Classical conditioning of the rabbit eyelid response with a mossy-fiber stimulation CS: II. Lateral reticular nucleus stimulation.

Stimulation of mossy fibers arising from the pontine nuclei can be used as a conditioned stimulus (CS) during classical conditioning of the eyelid/nictitating membrane response (NM). In the present experiment we stimulated another source of mossy fibers, the lateral reticular nucleus (LRN), as a CS for NM conditioning. LRN stimulation was an effective CS, resulting in learning, and the conditioned response to LRN stimulation showed normal extinction. Unpaired presentation of CS and US did not result in pseudo-conditioning. Lesions of the cerebellar dentate-interpositus region abolished the conditioned response but left the unconditioned reflex response intact. We suggest that mossy fibers may normally carry CS information to the cerebellum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical stimulation of brainstem nuclei: Elicitation, modification, and conditioning of the rabbit nictitating membrane response.

Electrical stimulation of the reticular formation, pars oralis of the spinal trigeminal, abducens, and accessory abducens nuclei was used to assess the role of these sites in the elicitation, reflex modification, and classical conditioning of the rabbit's nictitating membrane response (NMR). Although electrical brain stimulation of the targeted sites revealed comparable levels of unconditioned responses, the spinal trigeminal nucleus was the only site at which reflex modification and conditioned response acquisition occurred reliably. These findings suggest that a locus of conditioned stimulus and unconditioned stimulus interaction, mediating either or both reflex modification and NMR conditioning, is on the sensory side of the reflex arc, at the pars oralis of the spinal trigeminal nucleus. (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)     

Disrupted eyelid conditioning in a patient with damage to cerebellar afferents.

A 54-year-old woman with damage to cerebellar circuitry resulting from a cerebrovascular accident underwent classical conditioning of the eye-blink response to a tone conditioned stimulus (CS) and an air-puff unconditioned stimulus (UCS). In contrast to 5 age-matched controls who readily acquired the conditioned response (CR), emitting a mean of 56.7 CRs over 70 trials, the patient emitted only 6 CRs in 100 trials and never emitted 2 consecutive CRs. There were no differences in spontaneous blink rate, sensitivity to the air puff, or sensitivity to the tone between the experimental subject and the control subjects. That conditioning of the eye-blink response is disrupted in a human with damage to cerebellar circuitry is consistent with an accumulating body of literature indicating that the cerebellum is the essential site of plasticity for classically conditioned somatic responses. (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)     

Patches of synchronized activity in the cerebellar cortex evoked by mossy-fiber stimulation: questioning the role of parallel fibers

The discrepancy between the structural longitudinal organization of the parallel-fiber system in the cerebellar cortex and the functional mosaic-like organization of the cortex has provoked controversial theories about the flow of information in the cerebellum. We address this issue by characterizing the spatiotemporal organization of neuronal activity in the cerebellar cortex by using optical imaging of voltage-sensitive dyes in isolated guinea-pig cerebellum. Parallel-fiber stimulation evoked a narrow beam of activity, which propagated along the parallel fibers. Stimulation of the mossy fibers elicited a circular, nonpropagating patch of synchronized activity. These results strongly support the hypothesis that a beam of parallel fibers, activated by a focal group of granule cells, fails to activate the Purkinje cells along most of its length. It is thus the ascending axon of the granule cell, and not its parallel branches, that activates and defines the basic functional modules of the cerebellar cortex.     

Classical conditioning with electrical stimulation of cerebellum as both conditioned and unconditioned stimulus.

Stimulating electrodes were implanted in rabbit cerebellum, providing an electrical conditioned stimulus (CS) activating cortical parallel fibers and thence Purkinje and other cells, and an electrical unconditioned stimulus (US) activating underlying white matter and eliciting unconditioned responses. Paired CS-US presentations led to the development of conditioned responses, which showed extinction following CS-alone trials and reacquisition with significant savings on reinstatement of paired trials. Increased local excitability as a result of paired training (but not following unpaired stimulus presentations) was observed in cerebellar cortex, as manifested in substantial decreases in CS threshold for response elicitation in all subjects. This preparation offers a model for the study of plastic neuronal interactions within cerebellar networks critically involved in associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial reinforcement and instructional set in discrimination conditioning of the eyelid response.

