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Results for “Conditioning, Operant”

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PubMed1990

Operant conditioning of H-reflex in freely moving monkeys.

The H-reflex, the electrical analog of the stretch reflex or tendon jerk, is the simplest behavior of the primate CNS. It is subserved by a wholly spinal two-neuron reflex arc. Recent studies show that this reflex can be increased or decreased by operant conditioning, and that such conditioning causes plastic changes in the spinal cord itself. Thus, H-reflex conditioning provides a powerful new model for investigating primate memory traces. The key feature of this model, the conditioning task, originally required animal restraint. This report describes a new tether-based design that allows H-reflex measurement and conditioning without restraint. This design integrates the conditioning task into the life of the freely moving animal.

Animals↗

PubMed2003

Investigation of NH3 emissions from new technology vehicles as a function of vehicle operating conditions.

The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce aboutthis importantsource of particulate matter (PM) precursors. Test variables included the emission level to which the vehicle was certified, the vehicle operating conditions, and catalyst age. Eight vehicles with low-emission vehicle (LEV) to super-ultralow-emission vehicle (SULEV) certification levels were tested over the Federal Test Procedure (FTP75), a US06 cycle, a hot running 505, a New York City Cycle (NYCC), and a specially designed Modal Emissions Cycle (MEC01v7) using both as-received and bench-aged catalysts. NH3 emissions in the raw exhaust were measured by tunable diode laser (TDL) absorption spectroscopy. The results show that NH3 emissions depend on driving mode and are primarily generated during acceleration events. More specifically, high NH3 emissions were found for high vehicle specific power (VSP) events and rich operating conditions. For some vehicles, NH3 emissions formed immediately after catalyst light-off during a cold start.

Air Pollutants↗

PubMed2005

Extraction of sunflower oil by twin screw extruder: screw configuration and operating condition effects.

The objective of this study was to investigate the screw configuration allowing oil extraction from sunflower seeds with a twin-screw extruder. Experiments were conducted using a co-rotating twin-screw extruder. Five screw profiles were examined to define the best performance (oil extraction yield, specific mechanical energy and oil quality) by studying the influence of operating conditions, barrel temperature, screw speed and feed rate. Generally, the position and spacing between two reversed screw elements affected oil extraction yield. An increase of oil extraction yield was observed as the reversed screw elements were moved with increased spacing between two elements and with smaller pitch elements. In addition, oil extraction yield increased as barrel temperature, screw speed and feed rate were decreased. Highest oil extraction yield (85%) with best cake meal quality (residual oil content lower than 13%) was obtained under operating conditions of 120 degrees C, 75 rpm and 19 kg/h. Furthermore, the operating parameters influenced energy input. A decrease in barrel temperature and feed rate followed by an increase in screw speed increased energy input, particularly specific mechanical energy input. Effect of the operating parameters on oil quality was less important. In all experiments tested, the oil quality was very good. The acid value was below 2 mg of KOH/g of oil and total phosphorus content was low, below 100 mg/kg.

Food Industry↗

PubMed1989

Memory traces in primate spinal cord produced by operant conditioning of H-reflex.

1. Study of memory traces in higher animals requires experimental models possessing well-localized and technically accessible memory traces--plasticity responsible for behavioral change, not dependent on control from elsewhere, and open to detailed investigation. Our purpose has been to develop such a model based on the wholly spinal, largely monosynaptic path of the spinal stretch reflex. Previous studies described operant conditioning of this reflex and of its electrical analog, the H-reflex. In this study, we sought to determine whether conditioning causes changes in the spinal cord that affect the reflex and are not dependent on continued supraspinal influence, and thus qualify as memory traces. 2. Sixteen monkeys underwent chronic conditioning of the triceps surae H-reflex. Eight were rewarded for increasing H-reflex amplitude (HR increases mode), and eight were rewarded for decreasing it (HR decreases mode). In each animal, the other leg was an internal control. Over several months of conditioning, H-reflex amplitude in the conditioned leg rose in HR increases animals and fell in HR decreases animals. H-reflex amplitude in the control leg changed little. 3. After HR increases or HR decreases conditioning, each animal was deeply anesthetized and surgically prepared. The reflex response to supramaximal dorsal root stimulation was measured from the triceps surae nerve as percent of response to supramaximal ventral root stimulation, which was the maximum possible response. Data from both legs were collected before and for up to 3 days after thoracic (T9-10) cord transection. The animal remained deeply anesthetized throughout and was killed by overdose. 4. The reflex asymmetries produced by conditioning were still present several days after transection removed supraspinal influence: reflexes of HR increases animals were significantly larger in HR increases legs than in control legs and reflexes of HR decreases animals were significantly smaller in HR decreases legs than in control legs. 5. Reflex amplitude was much greater in the control legs of anesthetized HR decreases animals than in the control legs of anesthetized HR increases animals. 6. Chronic conditioning had at least two effects on the spinal cord. The first effect, task-appropriate reflex asymmetry, was evident both in the awake behaving animal and in the anesthetized transected animal. The second effect, larger control leg reflexes in HR decreases than in HR increases animals, was evident only in the anesthetized animal. By removing supraspinal control, anesthesia and transection revealed a previously hidden effect of conditioning.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1980

