Blocking of inhibitory conditioning within a serial conditioned stimulus-conditioned inhibitor compound: Maintenance of acquired behavior without an unconditioned stimulus

LEARNING

AND

MOTIVATION

14, 1-29 (1983)

Blocking of Inhibitory Conditioning within a Serial Conditioned Stimulus-Conditioned Inhibitor Compound: Maintenance of Acquired Behavior without an Unconditioned Stimulus S. STEFAN SOLTYSIK, GEORGE E. WOLFE, THOMAS NICHOLAS, W. JEFFREY WILSON, AND JOSE L. GARCIA-SANCHEZ University

of California,

Los Angeles

Well-trained classically conditioned stimuli, presented unreinforced, were protected from extinction when they were followed by a signal of the omission of the reinforcer (conditioned inhibitor Konorskian type) in eight cats. An aversive classical conditioning paradigm with shock as the reinforcer was used. Of several behavioral (leg flexion, vocalization) and organismic arousal (heart rate, respiration rate, respiration amplitude) measures of conditioned responses, the respiration amplitude changes were found to be most informative for the continuous assessment of elicited arousal of low and medium intensity. In all subjects conditioned stimuli presented during extinction in serial compound with the conditioned inhibitor elicited larger responses than did conditioned stimuli presented alone during extinction. The mechanism of protection from extinction in a paradigm in which the elicitor of learned behavior occurs prior to the conditioned inhibitor provides the organism with the mechanism for the maintenance of learned behavior in the absence of a reinforcer.

Blocking of excitatory conditioning has been demonstrated in several studies, starting with the seminal papers of Kamin (1968, 1969). It consists of the failure (or a reduction) of acquisition of a conditioned response to a Stimulus A paired with an unconditioned stimulus (US) if the Stimulus A is accompanied by a potent conditioned stimulus (CS) which fully predicts the occurrence of the US. Blocking of inhibitory conditioning was demonstrated in one study (Suiter & LoLordo, 1971). It consists of the failure (or a reduction) of the acquisition of inhibitory associative strength by a Stimulus B paired with the absence of the expected US if the Stimulus B is accompanied by a potent inhibitory conditioned stimulus (CI) which fully predicts the absence of the US. This research was supported by HD 05958. All correspondenceshould be addressed to S. Soltysik, MRRC, NPI-58-242, UCLA, Los Angeles. CA 90024. 1 OO23-9690183 $3.00 Copyright 0 1983 by Academic Press, Inc. All rights of reproduction in any form reserved.

2

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ET AL.

Blocking of inhibitory conditioning acquires new meaning when applied not to novel stimuli, but to positive CSs. The simplest case of such a paradigm occurs when the Cl fully overlaps or precedes the CS. This prevents the elicitation of any CRs by the CS. In a study by Choraiyna (1957, 1962) full protection from extinction (PFE) was observed for CSs presented in such a compound with the Cl. The value of such a mechanism for the preservation of CSs, when they are not reinforced in the presence of Cls, is obvious. It allows the organism to maintain the unreinforced CSs as elicitors of CRs for the occasion when the proper environmental context reoccurs, even though in the improper context they may occur without a US. All that is needed is that the improper situational context becomes a CI. Even more valuable, however, would be a mechanism which protects the CSs from extinction when the CS precedes the CI so that at least part of the CR is elicited on the nonreinforced trial. Such a paradigm for a serial CS-CI compound could be deduced from Miller and Konorski’s notion (1928) that an avoidance response serves as a CI and Konorski’s suggestion that this CI “somehow preserves” the aversiveness of the preceding CS (Konorski, 1948a, p. 231). A few studies have been performed to verify this idea. In only one (Soltysik. 1960) was some evidence obtained for protection from extinction by using a CS-CI compound in an appetitive conditioning procedure in one dog. However, the lack of any control group, and the nonaversive nature of the reinforcer. left open the question of the existence of any such protective from extinction mechanism in avoidance learning. In two other studies an aversive US and a CS-CI serial compound were used, but no evidence for PFE was found (LoLordo & Rescorla, 1966; Johnston, Clayton, & Seligman, 1972, unpublished, reported in Seligman & Johnston, 1973). However, no independent measures of inhibitory strength were used in these studies, and the alleged CIs might have been undertrained. Also, only visual stimuli were used as CIs in both unsuccessful experiments, and there is some indication that visual stimuli, at least in some species, might be ineffective as CIs. A more detailed critique of the above studies is presented in the Discussion. In this report we present results obtained with an improved aversive conditioning technique in cats (Wolfe & Soltysik, 1981) and with an experimental design which avoids some of the weaknesses of the earlier studies. In the improved technique the defensive arousal elicited by an aversive CS is not measured indirectly (e.g., by the CER technique as in Seligman 8z Johnston’s experiments, or by testing the CSs on the baseline of Sidman avoidance performance, as in LoLordo & Rescorla’s experiment), but directly in the form of heart rate IHR). respiratory. vocal, and leg flexion responses. Although blocking of inhibitory conditioning was observed in all these behavioral measures of a CR only

PROTECTION

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3

the respiratory changes elicited by the CSs and CIs are fully reported in this paper, because they were found to be the most promising indices of defensive arousal. Some initial observations and preliminary reports of these data were made by Soltysik and Wolfe (1980), Nicholas, Soltysik. Wolfe, and Wilson (1981), and Soltysik, Nicholas, Wolfe, Wilson, and Abraham (1982). Two important changes in procedure distinguish this study from the earlier unsuccessful experiments on protection from extinction. One is a choice of a trace conditioning procedure, and the other is a selection of a Konorskian type of CI, rather than a Pavlovian type or a “safety signal” type, as used in previous studies. The choice of a trace conditioning procedure was dictated by the finding from a pilot experiment that the delayed conditioning procedure introduces an additional signal, namely a termination of the CS, on nonreinforced trials. Such a signal becomes a CI after some training and may be responsible for the PFE in control subjects or tests. The selected procedure of inhibitory conditioning with the CI following the CS differs from the standard Pavlovian procedure, in which the CI is presented before or simultaneously with the CS. It should be realized, however, that the Pavlovian procedure of “conditioned inhibition” has only historical but no theoretical justification. A conditioned inhibitor was discovered serendipitously during the attempts at acquisition of a second-order CR (Vasil’ev, 1906; Mishtovt, 1906, 1907); hence the CI-before-the-CL3 procedure. The proposed procedure of the CI-afterthe-CT3 seems to be theoretically more correct. The Pavlovian CI is a predictor of an unreinforced CS, and as such may possess both inhibitory and excitatory (second-order CR?) components. Our type of CI, which we propose to label as a Konorskian CI. is a pure predictor of the omission of the US, and this is exactly what the CI, used in a PFE study, should be predicting. Finally, since the PFE phenomenon was postulated as an explanation of high resistance to extinction of the avoidance responses (Konorski, 1948b; Soltysik, 1963), where the putative CI occurs after the CS, but prior to the expected US, our procedure places the CI in a similar temporal relation to the CS and the anticipated onset of the US. GENERAL

