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At least 1,783 records · Page 99Linked to original sources
PubMed2001

Changing behavior within session: cyclicity and perseverance produced by varying the minimum ratio of a variable-ratio schedule.

Four pigeons repeatedly chose between a fixed-ratio (FR) 20 and a variable-ratio (VR) 40 schedule of reinforcement, in which the minimum ratio of the VR cycled within each session. The minimum ratio ascended and descended (ASCDESC), descended and ascended (DESCASC), or remained constant (unchanging). In Phase 1, 2 birds (Group 1) were exposed to ASCDESC series and 2 birds (Group 2) were exposed to the DESCASC series. Choice proportions changed with the cycling minimum ratio for Group 2 but not for Group 1. In Phase 2, Group 1 subjects were exposed to the DESCASC series and Group 2 subjects were exposed to the unchanging condition. Although Group 1's choice proportions appeared to be undifferentiated in Phase 2, Group 2's choice proportions continued to cycle for more than 100 sessions. Group 2 subjects were then moved to the ASCDESC series in the third phase, and choice proportions cycled with the minimum ratio as in the first phase. The descending portion of the series was the more powerful determinant of cyclicity. Response rates also changed with the minimum component ratio, a finding that goes against the claim of universality of a rise-and-fall within-session pattern of responding. That preference varied despite the constancy of the average ratio requirement suggests nonlinear averaging in quantitatively representing a variable schedule's value. The strong perseverance observed also lends support to a growing body of literature on history effects.

Animals↗
PubMed2006

Differential involvement of the central amygdala in appetitive versus aversive learning.

Understanding the function of the distinct amygdaloid nuclei in learning comprises a major challenge. In the two studies described herein, we used c-Fos immunolabeling to compare the engagement of various nuclei of the amygdala in appetitive and aversive instrumental training procedures. In the first experiment, rats that had already acquired a bar-pressing response to a partial food reinforcement were further trained to learn that an acoustic stimulus signaled either continuous food reinforcement (appetitive training) or a footshock (aversive training). The first training session of the presentation of the acoustic stimulus resulted in significant increases of c-Fos immunolabeling throughout the amygdala; however, the pattern of activation of the nuclei of the amygdala differed according to the valence of motivation. The medial part of the central amygdala (CE) responded, surprisingly, to the appetitive conditioning selectively. The second experiment was designed to extend the aversive versus appetitive conditioning to mice, trained either for place preference or place avoidance in an automated learning system (INTELLICAGE). Again, much more intense c-Fos expression was observed in the medial part of the CE after the appetitive training as compared to the aversive training. These data, obtained in two species and by means of novel experimental approaches balancing appetitive versus aversive conditioning, support the hypothesis that the central nucleus of the amygdala is particularly involved in appetitively motivated learning processes.

Acoustic Stimulation↗
PubMed1977

Schizophrenic subtypes and differential responsiveness to reward and punishment.

Variations in responsivity to primary, secondary asocial and interpersonal rewards and punishments between major schizophrenic subgroups were investigated in a probability learning study. The subgroups compared were process and reactive, paranoid and nonparanoid, long- and short-hospitalization, and long- and short-length of illness schizophrenics. No evidence of differential responsivity to these reward-punishment/modality combinations appeared between high and low scorers on any of the four schizophrenic subgrouping dimensions. The groups then were matched closely so that the effects of each individual difference measure could be evaluated independently of the other three. Again, no significant differences in responsiveness to the reinforcement/modality combinations appeared. The results do not support the view that any of the four dimensions relate to differential responsiveness to primary, secondary asocial or verbal reward or punishment--at least on relatively simple tasks.

Adult↗
PubMed2004

Verbal selective learning after traumatic brain injury in children.

Selective learning (SL), the ability to select items to learn from among other items, engages cognitive control, which is purportedly mediated by the frontal cortex and its circuitry. Using incentive-based auditory word recall and expository discourse tasks, we studied the efficiency of SL in children ages 6 to 16 years who had sustained severe traumatic brain injury (TBI) at least 1 year earlier. We hypothesized that SL would be compromised by severe TBI. Results indicated that children with severe TBI performed significantly worse than age-matched typically developing children on word- and discourse-level measures of SL efficiency with no significant group differences in number of items recalled from auditory word lists or declarative facts. We conclude that severe TBI disrupts incentive-based cognitive control processes, possibly due to involvement of frontal neural networks.

