance reflex. In another experimental series the same dogs were trained to perform an escape reaction. When the stimulating electrodes were displaced to new receptive areas, most dogs made use of their previous experience and performed the acquired instrumental movement, thus escaping the electric shock. INTRODUCTION Beginning with the study by Woodworth and Thorndike (13) a large number of investigations have been devoted to the phenomenon of transfer in instrumental learning (5, 6, 9, 10, 13). Althcugh a large body of evidence has been accumulated, this phenomenon still continues to be of current interest since it is an aspect of the general problem of instrumental reflexes. Among many other types of transfer of interest for the physiological study is that of perceptive transfer, i.e., the possibility of transferring to other stimuli a previously elaborated instrumental reac-

2 368 N. G. IVANOVA tion or of transferring to the same stimulus used in a different experimental situation. The transfer of an instrumental reaction from one stimulus to another has been explored in detail in the laboratory of Konorski (5). Much less studied is the transfer of an instrumental response to the uncmditional stimulus (US) itself. It is known, flor instance from the study by Zeleny (14), that a conditioned reflex (CR) movement to electric stimulation of a particular receptive field, may be also executed in respcmse to the stimulation of other receptive fields. Fonberg (9) has demonstrated an extremely weak transfer of the instrumental response upon transition to the US itself. Kozlovskaya (6) who elaborated in dogs an instrumental response (lifting and long-term holding of the left forepaw) to stimulation of the right hindpaw, failed to elicit a positive transfer of the instrumental response upon stimulation of another receptive field (the left hindpaw). Because the mechanism of transfer is not clear and the available evidence is slomewhat contradictory, it seemed interesting to study this problem further. METHOD Five dogs were used in the present study. They were first conditioned for a classical defensive reflex. Conditioned stimuli (CS; bell ring, light, buzzer) were first presented separately for periods of 5 sec and then were presented concurrently, for 1-2 sec, with stimulation of the right hindlimb using current exceeding by ma the threshold value. The dogs were then transferred to an instrumental situation. The CS for the instrumental m~ovement was one of the stimuli (bell) previously used in the classical situation which was first presented separately for 5 sec and then concurrently, also for 5 sec, with electrical stimulation of the right hindlimb. To avoid the US, the dog had to lift the left forepaw abolve a predetermined level and hold it there all the time while the US was present. If during the US the forepaw was lowered b'elow that level the dog received the shock. In tests with conditioning of the escape response, the electrical stimulation of the right hindpaw also stopped during the instrumental movement of the left forepaw. RESULTS During the elaboration of the instrumental avoidance reflex different dogs showed different degrees of motor activity with the left forepaw.

3 GENERALIZATION IN LNSTRUMENTAL REFLEXES 369 Three dogs, in which the left forepaw was inactive both during the separate presentation of the bell and during electrical stimulation, passively lifted this lirmb. Both passive and active movements of this limb discontinued the shock. It was found, however, that the preliminary long-term conditioning of dogs in the situation of classical defensive reflexes, strongly disrupted the subsequent elaboration of the instrumental avoidance reflex. These results are consistent with those of others (4, 8, 12). Because the elaboration of the instrumental response was accompanied by numerous painful stimulations, the stimulated limb was mloved in response to both the signal and the shock. In the process of interference of the motor responses of the right hindpaw and the left forepaw, the previously consolidated classical defensive response inhibited the formation of a new instrumental reaction. This result demonstrates the effect of negative transfer (according to Woodworth and Thorndike (13)) of c~onditioning in the classical situation on the development of the motor avoidance response in the instrumental situation. An instrumental avoidance reflex was elaborated in all the dogs after presentations of bell. It was found that the other stimuli of the classical CR (buzzer or light) applied in tests during the instrumental situation, elicited similar instrumental movements without preliminary conditioning (Fig. 1). These tests distinctly showed the phenomenon of positive perceptive transfer reported elsewhere (5). Fig. 1. Instrumental response to bell (A) and its transfer to buzzer (B) and light (C) in the dog Bobik. 1, time in sec, downward deflection: US applied during the action of CS; 2, instrumental movement; 3, movement of the right hindlimb to which US applied. In subsequent tests, all the dogs conditioned in the instrumental situation were returned to the classical situation in which avoidance was impossible. The CS for the classical CR was a remotely controlled touching of the dog's back. In three of the dogs, the touching began to elicit not only the CR