METHODS

Subjects Eight adult cats were used in this study. Five (A9, A17. A19, A20, A21) were obtained locally and had an unknown history. The remaining three subjects (A31, A32, A33) were born in the MRRC Kitten Colony at UCLA and came from the same litter. All cats were routinely vaccinated against feline distemper and feline viral rhinotracheitis. The subjects lived in individual cages and were maintained on a diet which consisted of ad lib Purina cat chow and water supplemented with canned tuna or chicken.

4

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ET AL.

Surgery, Apparatus, and Procedure

A detailed description of the apparatus and surgery has been published (Wolfe & Soltysik, 1981). Briefly, before training each subject was anesthetized and prepared with a cranial implant and an abdominal EKG electrode. The cranial implant served to immobilize the subject’s head during conditioning, as well as to attach the recording leads for monitoring EKG and respiration. The abdominal EKG electrode permitted the recording of relatively artifact free EKG, even from actively moving subjects. The apparatus consisted of a steel frame supporting a harness and a treadbelt (Fig. 1). In order to familiarize the animals with the apparatus before training, each subject was placed in the harness and stood on the treadbelt while the cranial implant was bolted to the steel frame. After 15 or 20 min, the subject was released. Training started with acquisition training during which the subjects had only CS-US trials and acquired conditioned responses. The details of the inhibitory training were developed in a preliminary experiment on one subject. Data are reported from two experiments differing slightly in design. Each design consisted of three consecutive stages: baseline, treatment, and test. In four cats a three-CS design was used, in which intermixed CS-CI, CS-US, and CS only trials were used in the TREATMENT stage, while testing consistent of CS-US and CS only trials. In three cats a two-CS design was used, in which no US trials were present during the treatment or test stages of the experiment. During training, stimulus presentation and timing were controlled electromechanically. The following stimuli were used as CSs or CIs. An air

FIG. 1. Schematic view of the treadbelt stand. Part of the frame and harness are not shown in order to visualize the attachment of hindleg and tail electrodes.

PROTECTION

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5

stream (AI) of 1 g force directed at the subject’s sacral region was delivered from a narrow tube (1 mm internal diameter) fixed about 3-4 cm above the skin. A clicking sound (CL) of 10 clicks per set was delivered from a loudspeaker placed behind the subject. A tone (TO) of 1000 Hz and 75 dB (above the ambient noise level) was delivered from the same loudspeaker. A light (LI) blinking 6 flashes per set was presented from a 10 x 10 cm panel of white opaque glass placed 20 cm in front of the subject’s head. A rotating object (RO) made from a small can and painted with black and white stripes, was situated horizontally in front of the subject’s head, above the light panel. Table I shows the stimuli presented to each subject. The duration of the stimuli used as CSs was 2 set and the duration of the stimuli used as CIs was 3 sec. The unconditioned stimulus (US) was a 60-Hz shock of 300 msec duration delivered through electrodes attached to the left plantar surface and to the tail, 4 cm above its base. The intensity of the shock varied slightly across subjects and ranged from 2.5 to 2.0 mA. The shock US was considered of appropriate intensity if it elicited a prompt leg ffexion without excessive general agitation. The CS-US interval in all subjects was 5 sec. Thus the CS-US trials consisted of a 2-set CS, followed by a 3-set pause and 300-msec US (trace conditioning). Inhibitory trials consisted of a 2-set CS followed immediately by a 3-set CI. The trials with different CSs as well as positive and inhibitory trials were presented randomly with some restrictions, such as avoiding consecutive presentation of the same CS-US trials or of inhibitory trials. The intertrial intervals were varied between 2 and 4 min. Each trial consisted of a IO-set pre-CS period, a 5-set CS-US interval or 5-set CS-CI sequence, and a IO-set post-US period. The ratio of CS-US to CS-CI trials and the number of trials per session TABLE 1 Stimuli Used as CSs and CIs CAT

CSl

CS2

CS3

CI

A09 Al7 A19 A20 A21 A31 A32 A33

AI RO CL CL AI CL LI RO

LI CL LI RO LI RO CL LI

RO AI AI LI RO -

CL TO RO AI CL LI RO CL

Note. AI = air stream; CL = clicker; LI = light; RO = rotor; TO = tone; CSI and CS2 = conditioned stimuli used for differential treatment; CS3 = control CS; CI = conditioned inhibitor.

6

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ET AL.

during TREATMENT and TEST stages were exactly the same in all subjects within the groups. The length of the TREATMENT stage varied across subjects in Experiment 1, depending on the rate of extinction of the CR to the nonreinforced CS, and ranged from 15 to 25 sessions. In Experiment 2 the TREATMENT stage lasted 15 sessions in all subjects. There were five sessions in the TEST stage in Experiment I, and three sessions in Experiment 2. The length of BASELINE stage was more variable because the training was carried out until a criterion of stable Cl was met. Acquisition

