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PubMed1991

Influence of extended practice on programming time, movement time, and transfer in simple target-striking responses.

Two experiments describe the effects of extended practice on the development of motor control programs for simple target-striking responses. In Experiment 1,400 right-hand trials of simple one-target and two-target striking tasks were performed. In Experiment 2,600 practice trials were given. Overall reaction time (RT) was faster for the one-target condition in both experiments, supporting a response complexity effect. Movement time (MT) for both conditions improved linearly with practice, suggesting that development of the motor control programs was still occurring. Subjects then transferred to a three-target condition for 50 trials, performing the transfer task with the right hand in Experiment 1, and with right and left hands in Experiment 2. Transfer to the three-target conditions produced execution errors in the form of failure to contact the second target and repetitive tapping on the third target. These results suggest that extensive practice may serve to firmly entrench a response sequence, making it difficult to implement a similar, but unique, motor control program. An interpretation in terms of automaticity and enhanced priming of behavioral and neural pathways is offered to account for these results.

Journal Article↗

PubMed1997

Effects of short-chain fatty acids on gastrointestinal motility.

Besides their action on gut morphology and function, short-chain fatty acids (SCFAs), produced by bacterial fermentation of carbohydrates in the colon, influence gastrointestinal motility. As they are not present in the stomach and proximal small intestine, SCFAs do not directly affect motility of these segments. However, caecal infusion of SCFAs as well as colonic fermentation of lactulose induce a relaxation of the proximal stomach in humans, indicating that SCFAs can affect motility at a distance from their site of production. Moreover, this suggests that SCFAs may be involved in the so-called "ileocolonic brake', i.e. the inhibition of gastric emptying by nutrients reaching the ileo-colonic junction. In the terminal ileum, where their concentration may increase following a colo-ileal reflux, SCFAs stimulate contractions and shorten ileal emptying, which may protect ileal mucosa against the potentially harmful effects of the reflux of colonic contents. Although SCFAs are produced and concentrated in the colon, their action on motility of this organ is not clearly understood and may depend on concentration, molecular structure of the acids, responsiveness of the colonic segments and animal species. The mechanisms of action of SCFAs on gastrointestinal motility are not completely elucidated. They may involve systemic humoral and neural pathways as well as local reflexes and myogenic responses.

Animals↗

PubMed1996

Handedness and performance variability as factors influencing mirror movement occurrence.

A finger flexion task was used to investigate the effect of hand preference and performance variability on intensity of mirror movement. Right- and left-handed subjects were asked to maintain target forces, with either their index or small finger, that represented 25, 50, or 75% of their maximum strength capacity for the active finger. Greater mirror movement occurred when the small finger was active, and where there was greater variability in task performance, while mirror movement intensity was less when the dominant hand and the index finger were active. These findings were consistent with the cortical activation explanation of motor overflow (Todor & Lazarus, 1986a), and suggest that task variability is an important factor influencing motor overflow production. It was concluded that, if performance variability reflects the efficiency of cortical activation underlying control of a voluntary task, then refined cortical control decreases the potential for motor overflow to occur. However, it is necessary to clarify the relationship between hand preference, performance variability, and motor overflow, perhaps by examining the neural pathways involved in motor overflow production.

Adult↗

PubMed1996

Recovery of automatic and cognitive functions in traumatic brain injury using the functional independence measure.

Automatic tasks are performed with minimal attentional guidance. Neural pathways subserving attention are often impaired in traumatic brain injury (TBI). Therefore, the process of automatization is crucial in skill development, due to the fact that it allows attention to be directed towards the more abstruse components of task [1]. Automatic and cognitive categories were created by aggregating three of the motor items and three of the cognitive items respectively of the Functional Independence Measure (FIM). The averages of these categories were calculated for every evaluation of the FIM, and their relationship to each other was examined. Over a 9-month period 24 patients were selected from a TBI population with a major component of diffuse axonal injury (DAI). Eighty-eight per cent (n = 21) of the patients reached independence for the automatic category, but only 29% (v = 7) reached this level for the cognitive category. When independence was achieved, the average time to do so for the automatic category 6.7 weeks) was not significantly different from the time it took to reach cognitive independence (6.9 weeks). It was found that there were significant statistical differences in the scores between the two categories. Premorbid IQ had no effect on these categories. However, the rate which these two categories increased, from the time of admission to discharge, was not significantly different.

