Long-term retention of the classically conditioned eyeblink response in rats.

Retention of the classically conditioned eyeblink response in rats was tested with a conditioned stimulus (CS)-alone extinction test and 2 sessions of reacquisition training. Retention of the eyeblink conditioned response (CR) during both tests was highest 24 hrs and 1 mo after initial acquisition. Three months after initial acquisition, responding during the CS-alone test was at baseline, but there was significant savings during reacquisition. By 6 mo after initial acquisition, the memory for the eyeblink CR was not expressed in either test. The group differences in retention, despite initial acquisition of the eyeblink CR to equal levels, suggest that rat eyeblink conditioning may provide a useful behavioral model for studying the neural processes underlying memory retention and loss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of a second-order classically conditioned response.

Following alleyway food-training on a 50% random partial reinforcement schedule and 10 forward 1st-order (CS1-UCS) conditioning trials elsewhere, forward 2nd-order (CS2-CS1) classical conditioning trials were initiated for 40 female albino rats (Group 1) and equivalent but backward (CS1-CS2) training was started for 20 additional Ss (Group 2). After each set of 2 CS1-UCS and 3 CS2-CS1 trials (or 3 CS1-CS2 trials for Group 2) were given, the CS2 was presented in the goal area of the alley on nonreinforced trials to assess its suppressing effect on total running times. While the performance of Group 2 to the CS2 was unchanged as a function of conditioning trials, Group 1 evinced both increasing suppression and skin conductance levels as 2nd-order training progressed. Maximum suppression was obtained by the 12th CS2-CS1 trial. (French summary) (16 ref.) (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)     

Extinction of a conditioned motor response following hypnosis.

The administration of a standard hypnosis induction procedure to 6 randomly assigned experimental Ss resulted in the disappearance of a recently acquired conditioned motor response. When hypnosis was terminated by another standard procedure the CR reappeared. On subsequent trials its appearance followed the usual extinction pattern. An equated control group (6 Ss) gave responses that followed the usual extinction pattern during both a extinction trials. Possible interpretations were considered and suggestions for further study made. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Five-year retention of the classically conditioned eyeblink response in young adult, middle-aged, and older humans

OBJECTIVE: To describe the clinical profile of demyelinating optic neuritis in African Americans. METHODS: The medical records of all patients with a diagnosis of optic neuritis examined at the Neuro-Ophthalmology Unit at the Emory University Eye Center (Emory) and at the Grady Memorial Hospital Eye Clinic (Grady), Atlanta, Ga, between 1989 and 1996 were retrospectively reviewed. PATIENTS: African American and white patients, aged 15 through 55 years, with a single initial episode of acute optic neuritis of unknown or demyelinative origin were included in the study. Study patients included 23 African American patients and 56 white patients examined at Emory as well as 10 African American patients examined at Grady. RESULTS: There were no significant differences among the African American study patients, the white study patients, and patients from the Optic Neuritis Treatment Trial (ONTT) regarding sex (P=.36), age (P=.73), or the presence of disc edema (P=.40), lesions found on magnetic resonance imaging (P=.43), or multiple sclerosis (P=.54) at the onset of an initial episode of optic neuritis. The Emory African American patients presented with more frequent severe visual loss (13 [93%] of 14 patients with a visual acuity < or =20/200) compared with Emory white patients (12 [39%] of 31 patients; P=.002) and with ONTT patients (161 [36%] of 448 patients; P<.001). At follow-up examination of at least 1 year, Emory African American patients had worse vision (9 [39%] of 23 patients <20/40, and 4 [17%] of 23 patients < or =20/200) compared with Emory white patients (5 [8%] of 63 patients <20/40, P=.001; 3 [5%] of 63 patients < or =20/200, P=.08), and with ONTT patients (29 [7%] of 409 patients <20/ 40, P=.0001; 12 [3%] of 409 patients < or =20/200, P=.01). Compared with ONTT patients, the Emory African American patients combined with the Grady African American patients had more frequent severe visual loss (visual acuity < or =20/200) at presentation (18 [90%] of 20 patients vs 161 [36%] of 448 patients; P<.001) and at follow-up examination of at least 1 year (6 [18%] of 33 patients vs 12 [3%] of 409 patients; P=.002). Seven (58%) of 12 African American patients with multiple sclerosis had a "neuromyelitis optica" presentation defined by the presence of neurological deficits limited to the optic nerves and spinal cord. CONCLUSIONS: The African American study patients with a single episode of demyelinating optic neuritis had visual acuities more severely affected at onset and after 1 year of follow-up compared with the white study patients and with patients in the ONTT. In the African American patients, multiple sclerosis occurred most frequently in a "neuromyelitis optica" form.     