and Processing

of Respiratory

Data

Respiratory data were obtained from a small thermistor placed in front of the subject’s nostril (for technical details see Wolfe & Soltysik, 1981). The frequency and intensity of inhalation and exhalation served as measures of respiration rate and respiration amplitude, respectively. Interestingly, it is the amplitude of respiration rather than its rate which seems to yield the most uniform and reliable data (Soltysik, Nicholas, Wolfe, & Wilson, in preparation). The respiration data were recorded on a thermosensitive paper at a paper speed of 1 cm/set (A in Fig. 2) and entered into a computer through a digitizing tablet (Houston Instrument HiPad). Figure 2 illustrates the computer analysis of a string of data points for respiration amplitude during one trial. First, an envelope of respiration amplitude was formed (B in Fig. 2). Next, the width of the envelope was sampled every .5 set creating 50 values to describe the amplitude changes during the trial (C in Fig. 2). Finally, each of the 50 amplitude values was converted into percentage of the mean of the 20 values from the IO-set pre-CS period (D in Fig. 2). This last conversion accounts for the uncertainty as to the real amplitude of respiration because of the changing placement of the thermistor between subjects and sessions, as well as different amplification setting of the strip chart recorder on a particular session or trial. A similar analysis was used to describe respiration rate data. Instead of sampling amplitude, the computer sampled the length of the interpeak intervals every .5 set and converted them into the respiration rate, i.e., number of respiratory cycles per minute. This procedure is described in more detail for heart rate conversion in another paper (Nicholas et al., 1983, in press). For the purpose of this study the average respiration amplitude and average respiration rate were calculated across a number of trials for each subject. The averaged data are shown in figures with superimposed responses from trials of differently treated stimuli. The statistical significance of the differences between two curves is evaluated by a time series analysis (Jones, Crowell. & Kapuniai, 1969) performed on the differences of compared curves.

PROTECTION

7

FROM EXTINCTION

1 set

r 25 D

FIG. 2. Calculation of respiration amplitude. (A) Respiration record produced on the strip chart for a single trial. Note the 60-Hz signal superimposed on the respiration tracing to indicate the occurrence of a vocalization. (B) The data are entered into a computer via a digitizing tablet by indication of peaks and troughs. The computer constructs an envelope by connecting consecutive peaks, forming the top line, and consecutive troughs, forming the bottom line. Data are absent during a vocalization. (C) The width of the envelope is measured at .5-set intervals, as indicated by the open dots on this curve. (D) Because of variation in the absolute amplitude of respiration from trial to trial due to changes in the position of the thermistor, data are standardized around the average pre-CS amplitude.

General Strategy for Obtaining the Phenomenon of PFE In general, the strategy adopted for observing and measuring the blocking of inhibitory conditioning was the following, First the subject was conditioned in such a way that two or three CSs and one CI were acquired (see Table 2). This BASELINE stage of training was completed when

8

SOLTYSIK

ET AL..

TABLE 2 General Outline of the Experiment Stage 1: BASELINE.

Acquisition

Types of trials CSl-us CS’L-us CSl-CI csz-CI

of the CSs and the Cl Behavioral outcome CSI-CR CS2-CR CSl-CR CSZ-CR

Stage 2: TREATMENT. Types of trials

Protection of CSl and extinction of CS2 Expected behavioral outcome

CSl-CI cs2

Types of trials

& CI -
CSl-CR & CI -
CSl cs2 Note. Where symbols: -

= is followed by; -

or smaller CR

= elicits; and - < = inhibits.

the CSs elicited leg flexion CRs and the CI suppressed them on at least 85% of trials. In the second, TREATMENT, stage, two CSs were presented without reinforcement an equal number of times during 20 (in Experiment 1) or 15 (in Experiment 2) sessions. However, one of them (protected CS) was followed by the Cl, whereas the other CS (unprotected) was presented alone. After a period of such nonreinforced presentation (i.e., extinction) both CSs were compared for their CR-eliciting capacity in the TEST stage of the experiment: they were presented alone, i.e., without either US or Cl, and the CRs elicited by them were recorded and compared. If presentation of a CS without a US causes extinction (i.e., the acquisition of inhibitory associative strength), and if the presence of the Cl, in a serial compound with a CS, prevents or retards extinction (by blocking the acquisition of inhibitory associative strength to the nonreinforced CS), then the two CSs should show a difference in their CR-eliciting strength in spite of the equal number of nonreinforced presentations. The stimulus which was presented nonreinforced, but in a compound with a CL should retain more of its CR-eliciting strength than the CS which was presented alone, unpaired with the US and unprotected by the Cl. Table 2 illustrates the composition of trials and the behavior observed or expected during the three stages of the experiment. The Problem of Equivalence qf the CSI and CS2

In the above outline of the procedure one of the CSs was protected from extinction while the other was not and the rates of extinction (or

PROTECTION

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9

savings in CR) were compared in the test stage. However, this design did not control for possible inherent differences between the CSs, such as salience and individual or species-specific properties which might account for differential rates of extinction irrespective of the protection by the CL It was necessary therefore, to retrain the subjects after completion of the three stages of the experiment and repeat the entire procedure with the CSl and CS2 reversed: the CS2 was serially compounded with the CI while the CSI was left unprotected. Thus, the data could be combined from both consecutive replications of the experiment and each of the CSs was equally represented in the protected and unprotected CS results. The Problem

of Total Removul

of the US and the Floor Effect

In the general outline of the experiment presented above, the US is totally removed from the experimental situation after Stage 1 (i.e., the acquisition of CSs and CI) is completed. Thus, not only will the unprotected CS undergo extinction, but also the entire situation will become an extinguished situational CS. This may reduce readiness to respond (by removing the expectancy of shock, or suppressing the response set) to such an extent that even if there are differences between the protected and unprotected CSs during testing, they may not be evident if the response level is near or subthreshold. To avoid this possible floor effect, one group of animals had a third, control CS (CS3) which was always reinforced with the US and which was presented in all three stages of the experiment. This variant of the experiment enabled us to maintain in one group of subjects the same ratio of reinforced trials throughout the experiment. In other words, the density of shock US occurrence in this particular group was unchanged across the stages of baseline, treatment, and testing. The other group of subjects was trained with only two CSs and had no US trials during Stages 2 and 3. EXPERIMENT

1

Four adult cats were trained with three CSs and one CI. Table 3 shows what stimuli were used in each subject. Before presenting the results, one episode from the inhibitory training in Cat A17 should be mentioned. Clicker, rotor, and air stream were used as CSs in this subject. The attempt to establish the light stimulus as a CI was unsuccessful. After 3 weeks of intensive training with the light CI no hint of suppression of the CRs was observed. The difference in percentage occurrence of the leg flexion response (which is the most easily inhibited CR) between the CS-US and CS-CI trials was, on the last 10 sessions, the following: - 13, 0, - 12, 25, 0, -25, 0, 0, - 12, - 17. (+ 100% is the perfect score with a response on each CS-US trial and no response on CS-CI trial).

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ET AL.

