Neural correlates of finger gnosis

Neuropsychological studies have described patients with a selective impairment of finger identification in association with posterior parietal lesions. However, evidence of the role of these areas in finger gnosis from studies of the healthy human brain is still scarce. Here we used functional magnetic resonance imaging to identify the brain network engaged in a novel finger gnosis task, the intermanual in-between task (IIBT), in healthy participants. Several brain regions exhibited a stronger blood oxygenation level-dependent (BOLD) response in IIBT than in a control task that did not explicitly rely on finger gnosis but used identical stimuli and motor responses as the IIBT. The IIBT involved stronger signal in the left inferior parietal lobule (IPL), bilateral precuneus (PCN), bilateral premotor cortex, and left inferior frontal gyrus. In all regions, stimulation of nonhomologous fingers of the two hands elicited higher BOLD signal than stimulation of homologous fingers. Only in the left anteromedial IPL (a-mIPL) and left PCN did signal strength decrease parametrically from nonhomology, through partial homology, to total homology with stimulation delivered synchronously to the two hands. With asynchronous stimulation, the signal was stronger in the left a-mIPL than in any other region, possibly indicating retention of task-relevant information. We suggest that the left PCN may contribute a supporting visuospatial representation via its functional connection to the right PCN. The a-mIPL may instead provide the core substrate of an explicit bilateral body structure representation for the fingers that when disrupted can produce the typical symptoms of finger agnosia

Apraxia: a review

Praxic functions are frequently altered following brain lesion, giving rise to apraxia - a complex pattern of impairments that is difficult to assess or interpret. In this chapter, we review the current taxonomies of apraxia and related cognitive and neuropsychological models. We also address the questions of the neuroanatomical correlates of apraxia, the relation between apraxia and aphasia and the analysis of apraxic errors. We provide a possible explanation for the difficulties encountered in investigating apraxia and also several approaches to overcome them, such as systematic investigation and modeling studies. Finally, we argue for a multidisciplinary approach. For example, apraxia should be studied in consideration with and could contribute to other fields such as normal motor control, neuroimaging and neurophysiology

Sound recognition and localization in man: specialized cortical networks and effects of acute circumscribed lesions

Functional imaging studies have shown that information relevant to sound recognition and sound localization are processed in anatomically distinct cortical networks. We have investigated the functional organization of these specialized networks by evaluating acute effects of circumscribed hemispheric lesions. Thirty patients with a primary unilateral hemispheric lesion, 15 with right-hemispheric damage (RHD) and 15 with left-hemispheric damage (LHD), were evaluated for their capacity to recognise environmental sounds, to localize sounds in space and to perceive sound motion. One patient with RHD and 2 with LHD had a selective deficit in sound recognition; 3 with RHD a selective deficit in sound localization; 2 with LHD a selective deficit in sound motion perception; 4 with RHD and 3 with LHD a combined deficit of sound localization and motion perception; 2 with RHD and 1 with LHD a combined deficit of sound recognition and motion perception; and 1 with LHD a combined deficit of sound recognition, localization and motion perception. Five patients with RHD and 6 with LHD had normal performance in all three domains. Deficient performance in sound recognition, sound localization and/or sound motion perception was always associated with a lesion that involved the shared auditory structures and the specialized What and/or Where networks, while normal performance was associated with lesions within or outside these territories. Thus, damage to regions known to be involved in auditory processing in normal subjects is necessary, but not sufficient for a deficit to occur. Lesions of a specialized network was not always associated with the corresponding deficit. Conversely, specific deficits tended not be associated predominantly with lesions of the corresponding network; e.g. deficits in auditory spatial tasks were observed in patients whose lesions involved to a larger extent the shared auditory structures and the specialized What network than the specialized Where network, and deficits in sound recognition in patients whose lesions involved mostly the shared auditory structures and to a varying degree the specialized What network. The human auditory cortex consists of functionally defined auditory areas, whose intrinsic organization is currently not understood. In particular, areas involved in the What and Where pathways can be conceived as: (1) specialized regions, in which lesions cause dysfunction limited to the damaged part; observed deficits should be then related to the specialization of the damaged region and their magnitude to the extent of the damage; or (2) specialized networks, in which lesions cause dysfunction that may spread over the two specialized networks; observed deficits may then not be related to the damaged region and their magnitude not proportional to the extent of the damage. Our results support strongly the network hypothesi

Cortical motion deafness

The extent to which the auditory system, like the visual system, processes spatial stimulus characteristics such as location and motion in separate specialized neuronal modules or in one homogeneously distributed network is unresolved. Here we present a patient with a selective deficit for the perception and discrimination of auditory motion following resection of the right anterior temporal lobe and the right posterior superior temporal gyrus (STG). Analysis of stimulus identity and location within the auditory scene remained intact. In addition, intracranial auditory evoked potentials, recorded preoperatively, revealed motion-specific responses selectively over the resected right posterior STG, and electrical cortical stimulation of this region was experienced by the patient as incoming moving sounds. Collectively, these data present a patient with cortical motion deafness, providing evidence that cortical processing of auditory motion is performed in a specialized module within the posterior STG

