Multisensory integration in weakly electric fish

Animals integrate information from across sensory systems, such as vision and hearing, to improve perception. To understand how neural circuits in the central nervous system integrate information from different senses, the responses of midbrain neurons to two categories of electrosensory stimuli in Eigenmannia virescens were studied. The first category of stimulus is electrical signals with frequencies below 50 Hz that are encoded in the activity of ampullary receptors. The second category is amplitude modulations of the electric organ discharge, which are encoded by p-type tuberous receptors. Six multisensory neurons were found that responded to both categories of stimuli. However, when the stimuli were presented simultaneously, the responses to one of the two categories were suppressed. Further, in six neurons that responded to one modality, responses were significantly reduced when the two categories of stimuli were presented simultaneously. These data suggest that multisensory information does not enhance neural responses