4 350 N. G. IVANOVA but also the instrumental flexion of the stimulated limb after the first application. In the other dogs, such movements appeared afte~ several tests. Although it was impossible for the dogs to avoid the US, instrumental movements persisted throughout the period of reflex conditiming ( combinations of stimuli), and in one dog (Janus) they could not be extinguished even after 250 applications of the touch CS without reinforcement (Fig. 2). These tests revealed considerable sluggishness Fig. 2. Transfer of instrumental response to touch as CS for classical defensive reflex. 1, time in sec, downward deflection: US applied during the action d CS; 2, instrumental movement; 3, movement of stimulated hindlimb. A, 1st combination of touch with US; B, 150th combination. of the instrumental avoidance reflex, which is consistent with the observations on man showing that if a subject is exposed only to instrumental learning, he learns only this form, which seem to him to correspond best to the environmental situations. Subsequently, the tests of Kozlovskaya with an abrupt change of the receptive field were repeated on the same dogs. The experimental procedure was the same as in the preceding tests, the only difference being that the animals were trained to escape from electrical stimulation of the right hindlimb by lifting the forepaw and holding it without the preliminary action of the CS. In some tests, the transfer of the instrumental response to the stimulation of the left hindlimb, of right forelimb and of the back was studid by abruptly changing the position of the stimulating electrodes, applying one or two stimulations to the new site. To rule out the effect of such a factor as the attachment of the cuff with electrodes to the limb, the cuffs were attached to all limbs throughout the period of study. A new receptive field (left hindlimb) was first stimulated after ordinary electrocutaneous stimulations of the right hindlimb. It can be seen from Fig. 3 that the first stimulation of the left hindpaw in

5 GENERALIZATION IN INSTRUMENTAL REFLEXES 371 the dog Bobik brought about a fast, phasic instrumental movement which interrupted the shock only for a short period of time. During the rest of that time there occurred unconditioned reflex movement of the stimulated paw. However, repeated stimulation of this limb elicited a specialized, tonic instrumental movement, having a longer latent period, which eliminated the painful stimulation. Fig. 3. Transfer of instrumental response to stimulation of a new receptive field - left hindlimb (B and C). A, state of instrumental escape reflex prior to test. Designations as in Fig. 1. An abrupt stimulation of the forepaw applied after several tests, likewise evoked an unconditicmed flexing of the stimulated paw along with a quite inadequate instrumental response. A second s;timulation elicited the same specialized instrumental movement of the left forepaw as during the conditioning of the escape response, but with a longer Fig. 4. Transfer of instrumental response to stimulation of right forelimb (A and B) and of the back 2 (C). Designations as in Fig

6 3'72 N. C. IVANOVA latent period (Fig. 4). Electrical stimulation of the back elicited, in one test, an adequate instrumental defensive response (Fig. 4). Similar results were obtained in the dog Janus. In the dog Joy, an abrupt change in the localization of the stimulation likewise elicited instrumental movements of the left forepaw, but these movements were less perfect than in the other two dogs. A question arose, however, whether the observed phenomenon of transfer of the instrumental response was associated with the beginning of elaboration of the escape reflex which usually involves a marked phase of effector generalization. To clear up this question, tests with an abrupt change of the receptive field were run for a second time in all dogs after and then after applications of the US under the ordinary conditions. These tests yielded the same results as the first tests, that is, despite a new localization of the stimulation, the dogs performed the previously learned instrumental movement which allowed them to avoid the nociceptive stimulation. It should be noted that in the dog Joy in which the instrumental response became more specialized in the process of prolonged conditioaing, stimulation of other areas of the skin surface in later tests elicited more adequate execution of the instrumental movement. ADalogous results were obtained in the dog Jim in another modification of the test, in which the procedure was begun with elaboration of the defensive reflex according to the method of Petropavlovsky. With electrical stimulation being applied to the left forepaw, a prolonged lifting and holding eliminated the nociceptive stimulation. After such an instrumental defensive reflex had been well stabilized (250 applications of US), the stimulating electrodes were placed on right hindlimb. This stimulation caused an unconditioned reflex flexion of the limb and a violent motor activity involving the left forepaw attached to the lever Fig. 5. Instrumental response to stimulation of the left forelimb (A) and to unexpected stimulation of the right hindlimb (B and C). Dog Jim. 1, instrumental movement; 2, US received; 3, period when US present if leg is lowered; 4, time in sec.