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 a classical conditioning paradigm on hind-limb flexor nerve response in immobilized spinal cats.

Maintained 50 adult cats on Flaxedil after spinal transection at T-12 under ether anesthesia. Experimental Ss were classically conditioned by electrical stimulation of the exposed superficial peroneal nerve (CS), paired with cutaneous shock to the ankle of the same limb (UCS). The CR was the gross efferent volley recorded from the exposed deep peroneal nerve. Controls were divided into unpaired CS and UCS, CS-only, and UCS sensitization groups. Results show that the experimental conditions produced increases in amplitude of the gross efferent volley while unpaired CS and UCS, and CS-only control conditions produced no change or a decrease in amplitude. The UCS sensitization group showed that no sensitization was present at the intertrial intervals used in experimental conditions. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversible lesions of the red nucleus during acquisition and retention of a classically conditioned behavior in rabbits.

Previous lesion, recording, and stimulation studies implicated the cerebellum and its associated brain-stem circuitry as essentially involved in classical conditioning of discrete, somatic muscle responses. A prior study of interpositus cooling showed that the formation of memory was prevented. The present study assesses the red nucleus (RN) for its role in the plasticity associated with learning and memory by using local cooling as a reversible lesion technique. A cooling probe was implanted lateral to the RN. Recording electrodes were implanted in the right RN and the left interpositus nucleus (IPN). Animals were trained for 6 days with the cooling probe activated. No behavioral CRs developed, and multiple unit recordings related to learning did not develop in the RN. However, a learning related model did develop in the IPN. After 5 days of training while cooling, animals were given 5 days of normal training (cooling probe inactive) to assess retention. Substantial savings were evident when normal training was given. CRs appeared quickly on the 1st day of normal training, and multiple unit models were present in both RN and IPN. Results support the idea that the red nucleus is a necessary efferent for the memory trace formed in the cerebellum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversible lesions of the cerebellar interpositus nucleus during acquisition and retention of a classically conditioned behavior.

Previous lesion, recording, and stimulation studies have implicated the cerebellum and its associated circuitry as essentially involved in classical conditioning of discrete, somatic muscle responses. In 2 experiments, the interpositus nucleus of the cerebellum as assessed for the plasticity associated with learning and memory of the nictitating membrane (NM) response by using local cooling as a reversible lesion technique. In well-trained animals (Exp 1), NM conditioned responses (CRs) were abolished during cooling of the interpositus but reappeared when the interpositus returned to body temperature. This cooling–warming protocol could be repeated many times. Cooling could be prolonged (1 session, ～1 hr) with recovery of NM CRs as tested on the next day. Multiple-unit recordings related to learning were also absent in the interpositus and red nucleus during cooling. In naive animals (Exp 2), both behavioral and unit CRs did not develop while training with cooling. There was no evidence of savings when training continued without cooling: Behavioral and unit CRs developed as if the animals were still naive. These results support the idea that the interpositus nucleus of the cerebellum is the critical locus for learning and memory of this classical CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classical conditioning of a flexor nerve response in spinal cats: Effects of tibial nerve CS and a differential conditioning paradigm.

Examined, in 4 experiments using 59 cats, the effects of a differential conditioning paradigm on the deep peroneal motor nerve response. Results show that flexor nerve response increases were produced when the conditioned stimulus/stimuli (CS) was delivered to the whole tibial nerve or to the medial plantar branch. The responses to CS/unconditioned stimuli presentations on the superficial peroneal nerve increased, whereas responses to CS presentations on the tibial nerve remained unchanged. However, lack of extinction effects in the superficial peroneal data suggests that stimulation of the tibial nerve potentiated superficial peroneal evoked responses. Furthermore, responses evoked by stimulation of either nerve increased when paired trials were given on the tibial nerve. These data demonstrate that stimulation of the tibial nerve potentiates responses to superficial peroneal nerve stimulation but that superficial peroneal nerve stimulation has no effect on responses to CS presentations to the tibial nerve. (7 ref) (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)     

Phenytoin blocks the reversal of a classically conditioned discriminative eyeblink response in rabbits

