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PubMed2000

Neural correlates of memory organization deficits in schizophrenia. A single photon emission computed tomography study with 99mTc-ethyl-cysteinate dimer during a verbal learning task.

Regional cerebral blood flow (rCBF) during a verbal learning task was measured using 99mTc-ethyl-cysteinate dimer and single photon emission computed tomography in 10 patients with schizophrenia and nine normal controls. Verbal repetition was used as a control task. The schizophrenic patients showed failure to spontaneously utilize implicit category information to learn the word lists. In the normal controls, rCBF in the left inferior frontal and left anterior cingulate regions was significantly increased during the verbal learning task, compared with the verbal repetition task. In contrast, there was no significant frontal lobe activation by the verbal learning in the schizophrenic patients. The patients had lower rCBF during the verbal learning task than the controls in the bilateral inferior frontal, left anterior cingulate, right superior frontal, and bilateral middle frontal regions. Activation in the left inferior frontal region was significantly positively correlated with categorical clustering in the task in the controls, but no such correlation was found in the patients. These results indicate that memory organization deficits in schizophrenia may be related to dysfunction in the prefrontal areas, especially in the left inferior frontal region.

Adult↗

PubMed1995

Propofol blood concentration and the Bispectral Index predict suppression of learning during propofol/epidural anesthesia in volunteers.

Propofol is often used for sedation during regional anesthesia. We tested the hypothesis that propofol blood concentration, the Bispectral Index and the 95% spectral edge frequency predict suppression of learning during propofol/epidural anesthesia in volunteers. In addition, we tested the hypothesis that the Bispectral Index is linearly related to propofol blood concentration. Fourteen healthy, male volunteers were studied on three randomly ordered days: no propofol, target propofol blood concentration 1 microgram/mL, and target propofol blood concentration 2 micrograms/mL. Each day, epidural anesthesia (approximately T11 level) was induced using 2% 2-chloroprocaine. Propofol was infused by a computer-controlled pump, and propofol concentration measured in central venous blood. We administered a Trivial Pursuit-type question task on all 3 days. The electroencephalogram was monitored continuously (Fp1, Fp2; reference, Cz; ground, mastoid). Propofol caused concentration-related impairment of learning. The propofol blood concentration suppressing learning by 50% was 0.66 +/- 0.1 microgram/mL. The Bispectral Index value when learning was suppressed by 50% was 91 +/- 1. In contrast, the 95% spectral edge frequency did not correlate well with learning. The Bispectral Index decreased linearly as propofol blood concentration increased (Bispectral Index = -7.4.[propofol] + 90; r2 = 0.47, n = 278). There was no significant correlation between the 95% spectral edge frequency and propofol concentration. In order to suppress learning, propofol blood concentrations reported to produce amnesia may be targeted. Alternatively, the Bispectral Index may be used to predict anesthetic effect during propofol sedation.

Adult↗

PubMed1994

Developmental changes in spatial learning in the Morris water-maze in young meadow voles, Microtus pennsylvanicus.

Spatial learning in pre- and postweaning meadow voles, (Microtus pennsylvanicus) was examined in a Morris water-maze task. The learning performance of 10-day-old (preweaning) and 15-, 20- and 25-day-old (postweaning) male and female voles was assessed by measuring the latency to reach a hidden platform by each animal twice a day for 5 days. Voles of all age groups were able to learn the spatial task with Day 10 and Day 15 voles acquiring the task more slowly than did Day 20 and Day 25 voles. There were no significant sex differences in task acquisition in any of the four age groups. In addition, although swimming speed was related to age, with older animals swimming faster than younger ones, differences in swim speed did not account for the faster acquisition by the older animals. These results show that both preweaning and postweaning voles can successfully learn a spatial task. This is in contrast to preweaning laboratory rats which cannot successfully acquire a similar spatial task. These findings indicate that there are species differences in the ontogeny of spatial learning, which are likely related to the ecological and behavioural developmental characteristics of the species. Furthermore, in contrast to the sex difference in water-maze performance obtained in adult, breeding meadow voles who demonstrate a sex difference, there were no significant sex differences in the spatial performance of the juvenile voles. This suggests that sex differences in spatial learning in the meadow vole do not appear until voles reach reproductive adulthood.

