Avoidance Learning Situation Research Articles

Activation patterns of dopaminergic cell populations reflect different learning scenarios in a cichlid fish, Pseudotropheus zebra

Dopamine is present in all vertebrates and the functional roles of the subsystems are assumed to be similar. Whereas the effect of dopaminergic modulation is well investigated in different target systems, less is known about the factors that are causing the modulation of dopaminergic cells. Using the zebra mbuna, Pseudotropheus zebra, a cichlid fish from Lake Malawi as a model system, we investigated the activation of specific dopaminergic cell populations detected by double-labeling with TH and pS6 antibodies while the animals were solving different learning tasks. Specifically, we compared an intense avoidance learning situation, an instrumental learning task, and a non-learning isolated group and found strong activation of different dopaminergic cell populations. Preoptic-hypothalamic cell populations respond to the stress component in the avoidance task, and the forced movement/locomotion may be responsible for activation in the posterior tubercle. The instrumental learning task had little stress component, but the activation of the raphe superior in this group may be correlated with attention or arousal during the training sessions. At the same time, the weaker activation of the nucleus of the posterior commissure may be related to positive reward acting onto tectal circuits. Finally, we examined the co-activation patterns across all dopaminergic cell populations and recovered robust differences across experimental groups, largely driven by hypothalamic, posterior tubercle, and brain stem regions possibly encoding the valence and salience associated with stressful stimuli. Taken together, our results offer some insights into the different functions of the dopaminergic cell populations in the brain of a non-mammalian vertebrate in correlation with different behavioral conditions, extending our knowledge for a more comprehensive view of the mechanisms of dopaminergic modulation in vertebrates.

Effects of a marihuana homologue (Pyrahexyl) on avoidance learning in the gerbil.

Pyrahexyl (synhexyl, 3-hexy1-7,8,9,10-tetrahydro-6,6,9-trimethy1-6H-dibenzo[b,d] pyran-l-ol) is a synthetic cannabis compound having behavioural effects similar to tetrahydrocannabinol (mc) one of the active principles of Cannabis sativa L (Hollister, Richards & Gillespie, 1968). Although pyrahexyl has been studied in man (Stockings, 1947; Parker & Wrigley, 1950; Thompson & Procter, 1953; Hollister & others, 1968), little is known of its specific behavioural effects except that it seems to have euphoriant properties. Recently, Abel (1969) found in rats that pyrahexyl markedly reduced the amount of time required to resume lever pressing for water after this activity had been suppressed by a fear-producing stimulus and Abel & Schiff (1969) reported that pyrahexyl increased curiosity in rats as measured by the time they spent observing other animals. We now report its effect in an avoidance learning situation. The particular testing procedure chosen assessed the effect of pyrahexyl on the acquisition of new behaviour rather than its effect upon a previously learned response as examined by Abel (1969). Six adult male Mongolian gerbils (Meriones Unguiculatus), 80-90 g, were injected intraperitoneally with 0.2 ml of a solution of pyrahexyl (2.3 mg/kg) in olive oil ; six control animals received only oil injections. After 2 h animals were placed individually into a standard two-compartment automated shuttle box (Lehigh Valley Electronics, Model 146-04) in which they could avoid being shocked through the grid floor by jumping over a barrier dividing the apparatus. An auditory signal was the conditioned stimulus and a 0.8 mA constant current electric shock the unconditioned stimulus. The conditioned stimulus preceded the onset of shock by 5 s. If an avoidance response was not made during this period, shock came on and remained on until the animal jumped over the barrier. Each presentation of the conditioned stimulus and the performance of a jumping response constituted a single trial ; 50 such trials were given each day with a 25 s interval between trials. A total of 250 trials was given over a 5-day test period. The test apparatus and recording equipment were completely automated and the animals were not disturbed once the daily test period had begun. Records were kept of the number of successful trials; the time taken to jump the barrier after each conditioned stimulus onset (jump latency); and the number of between trial jumps which were not associated with the conditioned stimulus. As shown in Fig. IA, pyrahexyl-injected animals made more avoidance responses on the first day of testing than did control animals ; this difference was statistically significant (t-test, Edwards, 1964; t = 1.89, P<0.05). By the second test day all animals had achieved high performance levels and no differences in acquisition of the avoidance response were found between groups on this or any subsequent day. However, analysis of variance (Edwards, 1964) showed that, compared to controls pyrahexyl-injected animals had significantly lower response latencies to the conditioned stimulus throughout the five day test period (F = 11, 21, df, 1, 10, P<0.01, see Fig. 1B). There was no effect of the drug on responding independent of presentation of the conditioned stimulus (between-trial jumps). The mean daily between-trial jump rates were : pyrahexyl animals, 5C = 12.19, range 2.8-47; control animals, X = 14.32, range 4-0-50.