TABLE 3 General Outline of Experiment Stage 1: BASELINE

Stage 2: TREATMENT

(>lO sessions)

Type of trial CSl-us cs2-us CSl-Cl cs2-Cl cs3-us

___.-

No. of trials in a session 2 2 6 6 2

(15-25 sessions)

Type of trial CSl-Cl es2

No. of trials in a session 6 6

1 Stage 3: TEST

(5 sessions) ~_ No. of trials in a Type of trial session CSI cs2

6 6

6 -.Note. CS3 = control CS. CSI and CS2 were retrained after the TEST and the entire procedure was repeated with the CS2 compounded with a Cl and the CSl presented alone. during the TREATMENT stage. cs3-us

6

cs3-us

At that stage we decided to substitute a tone for the light and there was a prompt acquisition of conditioned inhibition in the next seven sessions: 0, 50, 50, 88, 100, 88, 100. Results

Figure 3 presents the average changes in respiration amplitude on the CS-US trials and the CS-Cl trials in the last 10 sessions of baseline training. It should be remembered that each subject was run twice through the baseline, treatment, and test sessions, so that the same CS was once used as a protected CS (compounded with the Cl) and once as an unprotected CS (presented alone). The results are averaged from both series of sessions. The subjects were reasonably well trained and in each of them the response to the CS-CL is much smaller than the response on the CS-US trials. Of course the difference between the CS-US and the CS-Cl trials occurs only after the onset of the Cl, i.e., after the first 2 set of the CS. The average response to the CS on the CS-US trials, and to the CS-CI compound, from all seven subjects used in Experiments 1 and 2, are shown in Table 4. Table 4, which contains the data from this and the next experiment, gives a precise measure of the inhibition exerted upon the CR by the Cl. For each of the subjects, the averaged curve representing the changes in respiration amplitude on the CS-CL trials (during the baseline training) was subtracted from the curve representing the CS-US trials. A time series analysis (Jones, Crowell, & Kapuniai, 1969) performed on the differences between the corresponding data points from the two curves produced the t values which are labeled as inhibition scores. Underlined positive t values correspond to the differences which are statistically significant (with degrees of freedom =

PROTECTION

t:,

t

CAT k17 40

40

t

11

FROM EXTINCTION CAT Ai

t

cs

CAT A21

CFlT F126

ul ,\

us

40

x -0

-5

3--

s

In

-0

-5

B’

.*

.’ I.0 “.

13

- SECONDS SECONDS Frc. 3. Respiration amplitude responses during the last 10 BASELINE sessions for each subject, averaged across both replications. All subjects show a large decrease on CS-US trials (dotted lines) which is attenuated by the CI on CS-CI trials (smooth line, CI onset at arrow).

18 any score of 2.101 or larger is significant at the .05 level). The statistical evaluation of conditioned inhibition in the first four cats (from Experiment 2) confirms the visual impression from Fig. 3. There is no difference between the respiratory amplitude on the two kinds of trials during the first 2 set of the CS-US interval. Only Cat A17 shows a significant difference .5 set after the Cl onset; two other cats (A19 and A201 show significant inhibition 1 set after the CI onset and all four cats are significantly inhibited by the CI from the 4th set after the CS onset (i.e., from the 2nd set after the CI onset). Figure 4 presents the results of the TEST. Each curve represents an average of 60 CS alone trials: 2 replications of TEST x 5 days of extinction x 6 trials per session. The continuous line shows the response to a CS which during the TREATMENT stage was compounded with the CI, and the crosses show the response to a stimulus which was presented alone during the TREATMENT stage. As in Fig. 3, the data presented in Fig. 4 are from both TEST series, i.e., each of the CSs is

- 1.09 SO

- .50

1.32 .4

.oo

-1.19 .28

-.28

1.24 .4

Ave.

t(6)

P<

.97 .5

- .52

- .53 -.26

1.41 .02 - .71 - 3.33 - .25

3.51

2.29 1.35

7.11 3.29 -5 81 1.02 3.73

CS-US interval (sampled every .5 set)

TABLE 4 Scores in the CS-US Interval

5.99

6.7b 1.74

9.10 6.72 7.65 .57 9.40

9.12

10.93 260 -L.-

9.16 11.07 11.14 8.18 -lo.76

4.91

7.20 __ 13.42 2.69 8.48

-r

782

8.73

11.69 3.

-10.81 16.55 __ 5.29

7.99 15.22 5.05

.36 .75 4.11 4.56 7.81 5.07 4.16 .8 .5 .Ol .Ol .Oi .Ol .OOl __Note. Inhibition scores were obtained by performing a time series analysis on the differences between averaged data from all CS-US trials and all CS-Cl trials in the baseline sessions. Pre-CS values served to compute the autoregressive model and the results for the CS-US interval are presented at .5 second intervals. Since the positive response to the CS is a reduction in respiratory amplitude, most of the scores in the CS-US interval have negative values; therefore, to simplify the table the signs of the f values are reversed. The table is divided into the 2-set left portion which corresponds to the CS duration and the 3-set right portion which corresponds to the remainder of the CS-US interval or the duration of the CI. With df = 18 for each score the values of 2.101 or larger are significant at .05 level. and are underlined.

- .52 .02 .69 -2.17 - .93

- .92 - .08 - .48 .41

Al7 A19 A20 A21 A31 A32 A33

Cat

Inhibition

c, ~

E

2

s

PROTECTION

CCIT fI20

FROM EXTINCTION

13

CFIT 821 40

5.’ 10I -% SECONDS SECONDS FIG. 4. Respiration amplitude responses for each subject averaged across the TEST stages of both replications. Both the protected (smooth line) and the extinguished (crosses) stimuli were presented alone during this stage. The arrow marks the point at which the CI was presented during the TREATMENT stage for the protected stimulus. In all four cats the responseto the protected CS is greater than that to the extinguished CS.

represented in both curves, once as a protected CS and once as an unprotected CS. The animals in Experiment 1 were not overtrained, and a complete extinction to the unprotected CS was not required during the TREATMENT stage, which lasted 20 sessions. Therefore in Cats 20 and 21 there is only partial extinction of the respiratory CR to the unprotected CS. Nevertheless, in each subject a considerable difference in the amplitude of the response is evident. Table 5 presents the results of the time series analysis performed on the strings of numbers obtained by subtracting the averaged responses to the unprotected CS from the averaged responses to the protected CS. Obtained r values (labeled as PFE scores) are underlined when they reach statistical significance at the level of p -=L .05. Most of the scores in the last 3 set of the 5-set period after the C-S onset (which corresponds to the occurrence of the CI in the original training) are significant. Also several data points during the first 2 set after the CS onset, i.e., prior to the onset of the Cl, are significant in Cats Al9 and A20. The importance of this finding will be discussed later.

