Figure 10.

Proposed scheme of the polarization coding network in the central complex. A, Input pathways. Polarization vision information is transferred from the optic lobe to the lower unit of the anterior optic tubercle (AOTu-LU; open blue arrows) and reaches the LT and median olive (MO) via TuLAL1a/b neurons (Pfeiffer et al., 2005). TL2 and TL3 tangential neurons connect the LT and MO to different layers of the CBL (Träger et al., 2008). CL1a neurons are candidates to transmit polarization vision signals from the CBL to the PB. For clarity, this connectivity is only shown for one double column in each hemisphere (CL1a axons to the LT have been omitted). TB1 neurons integrate the signals within the PB and are the first neurons that contribute to the topographic representation of E-vectors in the PB columns (shown for two TB1 cells only) (Heinze and Homberg, 2007). Open, brown arrows indicate the columnar output of the two TB1 neurons. B, Output pathways. The output from TB1 neurons in the PB is likely transferred onto CPU1, CP1, and CP2 columnar neurons projecting to the lateral accessory lobes (LALs, red), the MO (blue), or the LT (violet; Heinze and Homberg, 2007). Of these, CPU1 neurons receive additional input in the CBU. A second pathway connects the CBL directly to the LT via small-diameter axons of CL1a/b neurons, not involving the PB. All terminals of columnar neurons within the LT and MO could potentially provide input to LAL-LT neurons (black), which connect these areas with the contralateral LAL. This neuron type, as well as CPU1 neurons, might synapse onto the LAL-pPC neuron, which provides a connection to the posterior protocerebrum. TB1 neurons provide another possible output from the PB to the posterior optic tubercle (POTu). Descending neurons might receive input from either of these regions (brown, open arrows), and/or from the LAL, to provide information flow to motor control circuits in the thorax. AOTu-UU, Upper unit of the anterior optic tubercle.