Fig 1.
Differences in fractional anisotropy in different hCN segments.
a) MRI masks of the hCN were automatically segmented into 3 medial (1-3) and 3 lateral (4-6) segments. b) For each of the segments, fractional anisotropy was averaged across all participants and slices. FA was seen to be lower in the medial segments 1 and 2 compared to the lateral segments 4 and 5 while no relevant difference was seen between the medial (3) and lateral (6) rostral segment.
Fig 2.
Summary of main fiber populations in axial slices above and below the AC.
Polarization microscopy reveals multiple fibers with approx. rostrocaudal orientation in the vicinity of the head of the caudate nucleus (CN): a) The ALIC stretches from the anterior thalamus (T) to the prefrontal white matter (yellow bundle in schematic drawing). Branching off, there are fibers i) that reach the pallidal globe and putamen (PG and Pt; brown), ii) that terminate in the CN (dark green), iii) that run parallel to the ALIC in the lateral half of the CN to then sharply turn laterally at its rostral border and presumably rejoin the ALIC (red). Medial to those fibers leaving the thalamus are some fibers which start at the anterior border of the bed nucleus of the stria terminalis (B). Some of those appear to join the ALIC (orange) while others are directed into the CN (light blue). b) Below the AC, lateral to the fornix (F) and medial to the ansa peduncularis (AP; violet) in the basal forebrain (BF), multiple fine fibers can be seen in the gray matter of B and BF that cross under the AC, with their lateral portion (light green) terminating in the accumbens nucleus (NAcc) and their medial portion (dark blue) entering the medullary layer below the cortex of Brodmann’s area 25 (BA 25).
Fig 3.
Fiber populations throughout different axial slices above and below the anterior commissure.
10 horizontal/transversal slices with a distance of 1 mm between each slice (i.e., every 10th slice), starting approx. 4 mm above the anterior commissure (#). Upper edge = rostral edge of slices; left = lateral; right = medial; inferior edge = posterior. On some slices the ALIC (*) presents as a compact bundle (b, e) while on others it is loosened by stripes of grey matter (Pontes grisei caudatolenticulares) connecting caudate nucleus (CN) and putamen (Pt; a, c, d). Below the level of the interhemispheric part of the AC, the ALIC thins out, marking the transition zone of caudate and accumbens nucleus (CN/NAcc; h-j). B = bed nucleus of the stria terminalis; F = fornix; PG = pallidal globe.
Fig 4.
Anatomical and DTI data of ex-vivo samples at 14 T compared to in-vivo DTI data at 3 T.
Axial sections at 14 T (a, b) and 3 T through the head of the caudate nucleus from superior to inferior with a slice gap of 1.4 mm reaching from approx. 3 mm above to 2 mm below the anterior commissure. 14T MRI allows the identification of larger fiber tracks within the hCN both based on diffusion trace (a), as well as on fractional anisotropy (b), and differences of FA between the medial and lateral parts are already visually detectable, especially in slices above the AC. 3T in-vivo imaging only reveals unspecific visual inhomogeneities on both FA maps (c) as well as trace (not shown) with no clear differences between medial and lateral parts of the hCN. The white box on the first 3T in-vivo image marks the sector displayed on 14T ex-vivo images.