This file was created by the Typo3 extension sevenpack version 0.7.14 --- Timezone: CEST Creation date: 2013-05-26 Creation time: 05-57-55 --- Number of references 18 article 4956 Cerebral Cortex 2008 11 18 11 2666-2673 Hypercapnia is often used as vasodilatory challenge in clinical applications and basic research. In functional magnetic resonance imaging (fMRI), elevated CO2 is applied to derive stimulus-induced changes in the cerebral rate of oxygen consumption (CMRO2) by measuring cerebral blood flow (CBF) and bloodoxygenation- level-dependent (BOLD) signal. Such methods, however, assume that hypercapnia has no direct effect on CMRO2. In this study, we used combined intracortical recordings and fMRI in the visual cortex of anesthetized macaque monkeys to show that spontaneous neuronal activity is in fact significantly reduced by moderate hypercapnia. As expected, measurement of cerebral blood volume using an exogenous contrast agent and of BOLD signal showed that both are increased during hypercapnia. In contrast to this, spontaneous fluctuations of local field potentials in the beta and gamma frequency range as well as multi-unit activity are reduced by ~15% during inhalation of 6% CO2 (pCO2 = 56 mmHg). A strong tendency toward a reduction of neuronal activity was also found at CO2 inhalation of 3% (pCO2 = 45 mmHg). This suggests that CMRO2 might be reduced during hypercapnia and caution must be exercised when hypercapnia is applied to calibrate the BOLD signal. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Department MRZ http://cercor.oxfordjournals.org/cgi/reprint/bhn023v2 Biologische Kybernetik Max-Planck-Gesellschaft en 10.1093/cercor/bhn023 aczappeA-CZappe kuludagKUludag axelAOeltermann KUgurbil nikosNKLogothetis article 4918 Magnetic Resonance Imaging 2008 9 26 7 961-967 The blood oxygenation level-dependent (BOLD) signal is an indirect hemodynamic signal which is sensitive to cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO2). Therefore, the BOLD signal amplitude and dynamics cannot be interpreted unambiguously without additional physiological measurements and, thus, there remains a need for a functional magnetic resonance imaging (fMRI) signal which is more closely related to the underlying neuronal activity. In this study, we measured cerebral blood flow with continuous arterial spin labeling, cerebral blood volume with an exogenous contrast agent and BOLD combined with intracortical electrophysiological recording in primary visual cortex of the anesthetized monkey. During inhalation of 6% CO2, it was observed that CBF and CBV are not further increased by a visual stimulus, although baseline CBF for 6% CO2 is below the maximal value of CBF. In contrast, the electrophysiological response to the stimulation was found to be preserved during hypercapnia. As a consequence, the simultaneously measured BOLD signal responds negatively to a visual stimulation for 6% CO2 inhalation in the same voxels responding positively during normocapnia. These observations suggest that the fMRI response to a sensory stimulus for 6% CO2 inhalation occurs in the absence of a hemodynamic response, and it therefore directly reflects the oxygen extraction into the tissue. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Department MRZ http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4SDNK82-1-1&_cdi=5112&_user=29041&_orig=search&_coverDate=09%2F30%2F2008&_sk=999739992&view=c&wchp=dGLzVtb-zSkzS&md5=a68ebcb9c19df1431bbf6ced51eeb30a&ie=/sdarticle.pdf Biologische Kybernetik Max-Planck-Gesellschaft en 10.1016/j.mri.2008.02.005 aczappeA-CZappe kuludagKUludag nikosNKLogothetis article 4808 Journal of Cerebral Blood Flow and Metabolism 2008 3 28 3 640-652 http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.nature.com/jcbfm/journal/v28/n3/pdf/9600564a.pdf Biologische Kybernetik Max-Planck-Gesellschaft en 10.1038/sj.jcbfm.9600564 aczappeA-CZappe josefJPfeuffer hellmutHMerkle nikosNKLogothetis jozienJBMGoense article 4630 Magnetic Resonance Imaging 2007 7 25 6 740-747 To understand the physiological mechanisms underlying the blood-oxygenation-level-dependent (BOLD) signal, the acquisition of data must be optimized to achieve the maximum possible spatial resolution and specificity. The term “specificity” implies the selective enhancement of signals originating in the parenchyma, and thus best reflecting actual neural activity. Such spatial specificity is a prerequisite for imaging aimed at the elucidation of interactions between cortical micromodules, such as columns and laminae. In addition to the optimal selection of functional magnetic resonance imaging pulse sequences, accurate superposition of activation patterns onto corresponding anatomical scans, preferably acquired during the same experimental session, is necessary. At high resolution, exact functional-to-structural registration is of critical