-.I1

Ave.

_____

1.67 .2

1.68

- .30 4.07 3.73 -xi -.I1 3.87 Iii

1.0

2.65 .05

1.48

_____

3.65 .Ol

2.25

I 3.75 .Ol

3.17 2.89 .05

4.22

3.98 4.59 .Ol

CS-US Interval sampled every .5 second ~____.__

~-~

7.26 .OOl

3.80

2.41

___. .~~

.._

2.97 .05

3.28

2.41

~--

-

2.59 .05

2.66

4.72 8.43 .69 3.15 1.72 1.00 .26

.-. 5.0

~~~

Note. PFE scores were obtained by performing a time series analysis on the differences between averaged data from all protected CS trials in the test sessions and all unprotected CS trials in the test sessions: pre-CS values served to compute the autoregressive model and the results for the CS-US interval are presented at ten .5-set intervals. Since the positive response to the CS is a reduction in respiratory amplitude. most of the scores in the CS-US interval have negative values; therefore, to simplify the table the signs of the t values are reversed. The table is divided into the 2-set left portion which corresponds to the CS duration and the 3-set right portion which corresponds to the remainder of the CS-US interval or the duration of the CL. The significant values t.05 level at df = 18) are underlined.

P<

.18 .9

- .75 .97 .52 .09 -3.34 1.10 .65

A17 Al9 A20 A21 A31 A32 A33

r(6)

0.5

CAT

~-

TABLE 5 PFE Scores in the CS-US Interval

; r

% c; -e ; m

PROTECTION

15

FROM EXTINCTION

Discussion The results of Experiment 1 fully support the prediction that a welltrained CI can block the acquisition of inhibitory conditioning. In each subject compounding of the CI with the CS protected the CR elicited by this CS from extinction. In contrast to previous studies (LoLordo & Rescorla, 1966; Johnston et al., 1972, unpublished: or Hendersen & Harris, 1979, unpublished) the CS3-US (control CS-US) trials were used in all stages of Experiment 1. As explained above this was done in order to avoid a possible floor effect. The PFE effect was very strong when the shock US was present in all stages of the experiment. Not only did it occur in all subjects for the late part of the CR, but it also was noticeable “retrogradely” (cf. Soltysik & Wolfe, 1980), i.e., during the early part of the CR which previously had occurred prior to presentation of the CI. Therefore we decided to carry out another experiment in which the US would be totally absent during the TREATMENT and TEST stages. EXPERIMENT

2

Three cats used in this experiment were littermates and were born in the Colony at UCLA. They had no prior experience with any training or any aversive stimuli. The training, treatment, and testing were exactly as in Experiment 1, except that only two CSs and one CI were used, and no US trials were used during the TREATMENT and TEST stages. The TREATMENT and TEST stages were shortened to I5 and 3 sessions. respectively, in anticipation of faster extinction when the US was totally withdrawn from the experimental situation. Table 6 illustrates the trial composition of each stage of the experiment for these three cats.

TABLE 6 General Outline of Experiment Stage 1: BASELINE

Stage 2: TREATMENT

(> 10 sessions)

Type of trial CSI-us cs2-us CSI-CI csz-CI

(15 sessions)

No. of trials in a session 2 2 4 4

Type of trial CSI-CI cs2

2 Stage 3: TEST (3 sessions)

No. of trials in a session

Type of trial

No. of trials in a session

6 6

CSI cs2

6 6

Note. After the TEST Stage the CSl and CS2 were retrained and the entire procedure was repeated with the CS2 compounded with a CI and the CS1 presented alone, during the TREATMENT stage.

16

SOLTYSlK

ET AL.

Results and Discussion Figure 5 presents the data from the three cats of this experiment, both for the BASELINE and TEST stages. As in the four cats from Experiment 1 (Fig. 3) there is good inhibition of the CR by the Cl in BASELINE. What should be stressed in this respect is a surprisingly good inhibitory

SECONDS

IAl f

2

c

2:

..,I

;

-4

f

-6

.I..

f3 -2 -8 ~~ s

cs -

-

us SEClOeHDS 1

SECONDS

SECONDS SECONDS 5. Respiration amplitude data from BASELINE (left) and TEST (right) stages of Experiment 2. During BASELINE, the CI (onset at arrow) effectively inhibits the CR on CS-Cl trials (smooth line) compared to the CR on CS-US trials (dotted line). During the TEST stage, the protected CS (smooth line) causes a larger response than the unprotected CS (crosses), although both were presented an equal number of times without the US. FIG.

PROTECTION

FROM EXTINCTION

17

effect in Cat A31 in which the CI was a flashing light i.e., a visual stimulus. Again, the PFE, or difference in the amplitude of the respiratory response to the protected and unprotected CS is evident in each subject. The inhibition scores and the PFE scores for these three cats are shown in Tables 4 and 5. Because there were no differences in the outcomes of Experiments 1 and 2, and the procedures were very similar. the data from all 7 subjects in Tables 4 and 5 were analyzed, separately for each time epoch, by a one-tailed t test. The results are shown in the two bottom rows of the tables. Thus, Table 4 reveals that the inhibition of the CR by a CI becomes significant in the group of 7 subjects, only I set after the CI onset. Table 5 confirms our earlier impressions (Sohysik 8z Wolfe, 1980) that the PFE effect is already present and significant I.5 set after the CS onset, i.e., prior to the time of Cl onset. The decrease of t values (PFE scores) at the end of the CS-US interval was caused by the irregularities and partial return towards the pre-CS level of the respiratory amplitude in the last second of the CS-US interval: this is normal even in the baseline training with the CS-US trials, and probably caused by the interference of movements and vocalizations which occur just prior to the expected shock. In general, the respiratory amplitude is the best index of low and medium intensities of arousal (CR) and therefore gives the highest scores for inhibition and PFE around the 4th set of the CS-US interval. To make this point clear, Fig. 6 presents the averaged responses from all seven subjects for the CS-US and CS-CI trials during the last two BASELINE sessions. Note the “shape” of the respiratory CR (smooth line with the SE bars) which turns up at the end of the 5-set CS-US interval; this reduces the difference between CSUS and CS-CI responses (inhibitory scores) for the last two data points.

SECONDS

6. Respiration amplitude responses from seven subjects during the last five sessions of the BASELINE training. Smooth lines (with the standard error bars at the data points) are from CS-US trials; squares (with the SE bars) are from CS-CI trials. Asterisks mark the data points at which the difference is significant (p < .Ol). FIG.

