Non-invasive assessment of cerebral blood flow changes during complex activation

Abstract

Background: The aim of this study was to cross-validate functional transcranial Doppler (FTCD) and brain single photon emission computed tomography (SPECT) using complex activation paradigm and to test the feasibility of FTCD in complex neuroactivation research. Methodology: The study was performed in the group of 60 healthy, right-handed subjects. Cerebral blood flow velocity (CBFV) was measured in both middle cerebral arteries (MCA) during baseline and during computer game interaction, using FTCD. Identical stimulus and response patterns were used in the subgroup of 15 subjects that underwent brain SPECT. Quantitative assessment of results was done to detect the percentage variation between the two measurements. Results: A statistically significant increase of cerebral blood flow (CBF) was detected by FTCD and brain SPECT (p<0.0001). In comparison between the two methods, statistically significant association (r=0.5608, P=0.030, coefficient of determination r2 = 0.3154) was detected only for CBFV increase in the right MCA and for the rightsided cerebral blood perfusion (CBP) increase, indicating that these two methods only partially measure the same characteristics associated with activation of specific brain areas. Conclusion: In comparison with SPECT, FTCD is not sufficiently sensitive method for evaluation of CBF changes during complex activation paradigm. Our study represents negative evidence and stand against the common belief that FTCD is as good as other neuroimaging methods used for CBF measurements during neuroactivation. Therefore, FTCD might not be a reliable and suitable method for evaluation of CBF changes during complex neuroactivation paradigm.

The scalability of common paradigms for assessment of cognitive function: A functional transcranial Doppler study

“…First, the differences in complexity of paradigms in the current study might not have been sufficient to induce differential CBFV responses, as proposed in terms of the compensation-related utilization of neural circuits hypothesis (CRUNCH) to recruit more neural activations matching with load increases [ 63 , 64 ]. As reported for other neuroimaging techniques (fMRI or SPECT), it provided greater activation in some specific brain areas, with increased task difficulty with verbal [ 54 ], arithmetic [ 56 ] or visual [ 30 , 65 ] paradigms. Although NVC assessment with fTCD has been rated as equivalent to that obtained with fMRI [ 66 ], this does not seem to be the case in our study, with respect to the ability of fTCD to reflect differences in complexity.…”