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PubMed1977

Tolerance to the effects of delta9-THC on shuttle-box performance and body temperature.

Two groups of rats were trained in a shuttle-box and received delta9-tetrahydrocannabinol (delta9-THC), either before or after being tested. The drug-before group showed tolerance--within 3-6 sessions--to the response-inhibiting effect of THC. The drug-after animals appeared also to be tolerant when they received delta9-THC before being tested. It is concluded that the tolerance to this effect probably is not learned, but has a physiological base. This is corroborated by the finding that during the same study all the animals developed tolerance to the hypothermic effect of delta9-THC.

Animals↗

PubMed1992

Investigation of beta-adrenergic modulation of synaptic transmission and postsynaptic induction of associative LTP in layer V neurones in slices of rat sensorimotor cortex.

Long-term potentiation (LTP) of synaptic transmission is considered to be a neuronal model of learning. Recently, the probability of induction of associative LTP in layer V cells in sensorimotor neocortex was shown to be much higher in the awake cat than in the slice preparation. We hypothesised that the loss of extrinsic noradrenergic activity in the slice might account for this difference, particularly since a beta-adrenergic enhancement of field potentials has been seen in this preparation. We therefore bath-applied noradrenaline (NA) or the beta 1-adrenergic agonist, isoprenaline (ISO) to elucidate the cellular basis of the enhancement of field potentials, and to see if the drugs increased the probability of induction of associative LTP in slices. We found that NA and ISO produced a dose-dependent, reversible reduction of spike accommodation and an increase in excitability but had no effect on the depolarizing slope or peak amplitude of sub-threshold EPSPs, and that drug application did not increase the probability of induction of LTP. We conclude that: (1) the enhancement of field potentials and late components of EPSPs (7) can be explained by the known actions of beta-adrenergic drugs on membrane currents in layer V cells, and (2) the lower probability of induction of associative LTP in slices cf. the awake cat cannot be due solely to the loss of noradrenergic activity.

Animals↗

PubMed1994

Plasticity in auditory cortical circuitry.

Recent studies have focused on the mechanisms and conditions yielding the short- and long-term plasticity exhibited by neuronal responses in the primary auditory cortex of adults. These investigations have examined factors operating at the cellular and intercellular levels, the effects of global behavioral states and the role of the cholinergic system, which could mediate between the global and local levels. A behaviorally gated unsupervised Hebbian-covariance rule can explain most of the bottom-up driven changes that were observed following sensory manipulation. However, additional supervised learning mechanisms are probably required to generate behavioral improvement. This suggestion has not yet been tested directly.

Animals↗

PubMed2005

Sequential behavior in the rat: a new model using food-reinforced instrumental behavior.

Sequential behavior, probably reflecting procedural learning, has intensively been investigated in humans. This work has mainly been done using so-called serial reaction time tasks. In such tasks, subjects have to respond rapidly to simple visual stimuli appearing at one of four locations by pressing a corresponding response key. Unknown to the subjects, these stimuli can follow a specific repeating sequence. Learning of such a sequence is typically inferred from faster reaction times to sequence as compared to random blocks of stimuli. In contrast to human subjects, the analysis of sequential behavior has received considerably less attention in rodents, possibly due to the lack of analogous animal models there. In order to establish such a model, a method was developed in rats to investigate serial reactions under conditions of random or sequential stimulus presentation. Operant testing chambers were used which consisted of four nose-poke holes with cue lights. These holes were arranged in a square fashion with a pellet receptacle in the center. The task of the rat was to rapidly respond to an illuminated hole by poking into it in order to obtain food. The stimulus locations varied permanently, and these changes pursued either a random or serial order. In three experiments with differing methodological details, responding under such conditions was analyzed with sequences consisting of 6, 12 or 13 positions. Evidence was obtained that rats can improve their performance under sequence as compared to random conditions, for example, with respect to the percentage of reinforcements obtained, or with respect to reaction times. Furthermore, methodological factors, like response requirements, were addressed which may critically affect experimental outcome. Together, this new kind of instrumental task might be useful to analyze sequential performance in the rat, and the brain mechanisms by which it is mediated.

