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)     

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)     

Age-related deficits in retention of the classically conditioned nictitating membrane response in rabbits.

Young and aged rabbits underwent classical conditioning of the nictitating membrane response (NMR) to a tone conditioned stimulus (CS) and a corneal airpuff unconditioned stimulus (UCS) for 18 consecutive days. Rabbits were then returned to their home cages for a 90-day period in which they received no further conditioning, but they were handled daily. On Day 91 they underwent retention testing during which the CS alone was presented 20 times. This was immediately followed by reacquisition in which the CS and UCS were again paired for 100 trials. Reacquisition was repeated on the following day. As in previous studies, aged rabbits acquired the conditioned response (CR) more slowly than young rabbits; however, by the end of acquisition, both groups reached similar asymptotic levels. Retention of the CR was significantly lower for aged than young rabbits. Reacquisition was also retarded in aged vs young rabbits. Nonassociative factors, such as sensitivity to the stimuli or general health, could not account for these differences. Data are discussed in terms of using retention of the conditioned eyeblink response as a model system for studying age-related memory deficits. (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)     

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)     

Hippocampal ablation prolongs immobility response in rabbits (Oryctolagus cuniculus).

Hypothesized that damage to the hippocampus would reduce tonic immobility in rabbits. 2 measures were used with 14 implanted and 6 control Dutch Belt rabbits: the number of successful inductions of tonic immobility in a test session and the duration of each successful immobilization. Both of these measures increased in Ss with hippocampal lesions rather than decreased as expected. It is suggested that the hippocampus may act to suppress any ongoing dominant or prepotent response, whether the response involves movement or cessation of movement. (28 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)     

Effects of frontal cortex lesions on differentiation and extinction of the classically conditioned nictitating membrane response in rabbits.

In Exp I 8 male New Zealand rabbits with frontal lesions, compared to 10 Ss with Visual Area II lesions, were impaired in relearning an auditory differentiation involving a classically conditioned defensive response (movement of the nictitating membrane). In Exp II it was shown that frontal lesions in 6 additional Ss also produced perseveration of this response in extinction. Analysis of these findings suggests that frontal lesions impair the ability to suppress conditioned nictitating membrane responses. Results support the view that frontal ablation produces a general impairment in overcoming strong response tendencies independently of the kind of response or reinforcement. (16 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)     

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

Analyzed efferent mechanisms controlling the nictitating membrane (NM) reflex response to air puff in the albino rabbit, using stimulation, lesions, and recording techniques with 52 New Zealand male Ss in 6 experiments. In brief, stimulation of the 6th nerve (abducens) yielded short-latency NM extension. Stimulation of the 4th and 7th nerves and the superior cervical ganglion had essentially no effect on the NM. Stimulation of the 3rd nerve caused short-latency retraction of the NM. Lesions and recording data were consistent with this result--the sole efferent neuronal control of NM extension was the 6th cranial nerve and of NM retraction was the 3rd cranial nerve. It is concluded that 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 3rd 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. (18 ref) (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)     

Differential effects of hippocampectomy on classically conditioned rabbit nictitating membrane response related to interstimulus interval.

The effects of hippocampal ablation on acquisition rates and temporal characteristics of classically conditioned nictitating membrane responses were examined in 54 New Zealand albino rabbits trained with a 150-, 300-, or 600-msec interstimulus interval. Acquisition rates were accelerated in the 150- and 600-msec groups. No effect was present in the 300-msec group. Response onset latencies were also affected in the 150-msec group. Results indicate that damage to the hippocampus influences the acquisition of classically conditioned responses only when temporal parameters are relatively complex. Findings also support the notion that the hippocampus modulates learned motor behavior by a neural model of the response to be executed. (21 ref) (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)     

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)     

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)     

Latent inhibition in the conditioned electrodermal response.

Measured the effects of preexposure to the CS, amount of pre-exposure, and delay between pre-exposure and conditioning in a classical electrodermal conditioning experiment with 139 female nursing students. 3 conditions were investigated: no delay, 1-hr delay, and 24-hr delay. In each of these delay conditions Ss were pre-exposed to either 100 or 50 presentations of the to-be-conditioned stimulus or 100 or 50 presentations of an irrelevant stimulus. Results were analyzed separately for long and short latency responses in terms of amplitude, magnitude, latency, recruitment, and frequency. It was found that CS pre-exposure reduced the frequency of responding regardless of delay or number of pre-exposures. There was a significant CS Pre-exposure main effect for short latency responses and a significant Trial Blocks * CS Pre-exposure interaction effect for long latency responses. Theoretical and methodological implications are discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An auditory conditioned stimulus modulates unconditioned stimulus-elicited neuronal activity in the cerebellar anterior interpositus and dentate nuclei during nictitating membrane response conditioning in rabbits.

Investigated the effects of the presentation of an auditory conditioned stimulus (CS) on unconditioned stimulus (UCS)-elicited neuronal activity in the anterior interpositus (AIPN) and dentate (DN) nuclei of the cerebellum during the initial stages of classical conditioning of the nictitating membrane (NM) response in rabbits. In Exp 1, a 500-msec CS (but not a 30-msec CS) facilitated UCS-elicited single-unit activity in the AIPN and depressed UCS-elicited activity in the DN during training. In Exp 2, lesions of the AIPN but not of the DN prevented acquisition of conditioned NM responses. The results are interpreted within the framework of a model of classical conditioning that proposes that conditioned neuronal activity that underlies behavioral plasticity develops from the modulation of UCS-elicited neuronal activity by the CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

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.