Know Thyself: Behavioral Evidence for a Structural Representation of the Human Body

Background: Representing one's own body is often viewed as a basic form of self-awareness. However, little is known about structural representations of the body in the brain.Methods and Findings: We developed an inter-manual version of the classical "in-between'' finger gnosis task: participants judged whether the number of untouched fingers between two touched fingers was the same on both hands, or different. We thereby dissociated structural knowledge about fingers, specifying their order and relative position within a hand, from tactile sensory codes. Judgments following stimulation on homologous fingers were consistently more accurate than trials with no or partial homology. Further experiments showed that structural representations are more enduring than purely sensory codes, are used even when number of fingers is irrelevant to the task, and moreover involve an allocentric representation of finger order, independent of hand posture.Conclusions: Our results suggest the existence of an allocentric representation of body structure at higher stages of the somatosensory processing pathway, in addition to primary sensory representation

not available

As cianobactérias pertencem a um grupo de organismos que surgiram no planeta há cerca de 3,5 bilhões de anos. Durante 270 milhões de anos elas dominaram, em um período que ficou conhecido como o Período das Cyanophyceae (Pré-Cambriano). Águas eutrofizadas oferecem os requisitos para haver floração aumentando as chances estatísticas de aparecimento de cianobactérias, inclusive as tóxicas. Há alteração substancial das características das comunidades e do ecossistema e, por seu potencial tóxico, esses organismos causam conseqüências danosas à integridade ambiental e à saúde pública. Essas florações são resultado da interação de fatores físicos, químicos e bióticos, evidenciados por crescimento explosivo - florações - de poucas espécies, freqüentemente as menos exigentes a gás carbônico. Entre as cianobactérias formadoras de florações destacam-se os gêneros: Aphanizomenon sp., Oscillatoria sp., Anabaena sp., Microcystis sp., Gloeotrichia sp., Cylindrospermospsis sp. e Nodularia sp. Entre as cianobactérias produtoras de toxinas destacam-se as espécies: Anabaena flos-aquae, Microcysits aeruginosa, Aphanizomenon flos-aquae, Oscillatoria agardhii, Cylindrospermopsis raciborskii e Nodularia spumigena. O problema para a saúde pública e ambiental relaciona-se à liberação das toxinas que sempre ocorre após a lise celular, devido ao uso de algicidas, ao estresse celular ou à senescência. As cianotoxinas - neurotoxinas, hepatotoxinas, endotoxinas (lipopolissacarídeos) - não causam os mesmos efeitos nos diferentes organismos que as ingerem. Para análises quantitativas e qualitativas das amostras fitoplanctônicas são necessárias rotinas laboratoriais, que têm início desde a coleta, estocagem, sedimentação e identificação das espécies ao microscópio. Em câmaras de sedimentação apropriadas é possível contar e identificar os organismos em questão. O volume celular é estimado por meio de formas geométricas, correspondentes às dimensões celulares dos organismos. O carbono orgânico e os pigmentos fotossintetizantes, principalmente a clorofila a, fornecem indicação da biomassa fitoplanctônica. A extração desta pode ser feita utilizando-se acetona, etanol ou metanol. Os métodos mais usados para determinação da concentração de clorofila a são: fluorimetria, espectrofotômetria e HPLC, este último o método mais preciso. No Brasil têm sido registradas ocorrências de florações de cianobactérias e a preocupação tem aumentado significamente após o caso de Caruaru (PE). Como é difícil prever as florações de cianobactérias potencialmente tóxicas, alguns métodos laboratoriais, como bioensaios, HPLC, CG, ELISA, Inibição de Fosfatase e Inibição de Acetilcolinesterase têm sido de grande ajuda na determinação das cianotoxinas, o que possibilita que as empresas abastecedoras de água tomem as providências cabíveis, quanto ao