Analysis of Variance↗

PubMed2006

The serial reaction time task in the rat: effects of D1 and D2 dopamine-receptor antagonists.

Sequential behaviour, probably reflecting procedural learning, has intensively been investigated in humans and monkeys using so-called serial reaction time tasks (SRTT), where serial stimuli are either presented in a random or sequential fashion. Learning of sequences is typically inferred from faster reaction times to such sequences as compared to random blocks of stimuli. Work with such tasks has shown that sequential behaviour seems to be mediated by specific brain systems, including the basal ganglia and the neurotransmitter dopamine. We have recently developed a rat version of the human serial reaction time task, in which rats have to respond to visual stimuli in one of four spatial locations by nose-poking in order to obtain food reward under a fixed ratio schedule (FR13). Here, we used a test version where random and sequential condition phases (10 min each) were alternated within-sessions. In support of our previous work, we found that well-trained (i.e. skilled) rats display superior performance under sequential than random conditions, namely, faster reaction times and higher response accuracies. Furthermore, we investigated the effects of selective dopamine-receptor blockade, by systemically administering SKF 83566, a D1 antagonist (.05-.15 mg/kg), or raclopride, a D2 antagonist (.05-.20 mg/kg), in two separate experiments. Both antagonists impaired responding to the conditioned visual stimuli in a dose-related way, i.e. they decreased, or even blocked, nose-poke rates. In those rats, which kept responding, the speeding of reaction times during sequential conditions was no longer observed with the D1 antagonist, whereas the enhancements in accuracy were preserved, or even enhanced as compared to vehicle. The D2 antagonist also impaired instrumental behaviour, but did not alter sequence effects on accuracy or reaction times. In contrast to responses to the conditioned stimuli, reaction times to the unconditioned stimuli (food pellets) were not substantially affected by either drug. These results are discussed with respect to methodological factors, and the possible role of dopamine for instrumental behaviour, in general, and sequential behaviour, in specific.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2006

Dynamic changes of apoptosis and expression of Bcl-2 family members in the posthatch hippocampus of Bengalese finches.

The hippocampus of songbirds plays an important role in spatial memory, and probably in song learning. Although prolonged neuronal generation and apoptosis are thought to be closely correlated with memory function, natural changes of the number of neurons and in apoptosis in the hippocampus of songbirds have not been fully investigated during development and in the adult. In the current study, we examined developmental changes in the volume and the number of neurons and apoptotic cells in the hippocampus of songbirds (Lonchura striata) from posthatch day (P5) to adulthood. Apoptotic cells were determined by Nissl staining and immunohistochemistry for cleaved caspase-3, a key apoptotic caspase executioner. The expression levels of Bcl-2 family member mRNA and protein, including Bcl-2, Bcl-xL and Bax, were also investigated. Our results indicated that: (1) the hippocampus volume significantly increased from P5 to P60, although the number of neurons remained stable in all studied stages; (2) the number of apoptotic cells was highest at P45, based either on the Nissl staining or on the immunohistochemistry for caspase-3; (3) Bcl-2 mRNA expression was high from P5 to adulthood, while Bax mRNA declined abruptly from P5 to adulthood, and Bcl-x mRNA was high after P45. Bcl-2 protein was only detected at P5 and P15, while detection of Bcl-xL and Bax proteins paralleled levels of mRNA expression. Our study provides detailed changes of apoptosis in the posthatch songbird hippocampus, suggesting an important role for caspase-3 and Bcl-2 family members in hippocampus apoptosis.

Age Factors↗

PubMed1996

Bisection and perception of horizontal lines in normal children.

Simple line bisection is a complex task in which both perceptual/attentional factors and motor factors are involved. Using a judgment task on prebisected lines it is possible to assess independently the role of perceptual/attentional factors. The judgment-bisection relationship was investigated in 37 preschool children aged 4-5 and 70 school children aged 10-12. At bisection, a clear shift of the right hand with age from right to left bisections was observed, more pronounced in right- than in left-handers, and probably related to learned patterns. At judgment, a slight but significant left side overestimation was observed. In right-handers, judgment was related to left-hand but not to right-hand bisection. It is concluded that motor (manual) factors strongly influence visuo-motor bisection in normal children, and it is suggested that the judgment-bisection relationship has to be systematically investigated when bisection is used as a task informing on space perception or on direction of attention.

