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PubMedDate not supplied

Classical conditioning of rabbits 2-1/2 to 4 years old using mossy fiber stimulation as a CS.

A basic issue in age-related deterioration in memory formation concerns the locus of the age changes. Changes in peripheral portions of the auditory CS pathway could account for the observed age differences in classical conditioning in rabbits. We bypassed peripheral portions of the CS pathway and input the CS more centrally by electrical microstimulation of mossy fibers in the pons. New Zealand White rabbits aged 2-1/2-4 years were compared to six 3-month-old control rabbits with electrode implantations in comparable areas. Training consisted of 108 trials per day in which stimulation CS was paired with a corneal airpuff US. Older rabbits took almost five times as long to condition as the young animals. Thus, age differences in eyelid classical conditioning cannot be entirely attributed to changes in the peripheral CS pathway. Changes in the nervous system occurring more centrally in the cerebellum appear to affect learning and memory.

Acoustic Stimulation↗

PubMedDate not supplied

Anticipatory nausea in cancer patients receiving chemotherapy: classical conditioning etiology and therapeutical implications.

The delivery of cytotoxic drugs in cancer treatment is often accompanied by posttreatment side effects (e.g., nausea). Moreover, there is evidence that cancer patients are at risk to develop these side effects in anticipation of chemotherapy (i.e., anticipatory nausea [AN]). AN can be explained as the result of a classical conditioning process with the cytotoxic drug as the unconditioned stimulus (US). Stimuli paired with the US (e.g., smells, tastes) can become conditioned stimuli (CSs) eliciting AN as the conditioned response (CR). The present study was conducted to test whether AN shows characteristics of a CR. Fifty-five ambulatory cancer patients were asked to record nine kinds of physical symptoms (e.g., nausea, vomiting, sweating) on time-scheduled symptom lists: after an infusion (indicating posttreatment symptoms) and prior to their next infusion (indicating anticipatory symptoms). Each measurement period covered a maximum of 48 hours. AN was reported by ten patients (18.08%). Data revealed (a) a statistically significant association between posttreatment nausea and vomiting, respectively, and AN; (b) the occurrence of AN increased with drug emetogenity (i.e., US-intensity); and (c) the duration of AN increased with temporal proximity to the infusion. The results support the conditioning model. Thus, it is proposed to prevent AN by classical conditioning techniques (e.g., overshadowing).

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1997

Imagery in human classical conditioning.

Many clinical strategies use patients' imagery to explore and treat phobic and posttrauma reactions, however little attention has been paid to the underlying assumption that imagery of relevant stimuli may help maintain conditioned behavior. In this article, the authors examine the premise that mental images can potentiate and substitute for physical stimuli in human classical conditioning. The authors review empirical evidence to detail the role of images of conditioned stimuli (CS) and unconditioned stimuli (US) during pre-exposure to stimuli, the actual pairing of the CS and US, and extinction when the CS is presented alone. The evidence suggests that mental imagery can facilitate or diminish the outcome of classical conditioning in humans and, more tentatively, that mental images can substitute for actual US and CS in autonomic conditioning. They argue that researchers should explore the role of mental imagery in conditioning through the use of advances in the measurement of imagery. Finally, they analyze anxiety and trauma reactions as examples of how applied areas can be used to explore and benefit from developments in this area.

Animals↗

PubMed2002

Classical conditioning of postural reflexes.

Unexpected external perturbations of body equilibrium elicit compensatory postural reflexes. The reflex patterns change only minimally, even after repetitive perturbations. This study addressed the question of whether classical conditioning can alter the reflex patterns. In the first session 27 healthy subjects were tested when standing on an unexpectedly tilting platform. Electromyographic (EMG) activity from different leg muscles and the vertical ground forces, from which the centre of vertical pressure (CVP) was computed, were recorded. In a subsequent session subjects were tested using the classical conditioning paradigm with the tilting platform as the unconditioned stimulus (US) and a prior auditory signal as the conditioning stimulus (CS). The decay of the unconditioned response (UR) observed in the first session was similar and small in all subjects. During conditioning, 22% of the subjects established conditioned responses (CR) in all muscles recorded (strategy 1). UR amplitudes of the anterior tibialis (TA) decayed more than in the first session. The resulting CVP excursions were similar to those observed in US-alone trials. The remaining subjects exhibited CR only in the gastrocnemius muscle but developed a substantial decay of UR, resulting in very small CVP excursions (strategy 2). Our data suggest that processing of US-preceding conditioning stimulus leads to different strategies in the control of postural adjustment with assumed underlying associative and non-associative plastic processes.