Acoustic Stimulation↗
PubMed1979

Facilitating generalization of on-task behavior through self-monitoring of academic tasks.

This study (1) examined whether a self-monitoring procedure taught in a laboratory setting would increase independent on-task behavior there and would generalize without further teaching to a classroom setting, and (2) analyzed the durability of the training effects over the course of 5 months for one subject and 10 months for two other subjects. Two multiple-baseline designs, one across three normal and the other across three deviant children, showed that self-monitoring of academic task-completions facilitated on-task responding for all subjects in the generalization (classroom) setting. A subsequent reversal design showed that these effects were durable, in two of the three subjects still available, at least as much as 1 year after commencement of training. This latter design also suggested that one subject who was not maintained by self-monitoring could be supported in on-task behavior by a peer who was maintained by self-monitoring.

Behavior Therapy↗
PubMed1995

Cocaine's effects on speech sound discriminations and reaction times in baboons.

Three adult baboons were trained using a psychophysical procedure to discriminate between different synthetic vowel sounds [symbol: see text]. Baboons pressed and held a lever down to produce a pulsed train of a single reference vowel that served as the standard stimulus. Animals were trained to release the lever only when this standard vowel sound changed to one of the four remaining comparison vowels. A lever release within 1.5 s of this change in vowel sounds was defined as a correct detection of the change from the standard vowel to one of the comparison vowels, and was reinforced. All baboons readily learned the vowel discriminations and detected vowel changes at the 90-100% correct performance level. Acute IM administration of cocaine prior to test sessions (0.00032-3.2 mg/kg) produced dose-dependent decrements in vowel discriminability. At the same time, cocaine shortened lever release latencies (reaction times) to the vowel stimuli in two of three baboons. The cocaine-induced decrements in vowel discriminability were correlated with the degree to which frequency differences occurred among the different vowels in that lower vowel discriminability scores were found for those vowels with smaller spectral differences from the standard vowel. Further, false alarm rates were not systematically affected by cocaine, indicating that the cocaine-induced decrements in vowel discrimination accuracy occurred in the absence of systematic changes in the reliability of the baboons' discrimination performances.

Acoustic Stimulation↗
PubMed1991

Effects of tetrahydroaminoacridine (THA) on functional recovery after sequential lesion of the entorhinal cortex.

Unilateral lesions of rat entorhinal cortex produce a transitory performance deficit on spatial learning tasks, such as reinforced alternation in a T-maze. Tetrahydroaminoacridine (THA), a cholinesterase inhibitor, was administered to determine its effects on behavioral recovery using a reinforced alternation task in a T-maze. Rate of recovery after unilateral entorhinal lesion was not affected by a low dose of THA (0.05 mg/kg), while a higher dose (5.0 mg/kg) impaired recovery. Behavioral recovery was subsequently evaluated in the same rats following lesions to the contralateral entorhinal cortex. Serial bilateral lesions of the entorhinal cortex are known to produce a prolonged performance deficit on the alternation task. The 0.05 mg/kg THA group exhibited an intermediate rate of recovery, between the undamaged control group and bilateral lesion-saline injected groups. The group receiving 5.0 mg/kg of THA after bilateral lesion did not differ from the bilateral lesion-saline group. The failure of THA to significantly improve functional recovery in rats with lesions of the entorhinal cortex indicates that the compound may have limited applicability in treating human neurodegenerative disorders such as Alzheimer's disease.

Acetylcholinesterase↗
PubMed1987

Effects of methsuximide and mephenytoin on the behavior of pigeons under a repeated acquisition procedure.

Learning impairment is a potentially serious side effect of antiepilepsy medications. The present study investigated the effects of methsuximide and mephenytoin on learning in pigeons performing under a repeated acquisition procedure. Given acutely, methsuximide (25, 50, 75, and 100 mg/kg) and mephenytoin (60, 120, and 240 mg/kg) produced generally dose-dependent decreases in rates of responding. High doses of each drug increased overall errors; a within-session analysis of error distributions also indicated learning impairment.

