Vision and electroreception: Integration of sensory information in the optic tectum of the weakly electric fishApteronotus albifrons

Summary

The responses of single neurons to visual and electrosensory stimulation were studied in the optic tectum of the weakly electric fishApteronotus albifrons. Most of the cells recorded in the region of the tectum studied, the anterior medial quadrant, were poorly responsive or completely insensitive to flashes of light or to bursts of AC electrical stimuli applied to the entire fish. However, these cells gave vigorous responses to moving visual or electrosensory stimuli. Most cells showed differences in their response contingent upon the direction of the stimulus movement and most received input from both the visual and electrosensory systems. Electrosensory responses to moving stimuli were depressed by jamming stimuli, 4 Hz amplitude modulation of the animal's electric organ discharge, presented simultaneously with the moving stimulus. However, the jamming signal presented alone typically evoked no response. Moving visual stimuli, presented simultaneously with the electrosensory, were usually able to restore the magnitude of a response toward its value in the unjammed situation. For most of the cells studied the receptive fields for vision and electroreception were in register. In some cases the visual and electrosensory components could be separated by presenting the two types of stimuli separately, or by presenting both simultaneously but with some amount of spatial separation, which causes the two to be misaligned relative to the fish. In other cases the individual responses could not be separated by spatial manipulations of the two stimuli and in these cases differences in the alignment of the two types of stimuli could cause changes in the intensity of the cells' responses.