7 GENERALIZATION IN INSTRUMENTAL REFLEXES 373 (Fig. 5). However, repeated stimulation of the right limb in this dog evoked a distinct purposive instrumental movement which eliminated the US. It seems app~opriate to refer here to yet another observation which confirmed the facts just described. They were obtained in the dog Tishka which had been previously used in tests on another problem. In this dog, an instrumental reslponse of avoiding the US had been firmly consolidated, the US having been applied for more than 300 times. The ordinary stimulation of the right hindlimb elicited in the dog an instantaneous lifting of the left forepaw, without, h nearly all cases, any unconditioned flexing of the stimulated limb. An abrupt change of the receptive field was made only in one test in which stimulation of the left hindpaw elicited an adequate instrumental tonic response of the left forepaw. When this stage had been completed in all dogs excepting the dog Jim, extinction of the instrumental response was attempted, by denying the dogs the possibility of lifting the left forepaw. In these circumstances, instrumental movements in response to shock were not evident at all, with the dogs lifting only the paw being stimulated. Stimulation of other receptive fields during that period, elicited no instrumental defensive response in any of the dogs, there being observed only chaotic movements of the stimulated limb, often accompanied by vocalization. After onset of an instrumental escape response and motor activity, repeated tests were run with stimulation of other, previously used receptive fields. As in the previous tests, stimulation of the left hindlimb and of the right forelimb as well as of the back resulted in the execution of a specialized instrumental reaction by the three dogs referred to above. However, the phenomenon of transfer was not observed in all the dogs used in the experiments. In two (Zhelty and Tom), tests with sudden stimulation of new receptive fields failed to produce positive results, as in Kozlovskaya's experiments. Electrical stimulation of the left hindlimb and the right forelimb as well as of the back brought about chaotic movements of these limbs. The left forepaw was involved in generalized motor activity but its movements differed strongly from instrumental movements of adaptive character. Those were phasic jerks of the paw which did not rid the dog of stimulation. In some cases, for example upon stimulation of the back, no instrumental responses occurred in these animals, and stim~lati~m presented during a spontaneous instrumental response completely inhibited the latter (Fig. 6). In no case did these dogs use the previously elaborated instrumental movement in order to escape painful stimulation of new body areas. Repetition of 4 - Acta Neurobiologiae Experimentalis

8 37-1 N. G. IVANOVA such tests during the further conditioning of the instrumental reflex ( applications of US) and during the period of specialization (400- Fig. 6. Absence of transfer in the dog Zhelty upon unexpected stimulation of the left hindlimb (B) and the back (C). A, instrumental defensive response to US upon stimulation of the ordinary receptive field- the right htndlimb. Designations as in Fig applications) produced the same results as in the initial tests, i.e., there was no transfer of the response to stimulation of new receptive fields. DISCUSSION The present results show that a perceptive transfer may occur in dogs. The animals execute the elaborated and consolidated movement both in response to the classical CS and upm changing the stimulation site. In one dog (Joy) transfer of the instrumental response to the same US was weaker at the stage of instrumental reflex conditioning characterized by chaotic CR activity (stage of effector generalization) than at the stage of specialization. As is known, generalization is common at the early stages of learning and becomes more limited upcn further conditioning (7, 9, 11). Thus, there is a substantial difference between the ordinary stage of generalization and the phenomenon of transfer of an instrumental motor reaction: unlike generalization, transfer may occur,only after the instrumental response has already developed and stabilized. What, then, is the mechanism of transfer? It is not possible as yet to provide a complete answer to this question although certain points can be made. It should be taken into consideration that the instrumental escape response forms under standard experimental conditions in which one and the same receptive field is constantly stimulated and that dog executes a whole set of other motor responses before it singles out the effective m'ovement. Because no other reactions excepting the flexing of the left forelimb are reinforced, one and the same stereotype consolidates in the dog's behavior. In the process of prolonged combinations

