INSTRUMENTAL MODIFICATION OF THE GSR

Four experiments investigated the effects of instructions, response-contingent shock, and the latency of the critical response on the GSR. Using a discrimination procedure, in which responding in the presence of one stimulus avoided shock while responding in the presence of another led to shock, it was found that relative to non-instructed, yoked-noncontingent conditions, instructed subjects responded at higher levels to the respond stimuli and at lower levels to inhibit stimuli. The effects of instructions appeared stronger than the effects of the shock contingencies. Only when the “contingent” GSR was of the “anticipatory” latency were differential effects obtained, however. No effects were observed in the absence of cognitive mediation.     

GALVANIC SKIN RESPONSE DURING AVOIDANCE LEARNING

Relations between galvanic skin response (GSR) and other variables during learning of a shock-avoidance task were observed. Ss operated a four-position switch as cued by visual stimuli: one always shocked, one never shocked, and two associated with switch positions which avoided the shock. Forty-eight Ss formed successive subgroups which exhibited: (1) progressively better avoidance learning with increased awareness instruction and (2) significantly decreased GSR when the correct avoidance had been learned. Analyses were made to differentiate autonomic responding due to reinforcement (i.e. number of shocks received) from that due to expectancy (anticipation of avoidance).     

Discriminative control of hyperdipsic drinking in the baboon

A baboon subject was surgically prepared with an arterial catheter and subsequently trained to elevate diastolic blood pressure with an operant schedule of food procurement and shock avoidance with associated discriminative stimuli. Blood pressure elevations developed in accordance with the requirements of the conditioning procedure. In addition, large-scale increases in water intake occurred on days when the conditioning sessions were in effect. Both blood pressure and water intake elevations were maintained when the conditioning procedure was changed to eliminate food reinforcement. Electrical monitoring of water spout contacts revealed that drinking occurred exclusively during response-produced SDS associated with food delivery, and did not occur either during response-produced SDS associated with electric shock, or during intertrial intervals. Because acute elevations in blood pressure preceded licking bouts, the drinking was not producing the pressor episodes. Overall, the data illustrate that drinking can occur in a systematic manner under the control of exteroceptive discriminative stimuli during non-skeletal response contingencies.     

AVOIDANCE CONDITIONING OF THE GSR: NATURE OF THE RESPONSE

The effects of avoidance conditioning of the GSR on HR responses were investigated. Seven Ss were allowed to avoid a shock if their GSR during a preceding 5.0 sec light was greater than a criterion magnitude. Each avoidance S had a yoked-control partner who received exactly the same series of shocked and nonshocked trials, regardless of his own GSR behavior. Sixty trials were given. Avoidance Ss gave significantly larger GSRs and cardiac deceleration took place at a significantly greater rate in the avoidance group. The results were interpreted as supporting the conclusion that when an avoidance paradigm is used to modify a particular autonomic response, the effects extend to other autonomic arousal or anticipatory responses. Each S was questioned in a post-training interview about his awareness of means of avoiding the shock. No S was able to verbalize any method that could be used to prevent shock from occurring.     

CLASSICAL CONDITIONING OF THE ELECTRODERMAL RESPONSE WITH NOVEL STIMULI

Most attempts to classically condition the electrodermal response (GSR) have used aversive stimuli. A series of 20 novel slides were used as unconditional stimuli in a delayed differential conditioning paradigm involving reinforced and unreinforced conditional stimuli. Thirty female Ss were given 10 habituation trials, 40 conditioning trials of which half were reinforced, and 10 extinction trials. Orienting response, anticipatory response, and post-conditional stimulus response components were analyzed separately for the different series. Differential conditioning was obtained for two of the responses during the conditioning and extinction series. The results indicate that a relatively mild novel stimulus can also effectively condition the GSR.     