Adolescent↗

PubMed1999

Auditory cortical plasticity: a comparison with other sensory systems.

The auditory cortex has a crucial role in higher cognitive functions, including the perception of speech, music and auditory space. Cortical plasticity, as in other sensory systems, is used in the fine tuning of the auditory system for these higher functions. Auditory cortical plasticity can also be demonstrated after lesions of the cochlea and it appears to participate in generating tinnitus. Early musical training leads to an expansion in the representation of complex harmonic sounds in the auditory cortex. Similarly, the early phonetic environment has a strong influence on speech development and, presumably, on the cortical organization of speech. In auditory spatial perception, the spectral cues generated by the head and outer ears vary between individuals and have to be calibrated by learning, which most probably takes place at the cortical level. The neural mechanisms of plasticity are likely to be the same across all cortical regions. It should be useful, therefore, to relate some of the findings and hypotheses about auditory cortical plasticity to previous studies of other sensory systems.

Animals↗

PubMed2000

Is Argentina ready for managed care?

The author describes the evolution and present status of health insurance and prepaid medical care in Argentina, with particular reference to the opportunities for the development of managed care systems and techniques there. He claims that as US health care corporations enter that country's marketplace there are lessons to be learned that will probably be applicable in other countries of the Americas.

Argentina↗

PubMed2000

After-effects of the common cold on mood and performance.

The present study examined whether volunteers who had recently had common colds showed impairments in mood and performance in the weeks following the illness. All volunteers (n = 24) were tested when healthy to provide baseline data for simple and choice reaction time tasks, attention and memory tasks and ratings of mood. When participants developed a cold (n = 13) they returned to the laboratory so that the illness could be verified. When they were symptom free they returned to the laboratory and repeated the procedure. They then completed the study with a final session 1 week later. Volunteers (n = 11) who remained healthy over 10 weeks were recalled as controls and also repeated the procedures. The results showed that those who had recently had colds showed few impairments in mental performance and mood. Taken together with the results of previous studies, this suggests that after-effects of viral infection are largely restricted to severe illnesses such as infectious mononucleosis and influenza. After-effects of colds may occur but these probably reflect poor learning at the time of the illness.

Adolescent↗

PubMed1976

Dietary fiber and diverticular disease.

Can the regular consumption of bran and other fibrous foods help in preventing diseases of the colon? Indirect evidence supports the idea, although much remains to be learned. It seems probable that bulkier feces could increase the diameter of the colon and prevent sudden sharp rises in pressure that are believed to be responsible for the formation of diverticula. For most people, fiber is probably harmless and it may do some good.

Cellulose↗

PubMed2001

If the NHS introduced a '50 procedures a year' policy, what proportion of consultant firms would be affected?

BACKGROUND: Governments, insurers, quality assurance agencies and others have used the higher volume = better quality relationship as a basis for health policy. This relationship is probably real enough to justify these policies. However, even if it were not real, there are other reasons why these and other organizations such as the National Health Service (NHS) may favour high-volume providers. This paper attempts to answer the question: 'If, for common elective procedures, the NHS instituted a high-volume purchasing policy that requires consultant firms to perform a minimum of "50 procedures a year", what proportion of consultant firms would be affected?' The aims of this study were to estimate the proportion of NHS consultant firms that perform common elective procedures less than 50 times a year and to estimate the proportion of firms that would have to stop providing these procedures if a '50 procedures a year' purchasing policy were introduced. METHOD: A descriptive analysis was carried out and modelling was performed on data stored in an NHS health episode statistics database of patients treated in West Midlands NHS facilities. For each of 12 common elective procedures we assumed that a volume threshold of at least 50 a year were set, and calculated the proportion of NHS consultant firms undertaking each procedure who performed less than 50 of those procedures each year and the proportion of firms who would have had to stop providing each procedure. RESULTS: All firms performing some procedures, e.g. cataract extraction, did so at least 50 times a year. By contrast, no firm repaired more than 50 recurrent inguinal hernias a year. If a volume threshold of at least 50 procedures a year were set for a basket of 12 common elective procedures, then about 40 per cent of firms would no longer be eligible to provide a procedure. Even if a lower 'one a month' threshold were set, about 20 per cent of firms would still not be eligible to provide that procedure. CONCLUSION: Introduction of a high-volume policy would affect a considerable number of firms, as many NHS consultant firms perform some common elective procedures infrequently. Some consultants would see the introduction of a high-volume policy as an opportunity to further specialize and super-specialize. Others would see it as a policy that restricts them to providing a narrower range of procedures, makes their professional practice less interesting, and reduces their professional autonomy. Postgraduate training institutions need to consider the possibility and implications of high-volume policies, as many junior doctors would probably need to learn to provide a narrower range of skills than at present.

