Differential conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Conducted 3 experiments with 213 male and female albino rabbits (Orytolagus cuniculus) to determine the time course and contents of conditioned stimulus/stimuli (CS) representations through an examination of differential conditioning of the S"s nictitating membrane response to 2 serial compounds. One compound (A-X+) was always paired with the unconditioned stimulus/stimuli (UCS), and the other (B-X–) was always presented alone. All 3 experiments entailed manipulation of the interstimulus interval between the initial distinctive element of each compound (A and B) and the 2nd shared element (X). The joint results reveal that (1) conditioned response (CR) acquisition to the initial elements depended on the presence of X in the A-X+ compound; (2) differentiation between A and B appeared across interstimulus intervals up to 4,600 msec; and (c) conditional control over responding following A and B appeared at interstimulus intervals of at least 4,600 msec and perhaps up to 12,600 msec. (51 ref) (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)     

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)     

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)     

Real-time processing of serial stimuli in classical conditioning of the rabbit's nictitating membrane response.

Real-time models contend that a CS gives rise to a cascade of hypothetical stimuli that govern CRs on a moment-to-moment basis. Experiments with the rabbit nictitating membrane response successfully extended these models to external stimuli. CRs were trained in sequence with an unconditioned stimulus/stimuli (UCS) (CSA–CSB–UCS). When the CSA–CSB interval was shortened, the CR was compressed; when the CSA–CSB interval was lengthened, the CR was broadened. Peaks appeared at 2 places, namely, one following CSA by a period equal to the CS–UCS interval and another following CSB by its CS–UCS interval. Outside the sequence, the individual CSs evoked CRs located between their respective CS–UCS intervals. When, however, the 2 CSs were trained separately, the CRs were appropriate to their respective CS–UCS intervals when tested alone or in sequence. The results are discussed in terms of the J. E. Desmond and J. W. Moore (1988) and S. Grossberg and N. A. Schmajuk (1989) models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid reacquisition in conditioning of the rabbit's nictitating membrane response.

Reacquisition after extinction often appears faster than original acquisition. However, data from conditioned suppression studies indicate that this effect may arise from spontaneous recovery and reinstatement of unextinguished contextual stimuli related to the unconditioned stimulus/stimuli (UCS). In the present experiments using the rabbit nictitating membrane preparation, spontaneous recovery was eradicated before reacquisition training. UCS contextual stimuli were controlled by retaining the UCS during extinction through explicit unpairings of the conditioned stimulus/stimuli (CS) and UCS. Attempts were also made to drive the associative strength of the CS into the inhibitory region by differential conditioning and conditioned inhibition procedures. In all cases, reacquisition was very rapid in comparison with a rest control. The results are discussed with respect to their implications for CS and UCS processing models of conditioning. (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)     

Temporal patterns of the rabbit's nictitating membrane response to compound and component stimuli under mixed CS–US intervals.

The acquisition of the rabbit's nictitating membrane response to a tone and light compound and to its components was examined when compound presentations were reinforced at one conditioned stimulus–unconditioned stimulus (CS–US) interval and individual component presentations were reinforced at another CS–US interval. Examination of the time course of the CRs revealed that (a) despite the mixture of CS–US intervals, conditioned response (CR) timing remained accurate, that is, CRs reached their peaks at the alternative points of US delivery; (b) the momentary magnitude of the CR to the compound was predominately an additive function of the CR magnitude to the individual components; but (c) there was modest evidence of differentiation between the compound as a unit and the individual components. The results are discussed in terms of their implications for the study of the neural substrates of temporal and sensory integration as they modulate CR acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The septohippocampal cholinergic system and classical conditioning of the rabbit's nictitating membrane response.

28 New Zealand albino rabbits received bilateral microinjections of scopolamine (1 μl) or saline into either the dorsal hippocampus (Exp I) or the medial septal nucleus (Exp II). Ss then underwent classical conditioning of the nictitating membrane response in which a light served as a CS and eye shock served as the UCS. Results indicate that whereas hippocampal injections of scopolamine had no effect on conditioning, scopolamine injected into the medial septum retarded acquisition of the response. A 3rd experiment indicated that this retardation of conditioning was not due to changes in sensitivity to either the CS or UCS. Results are discussed in terms of accumulating evidence that manipulations that produce certain patterns of activity in the hippocampus are detrimental to acquisition of the nictitating CR. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of US duration on classical conditioning of the rabbit's nictitating membrane response.