Air and shock two-way shuttlebox avoidance in C57BL/6J and 129X1/SvJ mice

Despite multiple advantages of the use of electric shock as an aversive stimulus, reasons exist for considering alternative aversive stimuli. In the present study, we examined and compared the acquisition of two-way shuttlebox avoidance with 275.8-kPa (40-psi) pulsed air and continuous 0.4-mA shock in two strains of mice commonly employed in targeted gene mutation research, C57BL/6J and 129X1/SvJ. Each trial consisted of a 5-s warning stimulus (WS, light) during which shuttling to the other side cancelled delivery of the aversive stimulus. Once initiated, the aversive stimulus remained active for 20 s or until an escape response occurred. For C57BL/6J mice, air and shock were equally and highly effective aversive stimuli. In contrast, air was less effective than shock for 129X1/SvJ mice. C57BL/6J mice outperformed 129X1/SvJ mice for both stimulus types. For 129X1/SvJ mice, longer escape latencies were observed initially for air, suggesting that shock is more effective. However, these differences in latency dissipated within the first seven sessions. Nevertheless, by the end of the 17-day study, asymptotic levels of avoidance proficiency were substantially lower for air than for shock in 129X1/SvJ mice. These results indicate that air is a suitable substitute for shock as an aversive stimulus in shuttlebox active avoidance; however, the relative efficacies of these aversive stimuli appear to depend upon the strain chosen for study.     

Generalization of conditioned blood pressure elevations: Schedule and stimulus control effects

By using a combination of food-reward, shock-avoidance, and visual biofeedback, all contingent upon diastolic blood pressure, baboons were conditioned, in 3–4 months, to raise their blood pressure 30–50% (25–40 mmHg) above preconditioning baseline levels, and maintain the increased pressure during daily 12-hr training sessions. Under conditions where exteroceptive stimuli reliably predict environment events, animals appear to learn to stop making the blood pressure increase response when discriminative periods of safety are in effect within sessions and when training sessions are over. By gradually eliminating feedback, withholding food rewards, and punishing short-term falls in diastolic pressure, elevations in blood pressure were maintained continuously during training sessions and for periods up to 2 hr following the offset of training sessions.     

The role of primate putamen neurons in the association of sensory stimuli with movement

Neuronal activity in the putamen of monkeys was recorded while they performed operantly conditioned body movements. Two categories of neurons were observed. Type I cells had tonic spontaneous discharges and responded to the sensory trigger stimuli for movements with excitation followed by inhibition or with only inhibition. These responses to the trigger stimuli disappeared when the conditioned movement was extinguished. Type II cells were characterized by phasic activity time-locked to the movement. Two subclasses of type II cells were observed. Type IIa cells exhibited phasic discharges before the first movement of a learned, repetitive sequence of arm or orofacial movements that were triggered by the sensory stimuli. Type IIb cells showed phasic activity modulation during each movement in one direction, either flexion or extension, in an unconditioned manner. Activity of the type IIa cells preceded the onset of EMG in prime mover muscles, while most type IIb cells were activated after the EMG had appeared. Thus, in both type I and type IIa cells the activity can be said to be behaviourally contingent. Type I cells show a movement contingent sensory response, and type IIa cells show movement-related activity that is contingent upon the triggering of the movement by a sensory stimulus.     

Escape-avoidance learning in two strains of inbred mice when two types of response can be alternatively effective

Three experiments demonstrated that escape-avoidance learning is closely related to the response type dominantly occurred in mice of an inbred strain. Inescapable shock elicited locomotion (L-typed response) in C57BL/6 mice, and rearing or jumping (R-typed response) in C3H/He (Experiment 1). In the shuttle-box situation where both of these responses can be effective to terminate CS tone and electric shock, C57BL established L-typed avoidance mainly, while C3H tended to learn avoidance by R-typed response (Experiment 2). The two strains learned the escape in the shuttle-box by the same types of response as they showed in avoidance learning (Experiment 3). These findings lead us to conclude that different inbred strains of mice innately react to electric shock by their specific types of response. Strain differences in escape-avoidance learning could thus be attributed to the compatibility of the specific response type with requirement of the task situation.     

