Eehav. Res. Thu. Vol. 21, No. 3. pp. 297-301, 1983 OOOS-7967)83:030297-05$03.00/O Printed m Great Britain Pergamon Press Ltd

THERAPY FOR HELPLESS MONKEYS

DOUGLAS K. RUSH,* SUSAN MINEKA and STEPHEN J. Suow

University of Wisconsin-Madison, Madison, WI 53706, U.S.A.

(Rewired 24 Noremhrr 1982)

Summary-During the course of pilot studies and two formal experiments examining the Icarned- helplessness phenomenon in rhesus monkeys, S subjects failed to escape in a shuttlebox following earlier experience with aversive stinlul~tion in primate-restraining chairs. The present report detatls a therapeutic manipulation designed to reverse these subjects’ maladaptive behavior in the shuttlebox. Introduction of a different fear stimulus (a net previously used to restrain the animals) was found to he effective in inducing shuttlebox escape and avoidance learning. The implications of the present findings for an understanding of the learned-helplessness phenomenon and their relevance to therapy for human depression are discussed.

INTRODUCTION

During the 1.5 years since the first publication of what has become known as the learned- helplessness phenomenon, much progress has been made in understanding the mechanisms responsible for the effects of lack of control. At present it seems that activity deficits (e.g. Anisman,

de Catanzaro and Remington, 1978), cognitive deficits (e.g. Jackson, Alexander and Maier, 1980) analgesic effects (e.g. Maier, Davies, Grau, Jackson, Morrison, Moye, Madden and Barchas, 1980), and biochemical changes (e.g. Weiss, Glazer and Pohorecky, 1976) are all factors that may play a role in explaining why animals either completely fail or are slow to learn a test task following treatment with uncontrollable aversive stimulation. ~nfortunate~y the int~rreIationships between and among all these factors have not yet been completely elucidated.

For the most part, investigators have varied treatment (e.g. Lawry, Lupo, Overmier, Kochevar, Hollis and Anderson, 1978) or test-task (e.g. Maier, Albin and Testa, 1973) parameters, or administered some manipulation such as a drug (e.g. Anisman, Remington and Sklar, 1979) between treatment and test task to elucidate either the boundary conditions for producing the learned-helplessness phenomenon or the mechanisms responsible for its occurrence. Considerably less attention has been directed toward reversing learned-helplessness effects once they have occurred. From the standpoint that learned helplessness may provide a model for understanding human depression (Sehgman, 1975) it is important to demonstrate parallels between manipulations which are effective in inducing helpless animals to respond adaptively and treatments which are therapeutic in depressed individuals.

To date, three procedures have been reported to be successful in reversing helplessness in animals.? Seligman, Maier and Geer (1968) and Seligman, Rosellini and Kozak (1975) utilized the behavior therapy of ‘putting through’ to reverse helplessness in dogs and rats, respectively. In this directive therapy, the helpless subjects were forcibly exposed to the required response (shuttling for dogs and bar-pressing for rats) by physically putting the animals through the motions of these responses and thus exposing them to the contingency between responding and escape from shock. This manipulation has been interpreted by Seligman (1975) as an analogue of some cognitive/behavioral therapies for depression.

A second parallel between treatments effective in curing depression and reversing helplessness is provided by the results of Dorworth and Overmier (1977), who reversed helplessness in dogs

*To whom all reprint requests should be addressed at: Cassella AG. ZNS Pharmakolo~ie. Hanauer Landstr. 526. 6000 Frankfurt 61. F.R.G.

TThese procedures are to be distinguished from ones that are administered following treatment but before the test msk (e.g. Williams and Maier. 1977), procedures which prevent the occurrence of helplessness and are not analogous to therapies for depression.

tl~, 21’3 CI 291

298 DOUGLAS K. RUSH ct al.

with electroconvuisive shock (ECS) therapy. Similar results have also been reported for rats (Brett, Burling and Pavlik, 1981).