abastecimento da população e cumprimento da Portaria 518, de 24 de março de 2004. No entanto a Portaria nº 518 do Ministério da Saúde mostra-se ineficaz pela falta de artigos sobre o gerenciamento dos corpos hídricos eutrofizados, que mostram alterações em suas características e que podem ser associados a problemas de saúde pública, e também pela falta de penalidades e outras sanções (exemplo: fiscalização) que auxiliem no cumprimento da legislação. Devido a isso, procedimentos e profissionais devem ser encontrados e treinados para o entendimento de como, onde e por que, as florações acontecem.Cyanobacteria are part of a group of organisms that have had a long evolutionary history extending to at least 3,5 billion years ago. During 270 million years they had been dominant, in a period that was known as the \"Age of Cyanophyceae\" (Early Cambrian Period or Proterozoic Era). Eutrophic waters offer the requirements for the blooms increasing statistically the chances of cyanobacteria emergence, including the toxic ones. There is substantial disturbance of characteristics of the communities and ecosystem and, because of their toxic potential, those organisms cause harmful consequences to the environmental integrity and public health. Those blooms are a result of an interaction of physical, chemical and biotic factors, evidenced by the proliferation of few species, frequently the least demanding ones to carbonic gas. Globally among the most frequently found freshwater cyanobacteria forming water-blooms it must be emphasized the following strains: Aphanizomenon sp., Oscillatoria sp., Anabaena sp., Microcystis sp., Gloeotrichia sp., Cylindrospermospsis sp. and Nodularia sp. Among the cyanobacteria producing toxins it must be emphasized the following species: Anabaena flos-aquae, Microcysits aeruginosa, Aphanizomenon flos-aquae, Oscillatoria agardhii, Cylindrospermopsis raciborskii and Nodularia spumigena. Environmental and public health problems are largely associated with the release of toxins occurring after cellular lisys, caused by the use of algicides, cell stress or senescence. Cyanotoxins - neurotoxins, hepatotoxins, endotoxins (lipopolysaccharides) - cause distinct effects in the different organisms ingesting them. For quantitative and qualitative analyses of phytoplanktonic samples they are necessary laboratory routines as collection, stocking, sedimentation and identification of the species performed by microscopic examination. It is possible to count and identify such organisms in appropriate sedimentation chambers. Cell volumes are calculated for each species from formulae for solid geometric shapes that most closely match the cell shape based on cell dimensions. Organic carbon and photosynthetic pigments primarily chlorophyll-a are used to estimate the biomass of the phytoplankton. Chlorophyll-a extraction can be made by using acetone, ethanol or methanol. The major methods used for determination of chlorophyll-a concentrations are fluorometry, spectrophotometry and HPLC. In particular, HPLC has been considered the most accurate analytical method. Occurrences of cyanobacteria blooms in Brazil have been recorded, and a concern has becoming increasingly significant after the Caruaru (PE) episode. It is difficult to foresee the potentially toxic cyanobacteria blooms, so some laboratory methods as Bioassays, HPLC, CG, ELISA, Inhibition of Phosphatase and Inhibition of Acetylcholinesterase have been of great help in the determination of the cyanotoxins, what permits that the health authorities take reasonable providences related to drinking water supplies and fulfill the Guideline 518, of March 24, 2004. Nevertheless, national legislation becomes inefficient by the lack of ordinances about the management of eutrophic water bodies, which may notably alter the characteristics of aquatic ecosystems and cause public health problems. Penalties and other sanctions to assist in enforcement of the legislation are also needed. Procedures must be taken and operators must be trained in order to clarify how, where and why blooms happen