Effects of additional cues on passive avoidance learning and extinction in rats with hippocampal lesions

Following the acquisition of a water-rewarded approach response in a straight runway, the effects of introducing shock in the goal box (passive avoidance - PA) or withdrawing reinforcement (extinction) were compared in hippocampal, cortical, and operated control groups of rats. Under standard test conditions, hippocampal groups were impaired in PA learning and showed strong resistance to extinction, relative to the control groups. When additional cues were provided such that external stimuli associated with goal box events could be easily detected early in the runway, performance differences between the hippocampal and control groups were eliminated in the PA test and significantly reduced in extinction. The results emphasize the inefficient processing by hippocampally-damaged animals of stimulus cues following a shift in experimental contingencies.     

Prediction of the Informational and Motivational Properties of "Right-Wrong" Knowledge of Results With the Skin Resistance Response

The magnitude and rate of habituation of the skin resistance response (SRR) to extrinsic “right-wrong” knowledge of results (KR) were used to assess the KR's motivational and informational properties in delayed matching of visual patterns. Two experimental groups of 20 college students each received KR which was either contingent or non-contingent upon their actual choices, and two control groups of 10 subjects each received no KR. The magnitude of the SRR elicited was found to be higher to “right” than “wrong” KR stimuli but was not affected by correctness of the subjects' choices. The relative rate of SRR habituation was rapid when a low frequency of “right” KR stimuli was provided and the KR stimuli were not contingent upon the subjects' choices, but it was slow if either a high frequency of “right” KR stimuli were provided or the KR stimuli were contingent upon the subjects' choices. The results indicated that the KR stimuli had motivational properties but very little informational value. It was concluded that the SRR may be useful in assessing the reinforcing value of a feedback stimulus in terms of its motivational and informational qualities independently from its effects on task performance.     

In utero cocaine, discriminative avoidance learning with low-salient stimuli and learning-related neuronal activity in rabbits (Oryctolagus cuniculus)

Daily injections of cocaine administered to pregnant rabbits (Oryctolagus cuniculus) throughout gestation were associated with neural and behavioral changes during development and in adulthood, including altered neuron structure and function in areas receiving dopaminergic projections and retarded Pavlovian eyeblink conditioning with low-salient conditional stimuli. Studies of discriminative avoidance learning have shown changes in learning-related cingulothalamic neuronal activity, but no behavioral learning impairment in cocaine-exposed offspring. Here, low-salient stimuli were used during discriminative avoidance conditioning. Impairments early in behavioral acquisition were found, as well as alterations of anterior cingulate and medial prefrontal cortical, medial dorsal thalamic, and amygdalar neuronal response profiles and learning-related neuronal activity. These results elucidate the neural processes, impaired by prenatal cocaine, that support conditioning with low-salient stimuli.     

Local norepinephrine depletion and learning-related neuronal activity in cingulate cortex and anterior thalamus of rabbits

Summary Multi-unit neuronal activity was recorded in posterior cingulate cortex (area 29) and the anterior ventral (AV) thalamic nucleus during discriminative instrumental avoidance learning wherein a response (stepping in an activity wheel) to a 0.5-s tone (CS⁺) prevented a foot-shock 5 s after CS⁺ onset. Presentations of a different tone (CS^-) on 50% of the conditioning trials in an irregular sequence with the CS⁺ did not predict shock and thus required no response. Two groups of rabbits received intracranial micro-injections of 6-hydroxydopamine (6-OHDA) to locally deplete the NE in area 29 or the AV nucleus. Vehicle was injected in the non-depleted area in each group and a third group received vehicle injections in both areas. Dopamine neurons in subjects that received 6-OHDA were protected by pre-treatment with GBR-12909. Neuronal data were collected during two pre-training sessions in response to the tones only and when the tones and shock were presented unpaired. Thalamically depleted rabbits made more, and cortically depleted rabbits made fewer, avoidance responses than controls during the early stages of behavioral acquisition, and cortically depleted rabbits made fewer responses than controls and thalamically depleted rabbits during extinction testing administered after the completion of acquisition. One effect of NE depletion on neuronal activity was entirely local: elimination of neuronal sensitization effects (enhanced discharges elicited by tones during the unpaired tone-shock pre-training treatment relative to pre-training with tones only). Other neuronal effects of NE depletion were system-wide, i.e., they occurred whether the depletion was cortical or thalamic. These were: attenuation of area 29 tone-elicited neuronal discharges and enhancement of AV thalamic discharges before and during training; elimination in area 29 of neuronal discrimination between CS⁺ and CS^-, induced in controls by CS⁺-shock pairings in the first conditioning session; induction of this neuronal discrimination, not present in controls, in the AV nucleus during the first conditioning session; attenuation of discharge enhancements elicited in controls by unexpected stimuli (presentation of auditory stimuli different in quality and incidence from the CS⁺). Excepting the noted losses at the outset of training, the results did not support an involvement of NE in the production of cingulate cortical or AV thalamic excitatory and discriminative training-induced neuronal activity. The system-wide alterations due to NE depletion implicated NE in the processing of unexpected events and in the production of dynamic neuronal patterns relevant to mnemonic retrieval. Several of the depletion-related neuronal changes were similar to the effects of hippocampal formation (subicular) lesions, suggesting that NE-dependent functions in area 29 and the AV nucleus are governed by hippocampal efferents, which may control the release of NE in these areas.     

