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)     

Cholesterol Modifies Classical Conditioning of the Rabbit (Oryctolagus cuniculus) Nictitating Membrane Response.

Cholesterol plays an important role in synapse formation, receptor function, and synaptic plasticity, and animal studies show that modifying cholesterol may improve learning and memory. Other data show that feeding animals cholesterol can induce beta amyloid accumulation. Rabbits (Oryctolagus cuniculus) fed 2% cholesterol for 8 weeks were given trace conditioning of the nictitating membrane response using a 100-ms tone, a 700-ms trace, and periorbital electrical stimulation or airpuff. Rabbits fed cholesterol showed significant facilitation of trace conditioning to airpuff and conditioning-specific reflex modification to periorbital electrical stimulation and airpuff. The cholesterol-fed rabbits had beta amyloid accumulation in the cortex, but little in the hippocampus. The data suggest cholesterol had facilitative effects that outweighed potential amnesic effects of cortical beta amyloid. (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)     

Cardiovascular classical conditioning in rabbits (Oryctolagus cuniculus) using appetitive or aversive hypothalamic stimulation as the US.

Examined the bar-press self-stimulation, shuttle-box preference, and cardiovascular classical conditioning of 2 groups of 6 male rabbits as a function of electrical stimulation of the medial or lateral hypothalamus. Results show that Ss having access to lateral hypothalamic stimulation bar-pressed to receive stimulation and made approach responses in the shuttle box. Ss having access to medial hypothalamic stimulation did not bar-press and made escape responses in the shuttle box. The cardiovascular UCRs of all Ss consisted of a blood-pressure increase and heart-rate decrease; CRs consisted of heart-rate decreases. Thus, while medial and lateral hypothalamic stimulation had different motivational properties, both provided effective UCSs for eliciting similar heart-rate CRs. Data indicate that cardiovascular changes elicited by hypothalamic stimulation are not merely global adjustments to aversive stimulation. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Role of Claustrum in Pavlovian Heart Rate Conditioning in the Rabbit (Oryctolagus cuniculus) : Anatomical, Electrophysiological, and Lesion Studies.

The role of the claustrum in Pavlovian heart rate (HR) conditioning was studied in the rabbit (Oryctolagus cuniculus) by (a) mapping claustral projections to the prefrontal cortex (PFC), (b) recording claustral single-unit discharge to sensory stimulation and conditioning stimuli during HR conditioning, and (c) assessing the effects of claustral damage on HR conditioning. Contralateral and ipsilateral claustral projections to the PFC were found. Claustral cells responded to nonsignal stimulation with increased discharge and also showed conditioned stimulus-evoked increases in discharge during Pavlovian HR conditioning. Moreover, claustral lesions diminished the magnitude of the HR-conditioned response without affecting the cardiac-orienting response to the conditioned stimulus or the cardiac-unconditioning response to the unconditioned stimulus, suggesting a role for the claustrum in associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Consequences of response-contingent change in unconditioned stimulus intensity upon the rabbit (Oryctolagus cuniculus) nictitating membrane response.

In a between-groups design using a total of 84 naive male and female rabbits, an instrumental contingency was superimposed on classical conditioning of the nictitating membrane response. Ss were exposed to a tonal conditioned stimulus (CS) and, if no conditioned response (CR) occurred, a 5.0-ma paraorbital electric shock unconditioned stimulus (UCS). UCSs of 5.0, 3.3, 1.7, and 0.0 ma, respectively, were contingent on occurrence of a CR in the CS-UCS interval for Ss in the 4 groups of the experiment. The group exposed to contingent UCS omission differed from the other 3 groups in percentage CR, onset latency, amplitude, and 2 indices of CR form, and those 3 groups generally did not differ significantly among themselves on these dependent variables. Results are interpreted to be contrary to "law of effect" formulations of classical conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of efferent neuronal control of the reflex nicitating membrane response in rabbit (Oryctolagus cuniculus)

Efferent mechanisms controlling the nicitating membrane (NM) reflex response to air puff in the albino rabbit were analyzed using stimulation, lesions, and recording techniques. In brief, stimulation of the sixth nerve (abducens) yields short-latency NM extension. Stimulation of the fourth and seventh nerves and the superior cervical ganglion has essentially no effect on the NM. Stimulation of the third nerve causes short-latency retraction of the NM. Lesions and recording data are consistent with this result - the sole efferent neuronal control of NM extension is the sixth cranial nerve and of NM retraction is the third cranial nerve. The NM extension response appears to be mediated by mechanical actions via retraction of the eyeball by the retractor bulbi muscle, and NM retraction appears to result from direct activation of muscle fibers in the NM by the third nerve. The superior cervical ganglion appears to play no role in reflex NM retraction in the rabbit, in contrast to its action in the cat.     

Classical differential and operant conditioning in rabbits (Oryctolagus cuniculus) with septal lesions.

