Animal behaviour relies on the integration of input of a number of external as well as internal sensory sources. The assembly of this information into a coherent and useful view of the external world is a basic challenge for the brain and a major focus of cognitive neuroscience (e.g. Stein and Meredith, 1993). Here we propose a project exploring the "merging of visual and electrosensory senses" in the weakly electric fish G. petersii. This animal is a promising model as electrophysiological and behavioural experiments can easily be conducted. Furthermore there is a huge knowledge concerning the basic principles of electrosensory information processing. Given the striking similarities in decoding of the electric sense and vision, the aim of the proposed study is to investigate how the brain encodes electrosensory and visual stimuli in G. petersii.
The similarities in decoding strategies of both sensory systems will further be exploited to investigate the role of multi-modal integration for orientation in the three-dimensional world. Recent findings (Ulbricht et al. 2003) suggest that the retinal morphology of Gnathonemus represents an adaptation to the turbid waters in which these fish live. Rather than being optimised in respect of light sensitivity, the retina of Gnathonemus seems to be specialized to detect moving and/or large objects within an extremely rough-screen image (turbid environment). It is hypothesized that the unusual morphology of the retina represents a peripheral filter for the detection of "relevant" objects (e. g., predators) whereas the rich background of small "irrelevant" environmental constituents is 'filtered out' of the image. Consequently it is expected that the organisation of the TO is optimised for the analysis of moving objects in turbid scenarios. In contrast to other teleosts, the TO of Gnathonemus is relatively small and the termination of retinal afferents is limited to a single layer (Lazaret)
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