Aging↗

PubMed1990

A review of two theories of learning and their application in the practice of nurse education.

From the range of learning theories which may be applied in the practice of nurse education, two contrasting theories have been selected. The 'conditions of learning and theory of instruction' (Gagne, 1985) derives from the behaviourist perspective in psychology, and Rogers' (1983) description of learning has evolved from the Humanistic School. This discussion initially focuses on Gagne's work beginning with a review of his 'conditions of learning', and is followed by a consideration of Rogers' approach through the 'facilitation of learning' (Rogers, 1983). The respective strengths and limitations of the two theories as applied in nurse education are then compared.

Behaviorism↗

PubMed1997

Defective learning in mutants of the Drosophila gene for a regulatory subunit of cAMP-dependent protein kinase.

Disruptions of a Drosophila gene encoding a regulatory subunit of cAMP-dependent protein kinase homologous to mammalian RIbeta (dPKA-RI) were targeted to the first (noncoding) exon of dPKA-RI via site-selected P element mutagenesis. Flies homozygous for either of two mutant alleles showed specific defects in olfactory learning but not in subsequent memory decay. In contrast, olfactory acuity and shock reactivity, component behaviors required for normal odor avoidance learning, were normal in these mutants. Northern and Western blot analyses of mRNA and protein extracted from adult heads have revealed a complex lesion of the PKA-RI locus, including expression of a novel product and over- or underexpression of wild-type products in mutants. Western blot analysis revealed reductions in RI protein in mutants. PKA activity in the absence of exogenous cAMP also was significantly higher than normal in homogenates from mutant adult heads. These two mutant alleles failed to complement each other for each of these phenotypic defects, eliminating second-site mutations as a possible explanation. These results establish a role for an RI regulatory subunit of PKA in Pavlovian olfactory conditioning.

Animal Structures↗

PubMedDate not supplied

Learning in the thick of it.

The U.S. Army's Opposing Force (OPFOR) is a 2,500-member brigade whose job is to help prepare soldiers for combat. Created to be the meanest, toughest foe that soldiers will ever face, OPFOR engages units-in-training in a variety of mock campaigns under a wide range of conditions. Every month, a fresh brigade of more than 4,000 soldiers takes on this standing enemy. OPFOR, which is stationed in the California desert, always has the home-court advantage. But the force being trained--called BLU FOR--is numerically and technologically superior. It possesses more resources and better, more available data. It is made up of experienced soldiers. And it knows just what to expect, because OPFOR shares its methods from previous campaigns with BLUFOR's commanders. In short, each BLUFOR brigade is given practically every edge. Yet OPFOR almost always wins. Underlying OPFOR's consistent success is the way it uses the after-action review (AAR), a method for extracting lessons from one event or project and applying them to others. AAR meetings became a popular business tool after Shell Oil began experimenting with them in 1998. Most corporate AARs, however, are faint echoes of the rigorous reviews performed by OPFOR. Companies tend to treat the process as a pro-forma wrap-up, drawing lessons from an action but rarely learning them. OPFOR's AARs, by contrast, generate raw material that is fed back into the execution cycle. And while OPFOR's reviews extract numerous lessons, the brigade does not consider a lesson to be learned until it is successfully applied and validated. It might not make sense for companies to adopt OPFOR's AAR processes in their entirety, but four fundamentals are mandatory: Lessons must benefit the team that extracts them. The AAR process must start atthe beginning of the activity. Lessons must link explicitly to future actions. And leaders must hold everyone, especially themselves, accountable for learning.