Behavioral changes in open-field and shuttle avoidance learning situations in rats with hippocampal lesions over a 40-day postoperative period

Behavioral changes in open-field and shuttle avoidance learning situations in rats with hippocampal lesions over a 40-day postoperative period

近交系マウスの自発活動成分と逃避‐回避成績の関係

We have insisted that the difference in the reactions of mice to an electric shock may be one of the most important determinants of their performances shown in escape-avoidance situations. In Experiment 1, we trained four inbred strains of mice (BALB/c, C3H/He, C57BL/6, DBA/2 J) in two-way avoidance learning situation. C57BL mice showed the best performance and C3H did the worst, while DBA and BALB mice were in-between the two. Especially, we observed C57BL mice had a strong tendency to run to the shock, while C3H mice had a tendency to jump and/or rear. In Experiment 2, we made clear that these reactions to shocks of C57BL and C3H didn't change easily but persisted even if those were inappropriate to the situation. The results suggested that the performance of mice in an escape-avoidance situation was closely related to the characteristic reactions of mice shown to the shock, which differed from strain to strain.

Learning in surgical and functional hemidecorticate rats: A preliminary study of compensation

A case is made for the conjoint use of surgical and functional hemidecorticate preparations in the investigation of compensation. Direct comparison of the effects of surgical and functional hemidecortication in rats in an active runway avoidance learning situation is reported. Trials to successively higher avoidance criteria, total avoidance responses, longest runs of consecutive avoidance responses, response latencies and running times are compared. None of these measures reveal differences between the two types of hemidecorticate preparation, although compared with a normal group both hemidecorticate groups show a deficit. The implications of this finding in terms of the compensation issue are discussed.

Learning in surgical and functional hemidecorticate rats: A preliminary study of compensation

A case is made for the conjoint use of surgical and functional hemidecorticate preparations in the investigation of compensation. Direct comparison of the effects of surgical and functional hemidecortication in rats in an active runway avoidance learning situation is reported. Trials to successively higher avoidance criteria, total avoidance responses, longest runs of consecutive avoidance responses, response latencies and running times are compared. None of these measures reveal differences between the two types of hemidecorticate preparation, although compared with a normal group both hemidecorticate groups show a deficit. The implications of this finding in terms of the compensation issue are discussed.

Fear inhibition and species specific defense reaction termination may contribute independently to avoidance learning

A series of three experiments was conducted to test the proposal of Cicala and Owen ( Learning and Motivation, 1976 , 7, 356–367) that warning signal termination reinforces avoidance learning by permitting fear to dissipate and that a feedback signal reinforces avoidance learning through conditioned inhibition of fear. A CER procedure with a second-by-second analysis was used to measure fear elicitation and fear reduction following classical conditioning or avoidance training. The results show that a feedback signal produces rapid and marked fear reduction, suggesting an inhibitory process. Although warning signal termination produced fear reduction, the slowness of this process suggests fear dissipation and not an inhibitory process. The combination of both events reduced fear no more effectively than a feedback signal alone. It is suggested that warning signal termination is effective in some avoidance learning situations not because it reduces fear, but possibly because it helps terminate an avoidance response that closely resembles a species specific defense reaction.

Warning signal termination and a feedback signal may not serve the same function

Three experiments were conducted to test the possibility that a feedback signal (FS) and warning signal termination (WST), while equally reinforcing in the avoidance learning situation, reinforce through different underlying mechanisms. The first experiment showed that the reinforcing properties of an FS are reduced more than those of WST when these stimulus changes are made unreliable by the presence of shock following a CR on specified trials throughout acquisition. Experiment 2 confirmed this effect on avoidance performance when only a few punishment trials were administered following asymptotic avoidance acquisition. Experiment 3 demonstrated this effect during avoidance extinction with and without the presentation of punishment trials between acquisition and extinction performance. The results provided no support for the expectancy explanation of avoidance learning and were interpreted as consistent with the assumption that WST reinforces by permitting fear to dissipate and that the FS reinforces through fear inhibition.