Attempted to distinguish the effects of UCS duration based on explicit pairings with the CS from the consequences of sheer exposure to the UCS in the rabbit nictitating membrane response. 228 albino rabbits received various proportions of CS (a 1,000-Hz tone) and UCS (a 60-Hz shock). Exp I revealed that there was an inverse relation between the overall level of CR acquisition and UCS durations of 50, l,500, and 6,000 msec. In addition, decrements in CR likelihood occurred within the daily sessions of 90 CS–UCS trials, and the magnitude of these within-session decrements was directly related to UCS duration. In Exp II, UCS duration of 50 and 6,000 msec were paired with the CS. When UCS exposure was equated, the UCS duration paired with the CS had a positive effect on CR likelihood. Conversely, in Exp III, the duration of interpolated UCSs had inverse effects on the rate of CR acquisition. In Exp IV, the opportunity for within-session decrements was eliminated by presenting only 1 CS–UCS trial per day, which resulted in a positive relation between CR likelihood and UCS duration. Results are discussed in terms of associative and performance hypotheses. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulation of the spinal trigeminal nucleus supports classical conditioning of the rabbit's nictitating membrane response.

Acquisition, extinction, and differential conditioning of the rabbit's nictitating membrane response to a tone conditioned stimulus were supported by electrical stimulation of the spatial trigeminal nucleus. Stimulation of the accessory abducens nucleus, the abducens nucleus, and the reticular formation at the level of the spinal trigeminal nucleus supported lower, transient levels of conditioning. The results are discussed in terms of stimulation of sensory inputs to the brainstem and cerebellum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related disruption of trace but not delay classical conditioning of the rabbit's nictitating membrane response.

16 6-mo-old and 15 36–60 mo old New Zealand albino rabbits underwent classical conditioning of the nictitating membrane response in either a delay conditioning (Exp I) or a trace conditioning (Exp II) paradigm. There was no difference between old and young Ss in the acquisition of the CR in the delay paradigm, nor were there any age-related differences in generalization to the tone CS or in sensitivity to the tone CS or eyeshock UCS. However, in the trace conditioning paradigm, old Ss acquired the CR significantly more slowly than young Ss. Because the same stimulus parameters and the same response were used in both experiments, it is unlikely that age-related differences in trace conditioning were due to stimulus sensitivity, motivation, or fatigue. Results are discussed in terms of how brain changes that accompany aging could differentially affect these 2 types of classical conditioning. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning-specific modification of the rabbit's unconditioned nictitating membrane response.

Robust classical conditioning modifies responding to the unconditioned stimulus (US) in the absence of the conditioned stimulus (CS), a phenomenon the researchers called conditioning-specific reflex modification. Unconditioned responses (URs) to periorbital stimulation varying in intensity and duration were assessed before and after 1, 3, or 6 days of paired, explicitly unpaired, or no presentations of tone and electrical stimulation. After 3 days of pairings, conditioned responding (CRs) reached 94%, and there was an increase in latency to the peak of URs. The peak latency increase was replicated in a 2nd experiment where rabbits reached asymptotic conditioning during 6 days of pairings. There was also a conditioning-specific increase in the amplitude of URs. There were no UR changes as a function of low level of CRs following 1 day of pairings. Data suggest that there are learning-specific changes in pathways mediating the US/UR, as well as in those mediating the CS/CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the hippocampus in blocking and conditioned inhibition of the rabbit's nictitating membrane response.