not available

As cianobactérias pertencem a um grupo de organismos que surgiram no planeta há cerca de 3,5 bilhões de anos. Durante 270 milhões de anos elas dominaram, em um período que ficou conhecido como o Período das Cyanophyceae (Pré-Cambriano). Águas eutrofizadas oferecem os requisitos para haver floração aumentando as chances estatísticas de aparecimento de cianobactérias, inclusive as tóxicas. Há alteração substancial das características das comunidades e do ecossistema e, por seu potencial tóxico, esses organismos causam conseqüências danosas à integridade ambiental e à saúde pública. Essas florações são resultado da interação de fatores físicos, químicos e bióticos, evidenciados por crescimento explosivo - florações - de poucas espécies, freqüentemente as menos exigentes a gás carbônico. Entre as cianobactérias formadoras de florações destacam-se os gêneros: Aphanizomenon sp., Oscillatoria sp., Anabaena sp., Microcystis sp., Gloeotrichia sp., Cylindrospermospsis sp. e Nodularia sp. Entre as cianobactérias produtoras de toxinas destacam-se as espécies: Anabaena flos-aquae, Microcysits aeruginosa, Aphanizomenon flos-aquae, Oscillatoria agardhii, Cylindrospermopsis raciborskii e Nodularia spumigena. O problema para a saúde pública e ambiental relaciona-se à liberação das toxinas que sempre ocorre após a lise celular, devido ao uso de algicidas, ao estresse celular ou à senescência. As cianotoxinas - neurotoxinas, hepatotoxinas, endotoxinas (lipopolissacarídeos) - não causam os mesmos efeitos nos diferentes organismos que as ingerem. Para análises quantitativas e qualitativas das amostras fitoplanctônicas são necessárias rotinas laboratoriais, que têm início desde a coleta, estocagem, sedimentação e identificação das espécies ao microscópio. Em câmaras de sedimentação apropriadas é possível contar e identificar os organismos em questão. O volume celular é estimado por meio de formas geométricas, correspondentes às dimensões celulares dos organismos. O carbono orgânico e os pigmentos fotossintetizantes, principalmente a clorofila a, fornecem indicação da biomassa fitoplanctônica. A extração desta pode ser feita utilizando-se acetona, etanol ou metanol. Os métodos mais usados para determinação da concentração de clorofila a são: fluorimetria, espectrofotômetria e HPLC, este último o método mais preciso. No Brasil têm sido registradas ocorrências de florações de cianobactérias e a preocupação tem aumentado significamente após o caso de Caruaru (PE). Como é difícil prever as florações de cianobactérias potencialmente tóxicas, alguns métodos laboratoriais, como bioensaios, HPLC, CG, ELISA, Inibição de Fosfatase e Inibição de Acetilcolinesterase têm sido de grande ajuda na determinação das cianotoxinas, o que possibilita que as empresas abastecedoras de água tomem as providências cabíveis, quanto ao abastecimento da população e cumprimento da Portaria 518, de 24 de março de 2004. No entanto a Portaria nº 518 do Ministério da Saúde mostra-se ineficaz pela falta de artigos sobre o gerenciamento dos corpos hídricos eutrofizados, que mostram alterações em suas características e que podem ser associados a problemas de saúde pública, e também pela falta de penalidades e outras sanções (exemplo: fiscalização) que auxiliem no cumprimento da legislação. Devido a isso, procedimentos e profissionais devem ser encontrados e treinados para o entendimento de como, onde e por que, as florações acontecem.Cyanobacteria are part of a group of organisms that have had a long evolutionary history extending to at least 3,5 billion years ago. During 270 million years they had been dominant, in a period that was known as the \"Age of Cyanophyceae\" (Early Cambrian Period or Proterozoic Era). Eutrophic waters offer the requirements for the blooms increasing statistically the chances of cyanobacteria emergence, including the toxic ones. There is substantial disturbance of characteristics of the communities and ecosystem and, because of their toxic potential, those organisms cause harmful consequences to the environmental integrity and public health. Those blooms are a result of an interaction of physical, chemical and biotic factors, evidenced by the proliferation of few species, frequently the least demanding ones to carbonic gas. Globally among the most frequently found freshwater cyanobacteria forming water-blooms it must be emphasized the following strains: Aphanizomenon sp., Oscillatoria sp., Anabaena sp., Microcystis sp., Gloeotrichia sp., Cylindrospermospsis sp. and Nodularia sp. Among the cyanobacteria producing toxins it must be emphasized the following species: Anabaena flos-aquae, Microcysits aeruginosa, Aphanizomenon flos-aquae, Oscillatoria agardhii, Cylindrospermopsis raciborskii and Nodularia spumigena. Environmental and public health problems are largely associated with the release of toxins occurring after cellular lisys, caused by the use of algicides, cell stress or senescence. Cyanotoxins - neurotoxins, hepatotoxins, endotoxins (lipopolysaccharides) - cause distinct effects in the different organisms ingesting them. For quantitative and qualitative analyses of phytoplanktonic samples they are necessary laboratory routines as collection, stocking, sedimentation and identification of the species performed by microscopic examination. It is possible to count and identify such organisms in appropriate sedimentation chambers. Cell volumes are calculated for each species from formulae for solid geometric shapes that most closely match the cell shape based on cell dimensions. Organic carbon and photosynthetic pigments primarily chlorophyll-a are used to estimate the biomass of the phytoplankton. Chlorophyll-a extraction can be made by using acetone, ethanol or methanol. The major methods used for determination of chlorophyll-a concentrations are fluorometry, spectrophotometry and HPLC. In particular, HPLC has been considered the most accurate analytical method. Occurrences of cyanobacteria blooms in Brazil have been recorded, and a concern has becoming increasingly significant after the Caruaru (PE) episode. It is difficult to foresee the potentially toxic cyanobacteria blooms, so some laboratory methods as Bioassays, HPLC, CG, ELISA, Inhibition of Phosphatase and Inhibition of Acetylcholinesterase have been of great help in the determination of the cyanotoxins, what permits that the health authorities take reasonable providences related to drinking water supplies and fulfill the Guideline 518, of March 24, 2004. Nevertheless, national legislation becomes inefficient by the lack of ordinances about the management of eutrophic water bodies, which may notably alter the characteristics of aquatic ecosystems and cause public health problems. Penalties and other sanctions to assist in enforcement of the legislation are also needed. Procedures must be taken and operators must be trained in order to clarify how, where and why blooms happen