The aim of the present study was to assess the role of vascular alpha 1D-adrenoceptors in the sympathetic vasopressor response in vivo. Specifically, we evaluated the effect of a selective alpha 1D-adrenoceptor antagonist, BMY 7378 (8-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-8-azaspiro(4,5)dec ane-7,9- dione 2HCl), on the vasopressor response induced by preganglionic (T7-T9) sympathetic stimulation in the pithed rat. The vasopressor response was dose-dependently sensitive to inhibition by intravenous BMY 7378 (0.1, 0.31, 1 and 3.1 mg/kg), doses of 1 and 3.1 mg/kg being equally effective. Like BMY 7378, 5-methylurapidil (0.1, 0.31, 1 and 3.1 mg/kg) antagonized the vasopressor response to spinal stimulation; doses of 1 and 3.1 mg/kg were also equally effective. In combination experiments, BMY 7378 (1 mg/kg, i.v.) and the alpha 1A-adrenoceptor antagonist, 5-methylurapidil (1 mg/kg, i.v.), showed an additive effect. The present results demonstrate that the alpha 1D-adrenoceptor subtype plays an important role in the pressor response to sympathetic nerve stimulation in the pithed rat, and confirm the participation of the alpha 1A-adrenoceptor subtype in the same response.     

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)     

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)     

Acquisition of the classically conditioned eyeblink response in humans over the life span.

Human subjects ranging in age from 18 to 85 years underwent classical conditioning of the eyeblink response to a tone conditioned stimulus (CS) and an air-puff unconditioned stimulus (UCS). There was a decline in percentage of conditioned responses with age. This decline was most noticeable in subjects over age 50. These conditioning deficits were not due to age-related changes in sensitivity to the tone CS or the air-puff UCS, nor could the conditioning deficits be attributed to an age-related decline in general cognitive abilities or to changes in spontaneous blink rates. The results are discussed in terms of using the classically conditioned eyeblink in humans in conjunction with the classically conditioned nictitating membrane response in rabbits as a model system for studying the neurobiology of age-related conditioning deficits. (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)     

Extinction of conditioned flavor preferences.

In a series of 4 experiments, the effects of extinction on flavor preferences conditioned by mixing flavor cues with a nutrient were examined. In each experiment it was observed that rats preferred a flavor cue that had not undergone extinction to one that had. In addition, this preference was reversed in subjects trained thirsty (Experiments 1 and 2) if the associated nutrient had been devalued prior to the test or the preference for the nonextinguished cue was attenuated by nutrient devaluation in subjects trained hungry (Experiments 3 and 4). The results suggest that extinction may weaken associations between the flavor and the specific sensory properties of the nutrient and, for subjects trained hungry, between the flavor and the motivational components of the nutrient as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early acquisition, but not retention, of the classically conditioned eyeblink response is N-methyl-D-aspartate (NMDA) receptor dependent

N-methyl-D-aspartate (NMDA) antagonists impair performance in some tasks, but whether they impair learning directly or through effects on sensorimotor performance remains controversial. Rats administered a competitive NMDA antagonist, CGP-39551, 24 hr before training could not acquire a classically conditioned eyeblink response. The associative deficit remained evident during training with a high-intensity conditioned stimulus, even though sensory reactivity was unaffected. The antagonist did not alter retention and thus did not affect motor performance of the task. These results extend and confirm studies that implicate NMDA-receptor activation in the acquisition of classically conditioned associations and specifically in tasks not dependent on the hippocampus for learning itself. Moreover, they substantiate recent claims that NMDA receptor activation (and by association, long-term potentiation) may be involved in early processes of procedural memory formation.     

Intertrial interval effects in classically conditioned fear to a discrete conditioned stimulus and to situational cues.

In Exp I fear was classically conditioned in a total of 240 female hooded and Sprague-Dawley rats with a discrete conditioned stimulus (CS) at intertrial intervals (ITIs) of 15, 45, 75, 105, 165, or 225 sec and in Exp II, with an additional 144 Ss, with or without a discrete CS at ITIs of 165, 225, or 285 sec. The amount of fear conditioned to situational cues and to the discrete CS plus situational cues was then measured by the learning of a hurdle-jumping response which allowed escape from the fear-eliciting stimuli. Results suggest that as ITI was lengthened fear conditioned to situational cues alone and to the discrete CS increased. However, following conditioning with a discrete CS, fear elicited by situational cues increased with ITI but then decreased, presumably because a discrimination had been formed between the situational cues and the compound of CS plus situational cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of Pavlovian conditioned inhibition.

Examined 2 procedures with potential for reducing Pavlovian conditioned inhibition in 4 experiments with 72 male Sprague-Dawley rats. The 1st, simple nonreinforced presentation, was suggested by a theory which has been successful with data from the acquisition of conditioned inhibition. However, nonreinforced presentation of a stimulus, either after conditioned inhibition training or intermixed with such training, failed to produce any loss of the inhibition controlled by that stimulus. The 2nd procedure involved removing the negative correlation between inhibitor and reinforcement. When this correlation was altered, in such a way as to continue UCS presentation, loss of inhibition occurred. (PsycINFO Database Record (c) 2010 APA, all rights reserved)