Changes in the motor response threshold to direct electric stimulation of the motor cortex during elaboration of conditioned reflex switching-over

During elaboration of switching-over of an alimentary salivary conditioned reflex to a defensive one in dogs, with foreleg passive flexion as a signal stimulus, excitability changes of opposite signs appeared in the cortical representation of the left foreleg. At the stage of elaborated switching-over, the threshold of the flexor reaction to a direct stimulation of the motor cortex became lower in the alimentary experimental situation (passive rise--milk) and rose in the defensive situation (passive rise--acid).     

Chaotic components in the high-frequency EEG of rabbit cortex during formation of a conditioned defensive reflex

The chaotic component of the high-frequency EEG of the rabbit cortex was studied during the development of a conditioned defensive reflex to nonrhythmic light stimulation with electric reinforcement applied to the animal's paw. Regular changes in the dynamic parameters of the chaotic component of the high-frequency EEG were demonstrated. Characteristic changes in the asymptotic evaluations of the correlational dimensionality of the attractor of the chaotic component (DCC) of the high-frequency EEG were detected in the cortical regions studied both during the action of the conditioned stimulus and in background conditions before presentation of combinations. These changes affected both the afferent and efferent cortical regions of the conditioned reflex arc, as well as regions not directly addressed by the conditioned or unconditioned stimuli. These results allow the dynamics of changes in the morphofunctional structures of the conditioned reflex to be seen at the cortical level during learning. Significant differences in the early and late stages of conditioned reflex formation were detected.     

The role of quinine chlorhydrate in the conditioned inhibition of the tarsal reflex in Drosophila melanogaster

The proboscis extension reflex (PER) can be elicited by applying a sucrose stimulation to the tarsus of a walking fly. This reflex decreases in frequency with repetition, presumably habituation, a nonassociative learning. If each sucrose stimulation is followed by a bitter stimulation, quinine chloride, the PER declines more rapidly, probably the result of conditioning, an associative learning. The present work shows that quinine chloride does not always inhibit PER suppressions but depends on the moment of delivery, being most effective when presented immediately after a sucrose stimulation. A bitter stimulus presented before, or simultaneously with a sucrose stimulation is less effective than habituation to sucrose alone. This experiment provides evidence for an interpretation in terms of cognitive association. The model of learning is not a Pavlovian conditioning as advanced by Medioni and Vaysse (1975), but corresponds to the punishment paradigm of Dyal and Corning (1973).     

Dynamics of evoked potentials at different points in the cat somatosensory cortex during elaboration of conditioned reflexes

In chronic experiments on cats a study was made of the spreading of evoked potentials (EP) in the somatosensory zones S1 and S2 in response to biologically significant tonal stimuli. The formation of conditioned connections enhances the capacity for polysensory reactions in different cortical somatic fields outside the zones of local projection of the unconditioned stimulus. As stable conditioned connections are formed, this capacity diminishes in relation to reinforced and, particularly, easily differentiated sounds: EP are more localized in response to the former, and disappear altogether when the latter are presented. The wide EP spreading in zones S1 and S2 is the longest in response to medium and fine differentiation tones, which points to the involvement of these zones in the integrative analysis of signals by their biological quality.     

The synaptic release of dopamine in the striatum of rats during the acquisition of a passive avoidance conditioned reflex

To study the striatal synaptic dopamine release during passive avoidance behaviour the intracranial microdialysis technique combined with radioenzymatic assay method was used in Sprague-Dawley rats. It was shown that the acquisition of passive avoidance conditioning and an unescapable footshock led to delayed increases in striatal synaptic dopamine release.     

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)     

Dynamics of conditioned reflex reorganization in the human visual system

The dymamics of absolute and relative changes in the brightness thresholds of letters recognition was studied in 21 subjects, under conditions of dark adaptation and molecular observation, before and after pairing of one of the letters with electrocutaneous stimulation of the index finger during one session. Isolated electrocutaneous stimulation was applied on the 10th or 35th day after the session. It has been found that after pairings the relative threshold of recognition of the letter previously paired with electrical stimuli (i.e. the threshold in relation to recognition thresholds for the other letters) becomes for three to three and a half hours significantly lower than the initial one. Then there sharply sets in a phase of threshold elevation. Both in the case of double and multiple tests, this phase persists for not less than 35 days. Following an isolated electrical stimulation, a momentary significant lowering of the threshold sets in only for the letter which was paired with it in the first sessions.     

Spatial-temporal organization of the functions of cortical neurons in a conditioned reflex to time

The impulse activity of neurons in the motor cortex of cats during the development of a conditioned food-procuring reflex in relation to a time interval of 2 min (CRT) was analyzed. It was demonstrated, by comparing the behavioral and neurophysiological correlates of the formation of the conditioned food-procuring reaction, that its formation is accompanied by extremely complex systemic transformations which are different for neuronal micro- and macrostructures. The systemic processes in the micro- and macrostructures differed with respect to the specific characteristics of spatial distribution, and with respect to the number, strength, and stability of the manifestation of the functional connections. The capacity of the neurons for functional orientation even at the initial levels of the formation of the reaction, an increase in the per cent of incidence of functional connections in the second half of the conditioned reflex interval, and the substantial destabilization of all neuronal units at the last, highest level of formation of the conditioned reflex food-procuring reaction were common to the micro- and macrostructures in this form of learning.     