Adult↗

PubMed1987

The contribution of classical conditioning to tolerance to the antinociceptive effects of ethanol.

In rats, ethanol increases the latency of the tail-flick reflex to radiant heat. Three experiments examined the contribution of classical conditioning to the acquisition of tolerance to this antinociception. Experiment 1 showed that the antinociception produced by ethanol was dose dependent. The results of Experiment 2 demonstrated that rats exposed to a series of ethanol injections paired with a distinctive environment developed tolerance to this antinociception. In Experiment 3, tolerance was more pronounced in animals that had been exposed to ethanol and tested in the distinctive environment than in animals that had received ethanol in a nondistinctive environment. In contrast to previous reports in the literature, these results show that animals need not practice the tail-flick reflex while intoxicated in order to develop tolerance. Additionally, the data suggest that classical conditioning may contribute to tolerance to the antinociceptive effects of ethanol.

Analgesics↗

PubMed1990

Classical conditioning of the eyeblink reflex in the decerebrate-decerebellate rabbit.

The purpose of these experiments was to test the hypothesis that a conditioned nictitating membrane reflex can be acquired in decerebrate rabbits in the absence of the cerebellum. Experiments examining the effects of large cerebellar lesions on the acquisition and performance of the conditioned reflex were performed in acutely prepared decerebrate rabbits. Most lesions encompassed all of the cerebellar nuclear regions ipsilateral to the eye receiving the unconditioned stimulus. In all rabbits included in this study the continuity between the cerebellar nuclei and the brainstem was interrupted, even in those preparations in which small regions of the nuclei were present in the lateral hemisphere. The findings demonstrate that these animals could acquire the conditioned reflex independent of whether conditioning had occurred prior to the cerebellectomy. Strong associativity was found between the latency of the conditioned response and the interstimulus interval between the conditioned and unconditioned stimuli. The behavior of the conditioned reflex observed in the decerebrate-decerebellate animals differed from that reported for awake intact rabbits in two ways. Once the conditioned behavior had been acquired, the percent of trials showing conditioned responses was somewhat less in decerebrate-decerebellate rabbits and was also more variable in these animals. The data demonstrate that the nictitating membrane reflex can be classically conditioned in the absence of the cerebellum, indicating that this structure is neither necessary nor sufficient for the acquisition of this type of conditioned behavior. In addition, an hypothesis is presented which addresses the difference between the data reported here and those previously reported by other laboratories based on observations in awake intact animals.

Animals↗

PubMed1986

Retardation of associative learning in the rabbit by an adenosine analog as measured by classical conditioning of the nictitating membrane response.

A series of 5 experiments examined the effects of the adenosine agonist, N6-(L-phenylisopropyl) adenosine (L-PIA) and its isomer, D-PIA, on the acquisition of conditioned responses in the rabbit. Extension of the nictitating membrane was classically conditioned to a tone and light stimulus presented for 800 msec before delivery of a 100 msec shock--the unconditioned stimulus--to the skin over the paraorbital region of the head. L-PIA (5.0 mumol/kg) retarded the rate of acquisition of conditioned responses to both the tone- and light-conditioned stimuli, while D-PIA, at doses of 5.0 and 10.0 mumol/kg, had no significant effect. Control experiments employing the explicitly unpaired presentations of tone, light, and shock stimuli indicated that the retarded acquisition of conditioned responses produced by L-PIA was due to an action on associative learning. L-PIA had no effect on the threshold of the shock's eliciting of the unconditioned response nor on the amplitude of the elicited response, but produced a large and significant reduction in the ability of the tone-conditioned stimulus to evoke conditioned responses. It was concluded that L-PIA blocked the rate of associative learning by decreasing the excitatory properties of conditioned stimuli. These effects of L-PIA suggest that endogenous adenosine may act to modulate the rate of associative learning.

