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: Region of interest masking of threshold activation maps (whisker and surrounding cortex) was used to obtain time series data from a mixed region of arterioles, parenchyma and venules (Fig. 5). The average time series (mean across all subjects), of the BOLD fMRI signal showed a positive signal change in the whisker barrel cortex in response to electrical stimulation of the whisker pad (Fig. 5a). The response peaked with a magnitude of ~ 3.5% at 4 s after stimulus onset, falling to a plateau (~ 1.5%) which was maintained until stimulus offset. In regions surrounding the whisker barrel cortex the time series showed reliable negative BOLD peaking with a magnitude of ~−1% at 8 s (Fig. 5a).
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