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At least 1,225 records · Page 68Linked to original sources
PubMed1996

An intracellular study of space and time representation in primary visual cortical receptive fields.

In contrast with previous knowledge based on extracellular recordings, the recent development of intracellular techniques in vivo (sharp electrode or 'blind patch') ideally allows experimenters to analyze and dissect the contribution of feedforward and lateral connectivity in the functional expression of a synaptic 'integration field'. We will present recent data which demonstrate that the visual receptive field of cortical neurons described at the level of subthreshold synaptic events extends over much larger regions of the visual field than previously thought, and that the capacity of cells to amplify subthreshold responses depends on the immediate past history of their membrane potential. Our data suggest that visual cortical receptive fields should not be considered as a fixed entity but more as a dynamic field of integration and association. Two types of dynamics can be argued for: 1) the spatial structure of the minimal discharge field (defined by suprathreshold activation of the cell) can be profoundly reorganized at least during development and most probably during selective phases of learning under the control of activity-dependent mechanisms. Adaptive changes in visual responses are thought to reflect long-lasting potentiation and/or depression of synaptic efficacies conveying ON- and OFF-center information; and 2) during sensory processing, reconfiguration of synaptic weights may be achieved on a much faster time-scale and linked to nor-linear properties of the postsynaptic membrane as well as that of recruited networks. Association of information available in the central part of the receptive field (RF) and of input coming from the reputedly 'unresponsive' regions surrounding it, or arising simultaneously from different parts of the visual field, might be suppressive in certain cases and capable of boosting hidden responses in other cases, depending on the global stimulus configuration.

Animals↗
PubMed2002

Regulation and function of local protein synthesis in neuronal dendrites.

It has long been shown that protein synthesis can occur in neuronal dendrites, but its significance remained unclear until relatively recently. Studies suggest that local protein synthesis has crucial roles in synaptic plasticity, the change in neuronal communication efficiency that is probably a cellular basis of learning and memory. Induced by neuronal activity, local protein synthesis provides key factors for the modification of activated synapses. In this review, we summarize the evidence for local protein synthesis and its functions in synaptic plasticity. We also discuss the molecular mechanisms by which neuronal activity induces the synthesis of proteins that allow for changes in synaptic function.

Animals↗
PubMed2000

2,3-Dihydro-dithiin and -dithiepine-1,1,4,4-tetroxides: small molecule non-peptide antagonists of the human galanin hGAL-1 receptor.

The neuropeptide galanin modulates several physiological functions such as cognition, learning, feeding behavior, and depression, probably via the galanin 1 receptor (GAL-R1). Using an HTS assay based on 125I-human galanin binding to the human galanin-1 receptor (hGAL-R1), we discovered a series of 1,4-dithiin and dithiipine-1,1,4,4-tetroxides that exhibited binding affinity IC50's to hGAL-R1 ranging from 190 to 2700 nM. Two of the dithiepin analogues, 7 and 23, behaved pharmacologically as hGAL-R1 antagonists in secondary assays involving adenylate cyclase activity and GTP binding to G-proteins. Analogues 7 and 23 were also active in functional assays involving galanin, reversing the inhibitory effect of galanin on acetylcholine (ACh) release in rat brain hippocampal slices and electrically-stimulated guinea pig ileum twitch.

Acetylcholine↗
PubMed1998

An expert system for assigning patients into clinical trials based on Bayesian networks.

Assigning patients into clinical trials is a knowledge and data intensive task. Eligibility determination for entry into a clinical trial is based upon specific inclusion and exclusion criteria. This paper investigates the use of an excerpt system to assist the physician through this task. This expert system uses Bayesian networks, a probabilistic method that can take advantage of pre-existing statistical knowledge. The paper also describes the feasibility of such a system by presenting the implementation of three clinical protocols. The experimental results reveal that the approach is feasible. The system gives correct eligibility scores when all evidence is available but also predicts eligibility when there is missing evidence. The system directs the physician to the protocols the patient is most eligible for, according to the current evidence. The system has the ability of learning its prior and conditional probabilities (expert knowledge) from training examples.

Algorithms↗
PubMedDate not supplied

Sleep deficits in rats with hereditary diabetes insipidus.

Interest in the Brattleboro diabetes insipidus rat has resurged with the recent increase in research on brain peptides. Various reports have suggested that in these rats, the impaired ability for memory consolidation is due essentially to a chronic lack of vasopressin. On the other hand, sleep stages and particularly the paradoxical phase of sleep have been shown to have a key role in the processes of learning and memory consolidation. Curiously, the possible involvement of sleep deficits in the impairment of memory function in the Brattleboro rat has never been suspected. Here I report a significant reduction (38%) in the daily duration of paradoxical sleep (PS) in the homozygous diabetes insipidus (HODI) rat compared to the heterozygous Long Evans strain. Normal or increased durations of PS were observed after intravenous (i.v.) administration of vasopressin but also when the normal daily water intake (240 ml) was infused i.v. These results provide direct evidence that PS deficits in the HODI rat are not due to the absence of vasopressin. They also suggest that the impaired ability for learning and memory processes are probably due to the impairment of PS rather than to some direct consequence of the hereditary lack of vasopressin.