Efficiency, Organizational↗

PubMed2003

Limit of spared pattern vision following lesions of the immature visual cortex.

Lesions of primary visual cortex sustained early in life spare certain aspects of visual processing that can be linked to expansions of bypass pathways to extrastriate cortex. They also trigger, in an age-dependent way, partial or complete transneuronal retrograde degeneration of beta (X) retinal ganglion cells, which are implicated in visual processing under conditions of low contrast. We used two-dimensional geometric patterns whose saliency was reduced by gradually increasing levels of superimposed masking lines, and by reductions in spatial contrast. Normative data were collected from intact cats, and baseline lesion data were collected from cats with lesions sustained as young adults (postnatal day 180, P180). Experimental data were collected from cats that sustained lesions on P1-3 or P26-30. For high contrast patterns, the adult group was impaired at both acquisition (sequential progressive levels of masking) and concurrent (parallel high and low levels of masking) performance, whereas the early-lesioned groups were impaired only at concurrent performance. All lesion groups were equally impaired when contrast was reduced to modest or lower levels. These results show that sparing of masked-pattern learning is limited to the high end of the spatial contrast domain.

Animals↗

PubMed1992

Protective effects of brain hypothermia on behavior and histopathology following global cerebral ischemia in rats.

The present experiments were designed to assess whether brain hypothermia can reduce the behavioral and histopathological deficits associated with global forebrain ischemia. Animals were subjected to 12.5 min of four vessel occlusion (4VO) with moderate hypotension, and brain temperature maintained at either 37 degrees C (4VO-37) or 30 degrees C (4VO-30). Behavioral tests designed to assess forelimb reflexes and sensorimotor function were given on post-operative weeks 2 and 4. Beginning in week 5, the rats were trained on a variety of navigation problems in the Morris water maze. Histopathological examination of the tissue 2 months following reperfusion revealed that 4VO-37 animals sustained substantial cell death in hippocampal region CA1 and moderate damage to the dorsolateral neostriatum. 4VO-30 animals showed minimal cell death in CA1 and neostriatum. There were no group differences for any of the sensorimotor measures, or for acquisition performance on either the simple place task or visible platform version of the water maze. In contrast, during acquisition of the learning set task, the performance of 4VO-37 animals was impaired relative to either of the other groups, whereas the performance of 4VO-30 animals was not significantly different from the sham controls. These data suggest that moderate intra-ischemic brain hypothermia provides long-lasting protection from behavioral deficits as well as neuronal injury following transient global ischemia.

Animals↗

PubMed1992

Venomous mammals.

It is not widely appreciated that mammals can be venomous in the manner of snakes and lizards. However, it was first demonstrated scientifically 50 years ago in the case of the American short-tailed shrew. Subsequently, similar evidence has been obtained from European shrews and the Haitian solenodon, but research in this area has been almost completely neglected for the last 20 years. In complete contrast to what has been learned about other animal venoms, the identity and mode of action of mammal venom toxins are still unknown. This review draws attention once more to the pioneering work undertaken in the 1940s and 1950s, exploring in more detail than hitherto why the implications of mammal venom are just as important as the chemistry and pharmacology of the phenomenon itself.

Animals↗

PubMed2006

The neural regions sustaining episodic encoding and recognition of objects.

In this functional MRI experiment, encoding of objects was associated with activation in left ventrolateral prefrontal/insular and right dorsolateral prefrontal and fusiform regions as well as in the left putamen. By contrast, correct recognition of previously learned objects (R judgments) produced activation in left superior frontal, bilateral inferior frontal, and right cerebellar regions, whereas correct rejection of distractor objects (N judgments) was associated with activation in bilateral prefrontal and anterior cingulate cortices, in right parietal and cerebellar regions, in the left putamen, and in the right caudate nucleus. The R minus N comparison showed activation in the left lateral prefrontal cortex and in bilateral cingulate cortices and precunei, while the N minus R comparison did not reveal any positive signal change. These results support the view that similar regions of the frontal lobe are involved in episodic encoding and retrieval processes, and that the successful episodic retrieval of newly learned objects is mainly based on a frontoparietal network.

