Fig 1.
After the baseline scans (PD: structural, fMRI: whisker BOLD, DTI: diffusion MRI, n = 30), the carotid vessels were ligated on each side one week apart. After a week of recovery, a semi-chronic (8 days) donepezil (3 mg/kg i.p., n = 14) or saline (n = 14) treatment was initiated. The first perfusion and structural (PD) measurements were carried out after the first dose of drug (donepezil or saline) and one week after the second carotid ligation. After the end of the semi-chronic treatment regime, functional, detailed structural and diffusion scans were acquired (scan 1). Two weeks later, second perfusion and structural scans were acquired, and then an additional week later, functional, detailed structural and diffusion scans were acquired (scan 2).
Fig 2.
Gray matter atrophy 5 weeks after stepwise BCCAo.
Blue-to-light-blue and red-to-yellow colors represent decreased and increased gray matter density 5 weeks after the BCCAo compared to baseline measurements, respectively (the treatment groups were pooled: n = 27 and n = 26, voxel-wise permutation test). Color bars represent p-values. The coordinates of the slices are represented in relation to bregma. The statistical images were enhanced using TFCE, corrected for multiple comparisons and overlaid on the population-mean gray matter probability map.
Table 1.
VBM clusters and local maxima.
Fig 3.
White matter microstructural changes 5 weeks after the stepwise BCCAo.
Blue-to-light-blue colors represent reduced fractional anisotropy (FA, middle) or mean diffusivity (MD, bottom) over the white matter TBSS skeleton (green) 5 weeks after the BCCAo (n = 25), compared to the baseline measurements (n = 23, the treatment groups were pooled) The color bar represents p-values. The coordinates of slices are represented in relation to bregma. The statistical images are overlaid on the population-mean FA map.
Fig 4.
Effect of acute donepezil on whole brain perfusion parameters one week after the stepwise BCCAo.
Top, left: Example gadolinium concentration-related ΔR2* tissue-response curve. The modeling of the measured ΔR2* as a linear mixture of a sigmoid basis for recirculation and a gamma-variate function for tissue-response allows the estimation of the time to peak (TTP), mean transit time (MTT), regional cerebral blood volume and flow (CBV and CBF), respectively. Top, middle and right: Whole-brain and voxel-wise differences in the TTP donepezil compared to saline treatment. Bottom: Whole-brain differences in the MTT, CBV and CBF, respectively. A significant (p = 0.01, saline: n = 13, donepezil: n = 12) difference was observed in the TTP between the saline-treated and donepezil-treated conditions, with the latter having a longer TTP.
Fig 5.
Mean baseline BOLD responses to whisker stimulation and their changes at 2 and 5 weeks after the stepwise BCCAo in the saline-treated group.
The mean activation evoked by the sensory stimulation in the saline-treated group before the stepwise carotid occlusion (upper row, n = 12). Contrast images show decreased BOLD response 2 weeks after (2 weeks difference from mean baseline; middle row, n = 12) and restored BOLD response at 5 weeks (5 weeks difference from mean baseline; bottom row, n = 12) after the stepwise carotid occlusion. The statistical z-score images were thresholded at Z>3.1 to construct the activation clusters. Afterwards, a cluster extent probability threshold of p<0.05 was applied to correct for multiple comparisons. Blue-to-light-blue colors represent decreased, while red-to-yellow colors represent increased, BOLD responses. Color bars represent z-values. The coordinates of the horizontal slices are presented next to the color bar on a sagittal view in relation to bregma. The statistical images were overlaid on an in-house standard template [58].
Table 2.
Local maxima of the mean BOLD responses to whisker stimulation in the saline group and their changes two and five weeks after the BCCAo.
Fig 6.
Mean baseline BOLD responses to whisker stimulation and their changes at 2 and 5 weeks after the stepwise BCCAo in the donepezil-treated group.
The mean activation evoked by the whisker sensory stimulation in the donepezil-treated group before the stepwise carotid occlusion (upper row, n = 14). Contrast images show that the treatment ameliorated the drop in BOLD responses 2 weeks (middle row, n = 11) after and restored responses 5 weeks (bottom row, n = 13) after the stepwise carotid occlusion. The statistical z-score images were thresholded at z>3.1 to construct the activation clusters. Afterwards, a cluster extent probability threshold of p<0.05 was applied to correct for multiple comparisons. Blue-to-light-blue colors represent decreased, while red-to-yellow colors stand for increased BOLD responses. The color bars represent z-values. The coordinates of the horizontal slices are presented next to the color bar on a sagittal view in relation to bregma. The statistical images were overlaid on an in-house standard template [58].
Table 3.
Local maxima of the mean BOLD responses to whisker stimulation in the donepezil-treated group and their changes two and five weeks after the BCCAo.
Fig 7.
Direct comparison of the BOLD responses to whisker stimulation between the donepezil- and saline-treated groups.
The statistical z-score images were thresholded at z>2.3 to construct the activation clusters. These (uncorrected) clusters are displayed in green (increased activation) and light blue (decreased activation). Then, a cluster extent probability threshold of p<0.05 was applied to correct for multiple comparisons. Dark blue represents significant (corrected) clusters of decreased activation in the donepezil group, whereas red colors stand for significant (corrected) clusters of increased BOLD responses (saline: n = 12, donepezil: n = 13). The coordinates of the horizontal slices are presented next to the color bar on a sagittal view in relation to bregma. The statistical images were overlaid on an in-house standard template [58].
Table 4.
Local maxima of the BOLD response differences between the donepezil- and saline-treated groups two and five weeks after the BCCAo.