Transient decrease in water diffusion observed in human occipital cortex during visual stimulation

Darquié, Anne; Poline, Jean‐Baptiste; Poupon, Cyril; Saint‐Jalmes, Hervé; Bihan, Denis Le

doi:10.1073/pnas.151125698

Cited by 163 publications

(169 citation statements)

References 51 publications

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“…18 Tracer studies do not typically enable reconstruction of line trajectories of fibers, making it difficult to assess the topographic connectivities within a pathway. While it has been possible to map human activation sites non-invasively with PET, 19,20 fMRI, [21][22][23] and potentially functional diffusion, 24 there had been no non-invasive way to trace neuronal connections in living humans. This motivated the development of DTT for non-invasive human studies.…”

Section: Biological Backgroundmentioning

confidence: 99%

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

et al. 2002

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We present a description, biological results and a reliability analysis for the method of diffusion tensor tracking (DTT) of white matter fiber pathways. In DTT, diffusion-tensor MRI (DT-MRI) data are collected and processed to visualize the line trajectories of fiber bundles within white matter (WM) pathways of living humans. A detailed description of the data acquisition is given. Technical aspects and experimental results are illustrated for the geniculo-calcarine tract with broad projections to visual cortex, occipital and parietal U-fibers, and the temporocalcarine ventral pathway. To better understand sources of error and to optimize the method, accuracy and precision were analyzed by computer simulations. In the simulations, noisy DT-MRI data were computed that would be obtained for a WM pathway having a helical trajectory passing through gray matter. The error vector between the real and ideal track was computed, and random errors accumulated with the square root of track length consistent with a random-walk process. Random error was most dependent on signal-to-noise ratio, followed by number of averages, pathway anisotropy and voxel size, in decreasing order. Systematic error only occurred for a few conditions, and was most dependent on the stepping algorithm, anisotropy of the surrounding tissue, and non-equal voxel dimensions. Both random and systematic errors were typically below the voxel dimension. Other effects such as track rebound and track recovery also depended on experimental conditions. The methods, biological results and error analysis herein may improve the understanding and optimization of DTT for use in various applications in neuroscience and medicine.

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Section: Biological Backgroundmentioning

confidence: 99%

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

et al. 2002

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“…Changes in the water apparent diffusion coefficient during neuronal activation reflect transient microstructural changes of the neurons or glia during activation. Darquie et al (2001) showed transient decreases in the diffusion of water in the human occipital cortex during visual stimulation. Such decreases coincided with an increase in the blood oxygenation level-dependent signal and was initiated at approximately 15 secs and reached a minimum approximately 45 secs after the onset of the visual stimulus.…”

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confidence: 96%

Is Brain Lactate Metabolized Immediately after Neuronal Activity through the Oxidative Pathway?

