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Very High Resolution Perfusion MRI of the Laminar Structure in Primate Visual Cortex

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons84326

Zappe,  A-C
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons83937

Goense,  JBM
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84063

Logothetis,  NK
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Zappe, A.-C., Goense, J., & Logothetis, N. (2007). Very High Resolution Perfusion MRI of the Laminar Structure in Primate Visual Cortex. Poster presented at 37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007), San Diego, CA, USA.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-CB4F-E
Abstract
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.