18

SOLTYSIK

ET AL.

The Extinction of the Protected CSs during the TEST The data presented above provide strong evidence for the PFE without, however, any information on how well the CSs were preserved after the TREATMENT stage. In the only previous study which showed a PFE effect in an aversive conditioning paradigm tin rats, using the light Cl and simultaneous CSlCI compound: Hendersen & Harris, 1979. unpublished), the PFE effect was present only on the first test trial. Therefore, the following two figures present the results from each consecutive TEST session. Figure 7 shows the results from Cats A17 and A19. The left graphs compare the responses to protected and unprotected CSs, prior to TREATMENT. Each of the two experimental CSs contributes equally to these curves, because each was used once as a protected CS, and later once as an unprotected CS. Ideally there should not be any difference between the responses to these CSs during the BASELINE training, as is indeed the case. The following five graphs. labeled 1 through V (Fig. 7). show the difference in the respiratory CR elicited by the protected and unprotected CSs during TEST. Cat A17 shows a small difference in the first TEST session (the average is from only six trials and there was one trial on which the animal had an anticipatory response prior to the unprotected CS onset.) The difference is huge on the three consecutive days, but a reversal occurred on the last TEST session. Cat Al9 had completely extinguished its response to an unprotected CS and had preserved the CR to the protected CS. This CR extinguished rather smoothly over 4 days. Figure 8 presents the data from Cats A20 and A21. There is an unexpected difference in the CR amplitude during the BASELINE training in Cat A20, mostly because of meowing occurring in the late part of the CS-US interval, which removed many data points, so that the averages are from a few trials on which the vocal CRs did not interfere with the pneumographic recording. In both cats the PFE is seen during all five TEST sessions. Cats from Experiment 2 had only three TEST sessions, because we did not expect as good a retention of the CRs as in subjects from Experiment I. The total removal of the shock US in the TREATMENT and TEST stages should have caused the extinction of the situational CR (response set, or expectancy of the US). and the subjects might have had an increased response threshold. Nevertheless, the PFE effect is noticeable during the 3 days of the TEST (Fig. 9). Thus, the data indicate that the post-PFE extinction may last several days, even in the total absence of the reinforcer or the CI in the experimental situation. Conditioned Inhibition and the PFE in the Respiration Rate Data Figure 10 shows the respiration rate responses on the CS-US and CSCI trials during BASELINE training. The curves are less regular than

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those representing the respiration amplitude changes, and in Cat Al7 the response to the CI was larger that that to the CS followed by the US. Again, excessive vocalizations in anticipation of the shock have removed many data points in the late part of the CS-US intervals on CS-US trials; therefore the late part of the CR (dotted line) is less reliably represented than the early part of it or the data from CS-CI trials. In general. the CI inhibits effectively the respiratory rate CRs. The data from the TEST sessions shown in Fig. 11 are also indicative of the PFE, but illustrate the problems with the rate measure. There are large differences between the subjects and in one subject (Cat A20) a deceleratory response occurred to the protected CS. The data from the remaining three cats (Fig. 12) also illustrate how less reliable, although generally supportive of the PFE, are the respiratory rate data as compared with the respiration amplitude CRs. GENERAL DISCUSSION

Several theories predict the phenomenon of protection (PFE). For example, a theory of protective inhibition

from extinction (Pavlov, 1927:

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Asratian, 1969), theories of consolidation (Soltysik & Zielinski. 1960). and most persuasively, the Rescorla and Wagner model of conditioning (Rescorla & Wagner, 1972; Wagner & Rescorla, 1972), all do so. However, they will not be discussed here because the present experiment was not designed to discriminate between them. There are several other issues, however, which should be reevaluated in light of the strong experimental support for PFE provided by this study. The Reality

of Protection

from Extinction

Contrary to previous studies with the CS-Cl serial compound (LoLordo & Rescorla, 1966; Johnston, Clayton, & Seligman, 1972, unpublished, cited by Seligman & Johnston, 1973), which specifically tested for PFE but found no evidence for it, the results of this study strongly support the existence of the PFE phenomenon. Not only did all the subjects show the PFE but it was remarkably evident even in Experiment 2 where the US was completely removed from the experimental situation during

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PROTECTION

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25

the TREATMENT and TEST stages. Thus, even the expected floor effect, caused by the extinction of the situational CSs, did not prevent the occurrence of a measurable PFE effect. The CR to a protected CS was not just marginally protected from extinction, but was of considerable amplitude, often comparable to the baseline amplitude on the first and second day of TEST (i.e., extinction), and required a few days of extinction to decrease to the level of the CR elicited by the unprotected CS. Moreover, as indicated in our preliminary report (Soltysik & Wolfe, 1980), the protective effect was found not only in the late components of the CR which were prevented by the CI from elicitation on the CS-Cl trials, but also in the early components of the CR which could not be prevented from elicitation because they occurred prior to the onset of the Cl. This “retrograde PFE” (Soltysik & Wolfe, 1980) wiH be discussed later. How then can the negative results of earlier studies be explained? No estimation of inhibitory strength of the CI was attempted in either of the studies that failed to find PFE (LoLordo & Rescorla, 1966: Johnston et ul., 1972). In LoLordo and Rescorla’s experiment, the training of the CI was rather brief (5 days) and the CI might have been insufficiently trained. A visual stimulus (turning off the light) was used as a CI against two tones serving as CSs. Dogs do not readily acquire conditioned inhibition to visual stimuli, as pointed out by Pavlov’s coworker (Mishtovt. 