Classical conditioning of hippocampal theta patterns in the rat.

Electrical stimulation (88 Hz) of the lateral hypothalamus elicited a sustained theta response at hippocampal recording sites in 11 male Sprague-Dawley rats immobilized with succinylcholine. By pairing this UCS with a 10-sec presentation of a light, conditioned theta responses were demonstrated in as few as 40 trials. Spectral analysis of hippocampal bioelectric patterns during acquisition, extinction, and reconditioning indicated that the earliest change as a result of conditioning was a loss of power in EEG frequency below 8 Hz, followed by the development of a peak at 8 Hz with further conditioning. Extinction was associated with an increase in power of the frequencies below 8 Hz. When the conditioned Ss were tested in the absence of the neuromuscular blocking agent, the CS elicited a theta response that was associated with slow motor activity on 70% of the trials. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instrumental conditioning of hippocampal theta and subsequent response persistence.

Following bar-press shaping of 24 male albino rats to a discrete-trial fixed-ratio (FR) 5 schedule of reinforcement; 16 were trained to produce either hippocampal theta (7.5-8.5 Hz) or nontheta (4-5 Hz) activity, while 8 served as a matched interreinforcement time control (yoked to the theta group). All Ss then returned to the FR-5 schedule on the lever response for 15 days, followed by 12 days of extinction. Results indicate that hippocampal theta production was learned more slowly than nontheta production but resulted in increased resistance to extinction of the subsequently performed lever response. These data are viewed as supporting the hippocampal theta-frustration hypothesis proposed by H. Glazer in 1972. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant autonomic conditioning and rod-and-frame test performance

Forty subjects were administered the portable rod-and-frame test (RFT) before and after operant autonomic conditioning training or control experiences. Ten subjects were assigned to each of four groups: a heart rate conditioning group; a false heart rate feedback group; a galvanic skin-response conditioning group; and a control group. Half of the subjects in the three experimental groups were informed of the response-reinforcement contingencies, and half were not informed. Informed subjects in the conditioning groups exhibited significantly lower portable RFT scores after conditioning. The results suggest that awareness of and control over autonomic functioning may be an important determinant of RFT performance.     

Operant conditioning in a quasi-therapy setting.

In 6 recorded interviews with student volunteers, S was asked to talk about himself. E differentially reinforced ("mm-hm" with a nod) positive or negative self-references, or reinforced not at all. Conditioning occurred re reinforcement of negative statement, not under conditions of reinforcement of positive references or nonreinforcement. No relationship was found between initial level of anxiety or emotional adjustment and conditionability. General, but not statistically significant, trends towards reduction of anxiety or improvement in adjustment were noted. Most Ss were unaware of therapist's manipulation of his verbalizations. Conclusion: a patient's verbalizations can be influenced by therapist's communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant eyelid conditioning in Trisomy 18: Replication and extension.

A profoundly retarded 6-yr-old child with extra No. 18 chromosomes (Trisomy 18) and a normal 7-mo-old infant were conditioned to emit operant eyeblinks and to maintain a head position in conformity with a variety of complex schedules of reinforcement. The experimental conditions included reinforcement for every eyeblink, reinforcement if the eyeblink did not occur, reinforcement after every 4 eyeblinks, reinforcement only after both eyeblinks and a certain head position occurred, and, finally, reinforcement for blinks or head position alone. The sessions were held at S's regular mealtimes, and spoonfuls of food were used as reinforcers. Both responses of both Ss increased or decreased in frequency depending upon the reinforcement contingencies. The response repertoire of the Trisomy 18 could be modified, and an application to the hospital ward was possible. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating entorhinal and hippocampal involvement in latent inhibition.

