Time-specific extinction and recovery of the rabbit's (Oryctolagus cuniculus) conditioned nictitating membrane response using mixed interstimulus intervals.

Extinguishing a conditioned response (CR) has entailed separating the conditioned stimulus (CS) from the unconditioned stimulus (US). This research reveals that elimination of the rabbit nictitating membrane response occurred during continuous CS-US pairings. Initial training contained a mixture of 2 CS-US interstimulus intervals (ISIs), 150 ms and 500 ms. The CRs showed double peaks, one for each ISI. When the 150-ms ISI was removed, its CR peak showed 2 hallmarks of extinction: a decline across sessions and spontaneous recovery between sessions. When a further stage of training was introduced with a distinctive CS using the 150-ms ISI, occasional tests of the original, extinguished CS revealed another hallmark of extinction, specifically, strong recovery of the 150-ms peak. These results support both abstract and cerebellar models of conditioning that encode the CS into a cascade of microstimuli, while challenging theories of extinction that rely on changes in CS processing, US representations, and contextual control. (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)     

Conditioning-specific reflex modification of the rabbit (Oryctolagus cuniculus) nictitating membrane response: Generality and nature of the phenomenon.

Conditioning-specific reflex modification (CRM) occurs when classical conditioning modifies responding to an unconditioned stimulus in the absence of a conditioned stimulus. This form of reflex modification suggests that learning modifies the unconditioned reflex pathway, Rabbit (Oryctolagus cuniculus) nictitating membrane responses to 5 intensities and 3 durations of airpuff (AP) or periorbital electrical stimulation (ES) were monitored before and after conditioning. AP tests detected strong CRM after conditioning with ES and modest levels of CRM after conditioning with AP. After conditioning with AP, ES tests failed to detect CRM. After conditioning with a stronger AP, CRM was again detected by AP tests. CRM is a general phenomenon but is more readily detected after training with a relatively aversive stimulus; thus, it may be a function of level of arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporally specific extinction of conditioned responses in the rabbit (Oryctolagus cuniculus) nictitating membrane preparation.

Extinguishing a conditioned response (CR) has entailed separating the conditioned stimulus (CS) from the unconditioned stimulus (US). This research reveals that elimination of the rabbit (Oryctolagus cuniculus) nictitating membrane response occurred during continuous CS-US pairings. Initial training contained a mixture of 2 CS-US interstimulus intervals (ISIs): 200 ms and 1,200 ms. The CRs showed double peaks, one for each ISI. When 1 ISI was removed, its CR peak showed the hallmarks of extinction: a decline across sessions, spontaneous recovery between sessions, and rapid reacquisition when the absent ISI was reintroduced. These results support real-time models of conditioning that segment the CS into microstimuli while challenging theories that rely on contextual control, US representations, CS processing, and response inhibition. (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)     

Scalar timing varies with response magnitude in classical conditioning of the nictitating membrane response of the rabbit (Oryctolagus cuniculus).

The present experiment was aimed at characterizing the timing of conditioned nictitating membrane (NM) movements as function of the interstimulus interval (ISI) in delay conditioning for rabbits (Oryctolagus cuniculus). Onset latency and peak latency were approximately, but not strictly, scalar for all but the smallest movements (.50 mm) were less variable, and their peaks were better aligned with the time of US delivery. These results are discussed with respect to their implications for current models of timing in eyeblink conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnitude and timing of nictitating membrane movements during classical conditioning of the rabbit (Oryctolagus cuniculus).