Activities of Daily Living↗

PubMed1977

Elevation of plasma corticosterone by swim stress and insulin-induced hypoglycemia in control and fluoxetine-pretreated rats.

Fluoxetine, a drug that inhibits serotonin inactivation by reuptake from the synaptic cleft and thereby enhances serotonin nerve function, was used to study the possible role of serotonin neurons in the activation of the pituitary-adrenal system of rats by swim stress or insulin-induced hypoglycemia. Fluoxetine pretreatment enhanced the elevation of plasma corticosterone produced by injection of L-5-hydroxytryptophan but did not significantly alter the elevation of plasma corticosterone by swim stress or by insulin-induced hypoglycemia, even when the stimulus was shown to be submaximal. The results suggest that serotonin neural pathways postulated to stimulate ACTH secretion are not involved in the activation of adrenocortical function by these stimuli.

5-Hydroxytryptophan↗

PubMedDate not supplied

Control of adrenocortical growth in vivo.

Adrenocortical growth is discussed with respect to its relation to body weight, elevated ACTH (provoked by sustained stress, adrenal enzyme deficiency, and adrenal enucleation), and unilateral adrenalectomy. It seems likely that these three conditions under which adrenal growth occurs are each controlled and mediated by different agents. Least is known about the growth of adrenals with the growth of the organism; however, because treatment with growth hormone is known to stimulate adrenal mitogenesis, and because adrenals grow in proportion to body growth by increasing cell number, it is proposed that this growth may be mediated by growth hormone (via somatomedin). ACTH causes primarily adrenocortical cellular hypertrophy which is subsequently followed by hyperplasia. It has been shown that the application of a sustained stressor, induction of adrenal enzyme deficiency and adrenal enucleation all result in persistent elevation in circulating ACTH levels and adrenal growth. It appears that the stimulus to ACTH secretion is a virtual or real decrease in corticosteroid feedback signal, and that ACTH secretion is regulated by corticosteroid levels. An additional humoral factor may be triggered by adrenal enucleation, and the possibility that a fragment of the N-terminal peptide of the ACTH precursor molecule plays this role is entertained. Finally, the evidence that the proliferative adrenal growth after unilateral adrenalectomy is mediated by afferent and crossed efferent neural pathways, and is regulated by aldosterone, pineal peptides and exposure to constant light is discussed.

Adrenal Cortex↗

PubMedDate not supplied

Ontogenic expression of putative feeding peptides in the rat fetal brain and placenta.

The well-demonstrated "fetal programming" paradigm is based on the observation that environmental changes can reset the developmental path and thus, gene expression during intrauterine development. As appetite-regulatory neural pathways develop in utero, we sought to determine the ontogenic expression of putative orexigenic and anorexigenic feeding-regulatory peptides in the fetal rat brain and placenta during the last third of gestation. Pregnant Sprague-Dawley rats (n = 12) at D14, D16 and D18 were sacrificed and fetal whole brain and placenta removed and examined for mRNA levels of orexigenic (neuropeptide Y (NPY), agouti-related peptide (AgRP)) and anorexigenic (cocaine and amphetamine regulated transcript (CART), pro-opiomelanocortin (POMC)) peptides and leptin receptor (OB-Rb) using real-time reverse transcription polymerase chain reactions (RT-PCR). For adult comparisons, the hypothalamus, cortex and cerebellum from male rats were also examined for feeding peptides. In the fetal brain and placenta, mRNA levels of AgRP decreased 10-fold from D14 to D16 and was undetectable at D18. Appetite inhibitory factors OB-Rb and CART mRNA levels increased from D14 to D18 in the brain and placenta. NPY and POMC expression remained unchanged from D14 to D18. The pattern of expression of feeding regulatory peptides in the fetal brain most closely resembled the expression profile of the adult cerebral cortex. The continued maturation of feeding regulatory mechanisms in late gestation indicates the potential for in utero programming of ingestive behavior.

