Visual responses of neurons in the pretectal nucleus lentiformis mesencephali to moving patterns within and beyond receptive fields in pigeons

Large-field patterns are effective stimuli for eliciting visual responses f rom neurons in the pretectal nucleus lentiformis mesencephali of nonmammals . The present study shows that stimulation beyond the receptive field does not contribute to the visual responses of neurons in the nucleus lentiformi s mesencephali in two respects. First, changes in the direction and velocit y of motion beyond the receptive field did not affect the visual responses of the pretectal cells to motion within the receptive field. Second, time d ifferences in the onset of stimulation within and outside the receptive fie ld did not influence the visual responses of the pretectal cells to motion in the receptive field, implying that there may be no long-range interactio n between the receptive field and its surrounding field. The present study also indicates that the pretectal cells are not only sensitive to the direc tion and velocity of motion, but also to the size and density of dots in a random-dot pattern moving through the receptive field. Taken together with previous studies, these results suggest that the receptive field of the pre tectal cells within the nucleus lentiformis mesencephali is large in size b ut well defined in boundaries, and that the pretectal cells respond to moti on of visual stimuli within but not beyond their receptive fields. Copyrigh t (C) 2001 S. Karger AG. Basel.