A trial-by-trial, subject-by-subject analysis was conducted to determine whether generation of the conditioned response (CR) occurs on a continuous or all-or-none basis. Three groups of rabbits were trained on different partial reinforcement schedules with the conditioned stimulus presented alone on 10%, 30%, or 50%, respectively, of all trials. Plots of each rabbit's nictitating membrane movements revealed that their magnitude rose in a continuous fashion. Response growth during acquisition followed a sigmoidal curve, and the timing of CR-sized movements was largely stable throughout the experiment. The results are discussed with respect to alternative models of CR generation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A midbrain–brain stem circuit for conditioned inhibition of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Conducted 2 experiments with 31 albino rabbits to determine the neural system responsible for the development of conditioned inhibition of the rabbit's nictitating membrane response (NMR). In Exp I, monopolar electrodes were implanted in a variety of midbrain and brain-stem loci. Following acquisition of a conditioned NMR each electrode was tested to determine whether electrical stimulation applied to the electrode inhibited the manifestation of a CR. The most dramatic reduction in the amplitude of the CR was produced by stimulating the nucleus of Darkschewitsch, the interstitial nucleus of Cajal, or the anterior portions of the red nucleus. This disruption of the CR was observed either when the stimulation was aplied prior to the onset of the CS or when the stimulation was applied after the initiation of the CR. In the 2nd experiment, radio-frequency lesions placed in the nucleus of Darkschewitsch, interstitial nucleus of Cajal, anterior portions of the red nucleus, or tegmental reticular formation prevented the development of conditioned inhibition. Lesions placed in the rootlets of the oculomotor nerve, posterior red nucleus, or dorsal tegmental nuclei did not prevent the develoment of conditioned inhibition. It is concluded that a midbrain/brain-stem circuit originating in the nucleus of Darkschewitsch and interstitial nucleus of Cajal is responsible for the development of conditioned inhibition of the rabbit's NMR. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuronal unit activity in the abducens nucleus during classical conditioning of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Recorded neuronal unit activity from the abducens (6th nerve) nucleus during conditioning of the nictitating membrane (NM) response in 16 male New Zealand white rabbits, using a tone CS, an air puff UCS, 250-msec interstimulus interval, and 60-sec intertrial interval. Ss were given 2 days of training (104 trials in 8 blocks/day) and 1 day of extinction. Control Ss were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units—multiple unit recording—was compared with the amplitude/time course of NM response. Between-blocks comparisons of neural and behavioral responses indicated almost perfect correlation during acquisition of the CR and a slightly lower correlation during extinction for the conditioning Ss. Within-blocks comparisons indicated close correspondence between histograms of unit activity and the amplitude/time course of the NM response for the conditioning Ss in all phases of training and for controls in the UCS trial blocks. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inactivation of the central nucleus of the amygdala abolishes conditioning-specific reflex modification of the rabbit (Oryctolagus cuniculus) nictitating membrane response and delays classical conditioning.

The central nucleus (CE) of the amygdala has been gaining attention for its importance in the plasticity underlying conditioned emotional responding. Already known for its role in nictitating membrane response (NMR) reflex facilitation, the CE may also be involved in conditioning-specific reflex modification (CRM)--changes in the NMR to the unconditioned stimulus (US) when tested in the absence of the conditioned stimulus following classical conditioning. To examine the CE's role in acquisition and/or expression of CRM, the authors temporarily inactivated the CE of rabbits (Oryctolagus cuniculus) with muscimol during NMR conditioning and/or during US testing. Results show that CRM was abolished by inactivation during US testing but intact following inactivation during NMR conditioning, suggesting that the CE is involved in CRM expression. Also, inactivation during conditioning delayed the development of conditioned NMRs. These findings show that the CE may act as an output center for expression of emotional responding in one situation (CRM) but is involved in facilitating plasticity in another (NMR conditioning). The authors propose that analysis of CRM may be an important corollary to current models for the treatment of posttraumatic stress disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Stimulus Selection in Eyelid Conditioning in the Rabbit (Oryctolagus cuniculus)": Erratum.

Reports an error in the original article by Perry S. Kinkaide (Journal of Comparative and Physiological Psychology, 1974[Jun], 86[6], 1132-1140). The lower portion of Figure 3 on page 1138 should have represented the last two conditions for Group T as Test AV and reTest AV. The last sentence of the caption should have been deleted. (The following abstract of this article originally appeared in record 1979-05368-001) Conducted 2 experiments, using a total of 24 female New Zealand white rabbits, in which a "visual" stimulus (V), either flashes or electrical stimulation of the optic chiasma, was reinforced in compound with a differentially reinforced (CS+) or nonreinforced (CS-) nonvisual stimulus. Visual stimulus control of conditioned eyeblink activity was acquired if V was reinforced in compound with CS- but was "blocked" when reinforced in compound with CS+. Both effects were demonstrable within Ss and were independent of the method of visual stimulation. Extinction and backward conditioning of chiasmic stimulation preceded retraining of 6 Ss. The establishment and blocking of visual stimulus control were again evident within Ss. The data are interpretable in terms of either attentional or associative theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnitude and timing of conditioned responses in delay and trace classical conditioning of the nictitating membrane response of the rabbit (Oryctolagus cuniculus).

The present experiment characterized conditioned nictitating membrane (NM) movements as a function of CS duration, using the full range of discernible movements (>.06 mm) rather than movements exceeding a conventional criterion (>.50 mm). The CS–US interval was fixed at 500 ms, while across groups, the duration of the CS was 50 ms (trace), 550 ms (delay), or 1050 ms (extended delay). The delay group showed the highest level of acquisition. When tested with the different CS durations, the delay and extended delay groups showed large reductions in their responses when their CS was shortened to 50 ms, but the trace group maintained its response at all durations. Timing of the conditioned movements appeared similar across all manipulations. The results suggest that the CS has both a fine timing function tied to CS onset and a general predictive function tied to CS duration, both of which may be mediated by cerebellar pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prefrontal control of trace versus delay eyeblink conditioning: Role of the unconditioned stimulus in rabbits (Oryctolagus cuniculus).

