T1 [FBbt_00003727]

T1

ID: FBbt_00003727

An intrinsic columnar neuron whose cell body lies in the cortex of the medulla. The fiber of the T1 cell body branches at the medulla surface to form a T-shaped linking fiber between a bush-like arborization in the distal part of a medulla column (M1 and M2), and a bundle of climbing fibers in the equivalent column of the lamina (Fischbach and Dittrich, 1989). Synaptic connections in the lamina are exclusively postsynaptic and include a large number of connections from lamina intrinsic (amacrine) neurons (Meinertzhagen and O'Neil, 1991; Rivera-Alba et al., 2011). In the medulla, it is strongly synapsed by centrifugal neuron C3 in medulla layer M2 and lamina monopolar neuron L2 (Takemura et al., 2008; Takemura et al., 2013). There is usually one of these cells per optic column (Nern et al., 2025).

Cell connectivity in the lamina was determined by analysis of semi-automated EM reconstruction of 749 serial sections of 21 complete lamina cartridges. The number of synaptic connections for T1 (presynaptic/postsynaptic) in a single lamina cartridge for each cell type was the following: R2 (-/2), R3 (-/2), R4 (-/2), Lai (-/54), C3 (-/1) and Lawf (-/1) (Rivera-Alba et al., 2011). Connectivity in the medulla was extrapolated from serial EM of 3 columns from a single sample (Takemura et al., 2008) or from 7 columns (Takemura et al., 2013).