Neurons of the toad's (Bufo bufo L.) visual system sensitive to moving configurational stimuli: A statistical analysis

Summary

• 1. The activity of 59 neurons situated at different points along the visual pathway of the toadBufo bufo (L.) were investigated quantitatively by extracellular microelectrode recording methods. The activity was recorded in response to a variety of moving configurational stimuli which traversed the excitatory receptive fields of these neurons: Various sized squares and stripes of different length, oriented either in or perpendicular to the direction of movement, were used as visual stimuli. The stimuli were moved at constant visual angular velocity. The neuronal activities were evaluated by five different methods (Fig. 1A-E). The electrode positions in the brain tissue for all neurons investigated were reconstructed histologically (Fig. 2A-C).

• 2. In the central layers of the optic tectum two statistically different neuronal populations were identified (Fig. 3A and B). Neurons of one population, class T5(1), were sensitive to the area of a moving stimulus and were activated mainly by configurational stimuli elongated in the direction of movement rather than by the extension of the same stimulus object perpendicular to the direction of movement (Fig. 5). Neurons of another population in the same layers of the optic tectum, class T5 (2), were found to be activated by elongation of a configurational stimulus in the direction of movement, but inhibited by extension perpendicular to the direction of movement (Figs. 4 and 6).

• 3. In the thalamic pretectal region neurons (class TH3) were recorded showing sensitivity to the area of a moving stimulus. They were activated mainly by configurational stimuli elongated perpendicular to the direction of movement rather than by extension in the direction of movement (Fig. 8).

• 4. The present data confirm our earlier results on stimulus configurationsensitivity andselectivity by neurons in the toad'sBufo bufo (L.) visual system.