importance, because even small differences in geometry, that arise when different sequences are used for functional and anatomical scans, can lead to misallocation of activ ation and erroneous interpretation of data. In the present study, we used spin-echo (SE) echo planar imaging (EPI) for functional scans, since the SE-BOLD signal is sensitive to the capillary response, together with SE-EPI anatomical reference scans. The combination of these acquisition methods revealed a clear spatial colocalization of the largest fractional changes with the Gennari line, suggesting peak activity in Layer IV. Notably, this very same layer coincided with the largest relaxivity changes as observed in steady-state cerebral blood volume measurements, using the intravascular agent monocrystalline iron oxide nanoparticles (MION). http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4NPHMMS-1-1&_cdi=5112&_user=29041&_orig=browse&_coverDate=07%2F31%2F2007&_sk=999749993&view=c&wchp=dGLbVlb-zSkzV&md5=ae3e0e8d6da5dafbaa0557f0ec1c1eba&ie= Biologische Kybernetik Max-Planck-Gesellschaft en 10.1016/j.mri.2007.02.013 jozienJBMGoense aczappeA-CZappe nikosNKLogothetis article 4288 Magnetic Resonance Imaging 2007 7 25 6 775-783 Noninvasive absolute quantification of cerebral blood flow (CBF) with high spatial resolution is still a challenging task. Arterial spin labeling (ASL) is a promising magnetic resonance imaging (MRI) method for accurate perfusion quantification. However, modeling of ASL data is far from being standardized and has not been investigated in great detail. In this study, two-compartment modeling of monkey ASL data in three physiological conditions (baseline, sensory activated and globally elevated CBF) is reported. Absolute perfusion and arterial transit times were derived for gray matter (GM) and white matter (WM) separately. The uncertainties of the model‘s result were determined by Monte Carlo simulations. The fitted CBF values for GM were 133 ml/min/100 ml at baseline condition, 165 ml/min/100 ml during visual stimulation and 234 ml/min/100 ml for globally elevated CBF after intravenous injection of acetazolamide. The ratio of GM to WM CBF was 2.5 at baseline and was found to d ecre ase to 1 .6 after application of acetazolamide. The corresponding arterial transit times decreased from 742 to 607 ms in GM and from 985 to 875 ms in WM. Monte Carlo simulations showed that absolute CBF values can be determined with an error of 11–15%, while the arterial transit time values have a coefficient of variation of 25–31%. With an alternative acquisition scheme, the precision of the arterial transit times can be improved significantly. The CBF values in the occipital lobe of the monkey brain quantified with ASL are higher than previously reported in positron emission tomography studies. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4NNYG0P-1-1&_cdi=5112&_user=29041&_orig=browse&_coverDate=07%2F31%2F2007&_sk=999749993&view=c&wchp=dGLbVtz-zSkWA&md5=0392 Biologische Kybernetik Max-Planck-Gesellschaft en 10.1016/j.mri.2006.11.028 aczappeA-CZappe reicholdJReichold CBurger bweberBWeber ABuck josefJPfeuffer nikosNKLogothetis article 2622 Magnetic Resonance for Medicine 2004 4 51 4 828-834 Functional magnetic resonance imaging (fMRI) experiments on tactile perception are difficult to perform because the special characteristics of an MRI environment restrict the experimental setup. Although recently developed actuators have made it possible to apply vibrotactile stimuli to the skin during an fMRI experiment, the projection of spatially extended patterns is still precluded. In order to examine the processing of tactile perception, a new pneumatically-driven tactile device (PTD) has been built. This device is capable of stimulating the skin, using arbitrary time sequences that consist of 2D tactile images up to 64 pixels. It is shown how the device is implemented in a 2 T fMRI environment, and show that it operates without generating artifacts. Dedicated software allows the generation of complex paradigms and provides a user-friendly interface to other brain mapping systems, as well as automated operation. This paper describes the PTD elucidates its features, and demonstrate its reliability by reporting results from an fMRI study based on an event-related protocol involving six subjects. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www3.interscience.wiley.com/cgi-bin/abstract/107641411/ABSTRACT Biologische Kybernetik Max-Planck-Gesellschaft Kirchhoff Institute fuer Physik, INF 227, 60120 Heidelberg aczappeACZappe TMaucher KMeier CScheiber poster UludagZGL2009 2009 4 17 3701 A BOLD signal model as a function oxygen extraction fraction and CBV was developed in order to determine change in oxidative metabolism from combined BOLD signal and CBF measurements. The new model is an alternative model to the widely used calibrated BOLD approach initally proposed by Davis and colleagues for GRE at 1.5T. The new model, however, takes also intra-vascular MRI signal into account and is developed for both GRE and SE from 1.5T up to 16.4T. In the current study, at 4.7T and 7T using SE and GRE, oxidative metabolism change during visual stimulation was determined in macaque monkeys. http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2009-03701.pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.ismrm.org/09/ Honolulu, HI, USA 17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009) kuludagKUludag aczappeA-CZappe jozienJGoense nikosNKLogothetis poster 5860 2008 6 104 http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.areadne.org/2008/home.html Biologische Kybernetik Max-Planck-Gesellschaft Santorini, Greece AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles en aczappeA-CZappe nikosNKLogothetis poster ZappeUL2008 2008 5 16 850 166 The BOLD signal is sensitive to cerebral blood flow (CBF), blood volume (CBV) and oxygen extraction. In the anesthetized monkey, we observe a vasodilatory ceiling effect during inhalation of 6% CO2 where CBF or CBV are not further increased by visual stimulation. In contrast, simultaneously measured local field potential responds to the stimulation as strong as during normocapnia. As a consequence, the stimulus-induced fMRI response during 6% hypercapnia has been found to be negative reflecting only the oxygen extraction from the blood. With this method, oxygen extraction can be imaged by means of fMRI without injection of an exogenous drug. http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2008-00850.pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.ismrm.org/08/ Toronto, Canada 16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008) aczappeA-CZappe kuludagKUludag nikosNKLogothetis poster 4694 2007 11 37 89.11 Using perfusion MRI with continuous arterial spin labeling (CASL) cerebral blood flow (CBF) can be measured directly at the capillary level [1]. The common belief is that perfusion MRI is more closely related to the neural activity than most functional MR imaging methods. It has successfully been used to reveal orientation columns in the cat, on the scale of ~1 mm [2]. It has been shown that the BOLD signal is higher in layer IV than in supra- and infragranular layers [3]. Since the BOLD contrast is a combination of several signals, we want to determine whether this reflects depth-dependent changes in CBF. Moreover, functional CBF (fCBF) can be interleaved with BOLD in the same scan to compute changes in oxygen consumption rate (CMRO2). We use striate cortex of the monkey which has a well-defined laminar structure, allowing determination of the precise location of functional CBF changes. MR imaging was performed on healthy adult monkeys (macaca mulatta) using a vertical 4.7T/40 cm primate scanner (Bruker Biospec) as described previously [4]. A saddle-shaped volume coil was used in combination with a 25 mm receive surface coil, and a cravat-shaped label coil for CASL, placed around the neck of the monkey. A labeling pulse of 2 s was followed by 200 or 800 ms postlabel delay (PLD), and images were acquired using a segmented, multi-slice GE-EPI with in-plane resolution of 375x333 μm and TE/TR of 11/3000 ms. The visual stimulus was a full field rotating checkerboard presented to both eyes. All data analysis was performed in MatLab (the Mathworks). We obtained robust high resolution fCBF maps in visual cortex with a signal-to-noise ratio of 25. The laminar profile of % fCBF obtained at 800 ms shows a clear peak at the level of the Gennari-line, i.e. in layer IV. At a short PLD a contribution from the larger pial vessels was seen in addition to a narrow peak in layer IV. The location of the cortical surface and the Gennari-line were identified based on anatomical scans. The PLD determines the relative contributions of the different vascular compartments. For scans with a sufficiently long PLD the functional signal represents the capillary fraction. For short PLDs our data show a contribution of arterioles to the fCBF map as hypothesized in [5]. Peak fCBF was observed in layer IV similar to the BOLD-results, possibly representing the higher metabolic activity of layer IV. In combination with calibrated BOLD this will allow determination of CMRO2 in vivo at high spatial resolution. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.sfn.org/am2007/ Biologische Kybernetik Max-Planck-Gesellschaft San Diego, CA, USA 37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007) en aczappeA-CZappe jozienJBMGoense nikosNKLogothetis poster 4428 2007 5 2007 616 136 High resolution fMRI allows us to determine more accurately the origins of the fMRI signal. This has shown that even at high field, the GE-BOLD signal has still a large vascular contribution [1]. Alternative methods like SE- and monocrystalline iron oxide nanocolloid (MION)-based methods have been shown to be spatially more specific than conventional BOLD, and are able to reveal functional subunits in the cortex [2-6]. Here we compare the specificity of BOLD and CBV fMRI methods in the macaque; its striate cortex shows very obvious laminar structure in anatomical images, allowing accurate determination of the precise location of the fMRI activation. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/ISMRM2007-Zappe_4428[0].pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.ismrm.org/07/ Biologische Kybernetik Max-Planck-Gesellschaft Berlin, Germany 2007 Joint Annual Meeting ISMRM-ESMRMB en aczappeA-CZappe nikosNKLogothetis jozienJBMGoense poster 3970 2006 5 14 2135 419 Perfusion-based imaging in the monkey primary visual cortex was performed at 7 T applying continuous arterial spin labeling (CASL). Increased perfusion sensitivity and SNR at high magnetic field (due to larger T1) was further optimized using a custom-made three-coil setup with a separate neck labeling coil. We investigated the labeling parameters to obtain relative fCBF changes in the anaesthetized monkey. We report excellent functional activation of striate cortex at high resolution of 0.75x0.9mm2 in-plane. Interestingly, the optimal parameter set for obtaining highest signal changes of rCBF are different from the reported values for imaging gray matter CBF. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/ISMRMproc_abstract_3970[0].pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.ismrm.org/06/ Biologische Kybernetik Max-Planck-Gesellschaft Seattle, WA, USA 14th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2006) en aczappeAZappe hellmutHMerkle josefJPfeuffer nikosNKLogothetis poster 3364 2005 5 13 1259 262 CASL experiments in the monkey brain were performed at 4.7 T and 7 T using a separate labeling coil. Increased sensitivity and SNR were achieved by a custom-made three-coil setup and high magnetic field with its increased T1. We report the development and optimization of the setup and first experiments in the monkey (macaca mulatta). Parameters for continuous labeling (label power, label duration, post label delay) were optimized to measure gray matter rCBF and fCBF changes, reporting excellent multi-slice coverage at high resolution of 0.75 – 1 mm in-plane. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf3364.pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.ismrm.org/05 Biologische Kybernetik Max-Planck-Gesellschaft Miami Beach, FL, USA 13th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2005) aczappeACZappe hellmutHMerkle nikosNKLogothetis josefJPfeuffer poster 2861 Magnetic Resonance Materials in Physics, Biology and Medicine 2004 9 17 Supplement 1 66-67 Arterial spin labeling is commonly used to measure cerebral blood flow (CBF) in the brain. Since CBF signal is intrinsically low, optimization of the signal-to-noise ratio (SNR) is critical. CASL with a separate labeling coil has the advantages of increased SNR, multi-slice capability, and absence of magnetization transfer. The CASL method has been applied successfully in rats1-3, and in human studies4. Its wider application especially on routine human MR systems is hindered by the advanced hardware and software requirements. Here, we report the development of CASL for use on monkeys. Increased sensitivity (SNR) was achieved because of utilization of an custom-made three-coil setup and the use of high magnetic field (7T) with its favorable T1. The feasibility of this approach is demonstrated with a flow phantom and with initial experiments in the monkey. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2861.pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis http://www.springerlink.com/content/k3prjt7wyxa33qbm/fulltext.pdf Biologische Kybernetik Max-Planck-Gesellschaft Copenhagen, Denmark 21st Annual Scientific Meeting of the ESMRMB 2004 10.1007/s10334-004-0046-8 aczappeACZappe hellmutHMerkle nikosNKLogothetis josefJPfeuffer conference 4290 Magnetic Resonance Materials in Physics, Biology and Medicine 2006 9 22 19 Supplement 1 121-122 Quantification of cerebral blood flow (CBF) using magnetic resonance imaging still suffers from many unresolved methodological issues. In this study we report the successful modeling of monkey CBF data, using the two-compartmental model introduced by Parkes et al. [1]. Absolute flow and transit times were derived including uncertainties of the assumed parameters as well as the signal noise. The precision of the model's result was investigated and an acquisition paradigm to maximize the information content is proposed. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/ESMRMb2006_Johannes_Reichold_[0].pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Abstract Talk http://www.esmrmb.org/index.php?id=/en/post_conference_information/2006/esmrmb_2006_congress.htm Biologische Kybernetik Max-Planck-Gesellschaft Warsaw, Poland 23rd Annual Scientific Meeting of the ESMRMB 2006 en 10.1007/s10334-006-0041-3 reicholdJReichold aczappeA-CZappe CBurger bweberBWeber ABuck josefJPfeuffer nikosNKLogothetis conference 4158 Magnetic Resonance Materials in Physics, Biology and Medicine 2006 9 21 19 Supplement 1 64 Activation maps acquired with perfusion-based FMRI are known to be more specific to the parenchyma and less sensitive to proximal draining veins compared to BOLD [1]. Here, the specificity of ASL activation maps in the nonhuman primate was investigated at high spatial resolution. Since the choice of labeling parameters can affect the specificity of the measured activation, the influence of the post-labeling-delay (PLD) and labeling-time (LT) on perfusion-based activation maps was evaluated. http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/esmrmb2006_aczappe_4158[0].pdf http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Abstract Talk http://www.springerlink.com/content/wvm3330668r40u55/fulltext.pdf Biologische Kybernetik Max-Planck-Gesellschaft Warsaw, Poland 23rd Annual Scientific Meeting of the ESMRMB 2006 en 10.1007/s10334-006-0040-4 aczappeA-CZappe jozienJBMGoense nikosNKLogothetis josefJPfeuffer conference 3841 2005 11 35 10.11 Cerebral metabolic rate of oxygen (CMRO2) can be obtained with magnetic resonance imaging (MRI) by calibrating BOLD using hypercapnia. CO2 administration influences BOLD by increasing and eventually stabilizing blood flow and volume respectively. This leaves blood oxygenation as the predominating (if not the only) factor affecting the magnitude of BOLD. Obviously, the above assortment implies that CO2 increase acts exclusively as vasoactive agent, without affecting neuronal activity and hence oxygen metabolism. Amongst others, the latter assumption was strengthened by the results of Schmidt and Kety in the 50s. Most of the fMRI studies report coupling of cerebral blood flow (CBF) and oxygen metabolism (the ratio of fractional changes in CBF and CMRO2 is n = 2). In this study we investigated the dependence of neural activity on enhanced CO2 concentration by means of simultaneous intracortical recordings and BOLD imaging in the anesthetized macaque monkey. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Abstract Talk http://www.sfn.org/absarchive/ Biologische Kybernetik Max-Planck-Gesellschaft Washington, DC, USA 35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005) en aczappeA-CCZappe kuludagKUludaq gregorGRainer nikosNKLogothetis conference ZappeMLP2004 2004 8 5 4 Arterial spin labeling is commonly used to measure cerebral blood flow (CBF). Since CBF signal is intrinsically low, optimization of the signal-to-noise ratio (SNR) is critical. CASL with a separate labeling coil has the advantages of increased SNR, multi-slice capability, and absence of magnetization transfer. Here, we report the development of CASL for use on monkeys. Increased sensitivity was achieved by utilization of a custom-made three-coil setup at high magnetic field (7T) with its favorable longer T1 values. The feasibility of this approach is demonstrated with a flow phantom and with initial experiments in the monkey. Measurements were performed on a vertical 7T/60cm system dedicated for monkeys, which was equipped with a second 1H transmit channel. A saddle-shaped volume coil was applied for RF transmission and surface coil was used for RF reception. For spin tagging at carotid- and vertebrate arteries a concavely-shaped dual loop coil set was built. Its design was based on angiographic scans and space restriction in the neck. All three RF coils were actively-decoupled and switched with a self-built logic unit and current driver. The flow phantom consisted of a saline-filled bottle with two flow tubes. Flow was adjustable from 20cm/s to 100cm/s. Single-shot, multi-slice GE-EPI was acquired at 1x1x2mm3 resolution (128x64x5, TR/TE=3500/12ms). A 2s labeling period was followed by a variable post-labeling delay prior to the imaging module. For CASL, the labeling frequency was switched in interleaved scans. The CASL three-coil setup was validated on the flow phantom. Maximum label efficiencies of 0.85 were reached with a labeling power of 0.3 and 2W on the phantom and in the monkey, respectively. CBF maps were aquired in the monkey with variable labeling periods and postlabeling delays. These first in vivo data demonstrate feasibility and potential for future functional studies to measure CBF, BOLD and CMRO2 changes. http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de http://www.kyb.tuebingen.mpg.de Department Logothetis Abstract Talk http://www.neuroschool-tuebingen-nena.de/index.php?id=284 Oberjoch, Germany 5. Neurowissenschaftliche Nachwuchskonferenz Tübingen (NeNa '04) aczappeA-CZappe hellmutHMerkle nikosNKLogothetis josefJPfeuffer