Neurons of the Central Complex of the LocustSchistocerca gregariaare Sensitive to Polarized Light

Abstract

The central complex is a topographically ordered neuropil structure in the center of the insect brain. It consists of three major subdivisions, the upper and lower divisions of the central body and the protocerebral bridge. To further characterize the role of this brain structure, we have recorded the responses of identified neurons of the central complex of the desert locust Schistocerca gregaria to visual stimuli. We report that particular types of central complex interneurons are sensitive to polarized light. Neurons showed tonic responses to linearly polarized light with spike discharge frequencies depending on e-vector orientation. For all neurons tested, e-vector response curves showed polarization opponency. Receptive fields of the recorded neurons were in the dorsal field of view with some neurons receiving input from both compound eyes and others, only from the ipsilateral eye. In addition to responses to polarized light, certain neurons showed tonic spike discharges to unpolarized light. Most polarization-sensitive neurons were associated with the lower division of the central body, but one type of neuron with arborizations in the upper division of the central body was also polarization-sensitive. Visual pathways signaling polarized light information to the central complex include projections via the anterior optic tubercle. Considering the receptive fields of the neurons and the biological significance of polarized light in insects, the central complex might serve a function in sky compass-mediated spatial navigation of the animals.

Linking the Input to the Output: New Sets of Neurons Complement the Polarization Vision Network in the Locust Central Complex

“…In the desert locust, a variety of neurons of the central complex is sensitive to dorsally presented polarized light, suggesting a key role of this brain area in sky compass orientation (Vitzthum et al, 2002;Homberg, 2004;Heinze and Homberg, 2007). In the present study we have characterized additional elements of the polarization vision network in the central complex.…”

“…Finally, we identified neurons that are suited to relay polarization vision information to descending pathways. When these data are combined with previously described cell types (Vitzthum et al, 2002;Heinze and Homberg, 2007), a general connectivity scheme of the polarization coding network in the locust central complex emerges (Fig. 10).…”

“…Three types of tangential neuron connect two small areas of the LALs, the lateral triangle and the median olive, to the CBL . These neurons are highly sensitive to the E-vector orientation of dorsally presented polarized light and respond to a rotating polarizer with tonic modulation of their firing rate (Vitzthum et al, 2002). Each cell is maximally excited when stimulated with a particular, preferred E-vector (⌽ max ), and is maximally inhibited at an E-vector 90°d ifferent from ⌽ max (polarization opponency).…”

Neural Organization and Visual Processing in the Anterior Optic Tubercle of the Honeybee Brain

“…We thus believe that this bi-lobed major AOTu compartment serves similar spatial processing functions in honeybees and locusts. The central body of insects presumably participates in polarized light coding, visual pattern recognition, spatial orientation, right-left maneuvering, and motor control (Strauss, 2002;Vitzthum et al, 2002;Liu et al, 2006;Wang et al, 2008). The AOTu output neurons may indirectly (via the LAL) provide the central body with the spatial information necessary for these tasks.…”

Polarization-Sensitive Descending Neurons in the Locust: Connecting the Brain to Thoracic Ganglia

“…At the neuronal level, polarization vision pathways in the brain have been studied most extensively in locusts and crickets (Labhart and Meyer, 2002;Homberg, 2004). In these insects, the central complex is a major processing stage for polarized light (Vitzthum et al, 2002;Homberg, 2007, 2009;Sakura et al, 2008;). showed that polarization-sensitive (POL-) neurons connect the central complex to the lateral accessory lobes and the posterior protocerebrum, brain areas that are innervated by intersegmental neurons (Williams, 1975;Strausfeld and Seyan, 1985;Okada et al, 2003).…”