Finaily. Beagley and Beagley (1978) demonstrated reversal of learned helplessness with septal lesions, a method which has not been, and is unlikely to be, used in treating depressed humans. Thomas and DeWald (1977) had previously shown that injection of atropine, a cholinergic blocker, directly into the septum prevented the development of helplessness. They suggested that inescapable aversive stimulation results in an inhibition of active responses mediated by the septal region, which is responsible for failure to escape in a subsequent task. Combining these results with other evidence that inhibition is mediated by the septum, for example, that electrical stimulation of the septal area induces passivity much like that shown by helpless animals, Beagley and Beagley (1978) hypothesized that a lesion in this forebrain nucleus would release inhibition and allow animals to escape normally, a hypothesis substantiated by their results.

Somewhat surprisingly, there seem to be no studies in which drugs have been administered as therapy for helplessness. Several studies have reported the preaention of helplessness by adminis- tering either human antidepressants, such as desmethylimipramine (e.g. Leshner, Remler, Biegon and Samuel, 1979) or substances used primarily in animal research, such as scopolamine (e.g. Anisman or rrl., 1979) either prior to the helplessness induction phase or prior to the initial test for a helplessness effect. Such studies provide support for the idea that failure to escape is at least partially biochemicalIy mediated and further strengthens learned helplessness as a model of human

depression. The present report details the results of a new therapeutic manipulation to reverse shock-induced

helplessness in rhesus monkeys. This therapy entailed the presentation to subjects of an aversive stimulus very different from the shock which failed to induce escape behavior. A net with which all subjects had previously been captured and restrained during the course of routine veterinary care was visually presented to subjects shortly after shock onset during shuttlebox testing. It was hypothesized that the net would induce active escape behavior and through pairing with shock would lead to active escape from and avoidance of shock without the net.

METHOD

Five rhesus monkeys (~~cucu ~~~utt~), 2 males and 3 females, ranging in age from 3 to 8 yr and in weight from 3.8 to 7.9 kg at the beginning of treatment served as Ss. All Ss were born in the laboratory and had varied previous experimental histories. Details of these histories are available from the authors upon request.

Apparatus

The shuttlebox in which therapy was administered was constructed of stainless steel (side) and

Plexiglas (top) and measured 140 x 70 x 70 cm (Rush, 1982). The Plexiglas top of the shuttlebox permitted viewing Ss via closed-circuit television (CCTV). The two halves of the shuttlebox were separated by a 30cm high barrier and a guillotine door, which when raised permitted shuttle responses through a 23 cm high opening. The floor on each side of the shuttlebox was constructed of 0.6 cm stainless-steel grid bars placed 2.2 cm apart (center to center). A shock generator (Lehigh Valley, Model 153 1) and Scrambler (Lehigh Valley, Model 13 I 1 SS) delivered constant current d.c. shock of 3.5 mA intensity. A noise generator providing 65 dB of white noise, as measured inside the shuttlebox, served to mask extraneous noises. All programming of experimenta events was carried out by automatic equipment located in a separate room.

Net therapy was administered with a net normally used to restrain animals in a small transport cage so they could be handled for, among other things, routine veterinary care. All Ss had experienced being restrained with this net, thus making it a salient and, most likely, aversive stimulus. The frame of the net (23 x 30 cm) and handle were constructed of aluminum tubing; the net itself from nylon cord.

Therapy for helpless monkeys 299

Procedure

Three of the helpless monkeys of the present study were Ss in the two experiments reported in Rush, Mineka and Suomi (1982). The other 2 monkeys were Ss in a pilot study. The treatments involved administration of a.c. (2 Ss) or d.c. (3 Ss) electric shocks of 4 mA (3 Ss) or 6 mA (2 Ss) intensity while the monkeys were restrained in primate-restraining chairs. Shocks were delivered to the feet and were controllable for 2 of the Ss and uncontrollable for 3 of the Ss. Over the course of 2-6 sessions Ss received either 120 (2 Ss), 180 (1 S), or 300 (2 Ss) shocks. For a detailed description of the treatments used to induce helplessness, see Rush et al. (1982).