Effects of situational variables on performance of inbred mice in active- and passive-avoidance situations.

A group of experiments were conducted to assess the interaction between environmental factors and specific genetic loci upon the performance of mice in avoidance learning situations. The performance of all mice was better in passive-avoidance than in active-avoidance situations. The performance of C57BL/6J mice was generally superior to that of DBA/2J mice. C57BL/6J mice usually avoided foot-shocks, while DBA/2J mice attempted to escape them. DBA/2J mice performed poorly in the presence of mild foot-shocks, while C57-BL/6J mice performed poorly in the presence of intense foot-shocks. Analysis of the data suggested that the loci involved probably exerted their influence by affecting the subject's response to its environment.

Passive-avoidance performance in mice: Evidence for single-locus inheritance

Variation in the performance of groups of 5-mo-old mice in a passive avoidance learning situation can be accounted for on the basis of a single locus model of genetic inheritance. Presence of the dominant allele (Ppb) leads to poor performance under conditions of high footshock, while homozygosity for the recessive allele (Ppd) produces successful performance under the same conditions.

Flooding as a function of shock level and length of confinement

In a one-way avoidance learning situation with rats, response prevention trials facilitated extinction as an increasing function of the duration of the prevention interval for shock levels below 1.8 mA. For 1.8 mA, extinction was a nonmonotonic function of the response prevention interval, with 15- and 210-sec durations showing the most facilitation of extinction. For all response prevention intervals except 15 sec, trials to extinction was a direct function of shock level. For 15 sec, it was an inverse function of shock level. The unexpected interaction of shock level with prevention interval was explained by invoking the concept of relief.

Compensation of a hemidecorticate learning deficit by manipulation of input redundancy

The procedure of peripherally compensating the instrumental learning deficit of the functionally hemidecorticated rat is investigated by simultaneously manipulating two input conditions, the duration and the intermittent structure of the warning signal in an avoidance learning situation. Increases in both the temporal redundancy and the patterning of the signal were found to correct hemidecorticate performance. The results are interpreted in terms of network redundancy of cortical information processing systems.

Some Behavioral Tests of Domestication in Norway Rats

AbstractFive experiments with wild and domestic rats (Rattus norvegicus) were designed to assess behavioral effects of domestication. The results, which must be considered preliminary, are supportive of the notion that domestication in the Norway rat has induced an adaptive fitness rather than degeneration: 1. Scar-marked captives showed the poor reproductive success typical of traditional attempts at initial laboratorization. In 10 such pairs, three of the females killed prospective mates and five of the six who produced litters cannibalized all or some of the offspring. Unscarred captives, assumed to represent higher social status in the wild population, produced litters in eight of ten pairings with no abnormal breeding or maternal behaviors. 2. Scar-marked captives were least dominant in water competition and were most likely to show abnormal behaviors, new wounds, and mortalities. Similar competitive groupings of domestic rats showed the expected difference in social behavior; fighting was less intense, social distance was less, and threat signals were rare compared to wild rats. Where wild and domestic rats were housed together, however, the intensity of social behaviors in the latter increased, even leading to deaths, although interaction was almost segregated between the two kinds of rats. 3. In an avoidance learning situation, wild-caught and wild F1 (laboratory raised) rats were markedly inferior in performance compared to domestic rats in paradigms with internally or externally cued warnings. 4. In another avoidance learning context, wild rats showed limited evidence of a passive style of learning while domestic rats showed clear evidence of active avoidance learning. These data suggest that learning styles may differ in the two kinds of rats and that definitive evidence of a learning difference will be difficult to obtain. 5. Daily patterns of responding for drinking water were more resistant to change in the wild rats, even at a substantial cost in water obtained, suggesting that domestication may have induced greater behavioral flexibility.