9 GENEKALIZA I'ION IN INSTRUMENTAL REFLEXES 375 of the US with instrumental movement of the forelimb there a certain pattern of movement is formed whereby the US acquires a triggering role in the execution of that movement. The more the connection USmovement is conditioned, the better the transfer. Stimulation of other receptive fields revealed enchanced excitability of effector structures responsible for the execution of instrumental movement, which is consistent with the concept of Asratyan (1, 2) concerning the formation 'of a local CR. When an instrumental response is extinguished, the significance of the CS is also extinguished, so that stimulation of other receptive fields likewise fails to elicit an instrumental response. It can be readily seen that upon an abrupt change of stimulation site, as during the elaboration of an instrumental reflex, the animal first executes a set of motor reactions (unconditioned movements of the stimulated limb as well as of the right hindlimb and the left forelimb) of which only one instrumental movement can produce escape from the US. In fact, transfer is also a manifestation of the formation of CR connections arising very quickly, after one or two applications of the stimulus, in contrast to the situation with the initial elaboration of the response. Transfer reveals an active search and emergency decision-making as to the requisite active movement. Unlike the elaboration of a motor habit which arises in the process of diverse chaotic actions and singling out of the effective movement, transfer arises suddenly during activity in an abruptly changed situation. Transfer of a motor habit suggests a high degree of adaptive equilibrium of the organism with the environment. The execution of transfer of an instrumental reaction under changed experimental conditions is a difficult task which cannot be performed by all animals. There appear to exist some central mechanisms capable of singling out, on the basis of previous experience, the general from the particular, this possibility being determined by the level of development of the nervous system in a given animal. REFERENCES 1. ASRATYAN, E. A The conditioned reflex and its integrative forms. Proc. XVIII Int. Congr. Psychol., Symp. 3 (Moscow) p ASRATYAN, E. A On the architecture of instrumental reactions (in Russian). Zh. Vyssh. Nerv. Deyat. 16: FONBERG, E Transfer of conditioned avoidance reaction to the unconditioned noxious stimuli. Acta Biol. Exp. 22: HOFFLAND, D. R Primary stimulus generalization and secondary extinction as a function of strength of conditioning. J. Comp. Physiol. Psychol. 55:

10 376 N. G. IVANOVA 5. KONORSKI, J Integrative activity of the brain. An interdisciplinary approach. Univ. Chicago Press, Chicago. 531 p. 6. KOZLOVSKAYA, J. B On mechanism of the functional structure of local avoidance reactions on dogs (in Russian). In E. A. Asratyan (ed.), Nervous mechanisms of the conditioned reflex activity. Mloscow, p MULLIN, A. D. and MOGENSON, G. J Effect of fear conditioning on avoidance learning. Psychol. Rep. 13: NAKAMURA, C. Y. and ANDERSON, N. H Test of a CER interpretation of the avoidance decrement phenomenon. J. Comp. Physiol. Psychol. 66: RAZRAN, G. H. S Stimulus generalization of conditioned responses. Psychol. Bull. 46: SPENCE, K. W Theoretical interpretation of learning. In S. Stevens (ed.), Handbook of experimental psychology. J. Wiley and Sons, New York, p THOMPSON, R. I? Function of auditory cortex of cat in fnequency discrimination. J. Neurophysiol. 23: WIESS, J. M., KRIECKHAUS, E. E. and CONTE, R Effects of fear conditioning on subsequent avoidance behavior and movement. J. Comp. Physiol. Psychol. 65: WOODWORTH, R. S. and THORNDIKE, E. L The influence of improvement in one mental function upon the efficiency of other functions. PsyChol. Rw. 8: , , ZELENY, G. P Physiological data on methods for elaboration conditioning (in Russian). Priroda 2: Received 3 July 1972 N. G. IVANOVA, Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Pyatnitskaya 48. Moscow, USSR.