(A) Typical gradient-echo coronal MR image of a rat brain obtained at 11.7T. Spatial resolution is 50 x 50 x 2,000 mm3. Overlaid on top of the image is a functional cross-correlation map. The color bar indicates the scale of cross-correlation coefficients. Pixels that best resemble the functional paradigm are located in the middle layers (IV-V) of the somatosensory cortex.

(B) High temporal resolution (40ms per point) averaged BOLD time courses obtained at 200 x 200 mm2 in-plane resolution from nine rats. The black bar indicates the 4-s stimulus. Time courses obtained from six-pixel ROIs located in layers I-III, IV-V, and VI (see Inset) are plotted in green, blue, and brown, respectively. Layers IV-V present the fastest onset time to stimulation, followed by layers I-III and VI. Vertical bars = +/- 1 standard error. The inset clearly shows the difference in onset times (error bars omitted for clarity).

(C) Typical BOLD onset time map. The color bar indicates the time scale of activation onset. The fastest onset times come from pixels located in the intermediate layers (IV-V) of the somatosensory cortex, whereas slowest onset times are found in the outer layers (I-III and VI). See Silva and Koretsky 2002 for details.