Stimulus significance and chlorpromazine effects on the expression of avoidance learning in mice

Mice trained in a one-trial passive avoidance learning situation were treated with chlorpromazine (2 mg/kg i.p.) 10 min before being tested 24 hr after training. The reduced expression of learned avoidance and the accelerated extinction noted under the influence of the drug were found to be offset if the experimental subjects had received prior training in a T-maze in which the discriminanda were the same as those used in the avoidance learning situation. These findings are related to a possible mechanism of action of the drug involving the reduction of apparent stimulus significance. The likely physiological basis of such a mechanism is briefly discussed.

The role of the CS and its relationship to the CR in avoidance conditioning

Two studies are reported which are concerned with the role of the CS and its relationship to the CR in the standard avoidance learning situation. Study I demonstrates that the decrement associated with a trace CS is greatly reduced in one-way avoidance as compared with two-way. The suggestion is made that the differences in CS effects is attributable to differences in task complexity. Study 2 varied CS duration and the CS-CR termination contingency. Rapid acquisition of the avoidance response was obtained only when the CS remained on for the entire CS-US interval unless terminated by a response. The results were discussed with respect to the theoretical aspects of maintenance and emergence of the avoidance response.

Physiological and behavioral consequences of postnatal maternal stress in rats

To investigate the effects of maternal stress on the offspring, independent groups of lactating rats were subjected to ether anesthesia and jugular venipuncture on Day 3, 6, or 9 post partum, or to shock on Day 3 post partum. At weaning, 162 pups from the litters of these and control mothers were used to assess adrenocortical activity either immediately upon removal from the nest or after 15 min exposure to a novel environment. In addition, 33 males and 33 females were weaned and tested as adults in an avoidance learning situation. Plasma corticosterone levels, both before and after novelty, were significantly higher in the weanling offspring of all treated mothers when compared with those of non-treated mothers. In adulthood the offspring of mothers stressed 3 days post partum were significantly different from all other groups and showed poorer avoidance learning.

The effects of chlorpromazine on the decay and consolidation of short-term memory traces in mice.

F1 hybrids of two highly inbred strains of mice were trained in a one-trial passive avoidance learning situation. Chlorpromazine, in doses of 0.5, 2.0 and 3.5 mg/kg, was administered at one of four injections times, 10 min before and 0.5, 2 and 10 min after learning. Pre-learning drug administration completely blocked acquisition of a learned avoidance response. Post-learning drug effects were more complex, involving reduced expression of avoidance learning but less rapid extinction of the learned response. The results were related to effects of the drug on short-term memory trace decay and consolidation.

A neural model for conditioned avoidance learning.

A mathematical model for learning of a conditioned avoidance behavior is presented. An identification of the net excitation of a neural model (Rashevsky, N., 1960.Mathematical Biophysics. Vol. II. New York: Dover Publications, Inc.) with the instantaneous probability of response is introduced and its usefulness in discussing block-trial learning performances in the conditioned avoidance situation is outlined for normal and brain-operated animals, using experimental data collected by the author. Later, the model is applied to consecutive trial learning and connection is made with the approach of H. D. Landahl (1964. “An Avoidance Learning Situation. A Neural Net Model.”Bull. Math. Biophysics,26, 83–89; and 1965, “A Neural Net Model for Escape Learning.”Bull. Math. Biophysics,27, Special Edition, 317–328) wherein lie further data with which the model can be compared.

The effects of scopolamine hydrobromide on one-way and two-way avoidance learning in rats.

Previous studies have shown certain striking similarities between the behavioral effects produced by some anticholinergic drugs and the effects produced by hippocampal destruction. To investigate this parallel more thoroughly, scopolamine hydrobromide was administered to rats in one-way and two-way active avoidance learning situations. The drugged animals showed improved learning of the two-way problem, reaching criterion in one-half the number of trials and making one-third as many errors as the saline injected controls. In the one-way task the drugged subjects performed slightly worse than control animals. These data correspond very closely to those from similar experiments using hippocampectomized subjects.

Incubation in one-trial passive avoidance learning: A cautionary note

Sixty rats were tested in a step-down passive avoidance learning situation in an attempt to define an incubation gradient when the effects of the heightened activity following the training trial were controlled. At training test intervals of 5 sec, 10 sec, and 3 h 1-trial learning was observed in the experimental groups in which the effects of activity were controlled, while the typical incubation gradient was observed in the absence of control over activity.