Health related behaviours of secondary students living in dormitory in Hungary

Background

Previous studies have shown that unhealthy eating habits and lack of exercise are still widespread among high school students. Hungary and many other countries have attempted to introduce campaigns and health education programs among adolescents to promote healthier lifestyle, but the effectiveness of these programs is unclear. Our aim was to investigate the consistency between knowledge and behavior in adolescents.

Methods

A self-administered questionnaire survey was conducted in 9 secondary schools’ student dormitories, involving 163 students. Descriptive statistics were estimated and chi2- test was used to compare the prevalence between groups.

Results

Of the participants 69.3% reported their health status good, girls and those students who studied in vocational school frequently considered their own health bad (p = 0.002). Almost all of them highlighted the importance of regular physical activity, but 27.7% had low physical activity. Daily consumption of fruit and vegetables seems to be characteristic just half of the students, the structure of their daily snacks consists more in sugar-sweetened snacks (21.7%) and energy dense beverages (22.8%). Students with higher level of health-consciousness rated better their own health status and took exercise more frequently, but the higher level of health-consciousness had not positive effect on the healthy food consumption (p = 0.143).

Conclusions

Our findings suggest lack of exercise and unhealthy eating habits were still widespread among high school students. The results of the study showed that adolescents have sufficient knowledge about healthy lifestyle, however, it has little impact on their health-related behaviour.

Key messages

The most important characteristic of an effective health promotion programme is its ability to change behaviour. Health promotion programmes should continue in schools, especially focus on behaviour changing interventions to effectively influence the health of the students.

A radiometabolite study of the serotonin transporter PET radioligand [(11)C]MADAM

INTRODUCTION

(11)C]MADAM is a radioligand suitable for PET studies of the serotonin transporter (SERT). Metabolite analysis in human and non-human plasma samples using HPLC separation has shown that [(11)C]MADAM was rapidly metabolized. A possible metabolic pathway is the S-oxidation which could lead to SOMADAM and SO2MADAM. In vitro evaluation of these two potential metabolites has shown that SOMADAM exhibited a good affinity for SERT and a good selectivity for SERT over NET and DAT.

METHODS

Comparative PET imaging studies in non-human primate brain with [(11)C]MADAM and [(11)C]SOMADAM were carried out, and plasma samples were analyzed using reverse phase HPLC. We have explored the metabolism of [(11)C]MADAM in rat brain with a view to understand its possible interference for brain imaging with PET.

RESULTS

PET imaging studies in non-human primate brain using [(11)C]SOMADAM indicated that this tracer does not bind with high amounts to brain regions known to be rich in SERT. The fraction of [(11)C]SOMADAM in non-human primate plasma was approximately 5% at 4min and 1% at 15min after [(11)C]MADAM injection. HPLC analysis of brain sample after [(11)C]MADAM injection to rats demonstrated that [(11)C]SOMADAM was not detected in the brain.

CONCLUSIONS

(11)C]SOMADAM is not superior over [(11)C]MADAM as a SERT PET radioligand. Nevertheless, [(11)C]SOMADAM has been identified as a minor labeled metabolite of [(11)C]MADAM measured in monkey plasma. [(11)C]SOMADAM was not detected in rat brain.

Correlation between crossed cerebellar diaschisis and clinical neurological scales

BACKGROUND

A common consequence of unilateral stroke is crossed cerebellar diaschisis (CCD), a decrease in regional blood flow (CBF) and metabolism (CMRglu) in the cerebellar hemisphere contralateral to the affected cerebral hemisphere. Former studies indicated a post-stroke time-dependent relationship between the degree of CCD and the clinical status of acute and sub-acute stroke patients, but no study has been performed in post-stroke patients.

OBJECTIVES

The objective of this investigation was to evaluate the quantitative correlation between the degree of CCD and the values of clinical stroke scales in post-stroke patients.

MATERIALS AND METHODS

We measured with positron emission tomography (PET) regional CBF and CMRglu values in the affected cortical regions and the contralateral cerebellum in ten ischaemic post-stroke patients. Based on these quantitative parameters, the degree of diaschisis (DoD) was calculated, and the DoD values were correlated with three clinical stroke scales [Barthel Index, Orgogozo Scale and Scandinavian Neurological Scale (SNS)].

RESULTS

There were significant linear correlations between all clinical stroke scales and the CCD values (Barthel Index and Orgogozo Scale: P < 0.001, for both CBF and CMRglu; SNS: P = 0.007 and P = 0.044; CBF and CMRglu, respectively).

CONCLUSIONS

The findings indicate that DoD can be used as a quantitative indicator of the functional impairments following stroke, i.e. it can serve as a potential surrogate of the severity of the damage.