Agouti-Related Protein↗

PubMed2001

Pharmacological treatment of acute spinal cord injury: how do we build on past success?

Most acute spinal cord injuries (SCI) do not involve complete transection of the spinal cord; typically, a rim of white matter survives. The potential for neurological recovery depends on optimal preservation of the ascending and descending white matter axons and their normal myelination. Pharmacologic strategies focus on the control of secondary injury processes, primarily lipid peroxidation (LP), and the salvage of as much white matter as possible. The first effective neuroprotective agent was methylprednisolone (MP), a glucocorticosteroid that in high doses improves neurological recovery in animals and humans following acute SCI. Tirilazad is a more targeted non-glucocorticoid LP inhibitor that has been shown to be neuroprotective and has fewer side effects than MP. Future SCI therapy is likely to encompass various neuroprotective agents, including inhibitors of LP, inhibitors of the nitric oxide-derived reactive oxygen species peroxynitrite, inhibitors of calpain (which is responsible for degrading the spinal cord cytoskeleton), and inhibitors of post-traumatic apoptosis of neurons and myelin-forming oligodendroglia. In addition, neuroprotective strategies will eventually be followed by neurorestorative agents that stimulate the plasticity of surviving neural pathways, and will be used in conjunction with other neurorestorative therapies like cell transplantation and gene therapy techniques.

Acute Disease↗

PubMed2001

Peripheral nerve protein, P0, as a potential receptor for Theiler's murine encephalomyelitis virus.

Theiler's murine encephalomyelitis virus (TMEV) belongs the family Picornaviridae. TMEV not only replicates in the gastrointestinal tract but also spreads to the central nervous system (CNS) either by a hematogenous or a neural pathway during natural infection. The DA strain of TMEV infects neurons during the acute phase, and glial cells and macrophages during the chronic phase, leading to a demyelinating disease similar to multiple sclerosis. Different virus-host receptor interactions in the peripheral and the neuronal cells could explain the pathways of viral spread from the peripheral to the CNS and neurons to glial cells. However, the receptor for TMEV remains unknown. P0 protein, a 28-31 kD glycoprotein, belongs to the immunoglobulin superfamily and constitutes 50% of the total myelin protein in the peripheral nerve. Other picornaviruses use members of the immunoglobulin superfamily as receptors. Thus we hypothesized P0 protein could act as a receptor for TMEV. In a virus overlay assay, radiolabeled TMEV bound to a 28-30 kD protein from the peripheral nerve of wild-type C57BL/6, but no binding was found in the peripheral nerve from P0-knockout mice. TMEV replicated fourfold higher in P0-transfected BW5147.G.1.4 cells than in mock-transfected cells. The increase in virus replication in the P0-transfected cell line was blocked by preincubation of the cells with anti-P0 antibody. A virus binding study showed that TMEV bound to P0-transfected cells but not to mock-transfected cells. The use of the P0 protein in Schwann cells as a receptor may be one mechanism by which TMEV spreads from the gastrointestinal tract to the CNS.

Amino Acid Sequence↗

PubMed2004

Psychopharmacological interactions between nicotine and ethanol.