Specific and unspecific neuronal mechanisms of cellular operant conditioning.

An analysis was carried out on spontaneous multiple-unit activity recorded through one chronically implanted electrode in the auditory cortex of awake cats. Statistical relations between the neurons were evaluated by crossinterval histograms of two cells. After determination of the pattern of background interaction between three neighboring units, a cat was stimulated with clicks or electrical shocks triggered by spontaneous spikes of the selected neuron, which is considered a variant of cellular operant conditioning. Shock was applied to muscles of the eyelid or ear. Rhythmical and random stimulations with cliks were used in control experiment. A neuronal microsystem is supposed to be an elementary cell network, which allows detection of new qualitative properties of cortical activity. At the level of such a micronet it is possible to describe the specificity of systemic neuronal activity in adaptive reactions. The analysis of crossinterval histograms reveals diverse participation in network function of neurons, differing in amplitudes of spikes. Two neuronal mechanisms of learning are suggested.

Animals↗

PubMed1994

Moderate induced hypotension provides satisfactory operating conditions in maxillofacial surgery.

Patients scheduled for maxillofacial surgery were randomly assigned to receive isoflurane (n = 22) or nitroglycerin (n = 18) in order to induce hypotension. Surgeons, blinded for the actual level of blood pressure and the technique used for inducing hypotension, were asked to rate operating conditions on a scale from 1 to 5. Systolic arterial pressure (SAP) and mean arterial pressure (MAP) were reduced by 26% for both groups. Although blood pressure levels showed little variation throughout the induced hypotension period, scores of 2 to 5 were given significantly more often at incision and at 30 min compared to the following measuring points (P < 0.01). In total, the surgical field was rated significantly more often with a score of 1 and 2 than with a score of 3 to 5 (P < 0.01). A relation between score and SAP and/or MAP could not be found. There was also no relation between scores and the technique used for hypotension. Our data suggest that, with the exception of the first half hour of surgery, on average a SAP of 89 mmHg and a MAP of 65 mmHg were sufficient to produce satisfactory operating conditions.

Adolescent↗

PubMed1985

Operant conditioning of somatosensory evoked potential (SEP) amplitude in rats. II. Associated changes in reflex and continuous non-timelocked movements.

Animals were rewarded for increasing (uptrain) or decreasing (downtrain) the amplitude of a 30 ms surface positive component of a somatosensory evoked potential (SEP) evoked by innocuous stimulation of the spinal trigeminal tract. The reflex movement produced by the evoking stimulus had a larger amplitude in uptraining than downtraining. This change in reflex amplitude suggests that operantly conditioning SEP amplitude was correlated with a change in innocuous somatosensory activity. There was no change in continuous non-timelocked movement associated with conditioning. This latter finding suggests that SEP conditioning is not necessarily mediated by such movement.

Animals↗

PubMed1981

Operant conditioning and discrimination of alpha: some methodological limitations inherent in response-discrimination experiments.

