Unraveling the functional organization of lobula complex in the mantis brain by identification of visual interneurons.

Abstract

The praying mantis shows broad repertories of visually guided behaviors such as prey recognition and defense against collision. It is likely that neurons in the lobula complex (LOX), the third visual neuropil in the optic lobe, play significant roles in these behaviors. The LOX in the mantis brain consists of five neuropils: outer lobes 1 and 2 (OLO1 and OLO2); anterior lobe (ALO); dorsal lobe (DLO); and stalk lobe (SLO), and ALO comprise ventral and dorsal subunits, ALO-V and ALO-D. To understand the functional organization of LOX, intracellular electrodes were used for recording from and staining neurons in these neuropils of the mantis (Tenodera aridifolia). The neurons belonged to three categories based on their response properties and morphologies. First, tangential ALO-V neurons projecting to ventromedial neuropils (VMNP) (TAproM1 and 2), tangential DLO (or ALO-D) neurons projecting to VMNP (TDproM1 and 2), and tangential ALO-V centrifugal neurons (TAcen) all showed directional sensitivity and sustained excitation to gratings drifting in preferred direction (outward-downward, inward-upward, outward-upward, inward-downward, and inward, respectively). Second, tangential OLO neurons projecting to VMNP or ventrolateral neuropils (VLNP) (TOproM or TOproL), columnar OLO commissural neurons (COcom), and SLO commissural neurons (Scom) all showed strong excitation to 2°-8° moving squares but little excitations to drifting gratings. COcom and SLO neurons ramified in both left and right LOX. Last, the class of tangential ALO-V neurons projecting to VLNP (TAproL1, 2, and 3) responded best to looming circles and showed little excitation to receding, darkening, and lightening circles.