Animals↗
PubMed2004

The neurobiology of tobacco dependence: a preclinical perspective on the role of the dopamine projections to the nucleus accumbens [corrected].

It is now widely accepted that nicotine is the primary addictive component of tobacco smoke and that a majority of habitual smokers find it difficult to quit smoking because of their dependence upon this component of the smoke. However, although nicotine replacement therapy elicits a clinically valuable and significant improvement in the number of quit attempts that are ultimately successful, its efficacy remains disappointingly low. This review considers some of the reasons for this problem. It focuses on the hypothesis that stimulation of the dopamine (DA) projections to the medial shell and the core of the nucleus accumbens play complementary roles in the development of nicotine dependence. The hypothesis proposes that increased extra-synaptic DA in the medial shell of the accumbens confers hedonic properties on behaviors, such as smoking, which deliver nicotine, and thereby increase the probability that the response is learned. It also summarizes the evidence that the primary role of the increased DA overflow, observed in the accumbal core of nicotine-pretreated individuals, challenged with nicotine, is the attribution of incentive salience to cues associated with delivery of the drug and the transition to Pavlovian responding to these conditioned stimuli. The review argues that sensitization of the DA projections to the accumbal core, and the behaviors that depend upon this process, play a pivotal role in the maintenance of the tobacco smoking habit and that it is this component of the dependence that is inadequately addressed by nicotine replacement therapy.

Conditioning, Classical↗
PubMed2005

Speciation: more likely through a genetic or through a learned habitat preference?

A problem in understanding sympatric speciation is establishing how reproductive isolation can arise when there is disruptive selection on an ecological trait. One of the solutions that has been proposed is that a habitat preference evolves, and that mates are chosen within the preferred habitat. We present a model where the habitat preference can evolve either by means of a genetic mechanism or by means of learning. Employing an adaptive-dynamical analysis, we show that evolution proceeds either to a single population of specialists with a genetic preference for their optimal habitat, or to a population of generalists without a habitat preference. The generalist population subsequently experiences disruptive selection. Learning promotes speciation because it increases the intensity of disruptive selection. An individual-based version of the model shows that, when loci are completely unlinked and learning confers little cost, the presence of disruptive selection most probably leads to speciation via the simultaneous evolution of a learned habitat preference. For high costs of learning, speciation is most likely to occur via the evolution of a genetic habitat preference. However, the latter only happens when the effect of mutations is large, or when there is linkage between genes coding for the different traits.

Adaptation, Biological↗
PubMed2004

Parental pain is not associated with pain in the child: a population based study.

BACKGROUND: Child pain is associated with adverse psychosocial factors. Some studies have shown an association between children's and parental pain. Children may "learn" pain behaviour from their parents. OBJECTIVES: To examine whether an association exists between parent and child pain, and, if so, whether this relationship persists after adjusting for psychosocial difficulties in the child. METHODS: 1326 schoolchildren took part in a questionnaire based, cross sectional survey. Parents of study participants were sent a postal questionnaire. Occurrence of body pain was ascertained using blank body manikins and, in children, psychosocial factors were assessed using the Strengths and Difficulties Questionnaire. Three child-parent pain relationships were examined: any child pain with any parental pain or with parental widespread pain; and child low back pain with parental low back pain. RESULTS: The risk of child pain associated with parental reporting of pain was minor, and non-significant. Even when both parents reported widespread pain, the relative risk of pain in the child, after adjusting for age and psychosocial difficulties, was 1.2 (95% CI 0.5 to 3.2). CONCLUSIONS: Parental pain is not a risk for child pain. Pain behaviour is not learned. Rather, child pain is probably attributable to individual factors and the social environment.

Adolescent↗
PubMedDate not supplied

Sentinel node detection with imaging probe.