The conditioned eyeblink (EB) response was studied with trace conditioning procedures in rabbits (Oryctolagus cuniculus) with lesions to the medial prefrontal cortex (mPFC) or sham lesions. Three experiments were performed in which either periorbital shock or a corneal airpuff served as the unconditioned stimulus (US) in separate groups of sham or mPFC-lesioned rabbits. Acquisition of the EB conditioned response (CR) was faster and reached a higher asymptote with the eyeshock US than with the airpuff US. However, mPFC lesion-induced trace conditioning deficits were obtained only in the groups that received the airpuff US. All rabbits showed normal delay conditioning and extinction. These results suggest that mPFC mediates trace EB conditioning when emotional arousal is low. However, in circumstances when emotional arousal may be high (i.e., during exposure to aversive periorbital shock), other structures (such as amygdala) may be activated to permit learning even in the absence of input from mPFC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies of binaural detection in the rabbit (Oryctolagus cuniculus) with Pavlovian conditioning.

A Pavlovian conditioned eyeblink response in rabbits (Oryctolagus cuniculus) was used to study psychoacoustical phenomena previously demonstrated in human listeners and other animals. This article contains the results of a tone-in-noise detection study to examine 2 psychoacoustical phenomena in rabbit and in human listeners: (a) the binaural masking level difference (BMLD) and (b) differential performance across reproducible noise masker waveforms. The rabbits demonstrated a BMLD comparable in size to other species. Significant differences in performance across reproducible noise masker waveforms were seen in the rabbits. This performance was compared with the performance of human listeners using the same set of waveforms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peripheral 6-hydroxydopamine administration in the rabbit (Oryctolagus cuniculus): Effects on Pavlovian conditioning.

Studied the effects of 6-hydroxydopamine (6-OHDA) administration (75 mg/kg, im) and adrenal enucleation on differential classical conditioning of somatic and cardiovascular changes in 32 New Zealand albino rabbits. Heart rate and blood pressure CRs were relatively large decreases in rate and slight depressor responses, respectively, which were both attenuated by 6-OHDA administration and adrenal demedullation. Frequency of eye-blink response to the reinforced CS was diminished by sympathetic interference during the middle sessions of conditioning, thus producing a decrement in eye-blink discrimination. EMG CRs, on the other hand, were not affected by peripheral catecholamine reduction. Results are discussed in terms of the role of afferent autonomic feedback in influencing the acquisition of somatomotor behaviors. (38 ref) (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)     

Stimulus selection in eyelid conditioning in the rabbit (Oryctolagus cuniculus).

Conducted 2 experiments, using a total of 24 female New Zealand white rabbits, in which a "visual" stimulus (V), either flashes or electrical stimulation of the optic chiasma, was reinforced in compound with a differentially reinforced (CS+) or nonreinforced (CS–) nonvisual stimulus. Visual stimulus control of conditioned eyeblink activity was acquired if V was reinforced in compound with CS– but was "blocked" when reinforced in compound with CS+. Both effects were demonstrable within Ss and were independent of the method of visual stimulation. Extinction and backward conditioning of chiasmic stimulation preceded retraining of 6 Ss. The establishment and blocking of visual stimulus control were again evident within Ss. The data are interpretable in terms of either attentional or associative theory. (24 ref) (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)     

Peripheral autonomic mechanisms and Pavlovian conditioning in the rabbit (Oryctolagus cuniculus).

Three experiments examined the effects of peripheral administration of 0–50 mg/kg atropine methyl nitrate and 6-hydroxydopamine hydrobromide on differential classical conditioning of eye-blink (EB) and heart rate (HR) responses in 102 New Zealand albino rabbits. Atropine decreased HR CR magnitude and increased baseline HR, although the latter declined somewhat over the 1st few sessions of the experiment. As baseline HR declined, EB CRs increased in Ss treated with atropine. However, the acquisition of the EB response was impaired in these Ss compared with Ss treated with saline. The administration of 6-hydroxydopamine produced an impairment of the HR response early and late during acquisition but had no effect on EB conditioning. Control experiments suggested that the impairments produced by methyl atropine were not due to general somatomotor deficits or to a differential sensitivity to the electric shock UCS. The conditioning data are consistent with B. C. Lacey and J. I. Lacey's (1974) peripheral afferent feedback hypothesis of autonomic-somatic relations. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)