12 normal New Zealand white rabbits and 12 with septal lesions received classical differential conditioning of the nictitating membrane response (NMR), followed by auditory generalization tests run in extinction. Although rate of acquisition and asymptotic responding to positive conditioned stimuli did not differ, septals responded more than normals to nonreinforced stimuli. Resultant decrements in differential conditioning could not be attributed to changes in auditory or shock thresholds or to increased spontaneous NMRs. Septals also responded at higher rates in both operant conditioning (barpresses reinforced with food pellets on a variable interval schedule) and extinction sessions. No difference in suppression in a passive avoidance task was found. Results are discussed in relation to R. A. McCleary's (1966) response disinhibition analysis of septal function, and an habituation hypothesis is considered. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Latent inhibition and stimulus generalization of the classically conditioned nictitating membrane response in rabbits (Oryctolagus cuniculus) following hippocampal ablation.

30 male and female New Zealand albino rabbits received 0 to 450 exposures of a tone CS prior to classical defensive conditioning of the nictitating membrane response based on an infraorbital eye shock UCS. Tone preexposure resulted in retarded conditioning in normal Ss, but was not present in Ss with bilateral dorsal hippocampectomy produced by aspiration. Controls with bilateral neocortical and callosal aspiration lesions demonstrated a latent inhibition effect similar to that shown by normal nonoperated Ss. The failure of CS preexposure to retard conditioning in hippocampal Ss was not due to differences in threshold of the conditioned response to the CS or to differences in response mechanisms as determined by tests of habituation and dishabituation of the UCR. A subsequent experiment with 24 Ss used combined-cue summation tests to confirm the fact that preexposure did not endow the tone with conditioned as well as latent inhibitory properties. Finally, tests of stimulus generalization along the auditory frequency dimension indicated flatter relative gradients for hippocampals than for nonoperated controls, with cortical controls in between. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition and extinction of a classically conditioned response in hippocampectomized rabbits (Oryctolagus cuniculus).

Compared the responses of 10 male albino rabbits with bilateral hippocampal lesions to those of 15 unoperated and 10 neocortically-lesioned controls. Experimental Ss acquired a classically-conditioned nictitating membrane response faster than the 2 control groups. After initial acquisition, Ss were given extinction training, alternated with reacquisition sessions, and a test of spontaneous recovery. Experimental Ss extinguished normally during initial sessions, but failed to show the significant savings exhibited by controls during subsequent extinction sessions. The test of spontaneous recovery failed to differentiate among the 3 groups. Experimental Ss given preoperative training showed essentially the same extinction deficit as Ss who had not been trained. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Conditioning During Amygdalar Inactivation on Training-Induced Neuronal Plasticity in the Medial Geniculate Nucleus and Cingulate Cortex in Rabbits (Oryctolagus cuniculus).

This study addressed the amygdala's role in avoidance conditioning in rabbits (Oryctolagus cuniculus). Intra-amygdalar muscimol infusion before 60 or 120 conditioning trials blocked training-induced neuronal activity (TIA) in the medial geniculate (MG) nucleus. One hundred twenty trials with muscimol blocked TIA permanently, during conditioning with muscimol and then later without muscimol; 60 trials with muscimol blocked TIA only when muscimol was present. Cingulate cortical TIA was blocked only when muscimol was present. Behavioral learning did not occur with muscimol, but later learning was facilitated (i.e., savings occurred) in rabbits initially given muscimol plus training. These results define the time period wherein amygdalar processes initiate TIA in the MG nucleus and suggest that distinct forms of amygdalar processes induce TIA in the MG nucleus and cingulate cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classical nictitating membrane conditioning in the rabbit (Oryctolagus cuniculus): Single alternation with differential intertrial intervals.

Investigated single alternation (SA) patterning behavior in 24 albino New Zealand rabbits by varying in 7 experiments the intertrial intervals (ITIs) following reinforced (R) and nonreinforced (N) trials. When short ITIs followed R trials and long ITIs followed N trials, reliable SA patterning was obtained. Neither (a) the presence of differential ITI cues, (b) the short ITIs prior to the N trials, nor (c) the early position of the N trial within the R-R interval were sufficient in and of themselves to support substantial patterning behavior; instead, each of these features apparently contributed to the patterning effect in a combined fashion. It is concluded that R- and N-trial aftereffects do not play an important role in conditioning the rabbit nictitating membrane. (18 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)     

Evolution of grass-cutter (Thryonomys swinderianus) inflammation markers: comparison with rabbit (Oryctolagus cuniculus) and rat (Rattus norvegicus)

An inflammatory reaction was induced in grass-cutters (Thryonomys swinderianus) by injecting turpentine. The changes in the plasma haptoglobin, fibrinogen, alpha 2 macroglobulin and immunoglobulin G was followed for 23 days by immunonephelometry. The results were compared to rat and rabbit. They showed that (a) the inflammatory reaction is delayed in the grass-cutter compared to rats and rabbits; (b) the concentration of haptoglobin increases less than in rat and rabbit; (c) the fibrinogen concentration is very low in the grass-cutter, despite hypercoagulability of blood; (d) the changes in the plasma alpha 2-macroglobulin in the grass-cutter seems to be comparable to that of rabbit alpha 1 macroglobulin in amplitude and in its slow return to the initial concentration; and (e) fibrinogen and haptoglobin are suitable markers for grass-cutter inflammation monitoring.     

