Is optical imaging spectroscopy a viable measurement technique for the investigation of the negative BOLD phenomenon? A concurrent optical imaging spectroscopy and fMRI study at high field (7 T).
Bottom Line: Often accompanying positive BOLD fMRI signal changes are sustained negative signal changes.These experiments suggested that the negative BOLD signal in response to whisker stimulation was a result of an increase in deoxy-haemoglobin and reduced multi-unit activity in the deep cortical layers.Furthermore their study utilised a homogeneous tissue model in which is predominantly sensitive to haemodynamic changes in more superficial layers.
Affiliation: Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. A.J.Kennerley@shef.ac.ukShow MeSH
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Mentions: Images of the stained slices can be linearly warped to one another where corresponding features are superimposed (Fig. 3a). The mathematical details of the warping have been described previously (Zheng et al., 2001). Penetrating blood vessels are used as fiducial markers between sections. Four matching points in each image defined an exact projection between the points; however, it was preferable to use a larger number of corresponding points to calculate the best (in least squares sense) projective transform. The surface section acts as a base template. The section immediately below is warped to fit over the surface section and then the section containing the barrel cortex (Fig. 3b) is warped to fit over the previously warped second section. The surface and warped barrel images are then superimposed to create a barrel map on the surface of the cortex to compare with the imaging results. For comparison with optical imaging results the surface section containing the stained vasculature is warped (using a similar method to that described above) to the vasculature seen in the endoscope images (Fig. 3c). The same warping parameters can then be applied to the histological section showing the stained somatosensory barrels and haemodynamic z-score maps from 2D-OIS superimposed to assess which cortical regions are active.
Affiliation: Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. A.J.Kennerley@shef.ac.uk