Epidemiological, clinical, and laboratory evidence has shown a positive correlation between cigarette smoking and ethanol use, and previous studies suggest some commonality in the neural pathways mediating effects of nicotine and ethanol. In this study, the subjective and behavioral interactions among nicotine, ethanol, and the nicotinic antagonist mecamylamine were investigated. The main objectives were to determine how the rewarding effects of nicotine might be modified by ethanol, and to compare the effects of ethanol with those of a nicotinic antagonist (mecamylamine). A total of 48 smokers who regularly consumed alcoholic beverages participated in four laboratory sessions presenting a 2 (nicotine vs. denicotinized cigarette smoke)x2 (10 mg oral mecamylamine hydrochloride vs. placebo)x2 (ethanol.5 g/kg vs. placebo) design, with ethanol as a between-subjects factor. Dependent measures included blood alcohol concentration (BAC), as assessed by breath alcohol detector; subjective drug effects; and rate of ad lib smoking during a 2-hr period. Results showed that peak BAC averaged.03 g/dl in the ethanol condition. Ethanol potentiated some of the subjective rewarding effects of nicotine, including smoking satisfaction, stimulant as well as calming effects, and relief of craving for cigarettes. During the ad lib smoking period, mecamylamine decreased satisfaction associated with the nicotine-containing cigarettes; mecamylamine also induced smoking but only in the placebo ethanol condition. These results highlight the potent interaction between ethanol and nicotinic systems, and suggest that ethanol can potentiate the rewarding effects of nicotine as well as offset some of the effects of a nicotinic antagonist.

Adult↗

PubMed2005

A sensitization-homeostasis model of nicotine craving, withdrawal, and tolerance: integrating the clinical and basic science literature.

Recent reports suggest that nicotine withdrawal symptoms are common among adolescents after a few weeks of intermittent tobacco use. No current model of nicotine dependence had predicted the rapid development of symptoms of dependence and withdrawal before the development of tolerance. We present a model that integrates neuroscience with clinical observations regarding how nicotine dependence develops, progresses, and resolves in humans. The central tenet of this sensitization-homeostasis model is that nicotine's dependence liability derives from its ability to stimulate neural pathways responsible for the suppression of craving. As a result of sensitization, the craving suppression produced by nicotine is magnified to superphysiological levels. The overinhibition of neurons responsible for craving initiates compensatory homeostatic measures that stimulate the craving pathways and result in craving when nicotine is absent. Separate homeostatic mechanisms are responsible for craving, withdrawal, and tolerance. The sensitization-homeostasis model is unique in its attribution of dependence to craving suppression, its attention to the temporal relationships among clinical features of nicotine dependence, and its extensive integration of clinical observations and basic science. It provides a framework for theory-based research.

Adolescent↗

PubMed2001

Intercorrelations among tests of lateralisation in the BALB/c mouse.

In order to examine the reliability of lateralised behaviours, BALB/c mice were tested in three different situations: the Collins paw preference test (PPT), the rotatory swimming test (RST), and the T maze test (TMT). The results showed a significant correlation between the scores of lateralisation in the PPT and the RST, but a lack of lateralisation in the TMT. Considering the tasks involved in these tests, these results appear to support the hypothesis of close links between lateralised behaviours, emotional processes, and neural pathways.

Journal Article↗

PubMed1973

Color-vision mechanisms in the peripheral retinas of normal and dichromatic observers.

It is possible that so-called normal trichromatic vision occurs only between the central blue-blind fixation area and about 30 degrees peripherally. Beyond about 30 degrees vision has been alleged to become dichromatic (red-green blind), and beyond about 60 degrees , monochromatic. Hence every form of color blindness may characterize various zones of the normal retina. We have studied mechanisms of peripheral color vision, mainly by measuring the spectral sensitivities of the blue-, green-, and red-sensitive systems, isolated by differential color adaptation. In normal observers the sensitivity of the blue-mechanism falls off about 2 log units by 80 degrees out. The green- and red-sensitive systems decline only about 0.7 log unit over the same range. Protanopes, deuteranopes, and tritanopes exhibit comparable changes. We have not found any color mechanism present centrally to be wholly lost peripherally. Nor, for dichromats, have we found any mechanism missing centrally to be present peripherally. Whatever evidences of peripheral color blindness have been observed appear to involve other mechanisms than failure of receptors, probably including some fusion of neural pathways from receptors to centers.

Color Perception↗

PubMed2004

Improvement of mouse memory by Myristica fragrans seeds.