Conducted a discrimination eyelid conditioning experiment with a total of 144 undergraduates in which either 50 or 100% of CS+ trials were reinforced under inhibitory, neutral, or facilitatory instructional sets. Variation in instructional set yielded receiver operating characteristic curves that indicated discrimination by the 100% reinforcement groups superior to that by the 50% groups during conditioning. However, the 50% groups displayed both superior resistance to extinction and superior discrimination in extinction. Discrimination declined during extinction under both reinforcement schedules. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CS–US contiguity and CS intensity in conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Two experiments examined 48 female albino rabbits' nictitating membrane response to serial-compound stimuli consisting of 2 distinctive CSs (CSA and CSB) that were followed by a shock UCS. In Exp I, CSA was a highly salient 93-db tone, and CSB was a moderately salient flashing light. The CSA/UCS interval was 800 msec, and the CSB/UCS interval was varied across 400, 600, and 800 msec. In Exp II, the flashing light served as CSA, and CSB was either a 73-, 85-, or 93-db tone. The CSA/UCS interval remained 800 msec, and the CSB/UCS interval was fixed at 400 msec. The CSB/UCS interval and CSB intensity determined the rate of CR acquisition to the compound. Yet, CR acquisition to CSB showed impairments relative to the level of responding in single CS-control conditions. However, the impairment in CR acquisition to CSB was attenuated by increasing CSB/UCS contiguity. The impairment in acquisition to the light CSB appeared to be primarily a consequence of the tone CSA's greater salience. However, impairments in CR acquisition to CSB appeared even when CSB had the combined advantages of CS/UCS contiguity and great salience relative to CSA. Results indicate a role for CSA's temporal primacy in determining CR acquisition to the components of a serial compound and are discussed in terms of selective-attention, generalization-decrement, and information hypotheses. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical motor neuron activity in the cat during classical conditioning with central stimulation as the CS and the US.

Studied the neuronal basis of associative conditioning in the cat by pairing stimulation of thalamocortical pathways as the CS with antidromic activation of pericruciate pyramidal tract (PT) cells as the UCS in a differential classical conditioning paradigm. For the 18 Ss in Exp I, the target thalamic nuclei for stimulation were nucleus ventralis posterolateralis (VPL) and nucleus ventralis lateralis. For the 10 Ss in Exp II, the target thalamic nuclei were VPL and nucleus cetromedian. Results show that thalamic stimulation was not an effective CS. The response of PT cells to thalamic stimulation did not change as a function of reinforcement with PT stimulation. These results do not support the hypothesis that the simple pairing of any 2 neural events is the essential mechanism underlying associative conditioning changes. Instead, they suggest that the combined activation of specific and nonspecific thalamic nuclei may be important in producing increases in responsiveness of PT neurons. (45 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)     

Classical conditioning and conditioning-specific reflex modification of rabbit heart rate as a function of unconditioned stimulus location.

Heart rate conditioning is used as an index of conditioned fear and is important for understanding disorders of anxiety and stress, including post traumatic stress disorder (PTSD). One important feature of PTSD is that patients generalize conditioned fear from danger signals to safety signals especially when the two signals have overlapping features. What has not been determined is whether generalization occurs between unconditioned stimuli with overlapping features. In the current experiment, heart rate conditioning and conditioning-specific reflex modification of rabbit heart rate were examined as a function of two different unconditioned stimulus locations. Heart rate conditioning occurred at identical terminal levels whether electrical stimulation was presented near the eye or on the back. Despite different heart rate response topographies to electrical stimulation at the two locations, conditioning-specific reflex modification was detected near the eye and on the back and appeared to generalize between the locations. Interestingly, only conditioning-specific reflex modification detected on the back persisted for a week after heart rate conditioning. This persistence may be a model for some features of post traumatic stress disorder. Overgeneralization of unconditioned responses to unconditioned stimuli similar to the trauma may also be an important aspect of PTSD modeled here. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Aversive second-order conditioning in the pigeon: Elimination of conditioning to CS1 and effects on established second-order conditioning.