New PET radiopharmaceuticals beyond FDG for brain tumor imaging

Brain tumors have a relatively high incidence (>14/100000 people/year) and represent a major cause of death in the population. The direct and indirect costs of brain tumors are high in the developed countries (5.2 bn EUR/year in the EU; 4.46 bn USD/year in the US). A combination of recent advancements in molecular neuroimaging, with positron emission tomography (PET) in the first place, providing clinicians with an improved diagnostic and therapy follow-up efficacy, novel approaches in the field of neurosurgery (including neuronavigation, intraoperative control of the nervous function, tumor histology and volume), and developments in treatment strategies (including new chemotherapeutics and new targeted agents, immunotherapies, sophisticated irradiation protocols) has in the past years improved the survival of brain tumor patients. A major component of further improvements is related to advancements in the development of novel molecular imaging biomarkers for brain tumor detection, including new PET radiopharmacons with high specificity, sensitivity and diagnostic accuracy. Despite the fact that FDG is the "working horse" of brain tumor imaging with PET and well over 90 % of diagnostic imaging studies in neuro-oncology are made with FDG world-wide, due to its sub-optimal specificity and sensitivity the search for non-FDG brain tumor PET radiotracers has been intensifying during the past decade in order to improve the diagnostic sensitivity, specificity and accuracy of molecular imaging of brain tumors. The most promising non-FDG brain tumor radiotracers include radioactively labeled nucleoside and amino acid analogues, tracers of oxidative metabolism, fatty acid metabolism and hypoxia, as well as receptor ligands of various kinds. The most widely tested non-FDG radiotracers include [11C]methionine (MET), [18F]fluorothymidine (FLT), [18F]fluoroethyl-l-tyrosine (FET), [18F]fluoro-α-methyltyrosine (FMT), [18F]fluoromisonidazole (F-MISO), 6-[18F]fluoro-dihydroxy-l-phenylalanine (F-DOPA), [11C]choline (CHO) and [18F]choline. The selective advantages of these radiotracers, compared to FDG, are varying, MET and FET appearing to be the most useful dedicated glioma radiotracers. Nevertheless, several other non-metabolic radiopharmaceuticals are also being tested or are in the validation phase. Although novel dedicated radiotracer candidates should offer an increased selectivity, specificity and diagnostic accuracy when compared to the recently existing brain tumor tracers, a dual or a multitracer approach may still offer the optimal solution in brain tumor imaging with PET in the near future.

Fenfluramine-induced serotonin release decreases [11C]AZ10419369 binding to 5-HT1B-receptors in the primate brain

The need for positron emission tomography (PET)-radioligands that are sensitive to changes in endogenous serotonin (5-HT) levels in brain is recognized in experimental and clinical psychiatric research. We recently developed the novel PET radioligand [(11)C]AZ10419369 that is highly selective for the 5-HT(1B) receptor. In this PET-study in three cynomolgus monkeys, we examined the sensitivity of [(11)C]AZ10419369 to altered endogenous 5-HT levels. Fenfluramine-induced 5-HT release decreased radioligand binding in a dose-dependent fashion with a regional average of 27% after 1 mg/kg and 50% after 5 mg/kg. This preliminary study supports that [(11)C]AZ10419369 is sensitive to endogenous 5-HT levels in vivo and may serve as a tool to examine the pathophysiology and treatment of major psychiatric disorders.

The receptor fingerprint of the human brain and its changes during life

With the help of PET one can explore the various neurotransmitter-neuroreceptor systems, their interactive balance and their changes during life, i.e., the human brain receptor fingerprint: the highly individual composition of, and balance among, the various receptor systems can be measured both qualitatively (the presence of various receptors in different brain regions) and quantitatively (the density of the receptors, their binding potential, occupancy, etc.). The understanding of the normal constitution of the primate brain neurotransmitter-receptor systems and their pathological changes requires multiligand receptor mapping, using various PET radioligands. Some major components of our brain receptor fingerprint strictly correlate with personality traits, character and temperament, and most probably, with "cognitive styles", as well. The brain receptor fingerprint is continuously changing during our normal life (maturation, ageing) and short term physiological or pharmacological challenges (sensory or cognitive processes, drug administration etc.) can also modify it. Social interactions, learning, habituation and other lasting interactions with our social and physical environment can significantly modify the receptor fingerprint. Pathological conditions, including neurological and psychiatric diseases strongly affect the normal neuroreceptor-neurotransmitter balance of the brain, as do pharmacological treatments or drug abuse.

