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. 2021 May 17;12:2859. doi: 10.1038/s41467-021-22915-5

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© The Author(s) 2021

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 5 — a BLA.am projections to visual processing areas. Top panels: whole brain sections with labeled fibers in ACAd, ACAv, MOs-fef, CP caudal dorsomedial, and deep layers of VISam and VISal following a BLA.am PHAL injection. Bottom panels: magnified versions of PHAL labeled fibers in visual associated areas. b Summarized brain-wide connections of BLA.am projection neurons. For full list of abbreviations see Table 1. c BLAa connections with ORBvl. BLA.am neurons project to ORBvl(I/II), while BLA.al neurons project to ORBl(V/VI). Projections in ORBvl from BLA.ac case were not validated. A CTb ORBvl injection solely back-labels BLA.am neurons confirming a BLA.am→ORBvl connection. ORBvl neurons do not project back to BLA.am as shown by the PHAL ORBvl injection. Schematic adapted from²¹ demonstrates pattern of inputs to frontal cortex from visual information processing areas like VIS, ACAd, ACAv, and PTLp, which is similar to prefrontal input patterns from BLA.am. d Anterograde map shows BLA.am projections to ACAv and MOs-fef validated with retrograde injections of CTb and FG (BLA.am→ACAv/MOs-fef). e Left: retrograde map with back-labeled neurons in visual LP following a retrograde tracer injection into BLA.am. Right: PHAL injection in visual LP labels fibers in BLA.am, and also LA, confirming LP→BLA.am/LA projections. f Left: anterograde map of BLA.am and BLA.ac projection fibers to CP caudal dorsomedial (CPc.dm) at ARA 61 superimposed with CP caudal domains. Right: a screenshot of our cortico-striatal map at ARA 61 showing projections from visual areas like VISp, VISam, VISal, ACA, RSP, and PTLp to CP caudal dorsomedial (http://www.mouseconnectome.org/CorticalMap/page/map/5). FG injection in CPc.dm back-labels BLA.am neurons confirming the BLA.am→CPc.dm connection. g Summarized brain-wide connections of BLA.al neurons. For full list of abbreviations see Table 1. h BLA.al projections to gustatory/visceral CP. Top left shows anterograde map of BLA.al projection fibers at ARA 53 superimposed with domains of CP intermediate (CPi). BLA.al neurons target CPi.vl and CPi.vm, which also receive input from AI, PIR, VISC, GU, and somatosensory and somatomotor regions associated with mouth regions. Retrograde tracers CTb 555 and CTb 647 in these CP domains back-label projection neurons in BLA.al. Bottom panels: CP caudal ventral (CPc.v), which receives input from GU and VISC is also targeted by BLA.al. A CTb injection in CPc.v back-labels BLA.al neurons to confirm this (BLA.al→CPc.v). i. Top: AId neurons target BLA.al and LA as shown with an AId PHAL injection. Bottom: BLA.al retrograde injection back-labels AId neurons (AId→BLA.al). j AIv shows weak projections to BLA.am and stronger projections to LA and BLAv. AIp neurons target mostly BLAv and BMAp. k. Retrograde map shows neurons in GU that project to BLA.al (GU→BLA.al). A FG injection in GU(V) reveals BLA.al projection neurons target GU [BLA.al→GU(V)]. l. Retrograde map shows back-labeled neurons in PF/VPMpc from BLA.al retrograde injection suggesting a PF/VPMpc→BLA.al connection. An anterograde AAV-RFP injection in the thalamic region labels BLA.al, validating the projection. m BLA.al projection neurons target somatomotor and somatosensory regions presumably associated with orofacial information processing including the MOs/MOp ul (upper limb) and SSp/MOp m (mouth). Retrograde tracer injections in these regions clearly label BLA.al neurons. See Table 1 for full list of abbreviations.