Studies on the operant conditioning of central nervous system activity have produced results interpreted as demonstrating that responses, certain properties of responses, or response-produced stimuli can function as discriminative stimuli. It is assumed that the feedback stimulus in biofeedback makes the subject aware of the internal response and that by becoming aware of the response, the subject can acquire voluntary control over it. In this context, awareness is operationally defined as the ability to use the response as a discriminative stimulus. Since direct evidence for the assumed relationship between control and discrimination is lacking, an attempt was made to test the hypothesis that discrimination of a response automatically leads to control over that response. The discriminative stimuli were the presence and absence of occipital alpha electroencephalograph (EEG) activity. Data from two experiments are reported. The first study, employing naive subjects, was designed to answer the following questions: (a) Since pilot data indicated that subjects seemed to match their responses to the more probable type of trial, would increases in the probability of a correct response result when the probabilities of alpha and nonalpha trials were held near .50? (b) If correct responding does increase, would performance of these subjects in an alpha feedback task be enhanced relative to that of subjects not previously given discrimination training? and (c) If subjects could not learn the discrimination task, would feedback training enhance their performance in a subsequent discrimination task? Results from this study indicate that holding the probabilities of alpha and nonalpha discrimination trials near .50 results in an absence of learning curves, but leaves open the possibility that sophisticated subjects are capable of discriminating alpha and nonalpha activity. The second study deals with two questions: (a) Can sophisticated subjects learn to discriminate occipital alpha activity from nonalpha activity? and (b) Does the procedure of providing subjects with salient stimuli, contingent on the presence and absence of alpha activity, establish stimulus control of the presence and absence of alpha activity? Results indicate that it is not possible to conclude that subjects can learn to discriminate alpha and nonalpha activity. However, learning to increase percent-time nonalpha or decrease percent-time alpha with respect to baseline levels by means of EEG-contingent stimulation provides subjects with the ability to suppress percent-time alpha in the absence of feedback. Information gained in both studies through subject interviews indicates that subjects most often acquired their control of alpha activity during feedback by a specific strategy and then used the strategy during the stimulus-control tests.

Alpha Rhythm↗

PubMed2001

Shaping attention span: an operant conditioning procedure to improve neurocognition and functioning in schizophrenia.

The high prevalence of neurocognitive deficits in schizophrenia, and their association with poorer outcomes, has created interest in treatments that can improve neurocognitive functioning in this illness. While a variety of rehabilitation interventions have been developed, many are not appropriate for the most severely ill patients, whose attention spans are so short that they cannot attend to the material being presented. For this population, the only neurocognitive rehabilitation methods with demonstrated effectiveness are those that involve the operant conditioning technique known as shaping. In this article, we review the rationale for the use of shaping-based methods as neurocognitive retraining techniques for treatment-refractory schizophrenia patients, review published reports using this intervention, and offer suggestions for the future development of this method from both clinical and research perspectives.

Attention↗

PubMed1993

Operant conditioning of the primate H-reflex: factors affecting the magnitude of change.

Primates can gradually increase or decrease H-reflex amplitude in one leg when reward depends on that amplitude. The magnitude of change varies greatly from animal to animal. This study sought to define the factors that control this magnitude. It evaluated the influence of animal age, muscle size (absolute and relative), background electromyographic activity (EMG) level, M response amplitude, initial H-reflex amplitude, performance intensity, and behavior of the contralateral leg. Fifty-four animals (Macaca nemestrina) underwent operant conditioning of the triceps surae H-reflex in one leg (the trained leg). Twenty-eight were rewarded for larger H-reflexes (HRup animals), and 26 were rewarded for smaller H-reflexes (HRdown animals). In the HRup animals, H-reflex amplitude in the trained leg rose to an average final value of 177% of its initial amplitude. Magnitude of increase varied widely across animals. Nine animals rose to 120-140%, 11 to 160-240%, three to 300% or more, and five remained within 20% of initial amplitude. In the HRdown animals, H-reflex amplitude in the trained leg decreased to an average of 69% of initial amplitude. Magnitude of decrease varied widely. Five animals decreased to 20-40%, seven to 40-60%, six to 60-80%, and eight remained within 20% of initial amplitude. Animal age, as assessed by weight, markedly affected HRdown conditioning, but not HRup conditioning. Heavy HRdown animals (> or = 6 kg) were more successful than light HRdown animals (< 6 kg). Thirteen of 14 heavy animals and only five of 12 light animals decreased to less than 80% of initial amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1981

A rapprochement of the operant-conditioning and awareness views of biofeedback training: the role of discrimination in voluntary control.

In order to adequately evaluate Cott, Pavloski and Black's claim that the discrimination of a physiological response is not necessary for the voluntary control of that response, this commentary presents a set of formal articulations and clarifications of intentional action, voluntary control, discrimination, awareness, and physiological response. It is concluded on logical grounds that Cott et al. are necessarily mistaken and that the conceptual foundations of the issue have not been clearly articulated heretofore. Based upon this discussion, a rapprochement is offered of the operant conditioning and awareness views of biofeedback training, demonstrating that the awareness view is essentially a tautology that aids us in understanding what is meant by "voluntary control of the physiological response." Finally, the issue of mediation in biofeedback-augmented self-regulation is reconceptualized and it is argued that the search for a "neurophysiological mechanism" of voluntary control is meaningless, reflecting a misappropriation of the concept of voluntary control.