Nitric oxide production in striatum and pallidum of cirrhotic rats

Ammonium and manganese are neurotoxic agents related to brain metabolic disturbances observed after prolonged liver damage. The aim of this study was to assess the production of nitric oxide (NO) in the brain of cirrhotic rats exposed to manganese. We induced cirrhosis by bile duct ligation for 4 weeks in rats. From brain, striatum and globus pallidus were dissected out, and NO synthase activity and the content of nitrites plus nitrates (NOx) were determined. In pallidum we found a diminished constitutive NO synthase activity from cirrhotic rats, independently of manganese exposure. This result was confirmed by low levels of NOx in the same brain area (P<0.05, two-way ANOVA). This finding was not related to protein expression of NO synthase since no differences were observed in immunoblot signals between cirrhotic and sham-operated animals. Results from present study suggest that the production of NO is reduced in basal ganglia during cirrhosis.

Limbic reductions of 5-HT1A receptor binding in human temporal lobe epilepsy

OBJECTIVE

To test the hypothesis that in mesial temporal lobe epilepsy (MTLE) there is involvement outside of mesial structures and that this involvement affects serotonin systems, thus suggesting a mechanism for affective symptoms in this population.

METHODS

Serotonin 5-HT1A receptor binding was studied with PET and [Carbonyl-11C]WAY-100 635 in 14 patients (6 with left-, 8 with right-sided mesial temporal lobe focus) and 14 controls. The 5-HT1A receptor binding potential was calculated for hippocampus, amygdala, orbitofrontal, insular, lateral temporal, and anterior cingulate cortex, in raphe nuclei, and in two regions presumably uninvolved in the epileptogenic process (parietal, and dorsolateral frontal neocortex).

RESULTS

The binding potential was reduced in the epileptogenic hippocampus (p = 0.0001) and amygdala (p = 0.0001) in all patients, including the six with normal [18F]FDG PET and MRI. It was also reduced in the anterior cingulate (p = 0.002), insular (p = 0.015), and lateral temporal cortex (p = 0.029) ipsilaterally to the focus, in contralateral hippocampus (p = 0.025), and in the raphe nuclei (p = 0.016).

CONCLUSION

Patients with severe MTLE show reduced 5-HT1A receptor binding potential in the EEG-focus, and its limbic connections. [(11)C]WAY-100 635 PET may provide additional information to EEG, [18F]FDG PET, and MRI when evaluating patients with intractable seizures. Reductions in 5-HT1A binding in the insula and cingulate suggest a mechanism by which affective symptoms in MTLE may result.

Autoradiographic evaluation of [11C]vinpocetine binding in the human postmortem brain

The main objective ofthe study was to evaluate with autoradiographic technique whether or not [11C]vinpocetine, a compound widely used in the prevention and treatment of cerebrovascular diseases (Cavinton, Gedeon Richter Ltd., Budapest), binds to specific sites in the human brain in post mortem human brain sections. Binding was assessed under four conditions: the incubation was performed using Tris-HCl buffer with or without the addition of salts (0.1% (weight/vol) ascorbic acid, 120 mM NaCl, 5 mM KCl, 2 mM CaCl2 and 1 mM MgCl2), with or without the addition of excess (10 microM) unlabelled vinpocetine. Measurements on digitized autoradiograms indicated that [11C]vinpocetine labelled all grey matter areas in the human brain to a similar extent and no significantly heterogeneous binding could be demonstrated among cortical or subcortical regions. The addition of excess unlabelled vinpocetine lowered the binding slightly in all regions. Although these results indicate that [11C]vinpocetine does not bind to human brain transmitter receptors or transporters with a high affinity (Ki < 10 nM), it cannot be ruled out that the compound binds to receptors and/or transporters with lower affinity.

PET studies on the brain uptake and regional distribution of [11C]vinpocetine in human subjects

OBJECTIVES

Vinpocetine is a compound widely used in the prevention and treatment of cerebrovascular diseases. It is still not clear whether the drug has a direct and specific effect on neurotransmission or its effects are due to extracerebral actions, such as changes in cerebral blood flow. The main objective of the present investigation was to determine the global uptake and regional distribution of radiolabelled vinpocetine in the human brain in order to explore whether it may have direct central nervous system effects.

MATERIAL AND METHODS

Three healthy subjects were examined with positron emission tomography and [11C]vinpocetine. The regional uptake was determined in anatomically defined volumes-of-interest. The fractions of [11C]vinpocetine and labelled metabolites in plasma were determined using high pressure liquid chromatography.

RESULTS

The uptake of [11C]vinpocetine in brain was rapid and 3.7% (mean; n = 4) of the total radioactivity injected was in brain 2 min after radioligand administration. The uptake was heterogeneously distributed among brain regions. When compared with the cerebellum, an a priori reference region, the highest regional uptake was in the thalamus, upper brain stem, striatum and cortex. Following an initial peak, the total concentration of radioactivity in blood was relatively stable with time, whereas the concentration of the unchanged compound decreased with time in an exponential manner.

