452 Fig. 8 Anterior continuation of the series shown in Fig. 7 to illustrate MRI correlations of pallidothalamic ﬁbre tracts (al, ﬂ, and ft), thalamic nuclei, and basal ganglia. Same conventions as in Fig. 7. Scale bars (left column): 10 mm DV 0 DV 0 DV 0 MD DV 0 R 10 fx AV 10 fx AV mtt 10 al fx VLp VLa MD AV mt1t0 ft fl STh fx SNr MB Cd GPi Cd ot fl al VA ot fl VA VLa A 20 A 17.5 A 15 A12.2 PuT GPe ac PuT GPe PuT GPe PuT fl GPi al Amg fl GPi Amg Cd ot Cd ot GPi GPe fx al ot ac fx fl ot fl al mtt al fx fl mtt ft fl STh fx fl ot ot Brain Struct Funct (2008) 212:443–463 ic al Cd GPi R Cd ic fl ot R sm fx ap R ot AV Pv VAmc VApc al fl fx ot AV VApc MD CL VAmc VLa ic mtt ft VMZI al fl MB AV VLpd MD CVLLpl VApc VLa ic CeM VM ft fl mtt ft STh fx SNr MB PuT GPe Cl B ac Amg GPe PuT GPe B PuT GPi al B Amg Cd fl GPi Amg Cd R ot GPi GPe PuT Cd Cl Cl mainly the parvocellular division of the ventral anterior (VApc) and VLa nuclei through the anterior part of the VM nucleus (Fig. 5, L9 and L9.9). In relation to the classic nomenclature, Forel ﬁeld H2 corresponds to the emergence of ﬂ ﬁbres from the internal capsule. The ﬁeld H1, on the other hand, is more difﬁcult to relate with the al or ﬂ because it contains both ﬁbre bundles. The most medial component of the ft seems to arise from al more than ﬂ (Fig. 5, L4.5, L5.4, and L6.3), which in turn joins the ft more laterally (Fig. 5, L7.2 and L8.1). Whether this apparent mediolateral gradient persists at the entrance of the tract into the thalamus cannot be determined at this point. At most posterior and medial levels (e.g. Fig. 5, 123 L7.2), the pallidothalamic ﬁbres form the so-called ‘‘H1 + H2’’ ﬁeld of Forel. At this level, the ft is not yet joined by all of the ﬂ ﬁbres. The transition between this part of ft and the ansa, as well as with ft proper containing both ﬂ and al ﬁbres, is unclear and cannot be identiﬁed on the basis of the present data. As best seen in the horizontal plane, the ft tract comes close to the mammillothalamic (mtt) tract which courses toward the anteroventral (AV) nucleus. This close vicinity of the two tracts occurs near midcommissural level (mcl; Fig. 5, sagittal planes L4.5 and L5.4; Fig. 6). The al, ﬂ, and ft are generally unstained with different markers, except for slight PV-ir in ft at subthalamic level (Fig. 3d). At pallidal level, the ‘‘negative’’ staining of al is