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PubMed1994

High-resolution chromatography of proteins in short columns and adsorptive membranes.

Short chromatographic columns prepared from stacks of microporous adsorptive membranes are promising for preparative-scale fractionation of even rather closely related proteins, but careful selection of operating conditions is needed for success. It has been shown that existing devices exhibit very low internal diffusional resistance, and that resolution is almost totally independent of percolation velocity. Total column length is short, however, and the number of plates exhibited under isocratic low-loading conditions is small, on the order of 100. Simulations using a large survey of protein thermodynamic data show that one can frequently obtain excellent protein separations in these short columns by using the sensitivity of protein adsorption equilibria to eluting solvent composition. In fact, some proteins can be separated in a single stage utilizing this 'on-off' behavior and properly selected solvent gradients. Solely on-off, or differential elution, behavior cannot often be depended upon under the mild conditions need for preparative operations. Carefully programmed gradient elution can frequently produce acceptable purification by maximizing both differential elution and differential migration, resulting in protein separations in columns of less than fifty plates. Means for doing this are described for some simple situations, and criteria are provided for selecting modulator gradient schedules.

Animals↗
PubMed1996

Biblical behavior modification.

Although we may have formalized and systematized the field of behavior modification in the last few decades, people around the world have been using behavioral change strategies throughout history. Premack's (1965) theory of reinforcement is often called "Grandma's rule" because grandmothers have long been using it (e.g. You must finish your vegetables before you may go out and play). Franks (1969, p. 4), in one of the first behavioral texts, gave historical examples from China, Turkey, France, and Italy. Knapp and Shodahl (1974) showed how Benjamin Franklin used behavior modification. And de Silva (1984, 1985) gave examples of behavior modification by the Buddha and other early Buddhists. Conspicuously absent from our literature are examples from the Judeo-Christian tradition. In this paper, we provide a number of behavior modification examples from the Bible (New International Version). Footnotes provide references for many more examples. In the discussion, we explore implications for education and therapy. Examples are grouped by the following categories: operant conditioning, respondent conditioning, modeling, and cognitive interventions. However, the Biblical examples, like contemporary case studies, do not always fall neatly into discrete categories. They often are a combination, particularly operant and respondent conditioning interweaving.

Behavior Therapy↗
PubMed2001

Time course of H-reflex conditioning in the rat.

This study sought to define the course of operantly conditioned change in the rat soleus H-reflex and to determine whether, like H-reflex conditioning and spinal stretch reflex conditioning in the monkey, it develops in distinct phases. Data from 33 rats in which the right soleus H-reflex was trained up (i.e. HRup mode) and 38 in which it was trained down (i.e. HRdown mode) were averaged to define the courses of H-reflex increase and decrease. In HRup rats, the H-reflex showed a large phase I increase within the first 2 days followed by gradual phase II increase that continued for weeks. In HRdown rats, the H-reflex appeared to show a small phase I decrease and then showed a gradual phase II decrease over weeks. In combination with other recent work, the data suggest that H-reflex conditioning begins with a rapid mode-appropriate alteration in corticospinal tract influence over the spinal arc of the H-reflex, which causes phase I change, and that the continuation of this altered influence induces gradual spinal cord plasticity that is responsible for phase II change. The results further establish the similarity of H-reflex conditioning in primates and rats. Thus, they encourage efforts to produce a single coherent model of the phenomenon based on data from the two species and indicate the potential clinical relevance of the rat data.

Afferent Pathways↗
PubMed2006

The misbehavior of value and the discipline of the will.

Most reinforcement learning models of animal conditioning operate under the convenient, though fictive, assumption that Pavlovian conditioning concerns prediction learning whereas instrumental conditioning concerns action learning. However, it is only through Pavlovian responses that Pavlovian prediction learning is evident, and these responses can act against the instrumental interests of the subjects. This can be seen in both experimental and natural circumstances. In this paper we study the consequences of importing this competition into a reinforcement learning context, and demonstrate the resulting effects in an omission schedule and a maze navigation task. The misbehavior created by Pavlovian values can be quite debilitating; we discuss how it may be disciplined.

Animals↗
PubMed1989

Cat red nucleus activity preceding movement depends on initiation conditions.

The activity of 98 Red Nucleus neurons was recorded in 3 cats operantly conditioned to perform a ballistic forelimb flexion movement triggered after a brief sound in a simple Reaction Time condition, or Delayed after the same sound in the presence of a tone cue. Fifty-eight task related neurons presented changes of activity in either one or both conditions. Forty-four of them were studied quantitatively and classified in 3 categories: 1) only 16% of the units presented similar changes of firing preceding the triggered or delayed movement; 2) most units (55%) presented different changes of activity in the two conditions: in the Delayed condition, the activation occurred earlier before the movement, and/or the change in magnitude was reduced or the pattern of activity was modified; 3) moreover, for 29% of the units, the change of activity observed before movement in the Reaction Time condition was severely reduced or even absent in the Delayed condition. For some of these neurons a building-up of activity was observed very early in the Reaction Time condition, during the preparatory period, well before the occurrence of the conditioned stimulus. These results show that the Red Nucleus activity preceding a movement is clearly dependent on its initiation conditions. The distinct patterns of unit firing observed in the Reaction Time condition and in the Delayed condition are tentatively related to the different preparation and initiation constraints determined by the behavioral conditions.