CONCLUSION

Vinpocetine, administered intravenously in humans, readily passes the blood-brain barrier and enters the brain. Its regional uptake and distribution in the brain is heterogeneous, indicating binding to specific sites. The brain regions showing increased uptake in the human brain correspond to those in which vinpocetine has been shown to induce elevated metabolism and blood flow. These observations support the hypothesis that vinpocetine has direct neuronal actions in the human brain.

An overview on functional receptor autoradiography using [35S]GTPgammaS

[35S]GTPgammaS binding autoradiography is a novel method to study the distribution and function of neurotransmitter receptors in tissue sections. This technique unifies the advantages of receptor-autoradiography and [35S]GTPgammaS binding, providing anatomical and functional information at the same time. Due to these two main features, it can also be called 'functional autoradiography'. [35S]GTPgammaS binding has long been used to study the first step of the intracellular signaling pathway, but until the mid 1990s it has only been performed on cell membrane extracts. Functional autoradiography evolved from this biochemical assay and ligand autoradiography, and is based on the increase in guanine nucleotide exchange at G-proteins upon agonist stimulation. With the technique, activation of G-protein-coupled receptors upon agonist binding can be detected, and, at the same time, the location of activated receptors can also be visualized. Thus only those presumably active G-protein-coupled receptors are visualized that can be involved in signal transduction. In the past 5 years the technique has become more and more frequently used in neuroscience, and it has been adapted to several receptors in different species, including also the human brain. [35S]GTPgammaS binding autoradiography can be used to describe the distribution of G-protein-coupled receptors. Some inferences on their coupling efficiency can also be drawn. Besides the localization of ligand binding sites, it provides information on the action of the ligand on the receptor: agonists, antagonists, and inverse agonists can clearly be distinguished. Moreover, [35S]GTPgammaS binding autoradiography can successfully be combined with other in vitro assays, like receptor autoradiography, in situ hybridization histochemistry, or even with biochemical and electrophysiological experiments. This review presents an overview on the history and the development of this technique. Its main advantages and limitations are summarized, together with a few basic technical questions. A number of experiments performed with [35S]GTPgammaS binding autoradiography so far, and some possible applications for the future, are also reviewed.

PET studies with carbon-11 radioligands in neuropsychopharmacological drug development

A basic problem in the discovery and development of novel drugs to be used in the treatment of neurological and psychiatric disorders is the absence of relevant in vitro or in vivo animal models that can yield results which can be extrapolated to man. Drug research now benefits from the fast development of functional imaging techniques such as positron emission tomography (PET) which trace radiolabelled molecules directly in the human brain. PET uses molecules that are labelled with short-lived radionuclides and injected intravenously into experimental animals, human volunteers or patients. The most frequent approach is to study how an unlabelled drug inhibits specific binding of a well characterised selective PET radioligand. The alternative direct approach is to radiolabel a new potential drug and to trace its uptake, anatomical distribution and binding in brain. Furthermore, the effects of a novel drug on physiological-biochemical parameters, such as glucose metabolism or blood flow, can also be assessed. The demonstration of quantitative relationships between drug binding in vivo and drug effects in patients is used to validate targets for drug action, to correlate pharmacological and physiological effects, and to optimise clinical treatment.

Brain radioligands--state of the art and new trends

Non-invasive radioligand imaging methods for brain receptor studies use either short-lived positron-emitting radionuclides such as 11C and 18F for positron emission tomography (PET) or single photon-emitting radionuclides such as 123I for single photon emission computed tomography (SPECT). PET and SPECT use radioligands which are injected intravenously into experimental animals, human volunteers or patients. The main applications of radioligands in brain research concern human neuropsychopharmacology and the discovery and development of novel drugs to be used in thetherapy of neurological and psychiatric disorders. A basic problem in PET and SPECT brain receptor studies is the lack of useful radioligands with appropriate binding characteristics. Prerequisite criteria need to be satisfied for a radioligand to reveal target binding sites in vivo. This section will discuss these important criteria and also review recent examples in neuroreceptor radioligand development such as selective radioligands for brain monoamine transporters.

[The effect of a single-dose intravenous vinpocetine on brain metabolism in patients with ischemic stroke]

The effect of a single-dose i.v. infusion of vinpocetine on the cerebral blood flow (CBF) and glucose metabolism of post-stroke patients was studied by measuring the regional and global cerebral metabolic rates of glucose (CMRglu) and the corresponding kinetic constants before and after treatment. Transcranial Doppler (TCD) and single photon emission tomography (SPECT) measurements were also performed. The cerebral glucose metabolism was significantly higher in the contralateral hemisphere than in the affected one before therapy. In the affected hemisphere the regional glucose metabolism was inhomogenous: relatively low values were measured in the stroke region, whereas it was increased in the peristroke region. Although a single-dose vinpocetine treatment did not affect significantly the regional or global metabolic rates of glucose, the glucose transport (both intracellular up-take and release) was strongly affected in the whole brain, in the contralateral hemisphere and in the peri-infarct area of the symptomatic hemisphere. A slightly increased (not significant, N. S.) cerebral blood flow could be observed in the contralateral and a decreased flow (N. S.) in the symptomatic hemisphere.