Adult↗

PubMed2004

Extinction deficit and fear reinstatement after electrical stimulation of the amygdala: implications for kindling-associated fear and anxiety.

Generalized seizures produced by electrical kindling of the amygdala in laboratory rats are a widely used animal model of temporal lobe epilepsy. In addition to seizure evolution amygdala kindling enhances emotionality. The relative roles of electrical stimulation and seizure induction in fear responding are unclear. Here we investigate this issue using extinction and reinstatement of fear-potentiated startle. After classical conditioning (light+footshock pairings) laboratory rats were fear extinguished with each light presentation followed by nonepileptogenic amygdala stimulation. In contrast to the normal extinction learning of control subjects, amygdala stimulated animals exhibited conditioned fear after 120 presentations of the nonreinforced conditioned stimulus (CS). In a second experiment electrical stimulation of the amygdala restored extinguished fear responding and the fear reinstatement was specific to extinction context. The reinstatement effect did not involve sensitized fear to the CS produced by amygdala stimulation. The possibility that electrical activation of the amygdala produces unconditioned fear was considered. Animals uniformly failed to demonstrate fear-potentiated startle using electrical stimulation of the amygdala as the unconditioned stimulus. This was the case with a subthreshold afterdischarge stimulus and a stimulation schedule that produced kindled seizures. The extinction deficit and fear reinstatement results were interpreted to suggest that amygdala stimulation activates acquired excitatory stimulus-affect neural connections formed during Pavlovian fear conditioning. Our data supports a model in which excitation of an amygdala-based memory-retrieval system reinforces the expression of learned fear behaviors.

Acoustic Stimulation↗

PubMed1997

Short-term odor memory: effects of posterior transection of the lateral olfactory tract in the rat.

Rats were trained on a series of novel 2-odor discrimination problems before and after combined unilateral bulbectomy and posterior transection of the contralateral lateral olfactory tract. In postoperative tests, experimental rats performed as well as controls when a short intertrial interval (30 seconds) was used but, in contrast to controls, failed to learn a 2-odor discrimination when the intertrial interval was 10 minutes. When tested on a reversal task, controls showed memory for original learning by making many errors while experimental rats quickly acquired the task. The results suggest that lateral olfactory tract afferents to posterior olfactory cortex may play a significant role in short-term memory for odors.

Animals↗

PubMed2005

Genetic and biochemical strategies for identifying Drosophila genes that function in circadian control.

Explicit biochemical models have been elaborated for the circadian oscillators of cyanobacterial, fungal, insect, and mammalian species. In contrast, much remains to be learned about how such circadian oscillators regulate rhythmic physiological processes. This article summarizes contemporary genetic and biochemical strategies that are useful for identifying gene products that have a role in circadian control.

Animals↗

PubMed2003

Evaluation of an improved automated analysis of freezing behaviour in rats and its use in trace fear conditioning.

Pavlovian fear conditioning in rodents often involves the assessment of freezing behaviour. Since human-based scoring is labour-intensive and subject to biases, several automated methods have been proposed, but few of them have been assessed for temporal definition. An accurate method for the automated analysis of freezing in rats is presented. It is based on a comparison of contrast from successive video images (Learn. Mem. 7 (2000) 58). A major improvement involves subtracting a previously recorded image of the empty background from each frame before processing. This simple operation greatly improves reliability, since it cancels the influence of video noise outside the region of interest in the image (the rat), and can also take advantage of the movements of a patterned animal over a textured background. The technique is compared with manual scoring and with the Anagnostaras method in a trace fear conditioning experiment. The method is appropriate to monitor the time course of freezing behaviour. The same system with a different threshold can also score locomotor activity. A quantitative evaluation of the residual errors inherent to automated methods is attempted.