Expectancy of the UCS during Avoidance Conditioning of the SCR

Two studies are reported which investigated the relationship between expectancy of the UCS (shock) and avoidance conditioning of the skin conductance response (SCR). Subjects were allowed to avoid the shock UCS if they gave criterion magnitude SCRs to a warning tone preceding the shock. Expectancy of the UCS was monitored on a trial-by-trial basis during the avoidance conditioning process. It was found in Experiment I that SCR conditioning occurred only among subjects who had accurate expectancies of shock omission relative to their yoked controls. However, those subjects who were able to accurately predict shock omission were not able to verbalize the response-reinforcement contingency during a postconditioning questionnaire. Experiment II revealed that only subjects with accurate expectancies concerning the shock behaved differently from their yoked controls when given informative instructions about the response-reinforcement contingency. These data indicate that individual differences in the accuracy of UCS expectancy are positively related to SCR avoidance conditioning. This relationship has gone undetected in previous research because of the exclusive reliance upon verbal postconditioning questionnaires.     

Brain stem reticular formation neuronal correlates of stimulus significance and behavior during discriminative avoidance conditioning in rabbits

Multiple-unit activity in the reticular formation of the midbrain and pons was recorded in rabbits during discriminative conditioning of locomotor (wheel-running) avoidance behavior. The conditional stimuli (CS+ and CS-) were pure tones of different auditory frequency, and the unconditional stimulus (US) was a constant-current footshock (1.5-2.5 mA) delivered through the grid floor of the wheel. The pontine, but not the midbrain, sites manifested development during behavioral acquisition, of brief-latency (10-40-ms) discriminative neuronal discharges (i.e., greater discharges to the CS+ than to the CS-). The greatest magnitude of the discriminative discharges in the rostral pontine loci occurred in the first conditioning session. The discriminative response in the caudal loci developed more slowly, and it persisted to the criterial stage of training. Both rostral and caudal pontine loci, during the interval from CS onset to US onset, manifested a progressive build-up of neuronal firing in anticipation of the behavioral response. The occurrence in the rostral and caudal pontine areas, respectively, of early- and late-developing discriminative discharges is analogous to effects observed in past studies in the limbic mesocortical and thalamic systems. These findings provide a basis for establishing the possible functional relatedness or independence of these analogous effects.     

Changes in the categorization of appetitive and aversive events during postnatal development of the rat

Environmental stimuli are not clearly categorized into appetitive and aversive classes during the first postnatal week. Three- and 6-day-old rats are highly activated by nominally appetitive (milk infusions) and aversive (foot shock) stimuli. Both evoked the same generalized behavioral responses (rolling, curling). By 12 days of age, these stimuli were responded to differently; mouthing and probing occurred in response to milk while flinching and escape responses were observed to shock. The affective properties of mild shock were found to be hedonically opposite for 6- and 12-day-old pups. Six-day-old showed an acquired preference for an odor paired with shock which increased with intensity (.1–.5 mA) similar to that observed with milk infusions. An acquired odor aversion was displayed by 12 days old using these shock parameters. These results suggest that young rat pups may not differentiate many appetitive and aversive events behaviorally or affectively until the second postnatal week.     