Neural networks for internal reading and visual imagery of reading: a PET study

Regional cerebral blood flow (rCBF) measurements with positron emission tomography (PET) were made on 10 volunteers in rest condition as well as while the subjects, with closed eyes, (i) internally listed the letters of the alphabet and cited the first verse of the Hungarian national anthem, (ii) visualised the capital letters of the alphabet, and (iii) visualised the capital letters of the first verse of the Hungarian national anthem. Significant changes in rCBF indicated various networks of cortical neuronal populations active during the tasks. Internal listing, as compared to the rest condition, activated the left precentral gyrus. Visualising the letters of the alphabet, when compared to the rest condition, activated a cortical network comprising fields along the banks of the left and right intraparietal sulci, the left medial frontal, precentral and occipital sulci, and the right superior frontal gyrus. Visualising the letters of the anthem, when compared to the rest condition, activated a cortical network comprising fields along the banks of the left and right intraparietal sulci, the left medial and inferior frontal gyri, and the right anterior cingulate gyrus. Contrasting the two visualisation tasks revealed task specific activation in the left lateral occipital gyrus (alphabet vs. anthem visualisation) and in the left anterior cingulate gyrus (anthem vs. alphabet visualisation). The data indicate that visual imagery of letters of the alphabet or a text engages a widespread network of cortical fields in the visual association cortices and the frontal cortex, without the engagement of the primary (V1) and secondary (V2) visual cortical areas. This finding supports the hypothesis that neuronal populations engaged by visual imagery and visual perception only partially overlap. The networks, activated in the visualisation tasks, have a core which is identical in the different visualisation tasks. The core network is complemented in a task-specific manner by the recruitment of additional cortical neuronal populations.

Role of sodium channel inhibition in neuroprotection: effect of vinpocetine

Vinpocetine (ethyl apovincaminate) discovered during the late 1960s has successfully been used in the treatment of central nervous system disorders of cerebrovascular origin for decades. The increase in the regional cerebral blood flow in response to vinpocetine administration is well established and strengthened by new diagnostical techniques (transcranial Doppler, near infrared spectroscopy, positron emission tomography). The latest in vitro studies have revealed the effect of the compound on Ca(2+)/calmodulin dependent cyclic guanosine monophosphate-phosphodiesterase 1, voltage-operated Ca(2+) channels, glutamate receptors and voltage dependent Na(+)-channels; the latest being especially relevant to the neuroprotective action of vinpocetine. The good brain penetration profile and heterogenous brain distribution pattern (mainly in the thalamus, basal ganglia and visual cortex) of labelled vinpocetin were demonstrated by positron emission tomography in primates and man. Multicentric, randomized, placebo-controlled clinical studies proved the efficacy of orally administered vinpocetin in patients with organic psychosyndrome. Recently positron emission tomography studies have proved that vinpocetine is able to redistribute regional cerebral blood flow and enhance glucose supply of brain tissue in ischemic post-stroke patients.

Cerebral blood flow and glucose metabolism in mitochondrial disorders

OBJECTIVE

To investigate cerebral metabolism by 2-[18F]fluorodeoxy-d-glucose (FDG) uptake using PET and cerebrovascular reverse capacity by transcranial Doppler sonography (TCD) in different mitochondrial diseases (mitochondrial myopathy; mitochondrial encephalopathy, lactacidosis, and stroke-like episodes [MELAS]; and chronic external ophthalmoplegia).

BACKGROUND

Previous studies on individual patients with mitochondriopathies revealed abnormal accumulations of mitochondria in endothelium, smooth muscle cells, and pericytes of blood vessels in different parts of the nervous system (cerebrum, cerebellum, sural nerve) and skeletal muscle. On this basis, some investigators suggested a pathogenic role of vascular involvement in the MELAS syndrome and other encephalopathies. smhd1

DESIGN/METHODS

The authors investigated neuronal metabolism and cerebrovascular involvement with PET in 5 cases and with TCD with acetazolamide stimulation in 15 cases. The patients were divided into three groups: 1) interictal MELAS (n = 4); 2) progressive external ophthalmoplegia (n = 6); and 3) pure mitochondrial myopathy and neuropathy (n = 5). The results were compared with those from matched normal control subjects. The diagnoses were based on clinical phenotype as well as histopathologic and molecular analysis.

