Temporal dynamics of the rabbit's nictitating membrane response in serial compound conditioned stimuli.

Two experiments, with 88 female albino rabbits, investigated conditioning of the nictitating membrane response to a reinforced serial compound stimulus. The serial compound was composed of a 400-msec CS (CSA), a trace interval of at least 2 sec, and a brief 2nd CS (CSB) prior to the UCS. The CSB duration was either 150, 250, or 400 msec in Exp I, and the CSB duration in Exp II was 400 msec. Exp I compared serial compound training to an "uncoupled" condition, which contained intermixed CSA–UCS trials and CSB–UCS trials. Exp II compared serial compound training with uncoupled training, 2nd-order conditioning (CSA–CSB/CSB–UCS), trace conditioning (CSA–UCS), and generalization testing that entailed CSB–UCS training and unreinforced tests with CSA. The serial compound, uncoupled, and 2nd-order conditioning procedures all produced high levels of responding during CSA, but only the reinforced serial compound procedure yielded an appreciable likelihood of CR initiation during the trace interval between CSA and CSB. The CRs during the trace interval were temporally distinct from the CRs during CSA and did not appear to be belated CRs to CSA itself. Results are discussed in connection with stimulus selection phenomena, for example, overshadowing and potentiation of toxicosis conditioning. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CS–US contiguity and CS intensity in conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Two experiments examined 48 female albino rabbits' nictitating membrane response to serial-compound stimuli consisting of 2 distinctive CSs (CSA and CSB) that were followed by a shock UCS. In Exp I, CSA was a highly salient 93-db tone, and CSB was a moderately salient flashing light. The CSA/UCS interval was 800 msec, and the CSB/UCS interval was varied across 400, 600, and 800 msec. In Exp II, the flashing light served as CSA, and CSB was either a 73-, 85-, or 93-db tone. The CSA/UCS interval remained 800 msec, and the CSB/UCS interval was fixed at 400 msec. The CSB/UCS interval and CSB intensity determined the rate of CR acquisition to the compound. Yet, CR acquisition to CSB showed impairments relative to the level of responding in single CS-control conditions. However, the impairment in CR acquisition to CSB was attenuated by increasing CSB/UCS contiguity. The impairment in acquisition to the light CSB appeared to be primarily a consequence of the tone CSA's greater salience. However, impairments in CR acquisition to CSB appeared even when CSB had the combined advantages of CS/UCS contiguity and great salience relative to CSA. Results indicate a role for CSA's temporal primacy in determining CR acquisition to the components of a serial compound and are discussed in terms of selective-attention, generalization-decrement, and information hypotheses. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time and stimulus specificity in extinction of the conditioned nictitating membrane response in the rabbit (Oryctolagus cuniculus).

The present experiments demonstrated that, in the rabbit nictitating membrane preparation, a conditioned response (CR) can be selectively eliminated in one portion of a conditioned stimulus (CS) while it is still paired with the unconditioned stimulus (US). Rabbits were initially trained with two stimuli (tone, light). Each was paired with the US by using a mixture of two CS-US interstimulus intervals (ISIs): 200 ms and 1,200 ms in Experiment 1; 150 ms and 500 ms in Experiment 2. The CRs showed double peaks, one for each ISI. Subsequently, one CS (A) was trained with only the longer ISI, whereas the other CS (B) continued to be trained with both ISIs. Consequently, the CR peak based on the shorter ISI disappeared for CSA but not for CSB. The later CR peaks during both CSA and CSB were maintained. These results support time-based models of conditioning. Implications for proposed mechanisms of extinction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discriminated lateralized eyeblink conditioning in the rabbit: An experimental context for separating specific and general associative influences.

