A comparison of classical eyelid conditioning in adults and infants

In a classical conditioning procedure an eyeblink-eliciting tap to the glabella (the flat region of skin between the eyebrows) was presented 500 ms after the onset of a mild l-kHz tone. As tone-tap presentations proceeded, the probability of an eyeblink during the latter part of the tone increased in both infants (median age 8 months) and adults, but the infants were slower to condition than the adults and were more variable. Overall, the latency of the conditioned response to tone was significantly longer for infants than for adults, but the latency of the unconditioned response to tap was significantly shorter for infants than for adults.     

Random control procedures in classical skin conductance conditioning

There have been differences in opinion concerning what constitute proper procedures for providing random controls in classical skin conductance conditioning. The present paper is a comment on selected aspects of a methodological discussion of control procedures and permissable inferences provided by Furedy, Poulos, and Schiffman (1975).     

A comparison of neuronal reactions during classical and instrumental conditioning under similar conditions

During the elaboration of an instrumental reflex, it is not obligatory to use a conditioned stimulus, which signals the necessity to generate an instrumental reaction in order to receive reinforcement. However, the presence of a conditioned stimulus simplifies analysis of instrumental reaction, which in this case is the response to the conditioned stimulus. On the other hand, it is necessary to distinguish between instrumental and classical conditioning, since in both cases the response to a conditioned stimulus increases. We studied neuronal analogs of classical and instrumental conditioning in the identified neurons responsible for the defensive closure of the pneumostome in the Helix mollusk under the same conditions. During classical conditioning, a mollusk received punishment after a tactile stimulus. During instrumental conditioning, a mollusk received punishment when an identified neuron did not generate an action potential in response to a tactile stimulus. The appearance of a painful stimulus did not depend on the generation or failure of a spike in the related control neuron. Another tactile stimulus, which was never paired with an unconditioned stimulus, was used as a discriminated stimulus. We also compared the behavior of such identified neurons during pseudoconditioning. The experiments were carried out in a semi-intact preparation. We examined how responses to the tactile and painful stimuli changed during different forms of training. It was shown that the dynamics of neuronal responses to a conditioned tactile stimulus were much more complex during instrumental conditioning and consisted of several phases. Throughout a learning session, neural system consecutively acquired information as to which kind of learning was presented, whether a reaction of the neural system must be generated or inhibited and which instrumental reaction is correct. We have demonstrated that response to a painful stimulus during classical conditioning decreases after short-term initial increase. However, during instrumental learning, the neurons controlling instrumental action remained highly sensitive to the unconditioned stimulus. Meanwhile, foreign neurons decreased their responses to the unconditioned stimulus. We may tentatively conclude that classical and instrumental paradigms are fundamentally different at the cellular level.     

Overtraining in classical conditioning: A comparison of motor and cardiac systems in dogs

Data from the analysis of the Overlearning Reversal Effect (ORE) noted in a simultaneous, visual discrimination task, and the lack of this effect in a position habit discrimination, led to the prediction that the ORE would not be noted in classical conditioning. It was further noted that very little work on discrimination learning had been reported in Pavlovian conditioning. The idea of schizokinesis, as observed by Gantt and others in classical conditioning, has been elaborated using the simple conditioning paradigm, and no data were available to test whether this same split would occur on a more complex level of conditioning, such as a discrimination task. To test these ideas, nine dogs were trained to a criterion of minimum discrimination, and then divided into three groups and given varying amounts of overtraining (OT). The discrimination task given the animal was to flex its paw during the CS+ signalling the onset of a brief shock. After the varying amounts of OT all groups were placed in extinction, followed by reversal training until each dog reached a criterion of minimum reversal. The results indicated 1) that the cardiac discrimination did not form before the motor discrimination; 2) extinction of differentiation was not significantly affected by the amount of OT given; 3) the mean level of responding in the motor system during extinction was highly correlated with the mean level of responding during the initial discrimination training; 4) OT had no effect on the speed of reversal of either the motor or the cardiac systems; 5) the speed of reversal learning in the motor system was highly correlated with the speed of initial discrimination.     

Further evidence against the classical conditioning model of McCollough effects

McCollough effects (MEs) have been portrayed by Murch (1976) as classically conditioned responses which result from the pairing of color (unconditioned stimulus) with line orientation (conditioned stimulus). In the present experiment, we sought evidence that ME characteristics resembled those of undisputed conditioned responses. According to Rescorla (1968) and others, conditioned responses may not develop if the unconditioned stimulus is presented in the absence as well as in the presence of the conditioned stimulus. However, in our experiment, MEs induced by inspection sequences containing presentations of color alone in addition to color/ contour pairs were not weaker than controls. This discrepancy challenges the applicability of the conditioning model to MEs.     

Contingency theory and the distinction between associative and non-associative effects in classical conditioning

There is evidence to suggest that CS-US contingency is the variable that determines the associative effects of a CS. It has been claimed that experiments where contingency is manipulated allow us to distinguish between excitatory and inhibitory associative effects, and suggest a solution to the problem of finding a control procedure for non-associative effects. It is argued, however, that unless we can find a priori grounds for defining a level of contingency at which there are no associative effects, these claims are not justified. The reasons for this are that we have no way of distinguishing experimentally between associative and non-associative contributions to the effect of a CS, and that without such a technique there is no possibility of locating the point of associative neutrality empirically.     

