Neuroscience 2005 Abstract
| Presentation Number: | 508.5 |
|---|---|
| Abstract Title: | Evaluation of iso-orientation maps in cat visual cortex revealed by functional MRI. |
| Authors: |
Wang, P.*1
; Moon, C.1
; Fukuda, H.1
; Kim, S.1
1Dept Neurobiol, Brain Imaging Research Ctr., Pittsburgh, PA |
| Primary Theme and Topics |
Sensory and Motor Systems - Vision -- Visual cortex: Functional organization and circuitry |
| Session: |
508. Visual Cortex: Topography I Poster |
| Presentation Time: | Monday, November 14, 2005 1:00 PM-2:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # W5 |
| Keywords: | Orientation Column, optical intrinsic signal, cerebral blood volume , Fourier analysis |
[Aim] The purpose of this study was to evaluate in the same cat the reproducibility, dependency on stimulus spatial frequency and similarity to the optical intrinsic signal (OIS) of iso-orientation maps obtained from blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV)-weighted functional magnetic resonance imaging (fMRI).
[Methods] BOLD-fMRI, CBV-weighted fMRI with monocrystalline iron oxide nanoparticle (10 mg/kg MION) and 570-nm OIS imaging were sequentially performed on the same anesthetized cats. An identical periodic visual stimulation (full-field moving gratings of 4 orientations alternated with homogeneous gray (10 s each) / period) was used in all measurements. Functional MRI at 9.4-Tesla was performed on a 2-cm x 2-cm area parallel to marginal gyrus (area 18) of one hemisphere with a surface coil. The position and orientation of a 1-mm thickness imaging slice (128 x 128 pixels) were determined based on cortical emerging veins with a high resolution venogram. By using Fourier analysis the orientation-specific activation (1/80 Hz) was extracted from signals on a pixel-by-pixel basis. After the MRI experiments OIS was performed on the same imaging area.
[Results] Although we consistently observed positive BOLD signals every visual stimulus, it was difficult to get spatially localized and reproducible iso-orientaion patches. In contrast, iso-orientation maps with CBV-weighted fMRI were highly reproducible. The orientation-specific CBV responses were evoked in a lower spatial frequency of stimulation, but much less in a higher frequency stimulation. The CBV-weighted fMRI maps matched well with the 570-nm OIS maps. These results suggest that the CBV-weighted fMRI is more suitable than BOLD for submillimeter-scale functional mapping.
[Acknowledgements] We thank Sung-Hong Park for MR venography and Michelle Tasker for animal preparation.
[Methods] BOLD-fMRI, CBV-weighted fMRI with monocrystalline iron oxide nanoparticle (10 mg/kg MION) and 570-nm OIS imaging were sequentially performed on the same anesthetized cats. An identical periodic visual stimulation (full-field moving gratings of 4 orientations alternated with homogeneous gray (10 s each) / period) was used in all measurements. Functional MRI at 9.4-Tesla was performed on a 2-cm x 2-cm area parallel to marginal gyrus (area 18) of one hemisphere with a surface coil. The position and orientation of a 1-mm thickness imaging slice (128 x 128 pixels) were determined based on cortical emerging veins with a high resolution venogram. By using Fourier analysis the orientation-specific activation (1/80 Hz) was extracted from signals on a pixel-by-pixel basis. After the MRI experiments OIS was performed on the same imaging area.
[Results] Although we consistently observed positive BOLD signals every visual stimulus, it was difficult to get spatially localized and reproducible iso-orientaion patches. In contrast, iso-orientation maps with CBV-weighted fMRI were highly reproducible. The orientation-specific CBV responses were evoked in a lower spatial frequency of stimulation, but much less in a higher frequency stimulation. The CBV-weighted fMRI maps matched well with the 570-nm OIS maps. These results suggest that the CBV-weighted fMRI is more suitable than BOLD for submillimeter-scale functional mapping.
[Acknowledgements] We thank Sung-Hong Park for MR venography and Michelle Tasker for animal preparation.
Supported by McKnight Foundation, NIH NS44589 & EB003324.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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