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: Nevertheless, using the prior that neuronal activity driving the negative BOLD is predominantly in the deeper cortical layers we can bias the spectroscopy algorithm to be more sensitive to changes in the deeper layers of the cortex. Fig. 7 shows that the heterogeneous model gives a better prediction of the time series of negative fMRI-BOLD signal. This can be seen from the fact that the heterogeneous model gradient is very close to 1. The correlation of the prediction to measurements is both very high (with different tissue models) which implies that the effect of the heterogeneous tissue model is primarily one of scaling.
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