Obstructive effect of a closed 12F urethral catheter during the emptying phase of cystometry in patients with a spinal reflex bladder

There is a group of malignant intrascrotal tumours which represent a very small number when compared to testicular neoplasias and which are known as paratesticular neoplasias. More than 90% belong to the sarcomatous species. From a clinical point of view and based on the patient's age, two groups can be distinguished: sarcomas affecting children and adolescents (primarily rabdomiosarcomas) and those occurring in adulthood, the more frequent histopathological variants being fibrosarcoma, leiomiosarcoma and liposarcoma. This work contributes five paratesticular sarcomas (two rabdomiosarcomas, one liposarcoma, one leiomiosarcoma and one fibrosarcoma). The features related to histogenesis, diagnosis (revealing signs and clinical examination), natural history (dissemination routes based on histopathology) and treatment are reported. With regard to treatment, both the local surgery (total orchiectomy by inguinoscrotal approach with or without hemiscrotectomy), and indications for lymphadenectomy and radiotherapy in relation to staging are discussed though insisting on the chemotherapy approach.     

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)     

Effect of a neoprene sleeve on knee joint position sense during sitting open kinetic chain and supine closed kinetic chain tests

The primary objective of the present study was to compare the effect of a neoprene sleeve on knee joint position sense during a sitting open kinetic chain test and a supine closed kinetic chain test. Young (24 +/- 2 years old), healthy subjects (18 men and 18 women) performed knee joint angle replication tests during open kinetic chain knee extension (sitting) and closed kinetic chain leg press (supine with an axial load of 15% body weight) before and after application of a neoprene sleeve over the dominant knee. The improvement in ability to replicate joint angles after application of the sleeve (sleeve effect) was significantly less during the supine closed kinetic chain test (0.3 degree +/- 1.4 degrees) than during the sitting open kinetic chain test (1.2 degrees +/- 1.1 degrees). The sleeve effect was inversely related to subjects' performance without the sleeve during both the sitting open kinetic chain and supine closed kinetic chain tests, suggesting that some people may derive greater benefit from the sleeve than others. Although the sleeve effects were small, particularly during the supine closed kinetic chain test, 72% of subjects felt that the sleeve improved their overall test performance. Future research is needed to establish the functional relevance of the small sleeve effects observed and to identify the characteristics of people who might derive greatest benefit from sleeve use.     

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)     

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.     

Ontogeny of conditioned inhibition in domestic chicks.

Used the combined-cue test to measure age-dependent changes in learned stimulus inhibitory control in 40 young Vantress * Arbor Acre chicks trained to key peck for heat reinforcement. Both 1- and 4-day-old chicks were given either 96 or 384 discrete trials in a successive discrimination test, and then their response latencies to the novel combined cue (S+, S-) and the prior S+ cue were compared with those of age-matched controls during extinction. Major findings are as follows: (a) One-day-old chicks showed significant response suppression to the combined cue only after receiving 384 discrete trials, whereas 4-day-old chicks showed significant response suppression after both 96 and 384 trials. (b) While control chicks (S+ training only) of both age groups pecked more quickly at the novel cue than at the prior S+ cue during extinction, only the younger chicks pecked more quickly at the novel cue as the number of their prior S+ responses increased. The main conclusion from these experiments is that even the 1-day-old chick has the capacity to acquire learned inhibitory stimulus control but does so at a slower rate than the 4-day-old chick. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food-reinforced inhibition of conditioned salivation in dogs.

12 mongrel dogs salivated to a tone that was followed by food, but not to a noise for which there was an added response dependency. The noise was followed by food if and only if they did not salivate. The addition of this response dependency vitiated the classically conditioned response to the noise. A yoked-control group of 6 Ss receiving the same sequences of stimuli and food salivated to both the tone and noise stimuli. It is generally concluded that neither the effects of stimulus-dependent reinforcement nor the effects of response-dependent reinforcement are restricted to either skeletal or autonomic responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual control over conditioned responding in a latent inhibition paradigm.

We used 1-, 2-, and 3-context designs to study the control exerted by contexts over freezing in rats exposed to a conditioned stimulus (CS) in advance of its pairing with a shock unconditioned stimulus. The latent inhibition observed when preexposure, conditioning, and testing occurred in the same context was attenuated if preexposure occurred in a different context to conditioning and testing. Latent inhibition (i.e., attenuated performance) was restored in a CS-specific manner if preexposure and testing occurred in the same context and conditioning in a different one. Latent inhibition was also reduced by a long retention interval but remained specific for a particular context–CS relation. Finally, CS preexposure resulted in contextual control over the expression of excitatory conditioned performance. The results are discussed in terms of memory, associative, and associative-performance models of CS-preexposure effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus-produced reflex inhibition in the rat during induction of and recovery from barbiturate anesthesia.

Reported 3 experiments which show that the inhibitory effect of a preliminary stimulus on the acoustic startle reflex was disrupted during the induction of sodium pentobarbital (40 mg/kg) in a total of 50 male Holtzman rats. In Exp I (n = 35) and II (n = 8), Ss were injected with the barbiturate, and a startle stimulus was presented either alone or preceded by a white noise burst. Results show that (a) stimulus inhibition was present immediately after injection, (b) was lost during a phase of hyperreactivity which accompanied induction of the anesthesia, and (c) recovered as reactivity diminished in the anesthetic state. Exp III showed that inhibition recovered during an intervening stage prior to complete areflexia and that this recovery revealed that the earlier and later inhibitory failure cannot be ascribed to a drug-dependent degradation in a hypothetical inhibitory system. It was suggested that the expression of reflex inhibition depends on the balanced interplay of excitatory and inhibitory processes which are differentially sensitive to drug intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)