Processing of infrared signals in the central nervous system of the western diamondback rattlesnake

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Some snake species such as pit vipers, boas and pythons perceive electromagnetic radiation in the infrared (IR) spectrum through a special organ known as the pit organ. Due to the width of the pit organ opening and the low number of infrared receptors (approx. 6000), the resulting image has a poor resolution with little information about the respective object. However, these snakes are able to perform a fast and precise strike towards their prey even in complete darkness. It is however still unknown whether the snakes use neuronal processes to effectively reconstruct information out of this low-resolution IR-image. We will thus investigate the nuclei of the infrared pathway (Nucleus of the lateral descending tract, LTTD; Nucleus reticularis caloris) in respect to potential image processing functions. A likely candidate for the implementation of lateral inhibition is the LTTD, which could therefore be considered as an analogue to the retina of the visual system. At the level of optic tectum infrared information is integrated by bimodal neurons into the visual system in a unique way. There, the lowly resolved image of the IR-system has to be integrated into the high-resolution image of the visual system. For a detailed investigation of this integrative process, prior information processing in the unimodal IR-pathway needs to be revealed first. Therefore, a second aim of this research project is to investigate the basic principles of image processing in the IR-System of pit vipers in respect to multimodal integration in higher brain areas. In addition, the interaction of the optic tectum with nuclei of the isthmic system will be investigated. This network provides the basis for focusing on the environmental stimulus most relevant for the animal. Since the IR-System plays a crucial role for pit vipers in perception of the environment, it is likely that the IR-System also influences the isthmic nuclei.