Four experiments demonstrated discriminated lateralized eyeblink conditioning in 38 male rabbits and showed how the phenomenon may be used to differentiate between the reflexive and emotive consequences of Pavlovian conditioning. Exps 1, 2, and 3 characterized how 2 conditioned stimuli (CSs), contemporaneously trained with left vs right paraorbital unconditioned stimuli (UCSs), can produce different CRs, each involving predominant closure of the eye ipsilateral to its UCS. Exp 4 showed how the associative tendencies controlled by additional stimuli could be evaluated by presentations in compound with such discriminanda: A 30-sec stimulus, presumed to acquire a conditioned emotional response but no eyeblink CR, equally potentiated the eyelid CRs elicited by both CSs. A 1,050-msec CS that evoked an eyeblink CR in isolation also increased the responding to both CSs but biased it toward its own lateralized CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overshadowing and summation in compound stimulus conditioning of the rabbit's nictitating membrane response.

Examined acquisition of the rabbit's nictitating membrane response to a light?+?tone simultaneous compound stimulus and its components as a function of the intensity of the tone. In Exp I, the tone intensity was varied across the values of 85, 89, and 93 db, and the CS–UCS interval was 400 msec. In Exp II, the tone intensities were 73, 85, and 93 db, and the CS–UCS interval was 800 msec. Exps III and IV further examined the effects of the 73-db CS–UCS tone at CS–UCS intervals of 400 and 800 msec. All experiments included control groups, which were trained with either a light or a tone CS. Overall results show repeated instances of overshadowing: the impairment of CR acquisition to one or both of the components of a compound. Two types of summation were obtained: within-Ss summation, in which Ss trained with a compound showed a higher level of responding to the compound than to either of its component CSs; and between-groups summation, in which a group trained with a compound showed faster CR acquisition than either of its corresponding control groups trained with a single CS. Results are discussed in terms of perceptual and distributive processing models of compound stimulus conditioning. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning with masked stimuli affects the timecourse of skin conductance responses.

In Pavlovian fear conditioning, an aversive unconditional stimulus (UCS) is repeatedly paired with a neutral conditional stimulus (CS). As a consequence, the subject begins to show conditional responses (CRs) to the CS that indicate expectation and fear. There are currently two general models competing to explain the role of subjective awareness in fear conditioning. Proponents of the single-process model assert that a single propositional learning process mediates CR expression and UCS expectancy. Proponents of a dual-process model assert that these behavioral responses are expressions of two independent learning processes. We used backward masking to block perception of our visual CSs and measured the effect of this training on subsequent unmasked performance. In two separate experiments we show a dissociation between CR expression and UCS expectancy following differential delay conditioning with masked CSs. In Experiment I, we show that masked training facilitates CR expression when the same CSs are presented during a subsequent unmasked reacquisition task. In Experiment II we show that masked training retards learning when the CS+ is presented as part of a compound CS during a subsequent unmasked blocking task. Our results suggest that multiple memory systems operate in a parallel, independent manner to encode emotional memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the cerebellar vermis and cerebellar hemispheres: Effects on heart rate conditioning in rats.

The effects of lesions of the cerebellum on the acquisition of heart rate (HR) conditioned responses (CRs) were examined in rats. Large lesions of the cerebellar vermis severely attenuated the acquisition of differentially conditioned bradycardic responses in restrained rats without affecting unconditioned HR responses to the tone conditioned stimuli (CSs) or the shock unconditioned stimulus/stimuli (UCS). In Exp 2, Ss were trained unrestrained, and under these conditions the CR was tachycardia in control Ss. Lesions of the vermis again severely attenuated acquisition of this CR without affecting unconditioned response (UCR) to the CSs or UCS. Bilateral lesions of the cerebellar hemispheres did not affect HR conditioning in either test procedure. The vermis of the cerebellum is an essential component of an HR conditioning circuit in the rat. The cerebellar hemispheres, which are involved in some discrete somatomotor CRs, have no essential functional contribution to HR conditioning. Results are discussed in relation to contributions from a forebrain system involved in HR conditioning and in relation to lateral cerebellar contributions to discrete somatomotor CRs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discriminative conditioning with different CS–US intervals produces temporally differentiated conditioned responses in the two eyes of the rabbit (Oryctolagus cuniculus).