Adenosine↗

PubMed1983

Paleostriatal lesions in the pigeon (Columba livia) potentiate classical conditioning: evidence from fixed-interval responding, free operant go-no-go discrimination, and alternation.

The paleostriatum augmentatum was the major site of interest for four experiments in which pigeons were given bilateral electrolytic lesions. Experiment 1 investigated the effects of lesions on key pecking for reinforcement on a 1-min fixed-interval schedule. The lesions were found to increase total response rates, but response timing was not disrupted in paleostriatal pigeons. In Experiment 2, naive subjects were given variable-interval baseline training and, in contrast to the results of Experiment 1, paleostriatal lesions did not increase responding. Go-no-go discrimination, which followed baseline training, revealed enhanced positive behavioral contrast in paleostriatal subjects, which was explained in terms of additivity theory, and together, the results of Experiments 1 and 2 suggested potentiated classical conditioning and paleostriatal pigeons. In Experiment 3, naive subjects were given spatial alternation training, and performance was temporarily impaired following paleostriatal lesions. The same paleostriatal subjects showed superior differentiation performance in Experiment 4 with a classical go-no-go alternation procedure (which also suggested potentiated classical conditioning), and it is argued that disruption of (irrelevant) response-produced information may account for paleostriatal superiority.

Animals↗

PubMedDate not supplied

Classical conditioning of human systolic pressure: replication and extension using three stimulus durations.

Recent efforts have demonstrated classical conditioning of human systolic pressure (De Leon, 1972). The present research attempted a replication with longer sessions and to maximize the CS+, CS- differentiation by varying CS+ durations. Student volunteers (N = 64) underwent four, 50 minute sessions, three conditioning and one extinction, distributed over two weeks. Shock (UCS) occurred intermittently in light-on (CS+) and never in light-off (CS-). Results closely replicated the earlier work, revealing a characteristic UCR, a significant CS+, CS- differential and, conditioned elevations failed to adapt within and across sessions. The pressure differential was inversely related to CS+ duration. Clarification of conditioning influences requires follow-up research on these clients outside of the laboratory. Nevertheless, these studies provide firm experimental evidence for implicating stimulus variables in the origins of certain hypertensive states.

Adolescent↗

PubMed1990

Learning of physiological responses: I. Habituation, sensitization, and classical conditioning.

Rats with chronic neuromuscular block (NMB) maintained by continuous infusion of alpha-bungarotoxin were classically conditioned. All rats showed reliable discriminative-conditioned tibial nerve firing, hind limb vasoconstriction, hypertension, bradycardia, and electroencephalographic (EEG) desynchronization. A regression analysis indicated that the conditioned vasoconstriction was neither centrally mediated by, nor inextricably linked to, skeletal (tibial) nerve firing. Throughout the experiment there were normal blood gases, pH, Na, serum protein, hematocrit, blood pressure, heart rate, vasomotor tone, and tibial nerve activity. The vital signs, EEG spectra, and cortical evoked potentials reflected regular sleep-wakefulness cycles and responsiveness to mild stimuli. The NMB rat preparation with its stable physiological state and fully intact central nervous system may be a useful model for a variety of physiological, medical, and neurobehavioral studies.

Animals↗

PubMed1996

Classic conditioning in aged rabbits: delay, trace, and long-delay conditioning.

Young (0.5 years) and aged (2+, 3+, and 4+ years) rabbits underwent acquisition of the classically conditioned nictitating membrane response in a delay (500-ms conditioned stimulus [CS], 400-ms interstimulus interval [ISI]), long-delay (1,000-ms CS, 900-ms ISI), or trace (500-ms CS, 400-ms stimulus-free period) paradigm. Collapsing across age groups, there is a general tendency for animals to acquire trace conditioning more slowly than delay conditioning. Collapsing across conditioning paradigms, there is a general tendency for aged animals to acquire more slowly than younger animals. Of greater significance, however, are the age differences in the different conditioning paradigms. In the delay and long-delay paradigms, significant conditioning deficits first appeared in the 4(+)-year-old group. In the trace conditioning paradigm, significant conditioning deficits became apparent in the 2(+)-year-old animals.

Aging↗

PubMed2004

Independent manipulation of emotion in an emotional stroop task using classical conditioning.