Elective Surgical Procedures↗

PubMed1996

Neurophysiological correlates of mental arithmetic.

Thirteen subjects were extensively trained on nine multiplication problems varying in difficulty. Practice was associated with a reaction time speed up and an attenuation of the problem size effect. The introduction of previously unpracticed problems led to a performance rebound to pretraining levels, indicating practice specificity. The eventrelated potentials were characterized by a late positive complex, followed by a positive slow wave. Offset latency of positive slow wave and preresponse amplitude at parietal electrodes showed practice specificity effects that systematically changed with practice and problem size, indicating an association with the load imposed on working memory. The peak of the late positive complex probably reflects task learning or adaptation effects because it was attenuated by practice predominantly at frontal electrodes, showed no practice specificity, and was not affected by problem size.

Adult↗

PubMed1978

Measurement of delay of gratification.

To determine if psychoanalytic and social learning theorists are referring to the same phenomenon when they speak of "delay of gratification", 26 college undergraduates were divided into high and low groups on the basis of their scores on a "money-spending" questionnaire (a social learning measure). The difference between these two groups with respect to Rorschach M responses (the psychoanalytic measure) was nonsignificant. It was suggested that psychoanalytic and social learning theorists are probably referring to different phenomena when they speak of "delay of gratification."

Journal Article↗

PubMed1997

Sheltered homeless children: their eligibility and unmet need for special education evaluations.

OBJECTIVES: This study described the proportion of sheltered homeless children in Los Angeles, Calif, who were eligible for special education evaluations because of a probable behavioral disorder, learning disability, or mental retardation, and to explore their level of unmet need for special education services. METHODS: This was a cross-sectional study of 118 parents and 169 children aged 6 through 12 years living in 18 emergency homeless family shelters in Los Angeles County, California. Parents and children were interviewed with standardized mental health and academic skill measures in English and Spanish. RESULTS: Almost half (45%) of the children met criteria for a special education evaluation, yet less than one quarter (22%) had ever received special education testing or placement. The main point of contact for children with behavioral disorders and learning problems was the general health care sector. CONCLUSIONS: School-aged sheltered homeless children have a high level of unmet need for special education evaluations, the first step toward accessing special education programs. Interventions for homeless children should include integration of services across special education, general health care, and housing service sectors.

California↗

PubMedDate not supplied

Effects of a psychiatric liaison program on internists' ability to assess psychosocial problems.

The ability to assess psychosocial problems of a group of primary care internal medicine residents education in a relatively unstructured psychiatric liaison program was compared to a group of internists who had no specialized psychiatric training. The primary care residents did not demonstrate a superior ability to assess patients' psychosocial problems when compared to internists without such training. The effectiveness of such unstructured liaison experiences (i.e., the Balint model of group supervision and teaching conferences) is questioned. The authors suggest that the main benefit of such informal approaches may lie in gaining initial attitudinal and administrative acceptance by nonpsychiatric physicians of liaison teaching programs. Formally structured, supervised learning experiences are probably necessary to effectively enhance internists' clinical skills and behaviors in dealing with the psychosocial and psychiatric aspects of medical care.