Alpha Rhythm↗

PubMed2006

Mathematical modeling of elution curves for a protein mixture in ion exchange chromatography and for the optimal selection of operational conditions.

Elution curves in ionic exchange chromatography (IEC) for a three-protein mixture (alpha-lactoalbumin, ovalbumin, and beta-lactoglobulin), carried out under different flow rates and ionic strength conditions, were simulated using two different mathematical models. These models were the Plate Model and the more fundamentally based Rate Model. Relatively low protein concentrations were used to avoid protein-protein interactions. Simulated elution curves were compared with experimental data not used for parameter identification. Deviation between experimental data and the simulated curves using the Plate Model was less than 0.0189 (absorbance units); a slightly higher deviation [0.0252 (absorbance units)] was obtained when the Rate Model was used. A cost function was built that included the effect of the different production stages, namely fermentation, purification, and concentration. These considered the effect on the performance of IEC; yield, purity, concentration and the time needed to accomplish the separation. Operational conditions in the IEC such as flow rate, ionic strength gradient and the operational time can be selected using this model in order to find the minimum cost for the protein production process depending on the characteristics of the final product desired such as purity and yield. This cost function was successfully used for the selection of the operational conditions as well as the fraction of the product to be collected (peak cutting) in IEC. It can be used for protein products with different characteristics and qualities, such as purity and yield, by choosing the appropriate parameters.

Chromatography, Ion Exchange↗

PubMed2001

Effects of operating conditions on selectivity of a plasma fractionator in double filtration plasmapheresis.

In a typical double filtration plasmapheresis treatment, plasma fractionation between albumin and some immunoglobulins associated with toxins is limited because none of the currently available plasma fractionators has a strict cutoff property for these proteins. Selectivity of immunoglobulins over albumin depends not only on the cutoff properties of the membrane but on the operating conditions such as the flow rate of the supplied plasma (Q(P)) and retained plasma to be discarded (Q(D)) in the plasma fractionator. We carried out an in vitro study using human plasma harvested by single plasma exchange treatments to assess the selectivity of a plasma fractionator, Evaflux 2A-F (Kawasumi Laboratories, Inc., Tokyo, Japan), under various operating conditions. The results of rate-constant filtration experiments showed that the concentrations in the feed tank and the sieving coefficient (SC) values of every protein were decreased slightly within 2 h after the start of the experiment because of membrane trapping, adsorption, and/or plugging. The time-averaged SC value of albumin increased with flow rate ratio (Q(P)/Q(D)) due to increasing filtration fraction (FF), but relative removal efficiency (mD/mP*) for albumin decreased with Q(P)/ Q(D) due to decreasing Q(D). For immunoglobulins, on the other hand, the SC values were almost unchanged, and the mD/mP* values increased with Q(P)/Q(D) due to an increase in FF. Both increasing Q(P) and decreasing Q(D) are effective means of improving selectivity between these proteins in the plasma fractionator. Membrane fouling is, however, obvious beyond a Q(P)/Q(D) value that is thought to be a critical point. Operation should be conducted below the critical Q(P)/Q(D) value, which depends on the patient's plasma components and the cutoff property of the membrane.

Humans↗

PubMed1985

Lack of effect of Pitressin on the learning ability of Brattleboro rats with diabetes insipidus using positively reinforced operant conditioning.

Brattleboro rats with hereditary hypothalamic diabetes insipidus (BDI) received daily subcutaneous injections of vasopressin in the form of Pitressin tannate (0.5 IU/24 hr). They were initially deprived of food and then trained to work for food reward in a Skinner box to a fixed ratio of ten presses for each pellet received. Once this schedule had been learned the rats were given a discrimination task daily for seven days. The performances of these BDI rats were compared with those of rats of the parent Long Evans (LE) strain receiving daily subcutaneous injections of vehicle (arachis oil). Comparisons were also made between these two groups of treated animals and untreated BDI and LE rats studied under similar conditions. In the initial learning trial, both control and Pitressin-treated BDI rats performed significantly better, and manifested less fear initially, than the control or vehicle-injected LE rats when first placed in the Skinner box. Once the initial task had been learned there was no marked difference in the discrimination learning between control or treated BDI and LE animals. These results support the view that vasopressin is not directly involved in all types of learning behaviour, particularly those involving positively reinforced operant conditioning.

Animals↗

PubMed2000

Operant conditioning of left-hemispheric slow cortical potentials and its effect on word processing.