1906, 1907), and there is a definite disparity in performance of more complex tasks with the use of auditory and visual stimuli in this species (cf. Pietrzykowska & Soltysik, 1975). This assumption of ineffectiveness of light stimuli as CIs is partly supported by the case of Cat A17, which was unable to use the blinking light as a CI. However, another cat in this study (A31) acquired the visual CI, and there are reports of visual CIs in cats (Khodorov, 1959). In rats (Jacobs & LoLordo, 1977, 1980) dimming the light may serve as a safety signal but there are no data on the effectiveness of visual stimuli serving as CIs of Pavlovian and Konorskian types. The problem is further confounded by the fact that the CI used in the above study might be of the wrong kind. There are at least five procedures which yield “inhibitory stimuli” or CIs, but there is no reason to assume that they are interchangeable in their functions: for instance, our preliminary observation suggests that a Konorskian CI (a signal of US’s omission) does not readily transfer into a Pavlovian CI (a signal of unreinforced CS). The CIs used in LoLordo & Rescorla’s experiment could be of still another variety (a safety signal, i.e., a predictor of a US-free period of time), because it was presented at the time of the expected US onset, and not before. The CI used in Johnston, Clayton, and Seligman’s, (1972) experiment not only was of a visual modality, but it had even more remote meaning (informational content) in that it was introduced only during the extinction phase of the experiment. Thus it was rather a cue of extinction procedure, and perhaps could also be

26

SOLTYSIK

ET AL.

qualified as a safety signal. Although the Rescorla and Wagner model does not distinguish between the Konorskian type of Cl and safety signals (cf. Wagner & Rescorla, 1972), it is probable that these two types of Cl have different properties and could not be as readily exchangeable in blocking experiments as purported by the theory that focuses on inhibitor?! strength, ignoring predictive (informational) aspects of these stimuli. For a detailed discussion and classification of “pure inhibitory” procedures, see Soltysik (in preparation). * The third study (Hendersen & Harris, 1979) also used rats and a light stimulus as a CI. In this study the training was longer (18 days) and an independent assessment of the inhibitory role of the CI was made. During the TREATMENT stage a simultaneous compound of the CS + CI was used. The obtained PFE effect was weak and shortlived; it was significant only on the first test trial. Thus, the negative or nearly negative results of the three studies which used aversive USs could be attributed to procedural differences such as brief training of CIs, use of improper type of CI, and perhaps, selection of a visual stimulus as a CL Retrograde Protection from Extinction This term was used in our earlier paper (Soltysik & Wolfe, 1980) to describe the fact that not only the late part of the CR is protected from extinction, but also the early part of the CR, which occurs before the onset of the CI and therefore is elicited even on the CS-Cl trials. This retrograde PFE is not predicted by the Rescorla-Wagner model. Strictly speaking, protection, according to the outlined mechanism of blocking, should parallel prevention from elicitation. Therefore it is easy to understand protection from extinction of the late (particularly consummatory in character) parts of the conditioned behavior, because they are not elicited by the CS-CI compound. Why are the early parts of the CR also protected? The simplest explanation could be provided by applying the RescorlaWagner model separately to consecutive time epochs within the CS-US interval. Late parts of the CS, which do not elicit CRs on CS-CI trials. are protected from extinction. A straightforward assumption of generalization between the late (protected) and early (unprotected) parts of the CS would account for retrograde protection from extinction. The fact that a retrograde PFE was found in our experiments and that only retrograde PFE could satisfactorily explain the avoidance responses within the context of two-factor theory of learning, requires reevaluation of the efforts to construct alternative explanations of maintenance of avoidance responses without an elicited fear CR (e.g., Herrnstein, 1969; Hineline, 1977; Seligman & Johnston, 1973). These theories were proposed in response to a need for explaining avoidance behavior without fear. There is, however. good reason to believe that fear remains a functional *

A

review

in prep.

PROTECTION

FROM EXTINCTION

27

motivation even in well-overtrained avoidance (cf. Mackintosh, 1974; Mineka, 1979), although its role (drive to act) and quality (conditioned pain?) may not be as simple as was assumed in original theories of the 1940s and 1950s (cf. Belles & Fanselow, 1980). The introduction of a Cl into the entire sequence of events constituting the avoidance response and the resulting blocking of inhibitory conditioning to unreinforced CSs (PFE) may help in explaining the dissociation between various measures of fear and operant performance, as well as the self-maintenance of avoidance behavior. REFERENCES Asratian, E. A. Mechanism and localization of conditioned inhibition. Actu Biologiue Experimentalis, 1969, 29, 271-291. Belles, R. C.. & Fanselow. M. S. A perceptual-recuperative model of fear and pain. The Behavioral and Brain Sciences, 1980. 3, 291-323. Chorqiyna, H. Some data concerning the mechanism of conditioned inhibition. Bulletin de L’Academie Polonuise des Sciences, Serie des sciences hiolo~iques. 19.57. 5, 387392. Chorqiyna. H. Some properties of conditioned inhibition. Acta Eiologiue Experiment&, 1962. 22, 5-13. Hendersen. R. W., & Harris, K. Inhibitory protection of conditioned fear from extinction. Unpublished manuscript, 1979. Herrnstein. R. J. Method and theory in the study of avoidance. Ps.who/ogicu/ Revielr,, 1969. 76, 49-69. Hineline, P. N. Negative reinforcement and avoidance. In W. K. Honig &J. E. R. Staddon (Eds.). Handbook of operun/ behavior. Englewood Cliffs. N.J.: Prentice-Hall. 1977. Pp. 364-414. Jacobs. W. J.. & LoLordo, V. M. The sensory basis of avoidance responding in the rat: Relative dominance of auditory or visual warning signals and safety signals. Learning and Motir,ation, 1977. 