Algorithms↗

PubMed2000

"To every thing there is a season"--social time and clock time in addiction treatment.

Research on therapeutic interventions and the development or efficacy of treatment services consider 'time' only as a technical, 'objective' condition. Time series analysis and cohort studies describe changes in addiction careers over time, but fail to take into account the role of 'subjective' or 'social time', e.g. the functions of organisational and individual patterns of time use and time budgets. This paper reviews the notion of 'time' in addiction treatment systems. More specifically, the explicit or implicit role played by 'the time factor' in specific types of treatment such as '12-step programs', in-patient, out-patient care and individual treatment plans differs considerably and implies a re-definition and interpretation of 'Past', 'Present' and 'Future'. Temporal conceptions and time estimations of patients and therapists may influence the access to treatment and treatment outcomes. Societal values--lack of time in affluent societies--and a general acceleration in the fields of communication, consumption, work and leisure are mirrored in the treatment system. Recovery as a long-lasting learning process stands in sharp contrast to the 'quick fix'. The question is raised whether a post-modern concept of time is gaining importance as a counter movement, promoting a more individualised and differentiated treatment response and not any longer based on assumingly objective, technical criteria such as cost-efficiency. More research is needed on group-specific time concepts in treatment programs and the acceleration hypothesis in treatment systems.

Adaptation, Psychological↗

PubMed2003

A review of the modulation of the startle reflex by affective states and its application in psychiatry.

OBJECTIVE: To provide an overview of startle reflex methodologies applied to the examination of emotional and motivational states in humans and to review the findings in different forms of psychopathology. METHODS: Pertinent articles were searched mostly via MEDLINE and PsycINFO. RESULTS: The startle reflex is a non-invasive translational tool of research that bridges the gap between animal and human investigations. Startle is used to study fear and anxiety, affective disturbances, sensitization, motivational states, and homeostasis. CONCLUSIONS: The startle reflex is highly sensitive to various factors that are of interest in the studies of emotional disorders and has promoted new areas of investigations in psychiatry. However, research in psychiatry is still in its infancy and most findings await replication. Future progress will benefit from the development of innovative and powerful designs tailored to investigate specific disorders. SIGNIFICANCE: The startle reflex has utility as a research tool to examine trauma-related disorders, fear learning, drug addiction, and to contrast affective states and emotional processing across diagnostic groups, but its usefulness as a diagnostic tool is limited.

Animals↗

PubMed2003

Health technology assessment: the contribution of qualitative research.

The pragmatism in health care has made health technology assessment (HTA) restrict its scope to a particular set of problems, c.q. methods. The "multidisciplinary and comprehensive nature" of HTA, as the concept is presented in certain definitions, is lacking. Health care is also dominated by a positivistic-rationalistic approach of evaluation. In contrast, social studies of evaluations learn that a major difference has to be made between scientific research on (potential) impact of a technology and valuing these effects. In this contribution, we will discuss how the positivistic scientific bias of current HTA practice can be made up with other research traditions. More specifically, we focus on the question of how social scientists and particularly how qualitative research can contribute to HTA, complementary to positivistic studies of evidence and efficacy.

Biomedical Research↗

PubMed1994

Developmental changes in perception of nonnative vowel contrasts.

Discrimination of 2 German vowel contrasts was examined in English-learning infants of 6-8 and 10-12 months of age using a head turn procedure. The younger infants were better able than the older infants to discriminate the nonnative contrasts, but performance at 6-8 months was below levels that have been reported for nonnative consonant contrasts. A 2nd experiment using a habituation looking procedure showed that 4-month-old infants discriminated both German vowel contrasts, but the 6-month-olds could not. The findings are consistent with previous consonant work, revealing a shift from a language-general toward a language-specific pattern during the 1st year of life. However, that shift begins earlier in development for vowels than for consonants.

Attention↗