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<div></div><h3 data-label="569600" class="ltx_title_subsubsection">Inputs </h3><div>We identified two classes of inhibitory, picrotoxin-sensitive (hence mediated either by GABA-A or Glutamate) inputs to the central complex. First, the two ring neuron types we tested (GB-Eo, L-Ei) target the wedge columnar neurons (E-PG, Figure&nbsp;<span class="au-ref raw v1">\ref{704309}</span>Ai), as has been suggested previously&nbsp;<cite class="ltx_cite raw v1">\cite{Mart_n_Pe_a_2014,Kahsai2012,Hanesch1989}</cite>. Note that the ring neurons presented here are non-canonical : they do not innervate the bulb but either the LAL or the Gall. Second, a class of LAL-NO interneurons (the GL-N1 neuron) provides another source of inhibitory input into the EB columnar system by targeting the P-EN neurons (Figure&nbsp;<span class="au-ref raw v1">\ref{704309}</span>Aii and&nbsp;<span class="au-ref raw v1">\ref{489066}</span>Aii). This connection is particularly interesting in the light of the finding that the P-EN neurons drive the rotation of the bump of activity in the heading representation system&nbsp;<cite class="ltx_cite raw v1">\cite{Green2017,Turner-Evans2017}</cite>. Since the left/right noduli segregation corresponds to individual cells coding turns in opposite direction&nbsp;<cite class="ltx_cite raw v1">\cite{Turner-Evans2017}</cite>,  the GL-N1 neurons are likely involved in strengthening or refining those turn related signals. Moreover, it is likely that other types of LAL-NO interneurons innervating other noduli compartments target P-FN neurons, but these pairs have not been tested extensively yet.&nbsp;</div><div></div><div> We also identified two excitatory inputs to the CX. First, a Gall to EB  neuron, whose innervation pattern in the EB is reminiscent of the columnar neurons, excites the E-PG neurons (the same class that carries the heading representation and is inhibited by ring neurons). Second, several columnar neurons share excitatory inputs in the PB, from the IS-P neuron (PB.b-IB.s-SPS.s, Figure&nbsp;<span class="au-ref raw v1">\ref{704309}</span>Aiii).  It is important to note that although we tested very few candidates in the FB, it is highly likely that this region receives many inputs from outside the CX.&nbsp;</div><div></div><div>The neurons listed here do not necessarily provide feed-forward input from outside the CX. For example, the gall ring neuron (GB-Eo), which is an inhibitory input to the E-PGs, likely participates in a feedback loop, as it receives excitatory input from P-EG neurons (Figure <span class="au-ref raw v1">\ref{704309}</span>Di). It is possible that this kind of loop between the columnar system and accessory structures input neurons is repeated in other places in the network. Another example would be the IMPL-F neuron, which receives input from the PF-LCre neuron in the LAL. Its target in the CX has not been identified so far, but since it is located in the FB, it likely involves the FB columnar system.</div><div></div><h3 data-label="352682" class="ltx_title_subsubsection">Outputs</h3><div>In contrast with inputs, we found few potential channels leaving the CX. The only output pathway identified in this dataset is presented in Figure&nbsp;<span class="au-ref raw v1">\ref{704309}</span>C, and connects the PF-LCre columnar neuron&nbsp;to a LAL interneuron through a strong, mecamylamine-sensitive, excitatory connection (shown in figure&nbsp;<span class="au-ref raw v1">\ref{489066}</span>Ai). This information is likely further processed in the LAL, as we found indications of inhibition upon PF-LCre stimulation in another LAL interneuron (WL-L). Even if we could not trace the circuit responsible for this inhibition, it likely involves an intermediate interneuron in the LAL. Once again, as this dataset does not include every single cell type of the CX, some outputs might easily have been missed. FB tangential neurons <cite class="ltx_cite raw v1">\cite{Hanesch1989}</cite>, for example, may also contribute output pathways.</div>