Figure 1

Agenesis of the corpus callosum and Probst bundle formation in adult BTBR mice. (A, B) Representative colour fractional anisotropy maps in a mid-sagittal plane of adult C57Bl/6 and BTBR mouse strains. Absence of the corpus callosum can be observed in BTBR mice (white arrow in (B)). A partial remnant of the hippocampal commissure is present in the BTBR mice (white arrowhead in (B)). The anterior commissure is preserved and is in a similar position in both mouse strains (open arrowheads in (A) and (B)). (C, D) Representative dorsal views of the tractography shows a large region of dispersed green streamlines connecting the two sides of the brain in C57Bl/6 mice (white arrows in (C)), whereas in BTBR mice this is absent (white arrows in (D)). In the coronal plane (E, F), the corpus callosum is formed in C57Bl/6 mice, whereas Probst bundles are present on both sides of the midline in BTBR mice (white circles in (F)). All callosal streamlines passing through the corpus callosum at the midline (white box in (E)) are shown in (G), and all streamlines passing through the Probst bundle in each hemisphere are shown in (H). The fibres within the Probst bundles run rostrocaudally, connecting hippocampal and basal forebrain regions. Orientations for the colour fractional anisotropy maps: red, rostrocaudal; green, mediolateral; blue, dorsoventral. Scale bar = 1 mm. ROI = region of interest; CC = corpus callosum, PB = Probst bundles; BTBR = BTBR T + tf/J.