The effects of emotional connotation on emotional Stroop interference in anxiety were examined. First, a classical conditioning paradigm was used in which neutral words and nonwords were paired with either negative or neutral pictures. These conditioned stimuli were then presented in an emotional Stroop paradigm. Finally, participants rated each word and nonword for emotional connotation. The high-anxious group demonstrated significant interference for the nonwords that had been negatively conditioned, and these effects did not dissipate over time. The affective rating data supported the view that nonwords, but not the words had been successfully conditioned in the high-anxious group. This experiment provides evidence for the importance of emotional connotation rather than confounded semantic factors in the emotional Stroop effect.

Adult↗

PubMed2001

Implicit attitude formation through classical conditioning.

We sought to demonstrate that attitudes can develop through implicit covariation detection in a new classical conditioning paradigm. In two experiments purportedly about surveillance and vigilance, participants viewed several hundred randomly presented words and images interspersed with critical pairings of valenced unconditioned stimuli (USs) with novel conditioned stimuli (CSs). Attitudes toward the novel objects were influenced by the paired USs: In a surprise evaluation task, the CS paired with positive items was evaluated more positively than the CS paired with negative items. This attitudinal conditioning effect was found using both an explicit measure (Experiments 1 and 2) and an implicit measure (Experiment 2). In a covariation estimation task involving the stimuli presented in the conditioning procedure, participants displayed no explicit memory for the pairings.

Adult↗

PubMed1997

Lateralization and behavioral correlation of changes in regional cerebral blood flow with classical conditioning of the human eyeblink response.

Laterality of changes in regional cerebral blood flow (rCBF) during classical conditioning of the human eyeblink response was studied and changes in rCBF were correlated with conditioned responses. In 10 normal volunteers, rCBF was mapped with positron emission tomography and H2(15)O during pairings of a binaural tone conditioned stimulus and an air puff unconditioned stimulus to the left eye. Control conditions consisted of explicitly unpaired presentations of the tone and air puff before (control) and after (extinction) pairings. During pairings, rCBF increased significantly in right primary auditory cortex (contralateral to air puff) and decreased significantly in left and right cerebellar cortex. There were also increases in rCBF in right auditory association cortex and left temporoccipital cortex. Decreases in rCBF were noted bilaterally in the temporal poles and in the left prefrontal cortex. Positive correlations between changes in rCBF and percent conditioned responses were located in middle cerebellum, right superior temporal cortex, left dorsal premotor cortex, right middle cingulate, and right superior temporal cortex. There were negative correlations in left inferior prefrontal cortex, left middle prefrontal cortex, and right inferior parietal cortex. The data replicate our previous findings of lateralized changes in rCBF following presentations of a binaural tone and air puff to the right eye and indicate that there are pairing-specific changes in primary auditory cortex and cerebellum that are not unique to the left or right hemisphere but are a function of the side of training. The commonalities as well as differences in regional involvement in our present and previous experiment as well as in other eyeblink studies illustrate the advantage of functional neuroimaging to quantify different strategies used by the brain to perform seemingly similar functions. Indeed, the data support the notion that learning-related changes can be detected in a number of specific, but not necessarily invariant, brain regions, and that the involvement of any one region is dependent on the characteristics of the particular learning situation.

Acoustic Stimulation↗

PubMed2006

Subcellular, cellular, and circuit mechanisms underlying classical conditioning in Hermissenda crassicornis.

A breakthrough for studying the neuronal basis of learning emerged when invertebrates with simple nervous systems, such as the sea slug Hermissenda crassicornis, were shown to exhibit classical conditioning. Hermissenda learns to associate light with turbulence: prior to learning, naive animals move toward light (phototaxis) and contract their foot in response to turbulence; after learning, conditioned animals delay phototaxis in response to light. The photoreceptors of the eye, which receive monosynaptic inputs from statocyst hair cells, are both sensory neurons and the first site of sensory convergence. The memory of light associated with turbulence is stored as changes in intrinsic and synaptic currents in these photoreceptors. The subcellular mechanisms producing these changes include activation of protein kinase C and MAP kinase, which act as coincidence detectors because they are activated by convergent signaling pathways. Pathways of interneurons and motorneurons, where additional changes in excitability and synaptic connections are found, contribute to delayed phototaxis. Bursting activity recorded at several points suggest the existence of small networks that produce complex spatiotemporal firing patterns. Thus, the change in behavior may be produced by a nonlinear transformation of spatiotemporal firing patterns caused by plasticity of synaptic and intrinsic channels. The change in currents and the activation of PKC and MAPK produced by associative learning are similar to those observed in hippocampal and cerebellar neurons after rabbit classical conditioning, suggesting that these represent general mechanisms of memory storage. Thus, the knowledge gained from further study of Hermissenda will continue to illuminate mechanisms of mammalian learning.

