Fig. 1: Tracer injections and analysis.

A Injections were placed via a glass capillary tube filled with tracer which was glued to a tungsten electrode for recording neural activity (reproduced with permission²⁸). B, D Parasagittal sections through the intraparietal sulcus. B This section was stained for myelin using the Gallyas method. LIPv is identified histologically by the more dense, extended intracortical myelin, LIPd by the two bands. C Nearest parasagittal section (to B) showing the CTb injection site in LIPd, taking a posterior approach. For LIPv, we took either a posterior approach (two animals) or a dorsal approach (one animal). D Nearest Nissl-stained section (to C) identifying the border (red line) between layers IV and V to be able to distinguish potential differences in the pattern of connectivity in supra- and infragranular layers. E Section stained for CTb shows the retrogradely labelled neurons. The high-resolution image (right) reveals the shape and granulated fill of individual neurons, which were the criteria for accepting a neuron as labelled. F Method for the data transformation of CTb labelled cells from an individual parasagittal sections into 3D maps of intrinsic LIP connectivity using two example injections. Top: Labelled cells were converted to density measures in 100 µm bins along the dorso-ventral axis, separately for supragranular (layers 2–4) and infragranular layers (5 and 6) (example M132L after LIPv injection). No smoothing across bins took place. Bottom: Then, data were aligned section-by-section along the medio-lateral extent of LIP (example M131L after LIPd injection). A – anterior, P – posterior, L – lateral, M – medial, D – dorsal, V – ventral.