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-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)     

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 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)     

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)     

Eyeblink conditioning in the rabbit (Oryctolagus cuniculus) with stimulation of the mystacial vibrissae as a conditioned stimulus.

Eyeblink conditioning is a well-understood paradigm for the study of learning and memory and has been successfully employed with the use of auditory and visual conditioned stimuli (CSs). In this study, vibrotactile stimulation of the mystacial vibrissae was examined as an alternative CS in the rabbit ( Oryctolagus cuniculus). The technique is described and acquisition of eyeblink conditioning (EBC) with stimulation of a single row of vibrissae in a delay paradigm is reported. Extinction of EBC with presentation of the CS alone is demonstrated, as well as reacquisition with stimulation of a single whisker. Finally, control experiments ensure that the CS has no auditory components. Ipsilateral presentation of the CS and airpuff is a more effective combination for training than contralateral presentations. Vibrotactile stimulation of the vibrissae as a CS will enable further examination of the neural correlates of learning in a well-characterized sensory system. (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)     

"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)     

Conditioning-specific reflex modification of rabbit (oryctolagus cuniculus) heart rate.

Conditioning-specific reflex modification (CRM) describes changes in rabbit (Oryctolagus cuniculus) nictitating membrane responses (NMR) to an unconditioned stimulus (US) when the US is tested by itself after pairings of tone and electrodermal stimulation. Although CRM has been replicated, it is unclear whether it occurs in response systems other than that of the NMR. The authors report that CRM of rabbit heart rate (HR) can occur following HR conditioning. A US that elicits HR acceleration before conditioning can elicit HR deceleration after conditioning. The rabbits' electrocardiograms showed both HR conditioning and HR CRM were correlated with an increased PQ interval--an index of parasympathetic function mediated by the vagus. The data suggest conditioned HR deceleration can generalize from conditioned stimulus to US as a function of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversible septal inactivitation disrupts hippocampal slow-wave and unit activity and impairs trace conditioning in rabbits (Oryctolagus cuniculus).

This study investigated the effects of medial septal microinfusion of the local anesthetic, procaine (MS Pro), on hippocampal neurophysiology and learning of the rabbit (Oryctolagus cuniculus) classically conditioned jaw movement (CJM) response. Both the percentage and the amplitude of hippocampal theta decreased after procaine administration, and unit recordings from the MS Pro group showed significantly smaller conditioning-related hippocampal neural responses than those from controls. The MS Pro group took significantly longer to reach learning criterion than did the control group. Interpreted in the context of previous studies, the present result suggests that nonselective blocking of all septal projection systems, as well as fibers of passage, using procaine can be less detrimental to learning than an imbalance between GABAergic and cholinergic septohippocampal projections, as produced by septal infusion of anticholinergics. (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)     

Eyeblink conditioning during an interstimulus interval switch in rabbits (Oryctolagus cuniculus) using picrotoxin to disrupt cerebellar cortical input to the interpositus nucleus.

The role of the cerebellar cortex in eyeblink classical conditioning remains unclear. Experimental manipulations that disrupt the normal function impair learning to various degrees, and task parameters may be important factors in determining the severity of impairment. This study examined the role of cerebellar cortex in eyeblink conditioning under conditioned stimulus?unconditioned stimulus intervals known to be optimal or nonoptimal for learning. Using infusions of picrotoxin to the interpositus nucleus of the rabbit cerebellum, the authors pharmacologically disrupted input from the cerebellar cortex while training with an interstimulus interval (ISI)-switch procedure. One group of rabbits (Oryctolagus cuniculus) was 1st trained with a 250-ms ISI (optimal) and then switched to a 750-ms ISI (nonoptimal). A 2nd group was trained in the opposite order. The most striking effect was that picrotoxin-treated rabbits initially trained with a 250-ms ISI learned comparably to controls, but those initially trained with a 750-ms ISI were severely impaired. These results suggest that functional input from cerebellar cortex becomes increasingly important for the interpositus nucleus to learn delay eyeblink conditioning as the ISI departs from an optimal interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reflex facilitation during eyeblink conditioning and subsequent interpositus nucleus inactivation in the rabbit (Orycotolagus cuniculus).

In eyeblink conditioning in the rabbit (Oryctolagus cuniculus), not only is a conditioned response (CR) acquired, but also the original reflex is modified as a function of training. In Experiment 1, by comparing unconditioned responses in unpaired and paired groups, 3 types of reflex facilitation were distinguished. One type was linked to exposure to the unconditioned stimuli (USs) and/or experimental setting. The 2nd type was related to the formation of the memory trace for conditioned eyeblink. The 3rd type was linked to the conditioned stimulus immediately preceding the US in the paired group. In Experiment 2, reversible inactivation of the interpositus nucleus (IPN) abolished the CR and reduced the CR-related reflex facilitation, indicating that the latter depends on the plasticity of the IPN. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Apparatus Exposure Produces Profound Declines in Conditioned Nictitating-Membrane Responses to Discrete Conditioned Stimuli by the Rabbit (Oryctolagus cuniculus).

The present experiments demonstrated that in the rabbit (Oryctolagus cuniculus) nictitacing-membrane (NM) preparation, exposure to the experimental apparatus produces profound declines in conditioned responding to a discrete conditioned stimulus (CS; Experiments 1, 2A, and 3). Moreover, this decremental effect is at most attenuated in only a minor way when the unconditioned stimulus (US) is presented during exposure to the apparatus (Experiment 2B). Controls for retention loss (Experiments 1 and 3) and for handling and placement in a different context (Experiment 3) did not produce significant declines in responding. These findings challenge theories of extinction that rely primarily on context-US associations but are more consistent with theories that assume context-CS-US associations. (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)     

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)     

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)     

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)     

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)