Animals↗

PubMed1983

Signaled tailshock is perceived as similar to a stronger unsignaled tailshock: implications for a functional analysis of classical conditioning.

Water-deprived rats given fixed-electrode, variable-intensity tailshock at random times rated each trial by pressing either a "high-aversiveness" or "low-aversiveness" lever in order to obtain water. Trials on which a warning signal preceded tailshock resulted in more "high-aversiveness" leverpressing than did otherwise equivalent unsignaled trials. The magnitude of this effect increased and decreased as a function of several parameters including signal-shock interval, signal duration, and range and absolute value of shock intensities but was never reversed despite efforts to achieve such a reversal. Variation in the size of the effect as a function of signal parameters as well as lick suppression scores indicated that the signal had acquired aversive characteristics, which suggests that the effect of the signal on lever choice was due largely to the aversiveness of the signal summating with the aversiveness of the tailshock. Several hypotheses concerning factors that might have either masked or prevented classically conditioned preparatory responses elicited by the signal from reducing tailshock aversiveness were tested and rejected. Despite the greater aversiveness of the signaled condition, when given the choice of receiving or not receiving the signal, the animals displayed a preference for signaled tailshock. Implications for the role of preparatory responding both in the preference-for-signaled-shock phenomenon and in classical conditioning are discussed.

Animals↗

PubMed1982

Concomitant classical conditioning of the rabbit nictitating membrane and eyelid responses: correlations and implications.

Simultaneous recordings of muscle unit activity from the muscles of the left and right eyelids (M. obicularis oculi) and recordings of the movement of the left nictitating membrane (NM) were taken during classical conditioning in the rabbit using a tone CS paired with an airpuff UCS to the left cornea. The unconditioned eyelid responses were found to be bilateral. The conditioned eyelid responses were also bilateral in most animals. Both the conditioned and unconditioned eyelid responses were larger on the left side. The conditioned responses of the left and right eyelids and the left NM were found to increase in magnitude and decrease in latency from the onset of the CS over training trials in almost the exactly same manner (correlations as high as .99). Behaviorally, the three responses could occur independently, suggesting that the cranial nuclei which control them (left abducens/accessory abducens, left facial nucleus, right facial nucleus) are not strongly coupled. Thus, for the learned response, it is suggested that the three nuclei are controlled by a common central system. This finding has implications for the nature of the engram--the essential neuronal circuitry encoding the learned response.

Abducens Nerve↗

PubMed1984

Alcohol tolerance in social drinkers: operant and classical conditioning effects.

Four groups of males (n = 6 each) were trained on a complex psychomotor task prior to attending five drinking sessions. They performed the task under the same dose (0.84 ml absolute alcohol/kg) on sessions 1-4. On session 5 they received a placebo. During these sessions, the first group (CR) received information and a monetary reward that was contingent on the display of nonimpaired performance under alcohol. The second group (IO) only received information about performance. The third group (NCR) received noncontingent information and reward, administered on a predetermined schedule. The fourth group (NR) received no information or reward for performance. These manipulations were predicted to influence the order of groups with respect to the rate at which tolerance developed over sessions 1-4. The findings confirmed this hypothesis, showing the rate of CR greater than IO greater than NCR greater than NR. The placebo session tested for the classically conditioned compensatory response unattenuated by alcohol. The strength of the response, observed as facilitated performance, was predicted and found to relate to the rate at which tolerance had developed (i.e., CR greater than IO greater than NCR greater than NR). This evidence for operant and classical conditioning effects in alcohol tolerance was considered to suggest that a consideration of their joint effects may be required to understand the contribution of learning to drug tolerance.

Adult↗