Classical nictitating membrane conditioning in the rabbit (Oryctolagus cuniculus) as a function of unconditioned stimulus locus.

Examined the effects of different placements of electrodes used to present a shock UCS on conditioning the rabbit nictitating membrane response (NMR) in 2 experiments with 32 New Zealand and 24 albino rabbits. Ss were conditioned with shock leads attached either circumorbitally, at the ear base, or at the ear tip. In 1 circumorbital shock group, nictitating membranes of both shocked and unshocked eyes were monitored. Circumorbital, ear base, and ear-tip shock yielded best to poorest performances, respectively, and the shocked membrane yielded better performance than the unshocked one. Analysis of UCR and CR latencies and peak amplitude, as well as slow motion films of responses, suggests that poorer performance resulted from the elicitation of other responses, of which the NMR may have been a secondary or indirect component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditional responding and intertrial-interval variability in classical conditioning in the rabbit (Oryctolagus cuniculus).

Examined the effects of modal intertrial intervals (ITIs) of 10, 60, and 300 sec on classical conditioning of the nictitating membrane response in 72 albino rabbits. The design permitted an assessment of conditional responding immediately following selected test ITI values and allowed an analysis of ITI-distribution variability effects. Between-group comparisons revealed a positive monotonic function relating modal ITI and conditioned responding in no-test-trial (low ITI variability) groups, but no significant effect of ITI in test-trial (high ITI variability) groups. Within-group findings include (a) a complex but systematic relationship between modal ITI and ITI-conditional response probabilities and (b) evidence of within-session performance increments during preasymptotic acquisition and within-session decrements during postasymptotic sessions. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Congruency effects between number magnitude and response force.

Numbers are thought to be represented in space along a mental left–right oriented number line. Number magnitude has also been associated with the size of grip aperture, which might suggest a connection between number magnitude and intensity. The present experiment aimed to confirm this possibility more directly by using force as a response parameter. Participants judged parity of a single digit by executing a weak or forceful key press. Response selection was faster when small digits required a weak response and large digits required a forceful response than when this mapping was reversed. These findings indicate an effect of number magnitude on the initiation of response intensity. There was no evidence for such an effect on response execution because the actually applied response force was not associated with number magnitude. These findings confirm a previously postulated link between different magnitude domains such as number magnitude and intensity as a basis for action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tone-induced changes in excitability of abducens motoneurons and of the reflex path of nictitating membrane response in rabbit (Oryctolagus cuniculus).

Tested excitability of the reflex nictitating membrane (NM) response to air puff and of the abducens motoneurons (final common path) to direct electrical stimulation (measured as amplitude of the evoked NM response) in 16 New Zealand albino rabbits at various times after onset and offset of a 350-msec tone. Excitability to air puff showed a substantial increase during tone on and a gradual decrease following tone off, in agreement with J. R. Ison and D. W. Leonard (see record 1971-22356-001). Excitability of motoneurons showed a similar marked increase during tone on, a transient decrease immediately following tone off, and then a gradual decrease. It is suggested that these excitability changes, which parallel closely the interstimulus-interval conditionability function reported by I. Gormezano (1966) for the same preparation, may provide an independent measure of the "molar stimulus trace." Excitability of abducens motoneurons tested in the intertrial intervals during subsequent tone-air-puff conditioning showed no consistent changes. Surprisingly, Ss given tone-abducens nucleus shock testing developed conditioned responses. In subsequent conditioning, using standard tone-air-puff training, they showed 85% savings in acquisition relative to nonstimulated controls. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttraining effects of amphetamine, chlorpromazine, ketamine, and scopolamine on the acquisition and extinction of the rabbit's conditioned nictitating membrane response.

Four experiments examined whether posttraining deliveries of drugs modified the performance of the rabbit's conditioned nictitating membrane response (NMR) during acquisition and extinction. The results show that ketamine accelerated, but that amphetamine, chlorpromazine, and scopolamine retarded, conditioning when the drugs were injected immediately after the completion of daily training sessions. However, all conditioning effects of the drugs were lost when their deliveries were delayed by 2 hrs after the end of training. During extinction, the only drug that altered conditioned performance was ketamine. Specifically, ketamine retarded the rate of extinction when the drug was given immediately after training. However, delaying ketamine by 2 hrs after training neutralized the drug's influence. These findings indicate that the NMR preparation should be useful in examining how the posttraining delivery of drugs influences associative processes in conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)