This study used anatomical cues to suggest a functional dissociation between the roles of the entorhinal cortex and the hippocampus in learning. The authors proposed that the highly convergent inputs to the entorhinal cortex indicate this region may be particularly important for selecting or compressing information. This hypothesis was tested in rabbits (Oryctolagus cunniculus) trained on an associative learning task that is a common index of stimulus selection. In this task, known as latent inhibition, preexposure to a stimulus (such as a tone) leads to slowed learning when the same tone is subsequently paired with an outcome (such as an airpuff to the eye). As hypothesized, rabbits with neurotoxic lesions of the entorhinal cortex failed to show slowed learning following preexposure (no latent inhibition) and learned the association faster than control rabbits. In contrast, hippocampal-lesioned animals showed normal (slowed) learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic-somatic interaction and hippocampal theta activity.

In 2 experiments, a total of 16 New Zealand rabbits were given extended differential classical conditioning training in which tones served as conditioned stimuli (CS) and shock to the eye served as the unconditioned stimulus (UCS). Corneo-retinal potential (CRP), heart rate (HR), and hippocampal EEG conditioned responses were measured. Changes in general somatic activity were also assessed. HR decelerations were associated with early stages of CRP discrimination, whereas HR accelerations and relatively more somatomotor activity were associated with later acquisition. These findings suggest that HR accelerations, associated with asymptotic CRP responding, are mediated via somatomotor changes. Although relatively more hippocampal theta activity was associated with later stages of conditioning, when somatomotor increases occurred theta was also prominent throughout acquisition. This finding suggests that either arousal properties of the CR are instrumental in producing theta or it is correlated with the associative properties of CS-UCS contingencies. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant conditioning of verbal behavior of dysthymics and hysterics.

Previous findings (Eysenck, 1955; Franks, 1956) indicated that neurotics of the dysthymic type react differentially to conditioning procedures than hysterics, and that conditionability is related to extraversion-introversion. The present study investigates the validity of these findings using verbal conditioning techniques. The results did not confirm the hypothesis; the Ss were not distinguished by ease of conditionability, measures of extraversion and anxiety, but were by Edwards (1957) Social Desirability scale. From Psyc Abstracts 36:04:4HI88G. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parallel augmentation of hippocampal long-term potentiation, theta rhythm, and contextual fear conditioning in water-deprived rats.

The influence of water deprivation on hippocampal long-term potentiation (LTP), theta rhythm, and contextual fear conditioning in 56 adult male rats was examined. In Exp 1, hippocampal EEG activity and perforant path LTP were assessed in pentobarbital-anesthetized rats. Water deprivation did not affect baseline cell excitability or low-frequency synaptic transmission in the dentate gyrus, but it increased the magnitude of perforant path LTP and elevated the proportion of theta rhythm in the EEG. In Exp 2, rats were classically conditioned to fear a novel context through the use of aversive footshocks. Water deprivation facilitated the rate of contextual fear conditioning but did not alter the asymptote of learning. Exp 3 demonstrated that the facilitation of contextual fear conditioning was not due to a change in unconditional shock sensitivity. These results suggest that water deprivation exerts an influence on contextual fear conditioning by modulating hippocampal LTP and theta rhythm and that these processes serve to encode contextual information during learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits on the radial maze and in fear conditioning: hippocampal processing and consolidation

Young adult, middle-aged, and old male F-344 rats were assessed for their hippocampal ability. This was accomplished by examining the animals on two different paradigms, each incorporating a simultaneous measure of hippocampal-dependent and -independent processing. The animals were fear conditioned and then tested for retention of the conditioning context and tone. This was followed by an 8-arm radial maze task which combined spatial working and cued reference memory elements. The two paradigms are compared in terms of task demands, potential confounds, and validity for aging studies. The results indicate that the performance of the animals on the two tasks is correlated. Age-related deficits limited to the hippocampal aspects of the above tasks were found, with no deficits found in the analogous but hippocampus-independent aspects of these tasks. The function of the hippocampus in incorporating new memories is time-related. Therefore, the possibility of age-related changes in consolidation was examined. It has previously been shown on the fear conditioning paradigm that the hippocampus is involved in retention of the aversive context for approximately 28 days. In the present study, an attempt was made to test the animals for retention of the conditioning context both early into the period of consolidation (10 days) and after consolidation should have been completed (52 days). The results indicate that, initially, the old animals show comparable retention to young rats. When examined later, young animals showed a stronger retention of the conditioning context than they had previously. The aged rats, however, did not seem to benefit from this additional period of time and in fact showed a decrease in retention of the conditioning context. The data are interpreted in terms of consolidation, alternative explanations of the data are presented, and suggestions are given for future research. Finally, the implications of such age-related changes in hippocampal consolidation on learning and memory are discussed.     