8, 448-466. Jacobs, W. J., & LoLordo. V. M. Constraints on Pavlovian conditioning: Implications for avoidance learning in the rat. Leurning und Motivation. 1980. 11, 427-455. Jones, R. H.. Crowell, D. H.. & Kapuniai. L. E. Change detection model for serially correlated data. Psychological Bulletin. 1969, 71, 352-358. Kamin, L. J. “Attention-like” processes in classical conditioning. In M. R. Jones (Ed.), Miami Symposium on the Prediction of Behavior 1967: Aversive Stimulation. Coral Gables, Fla.: Univ. of Miami Press, 1968. Pp. 9-31. Kamin. L. J. Predictability. surprise. attention. and conditioning. In B. A. Campbell & R. M. Church (Eds.). Punishment. New York: Appleton-Century-Crofts. 1969. Pp. 279-296. Khodorov. B. I. Some properties of the conditioned inhibitor. ZhLtrnut Vvsshei Nervnoi Deiatel’nosti, 1959, 5, 753-758. Konorski, J. Conditioned rejfexes und neuron organization. London: Cambridge Univ. Press, 1948. (a) Konorski, J. K voprosu o vnutrennem tormozhenii (On internal inhibition). In L. A. Orbeli. I. P. Razenkov, P. K. Anokhin, & K. Kh. Kekcheev (Eds.). Oh’edinennaia Sessia Posviashchennaia IO-ti letia so Dnia Smerti I. P. Puvluvu. Moskva: Izdatel’stvo Akademii Meditsinskikh Nauk SSSR. 1948. Pp. 225-229. (b) Konorski. J. Integrative uctivity qf‘ the brain. An interdisciplinury approach. Chicago/ London: The Univ. of Chicago Press, 1967. Krzhyshkovski. K. N. K fiziologii uslovnogo tormoza (On the physiology of the conditioned

28

SOLTYSIK inhibitor).

Transactions

of the

Society

ET AL.

of Russian

Physicians

in St. Petersburg,

1908.

75.

LoLordo, V. M., & Rescorla. R. A. Protection of the fear-eliciting capacity of a stimulus from extinction. Acta Biologiae Experimentalis. 1966, 26, 251-258. Mackintosh, N. J. The psychology qf animal learning. New York/London/San Francisco: Academic Press, 1974. Miller, S., & Konorski, J. Sur une forme particuliere des reffexes conditionnels. Comptes Rendus

des

Seunces

de lu Societe

de Biologic

et de ses Filiules.

1928.

99,

I 155-l

157.

Mineka. S. The role of fear in theories of avoidance learning. flooding, and extinction. Psychological Bulletin, 1979. 86, 958-1010. Mishtovt, G. V. Opyty tormozheniia iskustvennogo uslovnogo reflexa (zvukovogo) razlichnymi razdrazhiteliami [Experiments with inhibition of an artificial conditional reflex (to a sound) by various stimuli]. Trunsaction of the Society of Russian Physicians in St. Petersburg, 1906, 73. Mishtovt, G. V. Vyrabotannoe tormozhenie iskustvenoogo uslovnogo rejlexa (zvukovogo) na sliunnye zhelezy (Acquired inhibition of the artificial conditional reflex (to a sound) of the salivary gland). Doctoral Thesis, St. Petersburg, 1907. Nicholas, T., Soltysik, S., Wolfe, G.. & Wilson, W. J. Protection from extinction by blocking

qf

inhibitory

conditioning.

98th

Annual

Convention

of

the

American

Psy-

Los Angeles, Calif.. August 24-28. 1981. Nicholas, T., Wolfe, G., Soltysik, S. S., Garcia, J. L., Wilson, W. J., & Abraham, P. Postnatal development of heart rate patterns elicited by an aversive CS and US in cats. Pavlovian Journal of Biological Science, in press. Pavlov. 1. P. Conditioned rej?exes. London: Oxford Univ. Press, 1927. Pavlov, I. P. Lectures on conditioned rejlexes-Ttitenty-jih,e years of objective study sf the higher nervous activity fbehaviour) of animals. New York: International, 1928. Pietrzykowska, B.. & Soltysik. S. A failure to train the “same-different” differentiation of photic stimuli in dogs. Acts Neurobiologiue Experimentalis, 1975, 35, 27-38. Rescorla, R. A., & Wagner, A. R. A Theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F. Prokasy (Eds.), Classical conditioning II: Current research and theory. New York: AppletonCentury-Crofts, 1972, Pp. 64-99. Seligman. M. E. P., & Johnston, J. C. A cognitive theory of avoidance learning. In F. J. McGuigan & D. B. Lumsden (Eds.). Contemporary approaches to conditioning and learning. Washington, D.C.: Winston, 1973. Pp. 69-110. Soltysik, S. Studies on the avoidance conditioning: 3. Alimentary conditioned reflex model of the avoidance reflex. Acfa Biologiae Experimentalis. 1960, 20, 183-192. Soltysik, S. Inhibitory feedback in avoidance conditioning. Boletin de1 Institute de Estudios Medicos y Bioldgicos, MPxico. 1963, 21, 433-449. Soltysik. S., Nicholas, T.. Wolfe, G.. Wilson, W. J., & Abraham, P. Inhibitory associative chological

learning emotions

Association.

and and

its role motivuting

in maintaining processes

acquired are protected

behavior uithout from extinction.

reinforcement: HOW 5th Annual Conference

on Brain Research, Steamboat Springs, Colo.. January 23-30. 1982. Soltysik, S.. & Wolfe, G. Protection from extinction by a conditioned inhibitor. Actu Neurobiologiae Experimentalis. 1980, 40, 291-311. Soltysik, S., & Zielinski, K. The role of afferent feedback in conditioned avoidance reflex. In E. Gutmann & P. Hnik (Eds.), Central and peripheral mechanisms qf motor functions. Prague: Publishing House of the Czechoslovak Academy of Sciences, 1963. Pp. 215-221. Suiter. R. D., & LoLordo, V. M. Blocking of inhibitory Pavlovian conditioning in the conditioned emotional response procedure. Journal of Comparatir,e und Physiologicul Psychology. 1971, 76. 137-144.

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FROM EXTINCTION

29

Vasil’ev, P. N. Vliianie postoronnego razdrazhitelia na obrazovavshiisia uslovnyi reflex (The effect of an extraneous stimulus on the established conditional reflex). Transactions of the Society

of Russian

Physicians

in Sf. Petersburg,

1906, 73.

Wagner, A. R., & Rescorla, R. A. inhibition in Pavlovian conditioning: Application of a theory. In R. A. Boakes & M. S. Halliday (Eds.). Inhibition and IeaminR. New York/ London: Academic Press, 1972. Pp. 301-336. Wolfe, G. E., & Soltysik, S. S. An apparatus for behavioral and physiological study of aversive conditioning in cats and kittens. Behavior Research Methods & Instrumentation, 1981, 29, 637-642. Zbroiyna, A. On the conditioned reflex of the cessation of the act of eating. 1. Establishment of the conditioned cessation reflex. Acta Biologiae Experimentalis, 1958, 18, 137-162. Zimmer-Hart, C. L., & Rescorla, R. A. Extinction of Pavlovian conditioned inhibition. Journal of Compurative and Physiological Psychology, 1974. 86, 837-845. Received September 29, 1982 Revised December 8. 1982

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