Fig. 4: Connectivity of the AMd.dorsomedial and AMd.dorsal domains.

a Tracer injections across cortex and hippocampus label different AMd domains (ARA 61). Manually mapped tracer labels highlight their distinct locations in the AM. b AM grids recolored to visualize the domains identified by the Louvain are shown, and the ROIs that each domain connects with are listed. Note the common connections of AMd.medial and AMv with MPF areas, also evident in the raw data. c The matrix presents the identified Louvain groups (i.e., domains) and shows the injection sites that are grouped together based on the similarity of labeling they produce at each AM grid box. Sixteen cases (16 sections with AM labeling at ARA 61) were included in the analysis. Injection ROIs are indicated in the rows of the matrix. d A PHAL/CTB AM co-injection labels cells (layer VI) and terminals (layers I-V) in rostral (left) and caudal (right) ACAv/ACAd, suggesting rostral/caudal ACA↔AMd connections. Dashed circles denote location of co-injections in (e, f). e A PHAL/CTB co-injection made in rostral ACA labels terminals and cells specifically in the AMd.dorsomedial domain (rostral ACA↔AMd.dorsomedial) and AMv (rostral ACA↔AMv). f A PHAL/CTB co-injection made in caudal ACA labels terminals and cells specifically in the AMd.dorsal domain (rostral ACA↔ AMd.dorsal) and does not label AMv neurons. g A Cre-dependent AAV injection that traces mostly AMd.dorsal (+dorsolateral) neurons (AAVretro-Cre injection made in ACA/RSP) shows projections only in caudal ACA, confirming caudal ACA↔AMd.dorsal connections. h Quantified projections to ACAd, ACAv, PL, and ILA from traced AMd.dorsal neurons in (g), validate their stronger projections to ACAv compared to other ROIs like PL and ILA. i Multiple tracer injections across different ROIs in the same brain showcase the distinct AMd domains. j Summarized connections of the AMd.dorsomedial (left) and AMd.dorsal (right). k Rostral and caudal ACAv injections show that ACA connectivity is selectively with AM, and not AV nor AD. l This selective AM-ACA connection is also shown with tracer injections made in the AV and AMd of the same brain. Neither anterograde nor retrograde AV injections produce labels in ACA, while AMd retrograde injection labels neurons in ACA deep layers.