Operant conditioning of heart rate in free-moving dogs

Measurements of total body water and total exchangeable sodium, by isotopic dilution, and of total body potassium by whole body counting of the naturally occurring 40K isotope, were performed on stabilised paraplegic or tetraplegic subjects. Nineteen patients were investigated by the complete set of tests, six by only body counting. The results of total body potassium are expressed, following a uniform scale, as "relative values", which were established by the processing of reference values, from numberous paired healthy subjects.     

Operant conditioning principles in the treatment of a selectively mute child.

Reports the treatment of a 10-yr-old selectively mute girl. Over the course of 8 mo. of almost continuous contact, relatively normal speaking patterns were generated. At a 1-yr follow-up, her speech was indistinguishable from that of her classmates. She had improved even further in the "natural" environment and no new problems had developed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms underlying the plasticity of hippocampal stimulation-induced reward.

It has been reported that the slow acquisition of hippocampal self-stimulation can be markedly facilitated by pretreatment with a program of repeated daily hippocampal stimulation (kindling). Three experiments with 68 male Long-Evans rats investigated the neurophysiological basis of this effect. Exp I demonstrated that unilateral stimulation pretreatment produced a facilitation of learning to leverpress for stimulation delivered to the contralateral hippocampal electrode. Thus, there was a transfer of facilitation. In Exp II, it was shown that this transfer effect was not affected by lesion of the originally kindled focus, a result suggesting that the facilitated acquisition was not due to feedback to the kindled site. In Exp III, electrical activity during hippocampal self-stimulation was examined to explore the possible correlation between hippocampal reward and epileptiform activity. No relation was apparent: Leverpressing persisted even when no afterdischarge was elicited. Findings are consistent with the hypothesis that the facilitatory effect of stimulation reflects the development of transsynaptic potentiation. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating the conditioning and the anorectic effects of estradiol in female rats.

The present series of experiments challenges the ability of the hormone estradiol to act as an unconditioned stimulus in the conditioned taste avoidance (CTA) learning paradigm. We hypothesize that reductions in sucrose consumption observed after pairing it with estradiol are not indicative of associative learning, but due to the unconditioned expression of estradiol’s anorectic effects during the time of CTA assessment. Three experiments in which a sucrose solution was paired with estradiol were conducted to test this hypothesis. Experiment 1 demonstrated that female rats expressed a reduction in post-pairing sucrose consumption even though the anorectic effects of estradiol had subsided. Experiment 2 showed that although a low dose of estradiol produced anorexia, it did not elicit post-pairing reductions in sucrose consumption. Experiment 3 revealed that contingent pairing was a requirement for post-pairing reduction in sucrose consumption even when testing was done at a time when anorexia is expressed. These findings demonstrate the dissociability of the conditioning and anorectic effects of estradiol, providing evidence against the hypothesis. The results are discussed in terms of independent neural mechanisms underlying the disparate behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The hippocampus and reward: Effects of hippocampal lesions on progressive-ratio responding.

Two experiments investigated the effects of ibotenic-acid lesions of the hippocampus on food-rewarded performance under a progressive-ratio 10 schedule of reinforcement. The results of Experiment 1 indicated that rats with hippocampal lesions showed profound increases in breakpoint and enhancements in the efficiency of responding. In a second experiment the same rats were challenged with prefeeding, increases in the height of the response lever, and the substitution of sucrose-based for grain-based reward pellets. Responding in both groups was similarly reduced by prefeeding and increases in the effortfulness of responding, but lesioned rats were significantly more responsive to the change to sucrose reward. Overall, the results indicated that hippocampal damage increased responding by enhancing the activational or hedonic properties of the delivered food pellets, while not affecting food-motivation or the motor capacity to respond. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A re-examination of alpha feedback training: Operant conditioning or perceptual differentiation?