RESULTS

Cerebral glucose uptake was impaired in all patients, both with and without CNS symptoms, particularly in the occipital and temporal lobes. The vasoreactivity of the small arterioles to acetazolamide did not differ significantly between the patients and healthy control subjects or between the different groups of mitochondrial disorders.

CONCLUSIONS

MELAS does not appear to be a functional disturbance of arterioles leading to an ischemic vascular event. The clinical symptoms in MELAS are not the result of a mitochondrial angiopathy but are the consequences of a mitochondrial cytopathy affecting neurons or glia. There is no correlation between the decreased glucose metabolism and the duration of the disease.

Visual form discrimination from texture cues: a PET study

With the purpose of localising the cerebral cortical areas participating in the discrimination of visual form generated exclusively by texture cues, we measured changes in regional cerebral blood flow (rCBF) with positron emissions tomography (PET) and 15O-butanol as the tracer. The subjects performed two odd-one-out discrimination tasks: a form-from-texture discrimination task (in which a visual form was defined by differences in texture) and its reference task, the discrimination of texture. During task performance, activated fields were present bilaterally in the primary visual cortex and its immediate extrastriate cortex, the right lateral occipital gyrus, bilaterally in the fusiform and superior temporal gyri and posterior parts of the superior parietal lobules, along the medial bank of the right intraparietal sulcus, and in the right supramarginal gyrus. Other fields were found in the cingulate and prefrontal cortex. The findings demonstrate that the discrimination of visual form as defined by texture engages cortical fields that are widely distributed ion the human brain. In the visual cortex, the activated fields are present in both the occipito-temporal and occipito-parietal visual areas. These results suggest that the perception and discrimination of forms in the visual system requires the joint-activation of neuronal populations in the visual cortex.

Neuronal correlates of real and illusory contour perception: functional anatomy with PET

Illusory contours provide a striking example of the visual system's ability to extract a meaningful representation of the surroundings from fragmented visual stimuli. Psychophysical and neurophysiological data suggest that illusory contours are processed in early visual cortical areas, and neuroimaging studies in humans have shown that Kanizsa-type illusory contours activate early retinotopic visual areas that are also activated by real contours. It is not known whether other types of illusory contours are processed by the same mechanisms, nor is it clear to what extent attentional effects may have influenced these results, as no attempt was made to match the salience of real and illusory stimuli in previous imaging studies. It therefore remains an open question whether there are any brain regions specifically involved in the perception of illusory contours. To address these questions, we have used 15O-butanol positron emission tomography (PET) and a novel kind of illusory contour stimulus that is induced only by aligned line ends. By employing a form discrimination task that was matched for attention and stimulus salience across conditions we were able to directly contrast perception of real and illusory contours. We found that the regions activated by illusory contour perception were the same as those activated by real contours. Only one region, located in the right fusiform gyrus, was significantly more strongly activated by perception of illusory contours than by real contours. In addition, a principal component analysis suggested that illusory contour perception is associated with a change in the correlation between V1 and V2. We conclude that different kinds of illusory contours are processed by the same cortical regions and that these regions overlap extensively with those involved in processing of real contours. At the regional level, perception of illusory contours thus appears to differ from perception of real contours by the degree of involvement of higher visual areas as well as by the nature of interaction between early visual areas.

Brain uptake and plasma metabolism of [11C]vinpocetine: a preliminary PET study in a cynomolgus monkey

Vinpocetine, a vinca alkaloid, is a widely used therapeutic agent in patients with acute and chronic stroke. To reveal the mechanisms of vinpocetine action in the brain, vinpocetine was labeled with 11C. Positron emission tomography (PET) was used to determine the uptake and distribution of [11C]vinpocetine in brain regions and the trunk of a cynomolgous monkey in two independent measurements. The concentration of vinpocetine and its labeled metabolites was determined in blood and plasma using high-performance liquid chromatography (HPLC). Almost identical measurements were obtained in the two independent studies. After intravenous administration, following an initial peak, the total concentration of radioactivity in blood was relatively stable with time, whereas the concentration of the unchanged compound decreased with time in an exponential manner. The uptake of [11C]vinpocetine in brain was rapid, and 5% of the radioactivity totally injected was present in the brain 2 minutes after drug administration, indicating that the compound entered the brain readily. The radioactivity uptake was heterogeneously distributed among brain regions and was highest in the thalamus, the basal ganglia, and certain neocortical regions. The high brain uptake and the heterogeneous regional distribution indicate that direct central nervous system (CNS) effects of vinpocetine must be considered as explanation for the therapeutic effects. The detailed exploration of this suggestion requires further studies.