Forty-eight hours following treatment, active avoidance training was administered in the shuttlebox. The opening of the guillotine door and the onset of a 3 kHz tone, which raised the noise level 10 dB over that provided by white noise, served as a compound discriminative stimulus. Responses that occurred within 10 set of trial onset were recorded as avoidance responses and resulted in termination of the trial, i.e. termination of the tone and closing of the guillotine door. If the S did not make a response within 10 set of the beginning of the trial, 3.5 mA scrambled shock was delivered to the grid floor (and for some Ss the walls as well). A response over the barrier to the other side of the shuttlebox resulted in escape from shock and termination of the trial. If no response occurred after shock onset, the trial terminated automatically 30 set later. The session was terminated after 10 consecutive trials in which the S failed to escape shock. Trials were administered on a VI45-set schedule.

Net therapy sessions were the same as the active-avoidance session described above except that on certain trials the net was placed by an experimenter on top of the clear Plexiglas ceiling of the shuttlebox (in view of the S) 2-3 set following the onset of shock. If the S responded to the other side of the shuttlebox, the net was immediately removed. One trial without presentation of the net was alternated with 5 consecutive net trials, unless the S escaped or avoided on its own, in which case the net was not presented on the next trial. If the S failed to escape during this ‘no net’ trial, the sequence of five net-presentation trials alternated with one ‘no net’ trial was restarted. Net therapy was terminated when and if the S met a criterion of 20 consecutive avoidance responses in a single session. Net therapy sessions were usually spaced at l-week intervals and consisted of 40 trials per session.

RESULTS

Active-avoidance acquisition

In the first test for acquisition of escape/avoidance learning, 3 of the Ss escaped on 1 or 2 trials at the beginning of the session and then failed to escape on the next 10 consecutive trials. The other 2 Ss failed to escape from shock on any of the trials. All Ss were administered at least one retention test of 10 trials 7-60 days following the first acquisition session and all Ss failed to respond on any of the trials.

Net therapy sessions

For all 5 Ss, the net was effective in inducing escape behavior; all Ss responded by jumping over the barrier each time the net was presented. In addition, 3 Ss learned to escape and avoid shock even on trials when the net was not presented. One of these Ss required 27 net presentations and 2 sessions to learn, and the third S only 3 net presentations and 1 session to learn to avoid shock. The other 2 of the 5 Ss received 5 sessions of net therapy, during which they never escaped from shock unless the net was also presented. These 2 Ss also never avoided the net or the shock.

DISCUSSION

That subjects so readily escaped from the net but not from shock suggests that the net motivated active escape behavior much more effectively than shock. According to learned-helplessness theory (Maier and Seligman, 1976) the inability or failure to control aversive events induces a motivational deficit, a reduced incentive to initiate active responses to control events in a future

300 DOUGLAS K. RUSH et al.

situation. The difference in the motivational value of the net and shock may have stemmed from subjects’ differential experience in controlling these two stimuli. The subjects’ sole previous experience with shock was in a situation either in which the shock was uncontrollable or in which control of shock was not well learned.* Due to this experience, the subjects may have had a reduced motivation to respond in the shuttlebox when again confronted with shock.

In contrast to their experience with shock, the subjects of the present investigation had had both controllable and uncontrollable experiences with the net. Although they were unable to control the net when restrained with it for veterinary care (experiences which undoubtedly were responsible for its conditioned aversive quality), the net was sometimes only shown to subjects to elicit a withdrawal, i.e. escape response, a response which, for example, resulted in the subject entering a transport cage for transport from the home cage to a test apparatus (for example, the shuttlebox). The net then was an aversive stimulus from which subjects sometimes could and sometimes could not escape, i.e. their experience with the net was one of partial control. Such experience of partial control has been shown to be sufficient to prevent the development of helplessness in rats (Alloy and Bersh, 1979) and from the present results appears to have been sufficient to prevent a helpless reaction to the net in the shuttlebox. In summary. the monkey subjects in the present study either had no control or poorly learned to control shock, whereas the net was an aversive stimulus from which they had sometimes successfully escaped. This differential experience with these two aversive stimuli evidently resulted in the differential reaction to them in the shuttlebox in the present study, a helpless reaction to shock and a successful coping response to the net.