Assessed the role of contingent feedback in an alpha feedback training procedure with 40 undergraduates. Group 1 received auditory feedback whenever alpha activity was present in their EEG record. Group 2 (controls) heard a tape recording of feedback which had been produced by an experimental S. Although the groups did not differ significantly in alpha production, both showed significant increases in alpha activity during training with eyes closed. Experimental Ss differed from controls in reports of perceived ability to control feedback. Results indicate that contingent feedback does not necessarily function as reinforcement for operant control of EEG activity, but rather may only serve as a cue which aids in the identification of internal events. (French summary) (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant conditioning of H-reflex changes synaptic terminals on primate motoneurons

Operant conditioning of the primate triceps surae H-reflex, the electrical analog of the spinal stretch reflex, creates a memory trace that includes changes in the spinal cord. To define the morphological correlates of this plasticity, we analyzed the synaptic terminal coverage of triceps surae motoneurons from animals in which the triceps surae H-reflex in one leg had been increased (HRup mode) or decreased (HRdown mode) by conditioning and compared them to each other and to motoneurons from unconditioned animals. Motoneurons were labeled by intramuscular injection of cholera toxin-horseradish peroxidase. A total of 5055 terminals on the cell bodies and proximal dendrites of 114 motoneurons from 14 animals were studied by electron microscopy. Significant differences were found between HRup and HRdown animals and between HRup and naive (i.e., unconditioned) animals. F terminals (i.e., putative inhibitory terminals) were smaller and their active zone coverage on the cell body was lower on motoneurons from the conditioned side of HRup animals than on motoneurons from the conditioned side of HRdown animals. C terminals (i.e., terminals associated with postsynaptic cisterns and rough endoplasmic reticulum) were smaller and the number of C terminals in each C complex (i.e., a group of contiguous C terminals) was larger on motoneurons from the conditioned side of HRup animals than on motoneurons either from the conditioned side of HRdown animals or from naive animals. Because the treatment of HRup and HRdown animals differed only in the reward contingency, the results imply that the two contingencies had different effects on motoneuron synaptic terminals. In combination with other recent data, they show that H-reflex conditioning produces a complex pattern of spinal cord plasticity that includes changes in motoneuron physiological properties as well as in synaptic terminals. Further delineation of this pattern should reveal the contribution of the structural changes described here to the learned change in behavior.     

A model of hippocampal learning during classical conditioning.

During classical conditioning of the rabbit blink reflex, a large fraction of the hippocampal pyramidal neurons are recruited to respond to the conditioned stimulus (CS). The summed response of these neurons comes to match the whole time-amplitude profile of nictitating membrane movement, whereas some individual neurons respond only to part of this profile. A model is proposed that includes a learning rule to explain neuron recruitment and that uses a tapped delay line to account for the temporal learning properties of the system and the spectrum of individual unit responses. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and autobiographical memory: Dissociating episodic from semantic retrieval.

Cognitive aging research documents reduced access to contextually specific episodic details in older adults, whereas access to semantic or other nonepisodic information is preserved or facilitated. The present study extended this finding to autobiographical memory by using a new measure: the Autobiographical Interview. Younger and older adults recalled events from 5 life periods. Protocols were scored according to a reliable system for categorizing episodic and nonepisodic information. Whereas younger adults were biased toward episodic details reflecting happenings, locations, perceptions, and thoughts, older adults favored semantic details not connected to a particular time and place. This pattern persisted after additional structured probing for contextual details. The Autobiographical Interview is a useful instrument for quantifying episodic and semantic contributions to personal remote memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)