[Autoradiography of neurotransmitter receptors in whole human brain hemisphere sections]

Autoradiography is one of our most important tools to gain knowledge about neurotransmitter-receptors playing a key-role in information transmission between neurons. Autoradiography, in its most sophisticated form, is performed on whole human hemispheric sections. The main objective of the authors is to present this application of autoradiography. This in vitro method produces images with high spatial resolution that enable us to qualitatively and quantitatively characterize the regional distribution of the receptors under study. With this technique both the different receptor systems in various physiological and pathological conditions of the brain and the pharmacological parameters of the radioligand, itself, used for a given investigation can be analysed. As a consequence, the results of autoradiography can be successfully used in drug development and trial, brain research and, indirectly, in the every day practice of physicians (diagnosis, differentialdiagnosis, therapy). Autoradiography plays an important role in the validation of in vivo techniques (positron emission tomography, single photon emission tomography) and results in a more complex (in vivo and in vitro) insight into the neurochemical organisation of the brain.

[Cerebral uptake and metabolism of (11C) Vinpocetine in monkeys: PET studies]

Vinpocetine, a vinca alkaloid, is a therapeutic agent widely used in the treatment of acute and chronic stroke patients. To explore the uptake and distribution of vinpocetine in the primate brain, vinpocetine was labelled with 11C and positron emission tomography (PET) was used to measure the uptake and distribution of 11C-vinpocetine in the brain and the trunk of a cynomolgous monkey. HPLC was used to determine the concentration of vinpocetine and its labelled metabolites in blood and plasma. Following the radioligand's intravenous administration, after an initial peak, the total concentration of radioactivity in blood was relatively stable with time. The uptake of 11C-vinpocetine into the brain was rapid and about 5% of the total injected radioactivity was present in the brain two minutes after drug administration. These facts indicate that the compound passes the blood-brain barrier readily and enters the brain. The radioactivity uptake was heterogeneously distributed among brain regions. The highest concentrations were found in the thalamus, the basal ganglia and certain neocortical regions. In an earlier PET investigation on chronic stroke patients the highest increases in cerebral blood flow and glucose metabolism after intravenous vinpocetine treatment occurred in these anatomical structures. The heterogenous regional distribution of vinpocetine and the observation that the highest uptake values in brain structures go parallel with the greatest regional blood flow and glucose metabolic rate increases indicate that direct CNS effects of vinpocetine should be considered as an explanation for the therapeutic effects. The confirmation of this suggestion requires further investigations.

Cerebral effects of a single dose of intravenous vinpocetine in chronic stroke patients: a PET study

The effects of vinpocetine (Cavinton) on the cerebral glucose metabolism of chronic stroke patients are studied with positron emission tomography. The regional and global cerebral metabolic rates of glucose (CMRglu) and the kinetic constants related to them are quantified before and after single-dose intravenous vinpocetine treatment. These measurements are completed with transcranial Doppler sonography and single photon emission computed tomography to explore the possible mechanisms underlying the resulting changes in glucose uptake and metabolism in the brain. The authors' findings indicate that a single-dose vinpocetine treatment, although it does not affect significantly the regional or global metabolic rates of glucose, improves significantly the transport of glucose (both uptake and release) through the blood-brain barrier in the whole brain, the entire contralateral hemisphere, and in the brain tissue around the infarct area of the symptomatic hemisphere. These changes are in accord with increased blood flow in the entire contralateral hemisphere as well as decreased blood flow velocity and increased peripheral vessel resistance in the entire symptomatic hemisphere.

Visual form discrimination from texture cues: a PET study

With the purpose of localising the cerebral cortical areas participating in the discrimination of visual form generated exclusively by texture cues, we measured changes in regional cerebral blood flow (rCBF) with positron emissions tomography (PET) and 15O-butanol as the tracer. The subjects performed two odd-one-out discrimination tasks: a form-from-texture discrimination task (in which a visual form was defined by differences in texture) and its reference task, the discrimination of texture. During task performance, activated fields were present bilaterally in the primary visual cortex and its immediate extrastriate cortex, the right lateral occipital gyrus, bilaterally in the fusiform and superior temporal gyri and posterior parts of the superior parietal lobules, along the medial bank of the right intraparietal sulcus, and in the right supramarginal gyrus. Other fields were found in the cingulate and prefrontal cortex. The findings demonstrate that the discrimination of visual form as defined by texture engages cortical fields that are widely distributed ion the human brain. In the visual cortex, the activated fields are present in both the occipito-temporal and occipito-parietal visual areas. These results suggest that the perception and discrimination of forms in the visual system requires the joint-activation of neuronal populations in the visual cortex.