Colorado↗

PubMed1996

The utilization rate and pregnancy outcome of multifetal pregnancy reduction in the Nordic countries.

OBJECTIVE: To review the utilization rate and pregnancy outcome of multifetal pregnancy reductions (MFR) in the Nordic countries during the period January 1986-June 1992. STUDY DESIGN: All centers offering assisted conception in Denmark, Finland, Norway and Sweden were retrospectively surveyed by means of a questionnaire with regard to the number and methods used for MFR, pregnancy loss and the outcomes of the pregnancies. The response rate was 100%. RESULTS: During the period studied, 185 births of triplets or higher multiples occurred in Sweden, 120 in Finland and 102 in Denmark. MFR was performed in 42 women (Sweden 26, Finland 10, Denmark 6) but not in Norway at all. This gives an estimated average utilization rate of 1/7 multiple births of three or more in Sweden, 1/17 in Denmark and 1/12 in Finland. The most frequently used method was intracardiac or intrathoracic injection of a potassium chloride solution in gestational weeks 9-12. One pregnancy was reduced from seven to four fetuses, two from five to three, 10 from five to two, one from four to three, 17 from four to two, one from four to one, five from three to two, four from three to one and one from two to one. Nine (21%) pregnancies terminated in a spontaneous abortion within one week (n = 2) to several weeks (n = 7) after the procedure. Of the remaining 33 (79%) pregnancies which continued to delivery, two fetuses died in utero in the second trimester, three infants died perinatally and one child had transverse limb reduction defects. A successful pregnancy defined by the discharge home of at least one infant occurred in 79% of the cases. CONCLUSION: This study gives national estimates on the utilization rate of MFR. Although MFR is performed more frequently in Sweden than in Denmark and Finland, the overall figures remain low in the Nordic countries. The incidence of pregnancy loss in this study is somewhat higher than in several larger reported series, probably reflecting the learning curve of the procedure. It seems reasonable that MFR should be performed in only a few centers in the Nordic countries.

Female↗

PubMed2002

SIDS education in nursing and medical schools in the United States.

This study suggests there is a need to support the efforts already present to include SIDS in medical and nursing school curricula. Both programs have indicated a need for audiovisual and printed teaching materials. Consideration should be given to teaching materials that are easily updated such as computer-generated materials because of the many rapid changes that take place in SIDS research. Currently, textbooks are the most common source of educational material used by students. Textbooks could be supplemented with information from recent journals and current Web sites. Facilitation of clinical contact with families affected by SIDS is important. The availability of local SIDS resources should be stressed to both medical and nursing programs as well as opportunities for nursing student involvement in the activities of SIDS organizations. While lectures are often the only feasible way to deliver SIDS content to large groups of students, interactive teaching strategies and involvement with bereaved families probably would increase learning beyond the basic level. Nursing schools as well as medical schools, confronted with the realities of decreased faculty time and budgets, face major challenges in developing case-based curricula that prepare students for the next century (Zimmerman et al., 1997). To address these needs, curriculum notes were developed by the Education Working Party of the SIDS Global Strategy Task Force under the direction of Professor John C. Vance and printed in February 1998. The curriculum is divided into seven modules that include content and questions as well as references on a variety of issues. A problem-based learning package is included and is becoming increasingly popular as a teaching strategy (Amos & White, 1998; David & Patel, 1995). There is one case each for medical and nursing students in the curriculum package. This curriculum can be accessed at www. sidsaustralia.org.au. Other useful Web sites include: www.sidsalliance.org. The SIDS Alliance Web site provides support to families and information about SIDS. www.sidscenter.org. The National SIDS Resource Center Web site provides information and technical assistance for parents and professionals on SIDS and related topics. www.aap.org. The American Academy of Pediatrics Web site provides guidelines on sleep position and infant sleeping environment. www.asipl.org. The Association of SIDS and Infant Mortality Programs Web site includes publications and position papers. Finally, many states have SIDS services provided by professional programs and parent organizations. Students have the opportunity to work with these organizations to provide bereavement services and risk-reduction education. The organizations listed above can be contacted for further information.

Curriculum↗