The conditioned eyeblink response (CR) in rabbits is lateralized to the eye targeted by the unconditioned stimulus (US). However, a contralateral component has been reported during concurrent discriminative conditioning of the two eyes. The authors investigated CRs produced by both eyes during conditioning with 2 different interstimulus intervals (ISIs) in which a short conditioned stimulus (CS) was paired with a US to the left eye and a long CS was paired with a US to the right eye. Whether the 2 CSs were more or less similar (or identical), the short CS produced short-latency CRs in the left eye, whereas the long CS produced long-latency CRs in the right eye. The contralateral responses to a CS trained at one ISI were separable into temporal corollaries of the ipsilateral response (suggesting a bilaterality of the CR) versus those to a CS trained at another ISI (indicating generalization between the CSs). The results indicate that the neuronal substrates subserving CRs of the two eyes involve not only a dominant lateralization but also some avenue of bilaterality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the middle cerebellar peduncle disrupt acquisition and retention of the rabbit's classically conditioned nictitating membrane response.

Rabbits were classically conditioned to emit a nictitating membrane response (NMR) to either a light or tone conditioned stimulus (CS) paired with an eye shock unconditioned stimulus (UCS). They then received lesions of the middle cerebellar peduncle (MCP) or served as unoperated controls. Following surgery, they were given separate presentations of tone, light, and vibratory CSs, each paired with the eye shock UCS. In this way, conditioned responses (CR) to the previously trained light or tone served as a test of retention, whereas CRs to the remaining two conditioned stimuli (tone and vibratory or light and vibratory) served as a test of acquisition. The results of the study revealed that rabbits with complete lesions of the MCP showed disrupted acquisition and retention of the conditioned NMR to all stimuli, rabbits with partial MCP lesions also showed disrupted acquisition and retention to all CSs, but to a lesser degree, and animals with lesions that missed the MCP and unoperated controls both showed normal acquisition and retention of the conditioned NMR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning the unconditioned response: Modification of the rabbit's (Oryctolagus cuniculus) unconditioned nictitating membrane response.

Conditioning-specific reflex modification (CRM) occurs when classical conditioning modifies responding to a unconditioned stimulus/stimuli (UCS) in the absence of a conditioned stimulus (CS). Three experiments monitored rabbit (Oryctolagus cuniculus) nictitating membrane unconditioned responses to 5 intensities and 4 durations of periorbital electrical stimulation before and after CS or UCS manipulation. CRM occurred after 12 days of CS-UCS pairings but not following unpaired CS/UCS presentations or restraint. CRM survived CS-alone and CS/UCS-unpaired extinction of the conditioned response (CR) but not presentations of the UCS alone, although CRs remained intact. Thus, CRs could be weakened without eliminating CRM and CRM could be weakened without eliminating CRs. Data indicate CRM is a reliable, associative effect that is more than a generalized CR and may not be explained by habituation, stimulus generalization, contextual conditioning, or bidirectional conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning of physiological responses: II. Classical conditioning of the baroreflex.

The baroreflex can be classically conditioned. In neuromuscular blocked (NMB) rats, electrical stimulation of the aortic depressor nerve (ADN) and dopamine-produced blood pressure rise were effective unconditioned stimuli (UCS) for auditory discriminative classical conditioning. The conditioned response (CR) pattern (bradycardia, vasodilatation, and hypotension > 10 torr) closely resembled that of the unconditioned baroreflex. Conditioned stimulus (CS) specificity was demonstrated by discrimination of baroreflex-associated and nonassociated auditory stimuli, and also by elaborating depressor and pressor CRs to auditory CSs, which respectively had been associated with either baro-afferent (depressor) or tail-shock (pressor) UCSs. The conditioned baroreflex-magnitude increased with trials. These findings support quantitative models in which CRs interact with and calibrate the gain and dynamic properties of natural reflexes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampus and trace conditioning of the rabbit's classically conditioned nictitating membrane response.