For 3 of the 5 subjects, the pairing of the net-escape response with shock offset resulted in their learning to escape from and avoid shock. For 2 subjects. however, the previous experience with shock seems to have induced a helplessness effect so strong that even repeated pairings of escape from the net with escape from shock failed to lead either of these subjects to escape or avoid shock without the net. Perhaps these subjects manifested the cognitive deficit, a reduced ability to learn, which is postulated by learned-helplessness theory to occur following experience with uncon- trollable events. In spite of repeated escape from shock, these 2 subjects failed to learn the association between active responding and shock offset. Their behavior is reminiscent of some of the early reports of helplessness in dogs where dogs that occasionally escaped from shock reverted back to non-responding on future trials and failed to learn the escape response-shock offset contingency (Seligman, 1975). Another possibility is that these 2 subjects had learned a very strong inactivity response to shock during treatment (Anisman rt al., 1978) and in the shuttlebox continued to perform this response to shock. Although they actively escaped in response to presentation of the net, this may not have been sufficient to overcome the inactivity previously learned as a response to shock.

One possible explanation as to why these 2 subjects and not the others failed to learn stems from consideration of the kind of shock they were administered during initial treatment. Lawry et al. (1978) reported that continuous shock was more effective than pulsed shock and a.c. shock more effective than d.c. shock in producing helplessness in both rats and dogs. The 2 subjects which failed to learn to escape and avoid during net therapy were the only 2 subjects to receive a.c. continuous shock during initial treatment. The other 3 subjects all received d.c. pulsed shock which, according to the results of Lawry et al. (1978), is least effective in producing helplessness.

To the extent that helplessness is a useful model of human depression, the present results suggest that a change in reinforcer may be a useful therapeutic tool in the treatment of depression. In much

the same way that a different stimulus, the net, helped the subjects of the present investigation to cope with shock, therapies in which a depressed person learns to focus attention on reinforcing activities with salient motivational value may facilitate a return to normal behavior. The thera-

*Two of the 5 Ss putatively had control over shock offset during treatment. One of these Ss had failed to conststently escape from shock with short latency bar-press responses in a pilot study. This S often failed entirely to escape from shock (242, of the trials) and when he did escape, latencies ranged from 2 to 70 seconds (mean = 15). It is thus doubtful that he experienced a ‘sense of control’ during treatment. The other S more consistently terminated shock using a panel-press apparatus. This S’s subsequent failure to escape from shock may have been due to the fact that she too failed to acquire a ‘sense of control’. Her average response latency (4.9 set) in the second of the 2 treatment sessions was the longest of any of the 6 Ss in the group (Rush et al.. 1982. Expt I) and she fatled to escape on 5”; of the trials in that session.

Therapy for helpless monkeys 301

peutic technique of “time projection with positive reinforcement” (Lazarus, 1968) for example, attempts to help the depressed person shift attention to activities which are known to be reinforcing. Such a change in emphasis may provide the necessary motivation for a depressed person to demonstrate adaptive attempts to control the environment.

AcknoM?l~dgements-This research was supported by USPHS Grant No. MH-28485 from the National Institute of Mental Health, by Grant BNS77-06802 from the National Science Foundation, and by grants from the University of Wisconsin Graduate School to S. Mineka and S. Suomi. The authors would like to thank Rick Michalski. Bob Stellner and Lynn Ohman for their help m the collection of data.

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