After aversive 2nd-order conditioning was established in groups of female White Carneaux pigeons, conditioning to the 1st-order CS was eliminated by either nonreinforced presentations of CS or truly random presentations CS 1 and UCS. Subsequent testing of CS 2 revealed that nonreinforced CS presentations significantly reduced previously established 2nd-order conditioning, but truly random presentations of CS 1 and UCS did not. Data suggest that an association between the CS 2 memory and UCS memory was formed during 2nd-order conditioning. Results do not support conclusions drawn from previous research that indicated that rats form a direct association between CS 2 memory and CR in both appetitive and aversive 2nd-order conditioning preparations and that pigeons form an association between CS 2 and CS 1 memories in a 2nd-order autoshaping preparation. (French abstract) (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of UCS preexposure on excitatory and inhibitory rabbit eyelid conditioning: An associative effect of conditioned contextual stimuli.

Preconditioning experience with the UCS retards subsequent excitatory conditioning. Three experiments demonstrated that the UCS retardation effect is attenuated by associative manipulations of contextual stimuli of the UCS preexposure environment. The UCS retardation effect was reduced by (a) altering contextual stimuli between preexposure and conditioning (Exp I, 49 New Zealand male rabbits; Exp II, 28 Ss); and (b) latently inhibiting contextual stimuli subsequent to UCS (Exp III, 36 Ss). Although UCS preexposure retarded excitatory conditioning, results of Exp IV (48 Ss) demonstrated that UCS preexposure facilitated inhibitory conditioning. Overall findings indicate that an association between contextual stimuli and preexposed UCS contributes to the effects of preconditioning UCS experience on subsequent learning. (48 ref) (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)     

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)     

Connections to cerebellar cortex (Larsell's HVI) in the rabbit: A WGA-HRP study with implications for classical eyeblink conditioning.

Conditioned eyeblink responses are presumably learned in the cerebellum and relayed to motoneurons by way of the red nucleus. Projections from the red nucleus to cerebellar cortex (Larsell's lobule HVI) could be important for shaping temporally adaptive features of the conditioned response. Rabbits that had pipettes containing wheat germ agglutinated horseradish peroxidase (WGA-HRP) implanted unilaterally into HVI showed retrograde labeling of neurons within subregions of the contralateral red nucleus implicated in eyeblink conditioning by lesioning and recording studies. Retrogradely labeled neurons were also observed in the pontine nuclei, inferior olive, and spinal trigeminal nucleus pars oralis. Projections to HVI provide a possible neural substrate for implementing time-derivative computational models of learning in the cerebellum. Time-derivative models are capable of describing the timing and topography of conditioned responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the cerebellar vermis and cerebellar hemispheres: Effects on heart rate conditioning in rats.

The effects of lesions of the cerebellum on the acquisition of heart rate (HR) conditioned responses (CRs) were examined in rats. Large lesions of the cerebellar vermis severely attenuated the acquisition of differentially conditioned bradycardic responses in restrained rats without affecting unconditioned HR responses to the tone conditioned stimuli (CSs) or the shock unconditioned stimulus/stimuli (UCS). In Exp 2, Ss were trained unrestrained, and under these conditions the CR was tachycardia in control Ss. Lesions of the vermis again severely attenuated acquisition of this CR without affecting unconditioned response (UCR) to the CSs or UCS. Bilateral lesions of the cerebellar hemispheres did not affect HR conditioning in either test procedure. The vermis of the cerebellum is an essential component of an HR conditioning circuit in the rat. The cerebellar hemispheres, which are involved in some discrete somatomotor CRs, have no essential functional contribution to HR conditioning. Results are discussed in relation to contributions from a forebrain system involved in HR conditioning and in relation to lateral cerebellar contributions to discrete somatomotor CRs. (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)     

Learning of physiological responses: II. Classical conditioning of the baroreflex.

The baroreflex can be classically conditioned. In neuromuscular blocked (NMB) rats, electrical stimulation of the aortic depressor nerve (ADN) and dopamine-produced blood pressure rise were effective unconditioned stimuli (UCS) for auditory discriminative classical conditioning. The conditioned response (CR) pattern (bradycardia, vasodilatation, and hypotension > 10 torr) closely resembled that of the unconditioned baroreflex. Conditioned stimulus (CS) specificity was demonstrated by discrimination of baroreflex-associated and nonassociated auditory stimuli, and also by elaborating depressor and pressor CRs to auditory CSs, which respectively had been associated with either baro-afferent (depressor) or tail-shock (pressor) UCSs. The conditioned baroreflex-magnitude increased with trials. These findings support quantitative models in which CRs interact with and calibrate the gain and dynamic properties of natural reflexes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)