Korf

2006

J Cereb Blood Flow Metab

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In the central nervous system, lactate is formed under both aerobic and anaerobic conditions. The question is whether the generated lactate after neural excitation by glutamate is immediately metabolized. It has been hypothesized that lactate is formed after glutamate uptake in the glia, then released into the intercellular compartment and subsequently used by neurones (the so-called astrocyte-neuron lactate shuttle; Pellerin and Magistretti, 1994). In two recent reports (Schurr, 2006;Aubert et al, 2005), the question was addressed whether lactate could serve as a substrate for oxidative metabolism during nerve cell activation under aerobic conditions in vivo. Aubert et al (2005) designed a mathematical model to show that the time course of extracellular changes of lactate levels during enhanced neural activity could be interpreted as aerobic metabolism. Schurr (2006) summarized the arguments favouring the idea that in the functioning brain, lactate is the major end product of both aerobic and anaerobic glycolysis and that lactate subsequently serves as an oxidative substrate. For both reports, the results shown by Hu and Wilson (1997) are crucial. In that study, the perforant pathway of the rat was simulated for 5 secs once or repeatedly and the time course of extracellular lactate, oxygen, and glucose in the dentate gyrus of the rat brain was measured with rapidly responding biosensors. A single stimulation showed an initial decrease of all the analytes, followed by transient increases. After repeated stimulations, extracellular lactate was substantially increased, with a concomitant decrease of glucose and little, if any change of oxygen. This study and several others (e.g., De Bruin et al, 1990;Kuhr et al, 1988;Van der Kuil and Korf, 1991;Krugers et al, 1992) show that lactate is formed under conditions of enhanced neural activity which is-at least in part-associated with lower extracellular glucose. The time course of hippocampus lactate after a single stimulation (lasting 5 secs; Hu and Wilson, 1997) and detected with the biosensors is very similar to that seen with continuous flow analysis of microdialysates in rats, subjected to a single electroconvulsive stimulus with an intact entorhinalhippocampal glutamatergic pathway (Krugers et al, 1992). Modelling shows that such a time course can best be described by a very rapid (nearly immediate) increase of intracellular lactate that is subsequently released into the extracellular compartment via a carrier-mediated process (Kuhr et al, 1988).To appreciate the results of in vivo studies, a few cautionary remarks should be made. It should be realized that a lactate level is the net result of appearance and disappearance, which is a composite of the rates of lactate influx and efflux across the blood brain barrier, lactate influx and efflux across the membranes of brain cells, lactate formation from glucose and glycogen, lactate oxidation in any brain cells, diffusion to and from the site of the sensor, and also the size of extracellular space in brain and blood ...

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“…Our simulations suggest that under normal physiological conditions excitation-induced cell swelling is in the range of a few percent. For neuronal cells, such changes are confirmed by experimental studies (7). Significant changes of the cellular volume can be observed under conditions of a sustained increase in intensity of ongoing neuronal activity, reflected by increased gamma-frequency EEG power (20).…”

Section: Discussionmentioning

confidence: 70%

The influence of the chloride currents on action potential firing and volume regulation of excitable cells studied by a kinetic model

Berndt¹,

Hoffmann²,

Benda

et al. 2011

Journal of Theoretical Biology

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The influence of the chloride currents on action potential firing and volume regulation of excitable cells studied by a kinetic model, Journal of Theoretical Biology, doi:10.1016Biology, doi:10. /j.jtbi.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractIn excitable cells, the generation of an action potential (AP) is associated with transient changes of the intra-and extracellular concentrations of small ions such as Na + , K + and Cl − . If these changes cannot be fully reversed between successive APs cumulative changes of trans-membrane ion gradients will occur, impinging on the cell volume and the duration, amplitude and frequency of APs. Previous computational studies focused on effects associated with excitation-induced changes of potassium and sodium. Here we present a model based study on the influence of chloride on the fidelity of AP firing and cellular volume regulation during excitation. Our simulations show that depending on the magnitude of the basal chloride permeability two complementary types of responsiveness and volume variability exist: (i) At high chloride permeability (typical for muscle cells), large excitatory stimuli are required to elicit APs; repetitive stimuli of equal strength result in almost identical spike train patterns (markovian behaviour), however, long excitation may lead to after discharges due to an outward directed current of intracellular chloride ions which accumulate during excitation; cell volume changes are large. (ii) At low chloride permeability (e.g., neurons), small excitatory stimuli are sufficient to elicit APs, repetitive stimuli of equal strength produce spike trains with progressively changing amplitude, frequency and duration (short-term memory effects or non-markovian behaviour); cell volume changes are small. We hypothesize that variation of the basal chloride permeability could be an important mechanism of neuronal cells to adapt their responsiveness to external stimuli during learning and memory processes.

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Transient decrease in water diffusion observed in human occipital cortex during visual stimulation

Cited by 163 publications

References 51 publications

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

Is Brain Lactate Metabolized Immediately after Neuronal Activity through the Oxidative Pathway?

The influence of the chloride currents on action potential firing and volume regulation of excitable cells studied by a kinetic model

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