Animals↗
PubMed2004

Apoptosis: pathophysiology and therapeutic implications for the cardiac surgeon.

Cardiomyocyte apoptosis has been associated with the pathogenesis of heart failure as well as ischemic and inflammatory myocardial conditions. The aim of this study is to give a critical synopsis of cardiomyocyte apoptosis and identify methods to prevent or attenuate apoptosis in patients undergoing cardiac surgery. Clinical conditions and agents associated with decreased apoptotic index are early repair or replacement of valvular pathology before deterioration of ventricular function, afterload reduction with medication or intraaortic balloon pulsation in patients with acute increase in afterload or in hemodynamically compromised patients, decreasing catecholamine-induced cardiotoxicity by using beta-blockers, phosphodiesterase inhibitors, or early insertion of intraaortic balloon pulsation or ventricular assist device. Prompt coronary revascularization, which reduces myocardial ischemia time, is the most effective antiapoptotic therapy. Reduction of myocardial apoptosis associated with cardiopulmonary bypass and aortic cross-clamping are other therapeutic targets. Some investigational therapies include ischemic preconditioning and use of antiapoptotic medication such as the caspase inhibitors, antioxidants, calcium-channel blockers, the insulin-like growth factor-1, and the poly-adenosine diphosphate-ribose-synthetase inhibitors. Most of the therapeutic implications in reducing cardiomyocyte apoptosis are still in the experimental phase. Some options are already incorporated in the clinical practice of the cardiovascular surgeon. New therapeutic considerations include avoiding sustained and long-term use of catecholamines and reducing or avoiding cardiopulmonary bypass-when clinically feasible. Noncatecholamine inotropes should be preferred for patients undergoing heart failure surgery and for patients with low output syndrome after open-heart surgery. The lessons learned from apoptosis research reinforce more liberal and early insertion of intraaortic balloon pulsation or ventricular assist device in clinical low output states.

Animals↗
PubMed2006

Training delays reduce the choose-short effect with keylight, but not with food, duration samples in pigeons.

Pigeons were trained to match 2- and 8-s food samples. The delay on training trials was either 0s (group 0sF), 5s (group 5sF), or varied between 2 and 8s (M=5s, group 5sV). Testing at a delay that exceeded the training delay by 15s in each group revealed a robust choose-short effect in each group. The same pigeons then reacquired a previously trained matching task involving 2- and 8-s keylight samples. Different comparison stimuli were used on food-sample and keylight-sample trials. The delay on training trials was the same on both food- and keylight-sample trials. Extended-delay testing revealed a robust choose-short effect in all three groups when the durations were conveyed by food presentations, but only group 0sF revealed a choose-short effect when the durations were conveyed by keylight presentations. Hence, training with a nonzero delay, whether fixed or variable, reduces the choose-short effect with keylight durations but not with food durations. It was concluded that at least some of the psychological processes mediating performance differ as a function of the event that conveys the duration.

Animals↗
PubMed2004

Long-term behavioural alterations in female rats after a single intense footshock followed by situational reminders.

Post-traumatic stress disorder (PTSD) affects a vulnerable sub-population of individuals exposed to a traumatic event. This psychopathology induces long-lasting hypothalamo-pituitary-adrenal (HPA) axis hypoactivity, hyperarousal and avoidance of trauma-like situation. PTSD also manifests a high co-morbidity with anxiety disorders. The aim of the present study was to characterise long-term biobehavioural alterations in female rats in an animal model of PTSD consisting in an intense footshock (2 mA, 10s) followed by three weekly situational reminders. This procedure induced several long-term alterations: increased anxiety behaviour, reduced time spent in an 'aversive-like' context, altered social behaviour and blunted corticosterone response to stress. These results demonstrate that exposure to an intense footshock associated with repeated situational reminders elicited long-term disturbances which lasted more than 1 month after the footshock administration. Our findings suggest that this paradigm could provide a useful animal model of PTSD.

Animals↗