In Exp I, bilateral aspiration of the dorsal hippocampus produced a disruption of blocking of 30 New Zealand rabbits' nictitating membrane response in L. J. Kamin's (1968, 1969) 2-stage paradigm, but had no effect on the formation of a Pavlovian conditioned inhibitor in Exp II (27 Ss). Results of Exp I indicate that normal Ss and those with cortical lesions given conditioning to a light-plus-tone CS gave CRs to both light and tone during nonreinforced presentations of each (test phase). If, however, compound conditioning was preceded by tone acquisition, only the tone elicited a CR during testing; that is, blocking was observed. In Ss with hippocampal lesions, however, CRs were given to both light and tone during testing whether or not compound conditioning was preceded by tone acquisition. Data from Exp II show that Ss with hippocampal lesions could discriminate as well as normal Ss and those with cortical lesions between a light (CS+) and light plus tone (CS-). In addition, when the inhibitory tone was subsequently paired with the UCS in retardation testing, Ss in all 3 lesion conditions acquired the CR at the same rate. Thus, it appears that hippocampal lesions do not disrupt conditioned inhibition. Results are taken as support for the view that the hippocampus is responsible for "tuning out" stimuli that have no adaptive value to the organism. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aluminum-induced neurofibrillary degeneration disrupts acquisition of the rabbit's classically conditioned nictitating membrane response.

Rabbits received intraventricular injections of aluminum chloride, hydrochloric acid, or served as unoperated controls. On the 6th day postsurgery, they underwent 4 days (100 trials per day) of classical conditioning of the nictitating membrane response (NMR) to a tone conditioned stimulus and an air-puff unconditioned stimulus. Unoperated and hydrochloric acid control animals readily acquired the conditioned response. Aluminum intoxicated rabbits, in contrast, did not acquire the conditioned response over the 4 days of testing. This disruption of conditioning in aluminum-treated rabbits could not be attributed to deficits in sensory or motor processes or to illness. Neuropathological analysis revealed widespread neurofibrillary tangle formation in aluminum-treated animals. Furthermore, the degree of neurofibrillary degeneration was significantly negatively correlated with the degree of conditioning. The results are considered in the context of using the rabbit NMR preparation as a model system for studying age-related conditioning disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of backward pairings on the conditioning of the albino rabbit's jaw movement and nictitating membrane responses.

Evaluated backward conditioning of appetitive jaw movement and aversive nictitating membrane responses in rabbits, using 3 procedures: test trials, forward acquisition of the same response, and crossmotivational acquisition of the other response system. In both experiments, backward conditioning consisted of 3 conditioned stimulus/stimuli (CS) alone and 22 CS and unconditioned stimulus/stimuli (UCS) pairings. Contrasting the backward conditioning group with explicitly unpaired and no-treatment controls revealed that backward pairings produced no associative effects. The forward acquisition and crossmotivational acquisition tests suggest that excitatory backward acquisition of jaw movement was obtained. The forward acquisition test identified weak inhibitory conditioning of nictitating membrane responses, but the crossmotivational test implicated excitatory conditioning. (French abstract) (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)     

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)     

Effects of amygdala lesions on reflex facilitation and conditioned response acquisition during nictitating membrane response conditioning in rabbit.

Demonstrated that large lesions of the amygdala disrupt the maintenance of reflex facilitation of the unconditioned nictitating membrane (NM) response and slow the acquisition of conditioned NM responses in rabbits. Before behavioral training, the central nucleus of the amygdala and adjacent areas were lesioned electrolytically. In Exp 1, the lesioned animals exhibited no reflex facilitation of the unconditioned NM response at conditioned stimulus (CS)–unconditioned stimulus (UCS) intervals of 125–8,000 ms. In Exps 2 and 3, in which 1 CS–UCS interval (500 ms) was used, the lesions disrupted the maintenance of reflex facilitation but did not alter the facilitation exhibited in the 1st block of training. The lesions retarded the acquisition of conditioned NM responses when the 1,000-Hz tone CS intensity was 65 dB, but not when the intensity was 85 dB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trial distribution effects on postasymptotic performance and retention of the rabbit's (Oryctolagus cuniculus) classically conditioned nictitating membrane response.

Conditioned the nictitating membrane response to asymptote under identical experimental parameters in 3 groups of albino rabbits (N = 36). Subsequently, the 1st group was shifted to a longer modal intertrial interval (ITI) for further training, the 2nd group was switched to a shorter modal ITI, and the 3rd group was continued with intermediate ITI values. Results reveal (a) immediate incremental and decremental performance adjustments following the shift to longer and shorter modal ITIs, respectively, which were maintained over 10 postasymptotic sessions; (b) evidence of within-session performance decrements during postasymptotic conditioning; and (c) no evidence of retention losses in a retention test conducted 72 hr following the final conditioning session. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)