In 2 experiments, 36 New Zealand albino rabbits received classical conditioning of the nictitating membrane response in a trace conditioning paradigm. In this paradigm, a 250-msec tone conditioned stimulus (CS) occurred, after which there was a 500-msec period of time in which no stimuli occurred (the trace interval), followed by a 100-msec air-puff unconditioned stimulus (UCS). In Exp I, lesions of the hippocampus or cingulate/retrosplenial cortex (CRC) disrupted acquisition of the long-latency or adaptive conditioned response (CR) relative to unoperated controls and Ss that received neocortical lesions that spared the CRC. When Ss with hippocampal or CRC lesions were switched to a standard delay paradigm in which the CS and UCS were contiguous in time, they acquired in about the same number of trials as naive Ss. In Exp II, multiple-unit activity in area CA1 of the hippocampus was examined during acquisition of the trace CR. Ss had a 500-msec trace interval (Group T-500), received explicitly unpaired presentations of the CS and UCS, or underwent conditioning with a 2-sec trace interval. Group T-500 acquired the CR in about 500 trials. Early in training, there was a substantial increase in neuronal activity in the hippocampus that began during the CS and persisted through the trace interval. Later in conditioning as CRs emerged, the activity shifted to later in the trace interval and formed a model of the amplitude–time course of the behavioral CR. (65 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation or diminution of discrete motor unconditioned responses (rabbit eyeblink) to an aversive Pavlovian unconditioned stimulus by two associative processes: Conditioned fear and a conditioned diminution of unconditioned stimulus processing.

In 2 experiments using the rabbit conditioned eyeblink preparation, the conditions under which a Pavlovian conditioned stimulus/stimuli (CS) potentiates or diminishes the unconditioned response (UCR) were examined. Results indicate that, after discrimination training (CS+ vs CS–), the CS+ diminished UCR amplitude at the training interstimulus interval (ISI). When CS+ trials were segregated into trials on which a conditioned response (CR) did or did not occur, the CS+ diminished the UCR when it elicited a CR, but not when a CR failed to occur. When the CS-unconditioned stimulus (UCS) interval was lengthened to 10 sec, the CS+ reliably potentiated the eyeblink UCR on CR trials but did not potentiate responding on trials on which a CR was absent. Results are discussed in terms of the modulatory effects and temporal properties of conditioned fear and an associatively produced decrement in UCS processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampectomy disrupts trace eye-blink conditioning in rabbits.

The role of the hippocampus (HPC) in trace eye-blink conditioning was evaluated using a 100-ms tone conditioned stimulus/stimuli (CS), a 300- or 500-ms trace interval, and a 150-ms air puff unconditioned stimulus/stimuli (UCS). Rabbits received complete hippocampectomy (dorsal & ventral), sham lesions or neocortical lesions. Hippocampectomy produced differential effects in relation to the trace interval used. With a 300-ms trace interval, HPC-lesioned Ss showed profound resistance to extinction after acquisition. With a 500-ms trace interval, HPC-lesioned Ss did not learn the task (only 22% conditioned responses [CRs] after 25 sessions, whereas controls showed >80% after 10 sessions), and on the few trials in which a CR occurred, most were "nonadaptive" short-latency CRs (i.e., they started during or just after the CS and always terminated prior to UCS onset). The authors conclude that the HPC encodes a temporal relationship between CS and UCS, and when the trace interval is long enough (e.g., 500 ms), that the HPC is necessary for associative learning of the conditioned eye-blink response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning-dependent timing of Pavlovian eyelid responses: Differential conditioning using multiple interstimulus intervals.

Demonstrated that individual animals can concurrently acquire differently timed conditioned eyelid responses using a differential conditioning procedure in which distinctive CSs are individually paired with an unconditioned stimulus/stimuli (UCS), with each using a different interstimulus interval (ISI). This promotes robust conditioning, and the timing of the CRs is appropriate for the respective ISIs, differs for each CS to the extent that the ISIs are dissimilar, and is apparent in individual trials. This procedure was used to demonstrate that response timing is not a function of associative strength. These data suggest response timing is mediated by an ability to make temporal discriminations during the CS. The within-animals comparisons made possible by this differential conditioning should facilitate lesion and unit recording analyses of the neural basis of response timing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer across unconditioned stimuli in serial feature discrimination training.