Panic disorder: A product of classical conditioning

Contrary to the common view that all panic attacks have a single etiology, it is shown that a distinction must be made between initial attacks, for which there are many causes, and recurrent attacks (panic disorder) which have a common basis. Most initial panic attacks are attributable to the physiological effects of hyperventilation resulting from severe and prolonged anxiety. It has been claimed that the attacks are due to such symptoms as dyspnea, tachycardia and dizziness being misattributed to deadly illness or incipient insanity. We reject this view on several grounds, and in particular because of a pilot study that showed that such attributions follow the onset of panic. Apart from some biological cases, the common initial panic is an unconditioned response to a bizarre stimulus complex produced by excessive hyperventilation, and panic disorder is the result of contiguous stimuli, especially endogenous stimuli, being conditioned to the elicited anxiety. Treatment accords with principles of conditioning.     

Comparison of timing and classical conditioning

Four experiments with rats investigated if the timing of a stimulus (sound) correlated with the strength of a conditioned response (CR) to the stimulus. The timing (effective duration) of the stimulus was measured using the peak procedure, similar to a discrete-trials fixed-interval procedure. The rats were trained so that their response rate reached a maximum about 40 s or 60 s after the onset of a light; the time of the maximum measured from the start of the light (peak time) was the measure of timing. On some trials, the light was preceded by a short (5 s) or long (20 s or 30 s) interval of sound. We assumed that the difference in peak time after long and short sounds reflected the timing of the sound--if the sound was timed, the longer sound would produce a lower peak time; if the sound was not timed, the two durations of sound would produce the same peak time. The CR was lever-pressing during the sound. The sound was treated in various ways: presented alone (Experiments 1, 3, and 4), followed by food (Experiments 1, 3, and 4), preceded by food (Experiment 3), and followed by food after 20 s (Experiment 4). Treatments that produced no timing of sound produced no CR, and treatments that increased (or diseased) timing also increased (or decreased) the CR. The results suggest that there is overlap between the mechanisms that produce time discrimination and the mechanisms that produce classical conditioning.     

A microcomputer system for controlling classical conditioning experiments

A microcomputer-based laboratory system for controlling stimulus presentations and data acquisition in classical conditioning experiments is described. The system comprises an Intel 386/486-based microcomputer and a commercially obtained low-cost counter/timer board with input/output lines for stimulus timing and external device control. A simple, yet versatile custom-designed structured programming language is provided for performing an unlimited number of stimulus configurations and their sequences. In electrophysiological studies, the system can be flexibly connected to computer-controlled signal conditioning systems for the amplification and filtering of multiunit and evoked field potential responses and to high-speed data acquisition systems for sampling and analyzing the responses. The costs of reserving an entire microcomputer for experiment control are well compensated for by the simplicity and efficiency of programming and transportability of the control protocols between different setups and laboratories. Furthermore, a data acquisition and analysis system most suitable for the aims of a research project can be selected.     

The prefrontal-thalamic axis and classical conditioning

Using the New Zealand albino rabbit as an animal model, it has been determined that the medial prefrontal cortex is intimately involved in, and may be necessary for, acquisition of classically conditioned bradycardia. The interconnected nuclei of the medial thalamus, most notably the mediodorsal nucleus, conversely appear to be associated with the development of the tachycardia that accompanies classical conditioning of the eyeblink and nictitating membrane response. Neuroanatomical, electrophysiological, brain stimulation, and lesion data are reviewed, which support the conclusion that the prefrontal-thalamic axis is intimately involved in acquisition of classically conditioned visceral changes.     

A temporal-specific and transient cAMP increase characterizes odorant classical conditioning

Increases in cyclic adenosine monophosphate (cAMP) are proposed to initiate learning in a wide variety of species. Here, we measure changes in cAMP in the olfactory bulb prior to, during, and following a classically conditioned odor preference trial in rat pups. Measurements were taken up to the point of maximal CREB phosphorylation in olfactory bulb mitral cells. Using both drug and natural unconditioned stimuli we found effective learning was associated with an increase in cAMP at the end of the conditioning trial, followed by a decrease 5 min later. This early timing of a transient cAMP increase occurred only when the odor was paired with an effective drug or natural unconditioned stimulus (US). The data support the hypothesis that the rate of adenylate cyclase activation is enhanced by pairing calcium and G-protein activation and that the timing of transient cAMP signaling is critical to the initiation of classical conditioning.     

Use of classical conditioning procedures to control aggressive behaviors in children: a preliminary report.

This experiment tested the effectiveness of classical conditioning procedures in reducing children's aggressive behaviors in a classroom setting. As hypothesized, 11 boys and 14 girls who were shown pictures of aggressive scenes paired with the presentation of negatively evaluated words subsequently displayed significantly fewer aggressive responses than controls who had not experienced these conditioning procedures. A significant teacher/classroom effect was also found, which appeared to be a function of the level of the 3 teachers' permissiveness. Specifically, children's aggressive behaviors occurred more frequently in the classroom where a permissive atmosphere prevailed than in the classroom where a more restrictive atmosphere was maintained. In those classrooms where a permissive atmosphere prevailed, the children who were the same sex as their teacher tended to display more aggressive responses than those children who were the opposite sex from their teacher.