This study investigated whether language-related cognitive processes can be modified by learned modulation of cortical activity. Study participants received feedback of slow cortical potentials (SCPs) recorded above left-hemispheric language cortices and were reinforced for producing negative and positive shifts upon two different discriminative stimuli. In all subjects who achieved reliable control of left-hemispheric brain responses, substantial modification of word processing was observed. Behavioral modification could be documented in two experiments in which word probes were presented following discriminative stimuli. When negative shifts of the EEG were required, lexical decisions on words were substantially speeded, while they were slowed during positivity conditions. There was no indication for any performance difference between conditions in control subjects who failed to achieve control over SCPs after feedback training. This result was replicated in an experiment using lateralized-tachistoscopic stimulus presentation. Comparisons of word and pseudoword responses in both experiments indicated that behavioral modification was most pronounced for word responses. It was also not seen in a simple reaction time task not involving language materials. This argues against a global effect related to perception, visuo-spatial attention, or motor processes. We conclude that linguistic processes can be influenced by modification of cortical activity due to operant conditioning. In closing, tentative explanations of the present results based on theories of language and attention processes are being discussed.

Adult↗

PubMedDate not supplied

Operant conditioning of the EEG in two patients with epilepsy: methodologic and clinical considerations.

Methodologic and clinical considerations are discussed in sensorimotor rhythm (SMR) biofeedback research on two dissimilar but severe epileptic males. The first case, an akinetic epileptic who prior to feedback training experienced 80-100 clinical seizures every 10 hours, showed considerable seizure reduction after 6 months of SMR and epileptiform training. A number of methodologic and instrumentation advances were pioneered with the akinetic patient: (1) development of and ultra-sharp band-pass filter; (2) use of epileptiform inhibit and feedback circuitry; (3) use of monetary rewards as additional incentive; (4) use of correlational analysis for evaluation of acquisition in the major dependent variables and; (5) use of noncontingent feedback and reinforcement as control techniques. The second case, a psychomotor epileptic, also showed therapeutic benefit from SMR training. Clinical information regarding the effect of anticonvulsant medications on the course and therapeutic outcome of SMR training are described. In conjunction with operant conditioning of 12 Hz activity, corresponding changes for other EEG parameters are examined.

Adolescent↗

PubMed2001

Self-absorption effects in radially and axially viewed inductively coupled plasma-atomic emission spectrometry--the key role of the operating conditions.

Self-absorption effects leading to curvatures of the upper part of calibration graphs were investigated in multichannel detection ICP-AES. A dual view Optima 3000 ICP system was used to enable the simultaneous determination of 38 lines for both radial and axial viewing. Resonance and non-resonance lines were selected for both atomic and ionic lines. The concentrations of 22 standards were in the range 0.1-100 mg L(-1) and two sets of operating conditions, namely power and carrier gas flow rate, were used to evaluate their influence. It was found that these two conditions, and in particular the carrier gas flow rate, play a major role in self-absorption effects. Except for strongly absorbing lines, it was possible, under suitable conditions, to reduce or to suppress differences between self-absorption effects in radial and axial viewing, enabling extension of the range of linearity of axial viewing to higher concentrations. A diagnostic tool, based on emission line ratios, is proposed for detection of self-absorption. A calibration procedure is given for strongly absorbing lines affected by self-absorption even when operating conditions were optimized.

Journal Article↗

PubMed1998

Operant conditioning and the orbitofrontal cortex in schizophrenic patients: unexpected evidence for intact functioning.

Neuroimaging and neuropsychological studies have consistently implicated dorsolateral prefrontal cortex as abnormal in schizophrenia. However, other areas of frontal cortex have received far less attention. In particular, few studies have examined orbital frontal regions with other than olfactory tests. In the present study we wished to assess the functional capability of orbital frontal cortex using a test developed by Bechara et al. (1994) that assesses a subject's capacity to acquire a preference through reward and punishment, using a gambling task that involved gains and losses of play money. Thirty normal subjects and 12 patients with schizophrenia (three undifferentiated, eight paranoid, one schizoaffective) comprised the sample in the present study. We found that patients with schizophrenia exhibited a pattern of findings similar to that of normals and dissimilar to that of patients with known orbital frontal damage. In our study, both normal subjects and schizophrenic patients chose most frequently from decks of cards in which there were frequent rewards and infrequent penalties, as might be expected on the basis of operant conditioning literature. We also found that performance on this task was not correlated with tests of working memory or long-term memory, suggesting that the development of a preference may occur implicitly. Our findings also argue against a general deficit in schizophrenia, as performance on the gambling task appeared relatively uncompromised.

Adolescent↗