Memory is one of the most complex functions of the brain and involves multiple neural pathways and neurotransmitter systems. The present study was undertaken to investigate the effect of Myristica fragrans (MF) seeds on learning and memory in mice. The n-hexane extract of MF was administered orally in three doses (5, 10, and 20 mg/kg p.o.) for 3 successive days to different groups of young and aged mice. The learning and memory parameters were assessed using elevated plus-maze and passive-avoidance apparatus. The effect of MF extract on scopolamine (0.4 mg/kg i.p.)- and diazepam (1 mg/kg i.p.)-induced impairment in learning and memory was also studied. MF extract at the lowest dose of 5 mg/kg p.o. administered for 3 successive days significantly improved learning and memory of young and aged mice. This extract also reversed scopolamine- and diazepam-induced impairment in learning and memory of young mice. MF extract enhanced learning and retention capacities of both young and aged mice. The exact mechanism of the memory-improving effect of MF extract was not explored in the present study. But, the observed memory-enhancing effect may be attributed to a variety of properties (individually or in combination) the plant is reported to possess, such as antioxidant, anti-inflammatory, or perhaps procholinergic activity.

Animals↗

PubMed1980

Functional changes in autonomic nervous responses with ageing.

The effects of ageing on autonomic nervous responses have been investigated in 29 young adults, 64 healthy elderly in the age range 66 to 86 years, and 20 elderly in-patients with hypothermia, instability of bladder function or marked orthostatic hypotension. In the healthy elderly group, the beat-to-beat variation in response to postural change was significantly diminished, the vasoconstrictor response to cooling reduced and baroreflex sensitivity during lower-body negative pressure was decreased compared with young adults. Patients with an atronic bladder, determined by urodynamic tests, showed an even more marked decrease in baroreflex sensitivity. The multisystem nature of these autonomic disturbances suggests that physiological impairment may occur in autonomic neural pathways with ageing.

Adult↗

PubMed1985

The response of the colon to eating.

Much evidence indicates that there is an increased motor activity in the colon from eating in several species of animals. Though some of this effect may be cephalic in origin, the greater part of the response results from the arrival of food in the stomach and proximal intestine. Chemoreceptor stimulation appears to be more important than mechanoreceptor stimulation in bringing about this effect. The means by which this effect comes about could be either hormonal or neural. Several polypeptide hormones released from the proximal gut by eating are candidates. Neural pathways through both parasympathetic and sympathetic systems could be responsible. The exact nature of the change in colonic motility that is produced is unknown. It could involve changes in the pacemakers for colonic contractions (the electrical slow waves of the colon and the migrating spike burst of the colon), changes in the excitability of the colonic musculature or changes in colonic mucosal function.

Animals↗

PubMed1979

Pituitary microadenoma and primary lymphoma of brain associated with hypothalamic invasion.

A case of primary histiocytic lymphoma involving the left temporal lobe and hypothalamus is presented. This lesion was associated with a pituitary microadenoma shown immunohistochemically to contain prolactin and with lactational changes in the breasts. The interruption by the neoplasm of neural pathways from cells producing prolactin inhibitory factor in the hypothalamus and increased production of prolactin by the pituitary are suggested as the probable mechanism. The association of lactational changes in the breasts with primary lymphoma of the brain has not been reported.

Adenoma↗

PubMed1982

Suppression of antidiuretic hormone hypersecretion during surgery by extradural anaesthesia.

The concentrations of antidiuretic hormone in plasma and urine were determined in three groups of patients submitted to the same operative procedure. Seven (group I) underwent general anaesthesia with thiopentone, fentanyl and nitrous oxide and received an infusion of isotonic saline solution 5ml min-l. Seven patients (group II) anaesthetized similarly, received isotonic saline solution 15 ml min-1. In group III (five patients) anaesthesia was produced by extradural blockade. Surgery under general anaesthesia induced a significant increase in plasma and urine ADH concentrations which were not modified by the fluid load. Extradural anaesthesia suppressed almost completely the release of ADH during surgery. This effect of extradural anaesthesia could be related to the interruption of conduction along nociceptive neural pathways.

Aged↗