The transfer of conditioned modulation across CS and unconditioned stimulus/stimuli (UCS) was examined in 3 experiments that used Pavlovian appetitive training procedures with rats. In Exp 1, after training in a positive patterning discrimination (X→A+/X-/A-), X increased CR elicited by another trained-then-extinguished CS as long as that CS had been trained with the same UCS as was used in discrimination training. In Exp 2, after training with a feature-negative discrimination (X→A-/A+), X inhibited CR elicited by another trained-then-extinguished CS as long as that CS had been trained with the same UCS. Exps 1 and 2 used a between-groups design, and Exp 3 used a within-groups design. In Exp 3, rats were trained in a feature-positive discrimination (X→A+/A-). In transfer tests, X increased CR elicited by another CS trained then extinguished with the same UCS from training. This increase was greater than the X increased CR elicited by another CS trained then extinguished with a different UCS from training. Results supported the suggestion that features trained in serial discrimination tasks influence behavior indirectly by transiently raising or lowering the threshold for activation of the UCS representations by its target stimuli and by any other stimuli that may be associated with that UCS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative effects of US preexposure: Modulation of conditioned responding by an excitatory training context.

Conducted 2 experiments with 120 naive Sprague-Dawley rats to examine factors that contribute to retarded emergence of conditioned responding to a conditioned stimulus/stimuli (CS) trained in a context in which unsignaled unconditioned stimulus/stimuli (UCS) had previously been administered. In both experiments, water-deprived Ss were used in a conditioned lick suppression task to measure the conditioned response (CR) elicitation potential of the CS and the training context. From Exp I, it was determined that nonreinforced exposure to the excitatory context after UCS preexposure and prior to CS–UCS pairings in that context eliminated the CR deficit observed on a subsequent test of the CS. From Exp II, it was determined that the recovery induced by contextual deflation after CS training was specific to deflation of the context in which the CS was trained as opposed to another excitatory context. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of signaling intertrial unconditioned stimuli in autoshaping.

Context–UCS associations have been suggested as the mediator of the response decrement that occurs when extra UCSs are added to the intertrial intervals (ITIs) of a standard Pavlovian conditioning situation. The present autoshaping experiments were concerned with the effect of signaling those extra UCSs, since such signaling might be expected to lessen their ability to condition the context. In Exp I, 16 female Carneaux pigeons were trained in Skinner boxes before receiving pretraining with the CS to be used as the signal of the ITI UCSs. During the main training, Ss were given autoshaping with a keylight CS. Exp II used a tone CS with 31 Ss. Results show that signaling the ITI UCSs did reduce their detrimental effects in responding to the CS. To determine whether that reduction was due to an impact of signaling on the target-CS/UCS association or on performance to the target-CS, Exp III examined responding to differentially trained CSs in a common context, as well as responding to identically trained CSs in differentially trained contexts with 32 Ss. More responding occurred to the CS trained with signaled, as compared with unsignaled, ITI UCSs; further, there was more responding to that CS in the more highly valued context. Results suggest that contextual value does interact with CS–UCS learning and may also affect performance to the CS. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Learning of physiological responses: II. Classical conditioning of the baroreflex": Correction to Dworkin and Dworkin (1995).

Reports an error in the original article by B. R. Dworkin and S. Dworkin (Behavioral Neuroscience, 1995[Dec], Vol 109[6], 1119–2136). On pages 1127, 1130, and 1136, there were 3 substantive errors concerning particular readings, as well as an equation in the summation containing an error. The corrections are supplied. (The following abstract of this article originally appeared in record 1996-22224-001.) The baroflex can be classically conditioned. In neuromuscular blocked (NMB) rats, electrical stimulation of the aortic depressor nerve (ADN) and dopamine-produced blood pressure rise were effective unconditioned stimuli (UCS) for auditory discriminative classical conditioning. The conditioned response (CR) pattern (Bradycardia, vasodilatation, and hypotension?>?10 torr) closely resembled that of the unconditioned baroflex. Conditioned stimulus (CS) specificity was demonstrated by discrimination of baroflex-associated and nonassociated auditory stimuli, and also by elaborating depressor and pressor CRs to auditory CSs, which respectively had been associated with either baro-afferent (depressor) or tail-shock (pressor) UCSs. The conditioned baroreflex-magnitude increased with trials. . . (PsycINFO Database Record (c) 2010 APA, all rights reserved)