A once-square-inch-field-of-view mini gamma camera, whose first prototype was built by us in 1998 and given the name imaging probe (IP), was initially employed in sentinel lymph node (SLN) detection. This is probably the best way of learning how to use it. In the present work IP was used for SLN localization by a medical team that, after having been trained by the group of nuclear physicians of "La Sapienza" University who designed and first used the detector, used IP at their own hospital to 1) acquire experience for future use during surgery (a cooperative project on IP-radioguided orthopedic surgery is ongoing) and 2) start multicenter trials with IP. The SLN was identified and localized with IP and a non-imaging probe, Neoprobe 2000, in six patients with breast cancer who underwent lymphoscintigraphy for SLN biopsy. The operators who used Neoprobe and IP were blinded to each other's findings and to the results obtained with the large-field-of-view Anger camera that was used for lymphoscintigraphy. The Anger camera, IP and Neoprobe detected seven SLNs in six patients. The mean detection time was 2 mins 6 s (standard deviation (SD) 26 s) with IP, and 2 mins 18 s (SD 47 s) with Neoprobe 2000. The SLN that was most difficult to find was detected in 2 mins 56 s with IP and 3 mins 45 s with Neoprobe. The operators' subjective impression of having detected the SLN was "absolutely sure" for 7/7 nodes with IP and "absolutely sure" for 5/7 nodes with Neoprobe.

Breast Neoplasms↗
PubMed2006

Biomechanical, morphological, and histological analysis of early failures in hip resurfacing arthroplasty.

The present revival of hip resurfacing arthroplasty may be related to an increase in early failures owing to the challenging technique of the procedure. Fifty-five retrieved implants were analysed with respect to wear, cement mantle and cement penetration, fracture and head morphology, as well as standard histology. Femoral neck fractures occurred in median after 102 days. The time to failure was shorter for older women. Major deviations from the suggested cement mantle thickness and cement penetration were found. Indications for high trauma during implantation leading to early failure due to weakening of the femoral neck were also observed. Some failures had signs of pseudarthrosis beneath the implant. Four different fracture patterns with different mean survival times were identified. Observed wear was minor with the exception of that due to alignment mistakes (rim loading). The cups were not damaged by the failures. Histological results indicate that avascular necrosis is not necessarily connected with this kind of endoprosthetic surgery. Most of the failures analysed can probably be attributed to the 'learning curve' effect, which is an unsatisfactory situation.

Aged↗
PubMed1974

Contingency spaces and measures in classical and instrumental conditioning.

The contingency between conditional and unconditional stimuli in classical conditioning paradigms, and between responses and consequences in instrumental conditioning paradigms, is analyzed. The results are represented in two- and three-dimensional spaces in which points correspond to procedures, or procedures and outcomes. Traditional statistical and psychological measures of association are applied to data in classical conditioning. Root mean square contingency, Ø, is proposed as a measure of contingency characterizing classical conditioning effects at asymptote. In instrumental training procedures, traditional measures of association are inappropriate, since one degree of freedom-response probability-is yielded to the subject. Further analysis of instrumental contingencies yields a surprising result. The well established "Matching Law" in free-operant concurrent schedules subsumes the "Probability Matching" finding of mathematical learning theory, and both are equivalent to zero contingency between responses and consequences.

Avoidance Learning↗
PubMed1976

The effect of rearing environments on the contrafreeloading phenomenon in rats.

Eight naive rats were reared in enriched or impoverished environments for 39 days after weaning and then lived in operant chambers, in which they could obtain food pellets freely or by lever pressing, for 25 or 30 days. The animals raised in an impoverished environment acquired the bar-press response quickly when placed in the operant chambers and maintained a preference for obtaining food via bar pressing. Animals raised in an enriched environment did not learn to lever press, as demonstrated by low levels of responding and the lack of bar pressing when free food was subsequently removed. It was concluded that restricting animals' postweaning environments facilitated learning in a choice situation, probably because of increased activity levels. The results are interpreted in relation to previous studies on rearing environments and on contrafreeloading.

Journal Article↗
PubMedDate not supplied

Quantification of tracking eye movements in normal subjects.

Voluntary tracking eye movements were analysed in 20 normal subjects whose gaze was fixed on a visual target moving at six different constant velocities between 10 degrees s-1 and 60 degrees s-1. Tracking ability was quantified according to four parameters. The mean value and dispersion of each parameter at each velocity were determined. The maximum velocity gain of smooth pursuit was, on average, 0.98-0.75, gradually diminishing with increasing target velocities of 10-60 degrees s-1. Amplitude of smooth pursuit decreased gradually and was replaced by superimposed saccades at increasing target velocities. Saccades with amplitudes of 3-10 degrees were present at all target velocities, while those greater than 10 degrees occurred mostly at target velocities above 30 degrees s-1. Square waves were rare but equally frequent at all target velocities and seemed to occur randomly during tracking eye movements. An additional group of 9 subjects was investigated twice. Mean values of maximum velocity gain of amplitude of smooth pursuit and of frequency of superimposed saccades were higher on the second occasion, probably reflecting the effect of learning. Co-operation and interaction of the smooth pursuit and the saccadic subsystems to produce the voluntary tracking were discussed.

Adaptation, Ocular↗
PubMedDate not supplied

[Video-assisted thyroidectomy with minimally invasive central cervicotomy: initial experience in an endocrine surgery division].

