Fig. (2).

Direct comparison of imaging fields. We show high correlation between the vascular structure shown in (a) post mortem histological sections and (b) fMRI BOLD and CBV statistical maps for 5 subjects (post-mortem histology was not performed on 1 animal). In particular in all animals we found a significant BOLD response in the large veins running in a lateral-medial direction draining the active area of parenchyma containing the whisker barrel field. No commensurate changes in CBV were observed in the draining veins. Data suggested a high correlation of CBV changes to the barrel region and overlying arterial structures (running in an anterior-posterior direction). Two regions of interest were selected; one covered the barrel cortex and the second was centred on the draining vein region. Averaged times series across trials and animals of both BOLD and CBV changes to whisker stimulation resulted (c).