Action Potentials↗
PubMed1990

The use of conditioned cues associated with air hunger as reinforcers: a case report.

During the operant conditioning of eating behavior with a 3-year-old boy who breathed with the aid of a respirator, it was discovered serendipitiously that the patient had apparently associated certain secondary cues with the experience of air hunger. An attempt was made to use these cues as secondary reinforcers to condition eating behavior. The results were dramatic. Implications for the use of conditioned cues associated with air hunger as secondary reinforcers in the conditioning of respiratory, and possibly other, patients are discussed.

Anorexia↗
PubMedDate not supplied

"Reinforcement" in behavior theory.

In its Pavlovian context, "reinforcement" was actually a descriptive term for the functional relation between an unconditional and a conditional stimulus. When it was adopted into operant conditioning, "reinforcement" became the central concept and the key operation, but with new qualifications, new referents, and new expectations. Some behavior theorists believed that "reinforcers" comprise a special and limited class of stimuli or events, and they speculated about what the essential "nature of reinforcement" might be. It is now known that any stimulus can serve a reinforcing function, with due recognition of such parameters as subject species characteristics, stimulus intensity, sensory modality, and schedule of application. This paper comments on these developments from the standpoint of reflex behavior theory.

Animals↗
PubMed1988

Electrical safety during electrophysiological testing.

This report describes the inadvertent induction of non-sustained atrial and ventricular arrhythmias due to the malfunction of a programmable cardiac stimulator. The malfunction occurred when line power resumed after a brief municipal power outage ("blackout") during an invasive electrophysiological study. The stimulator spontaneously delivered very high frequency pulses through the electrode catheter to the myocardium which resulted in atrial and ventricular arrhythmias. During bench testing, the stimulator delivered a continuous train of high frequency output pulses (greater than or equal to 1 mA) when line voltage resumed normal level after it had dropped below 65 VAC. Electrical safety during electrophysiological testing requires a stimulator design which is immune to altered operating conditions, and which shuts down if abnormal operating or output conditions are detected.

Arrhythmias, Cardiac↗
PubMed1982

Plasma lactate levels during baseline and blood pressure conditioning in the baboon.

Lactic acid in arterial blood, systolic and diastolic blood pressures, and heart rates of baboons were examined for three naive subjects, and for five experimental subjects during baseline conditions and during training to elevate diastolic blood pressure through operant conditioning methodology. Lactic acid and cardiovascular levels were determined at rest (9 a.m.), and at 12:30 and 3:00 p.m. (during conditioning sessions, for trained subjects). At rest (baseline) lactic acid levels and cardiovascular measures were similar for conditioned and naive subjects. During conditioning sessions, blood pressures but not heart rates were significantly elevated. Plasma lactate increased from morning to afternoon in both naive and trained subjects, but at three hours of conditioning, trained subjects had significantly higher lactate levels than when at rest and when compared to naive subjects at the same time of day. This study provides normative data for plasma lactate in the laboratory baboon and also indicates metabolic changes (which may be related to increased muscular work) as part of concurrent changes in multiple systems (e.g., neural, hormonal) which accompany conditioned blood pressure elevations.

Animals↗
PubMed1986

Activities of single neurons in midbrain and thalamus of cats during conditioned nocifensive behavior.

Extracellular recordings of neuronal activity were performed in 3 conscious cats in the rostral mesencephalic reticular formation (MRF) and in the nucleus posterior (PO) of the thalamus. The animals were trained by operant conditioning to operate a panel switch with a forepaw to escape a noxious cutaneous heat stimulus. We recorded 12 neurons in the MRF, which responded in association with this nocifensive behavior. Some of the neurons increased their firing rate before the noxious stimulus was terminated, whereas other neurons responded immediately afterwards. The activity of these neurons, however, could be related to the animal's behavior, which was independent of the noxious stimuli. It was found that the neurons showed changes in firing patterns when the animal reacted to a discriminative light stimulus in order to obtain a milk reward. In the PO of the thalamus we did not find any neurons, which could be activated by noxious heating or any nocifensive-related behavior. Modification of the discharge patterns, however, occurred in relation to sensory events and behavioral acts.

Animals↗
PubMedDate not supplied

Conditional fear, anxiety, and morphine-seeking behavior.

Two Cebus albifrons monkeys were given discriminative operant conditioning with visual stimuli, with Sidman avoidance and punishment as the components. The instrumental response was an unelicited increase in skin conductance. Both animals had surgically implanted catheters for automatic injection of morphine into the heart. After autonomic conditioning, the animals were given the opportunity to self-administer the morphine by touching the primate press panel that displayed the visual stimuli. One contingency-free segment per session was used for morphine injection, while the contingencies remained in force during the other segments. One of the monkeys made significantly more skin conductance responses during avoidance than during punishment, and this monkey received ten times as many shocks in punishment. This monkey also made more responses overall and had a much higher heart rate than the other animal. The other monkey did not differentiate significantly autonomically and received equal numbers of shocks in avoidance and punishment. The monkey that showed autonomic differentiation made significantly (and increasingly) more panel-presses during punishment than during avoidance. The other animal showed hardly any tendency at all to panel-press.

Animals↗