[Cerebral positron emission tomographic study in systemic lupus erythematosus]

The cerebral glucose metabolism in eight patients with systemic lupus erythematosus (SLE) and in five healthy controls were examined by positron emission tomography (PET) using 18-F-labeled deoxy-glucose (FDG) as tracer. One of the eight patients had no abnormality by magnetic resonance imaging (MRI), three of them had cerebral atrophy and four patients had multiple white matter hyperintensities and vascular infarcts in the striatum as assessed by MRI. With FDG-PET, inhomogeneous multifocal cerebral glucose hypometabolism was detected, more frequently in the temporal lobe of right hemisphere. The PET findings did not correlate always with the neurological symptoms. Abnormalities in brain metabolism can be detected more frequently by PET, than morphological changes by MRI, indicating the involvement of the central nervous system.

[First Hungarian experiences with positron emission tomography (PET) studies. Members of the PET working group]

Diagnostic investigations commenced on the 28th of June 1994 in Hungary's and Central Europe's first PET Centre at the University Medical School of Debrecen. The Centre is equipped with a GE 4096 Plus whole body PET scanner. A metabolic tracer, 18F-deoxy-D-glucose (FDG), was used in the investigations. During the first 15 months 249 PET investigations were made in the Centre of which 242 were diagnostic and 7 normal subjects served as control for the patient studies with brain scans. The number of oncological indications (intra- and extracranial tumours, Hodgkin's lymphomas) was n = 105 (43.4% of the 242 diagnostic examinations), neurological investigations (without intracranial tumours) formed the dominant group (n = 117; 48.3%), whereas the number of cardiological indications was 20 (8.3%). The oncological studies included those of intracranial tumours (n = 76; 31.4%); thyroid tumours (n = 9; 3.7%); Hodgkin's lymphomas (n = 7; 2.9%) and other extracranial tumours (n = 13; 5.4%). The distribution of different neurological and psychiatric investigations was as follows: localization of focal epileptogen zone (n = 60; 24.8%); differential diagnosis of dementias (n = 30; 12.4%); exploration of cerebrovascular diseases (n = 10; 4.1%); and other neurological diseases (n = 17; 7.0%). The main objective of the cardiological PET investigations was the exploration of viable myocardium. The present paper overviews both the procedures (including administrative issues, as well) and the results of the first 249 FDG-PET investigations.

Assumptions and validations of statistical tests for functional neuroimaging

We contrast two statistical methods: three-dimensional cluster analysis and statistical parametric mapping. We show that three-dimensional cluster analysis is based on a neurobiological theory of the regulation of blood flow and, unlike statistical parametric mapping, carries a minimum of assumptions that are tested. Statistical parametric mapping is a formal approach, which is based on a multitude of assumptions of which the majority have not been validated. We also demonstrate that in practice three-dimensional cluster analysis has a reasonable balance between sensitivity and the probability of false positives, giving high reproducibility with data on e.g. colour discrimination.

[Positron emission tomography: foundations and applications]

Positron emission tomography (PET) is a non-invasive biomedical imaging technique whereby the distribution of biological tracer molecules, labelled by positron emitting isotopes, in the living body can be studied quantitatively. As theoretically an metabolically active molecule can be labelled, the technique is applicable to the measurement of any biochemical or physiological process in proper anatomical context. The introduction of PET has revolutionised the exploration of normal physiological functions. With the help of technique, among others, anatomical structures underlying mental functions can be localised in the human brain, the receptor architecture of the nervous system can be mapped, or the kinetics of pharmacons can be properly measured and modelled. In the clinical practice, PET has proven to be a uniquely useful diagnostic technique in neurology, psychiatry, cardiology, and oncology in establishing primary diagnosis and differential diagnosis, designing therapeutic interventions as well as assessing their efficacy. Hungary's and Central European region's first PET center has been established at the University Medical School in Debrecen.

Cortical representation of self-paced finger movement

We compared the cortical fields activated by simple, self-paced index-finger flexions with those activated during visually triggered movement and rest using PET. Of 12 fields detected during self-paced movement compared to rest, three were located in the classically defined motor areas: primary motor area (M1), premotor cortex (PM) and supplementary motor area (SMA). The latter extended into the cingulate motor area (CMA). Four corresponding clusters were also found when triggered movement was subtracted from self-paced movement. The change in regional cerebral blood flow (rCBF) was greater in SMA than in PM during self-paced movement compared with either control. We conclude that repetitive, self-paced index-finger flexions can activate SMA, PM and CMA, and that this movement activates SMA more strongly than PM.

Activation by attention of the human reticular formation and thalamic intralaminar nuclei

It has been known for over 45 years that electrical stimulation of the midbrain reticular formation and of the thalamic intralaminar nuclei of the brain alerts animals. However, lesions of these sectors fail to impair arousal and vigilance in some cases, making the role of the ascending activating reticular system controversial. Here, a positron emission tomographic study showed activation of the midbrain reticular formation and of thalamic intralaminar nuclei when human participants went from a relaxed awake state to an attention-demanding reaction-time task. These results confirm the role of these areas of the brain and brainstem in arousal and vigilance.