STIMULUS CONTROL OVER OPERANT GALVANIC SKIN RESPONSES

Operant conditioning of the galvanic skin response (GSR) using a discrimination procedure was attempted in both acquisition and extinction. During acquisition male Ss were given contingent reinforcement during S+ intervals and noncontingent reinforcement during S– intervals. All reinforcement was withheld during extinction. A criterion response was defined as a .5% increase in skin resistance occurring in the absence of electromyogram (EMG) or respiration irregularities. A frequency analysis of GSRs showed that stimulus control was obtained in extinction but not in acquisition. Interpretations based upon skeletal mediation and adaptation were not supported.     

Phenotypic and genetic relations between initial response to electric shock and rate of avoidance learning in mice

The first experiment was designed to determine what proportion of the betweenstrain variation in rate of avoidance learning could be attributed to strain differences in sensitivity and response topography to electric shock. Measures of jumping at six shock intensities for four inbred strains were collected in a pretest of shock sensitivity. They were then used to derive a shock intensity for each strain which yielded the same amount of jumping for all strains. Avoidance training was administered to other mice of the same age and strains using the same apparatus and shock source as in the pretest. When training was given with a 180 a shock, significant strain differences were observed in latency of the first escape and total errors to a learning criterion during both jump-out and one-way avoidance training. A large strain by training procedure interaction was found, as well. When training was administered with shock levels which yielded equal jumping in the pretest, strain differences in latency of the first escape were totally eliminated. However, the magnitude of strain differences in the rate of avoidance learning was not changed substantially. A second experiment examined two F₁ hybrid strains and a four-way cross of the inbred strains tested in the first experiment. Results indicated that initial response to shock is characterized by intermediate inheritance, while rate of avoidance learning exhibits significant dominant inheritance. Although significant genetic differences in both initial response to shock and rate of avoidance learning were detected in the present experiments, it is concluded that the former cannot account for the latter.This research was supported in part by Grant APA-398 from the National Research Council of Canada.     

Pavlovian excitation,internal inhibition,and their interaction with free operant avoidance as a function of age in rats

The central hypothesis was that, in young as compared with adult rats, Pavlovian excitation is weaker and extinguishes more slowly, whereas internal inhibition is weaker but extinguishes more rapidly. In Experiment I, the suitability of free operant (Sidman) avoidance as a baseline for measuring Pavlovian effects was assessed in 5 age groups between 19 and 98 days of age trained in a shuttle box. Although clear age-related increases were evident in avoidance capacity, efficient “high criterion” avoiders were found in all age groups, indicating that the response was suitable. In Experiment II, groups of 26-, 38-, and 95-day-old rats first received Pavlovian aversive excitatory and differential inhibitory conditioning, or the conditional stimuli and shock randomly, or no treatment. Three days later they received free avoidance training. Prior Pavlovian conditioning facilitated subsequent avoidance learning in young subjects, but depressed it in adults. Among “high criterion” avoiders, such effects were absent. Following the avoidance training phase, 3 age groups of matched “high criterion” avoiders received conditioned stimuli superimposed on the baseline (a conditioning test). These results confirmed the central hypothesis.     

Effects of dexamethasone on discriminative fear conditioning in pigs

Eight pigs were trained in a shuttle-box to avoid electric shocks according to a continuous avoidance schedule. After stabilisation of the response rate they were submitted to a discriminative Pavlovian fear conditioning. In a subsequent test session, presentation of the CS+ increased the avoidance response rat at a greater extent than the CS?. Dexamethasone (0.2 mg/kg) administered before Pavlovian conditioning and before test sessions enhanced the increase in avoidance response rate to both CS presentation, irrespective of its type. Results are interpreted in terms of DX effects on response inhibition processes.