Minimally invasive video-assisted thyroidectomy, a recently developed technique, has been shown to be feasible and safe. Nevertheless, to obtain the best results, the surgeon should be well trained in endoscopic surgery. We attempted to answer the question whether an endocrine surgery division with no previous experience in endoscopic neck surgery could easily import the new technique. The inclusion criteria were nodules < or = 3.5 cm diameter or thyroid lobe volume less than 15 ml, and no thyroiditis or previous neck surgery. Suspect malignant nodules were excluded. The procedure was carried out through a 20 to 30 mm central neck incision, with external retraction and no neck insufflation. The vessels were ligated or closed by means of clips. From March 2004 to March 2005, 127 thyroidectomies were performed, of which 36 were thyroid lobectomies. Of these, 12 lobectomies by minimally invasive video-assisted thyroidectomy were performed for monolateral goiter (4 left, 8 right). There were no intraoperative complications. No recurrent laryngeal nerve palsy or permanent hypoparathyroidism occurred. The mean operative time was 74.4 min (median: 70; range: 45-115). The results, in terms of patient comfort, reduced postoperative pain and cosmetic quality were excellent. The technique allowed careful assessment of the inferior and superior laryngeal nerve. Thorough haemostasis was aided by the magnification of the image and optimal illumination. The learning curve appeared short, owing probably to previous experience in conventional endocrine surgery and the closer similarities of minimally invasive video-assisted thyroidectomy to enhanced-view conventional surgery than to laparoscopic surgery. In our experience the clinical impact was limited as a result of the small percentage of patients fulfilling the strict inclusion criteria.

Adenoma↗
PubMedDate not supplied

[Teaching monkeys complex behavioral tasks].

Differences of two ways of training were shown in two monkeys. Random order of alteration of two conditioned signals was extremely ineffective. The use of a special algorithm of signals' administration dependent on the behaviour of a monkey made the learning of complicated tasks possible. Probable mechanisms of the effect described are discussed.

Algorithms↗
PubMed1998

Similarities and interactions between GABAergic and glutaminergic systems.

Harmonious interactions between neurotransmitter systems are important for regulating the activity in the central nervous system (CNS). gamma-Aminobutyric acid (GABA) and glutamate (Glu) are major inhibitory and excitatory neurotransmitters in the mammalian central nervous system. Neuronal excitability, probably synaptic plasticity, cognitive performance, learning and memory processes frequently the results of the balance of GABAergic inhibitory and glutaminergic excitatory inputs.

Animals↗
PubMed2024

PredIL13: Stacking a variety of machine and deep learning methods with ESM-2 language model for identifying IL13-inducing peptides.

Interleukin (IL)-13 has emerged as one of the recently identified cytokine. Since IL-13 causes the severity of COVID-19 and alters crucial biological processes, it is urgent to explore novel molecules or peptides capable of including IL-13. Computational prediction has received attention as a complementary method to in-vivo and in-vitro experimental identification of IL-13 inducing peptides, because experimental identification is time-consuming, laborious, and expensive. A few computational tools have been presented, including the IL13Pred and iIL13Pred. To increase prediction capability, we have developed PredIL13, a cutting-edge ensemble learning method with the latest ESM-2 protein language model. This method stacked the probability scores outputted by 168 single-feature machine/deep learning models, and then trained a logistic regression-based meta-classifier with the stacked probability score vectors. The key technology was to implement ESM-2 and to select the optimal single-feature models according to their absolute weight coefficient for logistic regression (AWCLR), an indicator of the importance of each single-feature model. Especially, the sequential deletion of single-feature models based on the iterative AWCLR ranking (SDIWC) method constructed the meta-classifier consisting of the top 16 single-feature models, named PredIL13, while considering the model's accuracy. The PredIL13 greatly outperformed the-state-of-the-art predictors, thus is an invaluable tool for accelerating the detection of IL13-inducing peptide within the human genome.

Humans↗
PubMed1995

[The role of quinine chlorhydrate in the conditioned inhibition of the tarsal reflex in Drosophila melanogaster].

The proboscis extension reflex (PER) can be elicited by applying a sucrose stimulation to the tarsus of a walking fly. This reflex decreases in frequency with repetition, presumably habituation, a nonassociative learning. If each sucrose stimulation is followed by a bitter stimulation, quinine chloride, the PER declines more rapidly, probably the result of conditioning, an associative learning. The present work shows that quinine chloride does not always inhibit PER suppressions but depends on the moment of delivery, being most effective when presented immediately after a sucrose stimulation. A bitter stimulus presented before, or simultaneously with a sucrose stimulation is less effective than habituation to sucrose alone. This experiment provides evidence for an interpretation in terms of cognitive association. The model of learning is not a Pavlovian conditioning as advanced by Medioni and Vaysse (1975), but corresponds to the punishment paradigm of Dyal and Corning (1973).

Animals↗