Direct-current magnetic fields of 10 to 100 gauss cause a significant short-term reduction of the in vitro electroretinographic b-wave response in turtle retina. This response compression is not accompanied by the usual reduction in retinal sensitivity that occurs with background illumination. Furthermore, this effect is obtained only briefly after the offset of ambient lighting in the diurnal light-dark cycle of nonhibernating animals.

Single-unit recordings in the frog''s optic tectum have demonstrated the existence of a systematic spatial separation between the direct contralateral and indirect ipsilateral excitatory receptive fields. Marked differences in this spatial organization were found between paralyzed and anesthesized animals.Significant latency differences were found between sustained (class I/II) and transient (class III) contralateral fibers. Corresponding latency differences were also seen in ipsilaterally driven responses. It is suggested that there may be at least two different classes of ipsilateral fibers.The existence of binocular interaction at the level of the afferent terminal arborizations was investigated, utilizing temporally asynchronous dichoptic stimulation. No such phenomena were seen in curarized animals. These findings are discussed in terms of possible velocity and direction sensitivity mechanisms.

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