Excision and rotation of the developing Amblystoma optic tectum and subsequent visual behavior

Observations on the formation of the brain and of nerve connections following embryonic manipulation of the amphibian neural tube

“…Our findings are, in large part, consistent with observations reported by Crelin (1952). He rotated tectal rudiments of Aa t various emb and later tested optokinetic reactions of the operated animals.…”

“…There are two incidental observations, which we have not pursued systemati cally. First, when a piece of neural tube is cut out and discarded, the missing tissues usually are replaced, and a brain which is indistinguishable from that of an unoperated animal is later formed (see Crelin 1952). On the other hand, if the cut piece is rotated or translocated, such an embryological regulation rarely occurs, and a grossly abnormal brain, such as those illustrated in this paper, develops from the surgically disturbed neural tube.…”

Observations on the formation of the brain and of nerve connections following embryonic manipulation of the amphibian neural tube

“…Our findings are, in large part, consistent with observations reported by Crelin (1952). He rotated tectal rudiments of Aa t various emb and later tested optokinetic reactions of the operated animals.…”

“…There are two incidental observations, which we have not pursued systemati cally. First, when a piece of neural tube is cut out and discarded, the missing tissues usually are replaced, and a brain which is indistinguishable from that of an unoperated animal is later formed (see Crelin 1952). On the other hand, if the cut piece is rotated or translocated, such an embryological regulation rarely occurs, and a grossly abnormal brain, such as those illustrated in this paper, develops from the surgically disturbed neural tube.…”

The evolution of the retinotectal map during development in Xenopus

“…before the outgrowth of retinal ganglion cell axons. The time of tectal polarization is not known since the only attempted experiments on the tectum comparable to the embryonic eye rotations, did not give clear results (Crelin 1952). Our present findings show that, if the development of an ordered map does indeed require the prior polarization of the retina and tectum, such tectal polarization has occurred by stage 48 in Xenopus.…”

Retention of the original topographic polarity by the 180° rotated tectal reimplant in young adult goldfish

“…On the other hand, the topographic polarization of the optic tectum has not been well explored experimentally as yet. Crelin (1952) reported that when the presumptive optic tectum was rotated 1800 in Ambystoma at an early embryonic stage (Harrison stage 31) before the retinal polarization became fixed, the animal later showed normal vision. When the tectum was reimplanted at a later stage, however, the grafted tectal tissue did not survive.…”

Observations on the formation of the brain and of nerve connections following embryonic manipulation of the amphibian neural tube

“…Our findings are, in large part, consistent with observations reported by Crelin (1952). He rotated tectal rudiments of Aa t various emb and later tested optokinetic reactions of the operated animals.…”

“…There are two incidental observations, which we have not pursued systemati cally. First, when a piece of neural tube is cut out and discarded, the missing tissues usually are replaced, and a brain which is indistinguishable from that of an unoperated animal is later formed (see Crelin 1952). On the other hand, if the cut piece is rotated or translocated, such an embryological regulation rarely occurs, and a grossly abnormal brain, such as those illustrated in this paper, develops from the surgically disturbed neural tube.…”

The evolution of the retinotectal map during development in Xenopus

“…before the outgrowth of retinal ganglion cell axons. The time of tectal polarization is not known since the only attempted experiments on the tectum comparable to the embryonic eye rotations, did not give clear results (Crelin 1952). Our present findings show that, if the development of an ordered map does indeed require the prior polarization of the retina and tectum, such tectal polarization has occurred by stage 48 in Xenopus.…”

Retention of the original topographic polarity by the 180° rotated tectal reimplant in young adult goldfish

“…On the other hand, the topographic polarization of the optic tectum has not been well explored experimentally as yet. Crelin (1952) reported that when the presumptive optic tectum was rotated 1800 in Ambystoma at an early embryonic stage (Harrison stage 31) before the retinal polarization became fixed, the animal later showed normal vision. When the tectum was reimplanted at a later stage, however, the grafted tectal tissue did not survive.…”

Observations on the formation of the brain and of nerve connections following embryonic manipulation of the amphibian neural tube

“…Our findings are, in large part, consistent with observations reported by Crelin (1952). He rotated tectal rudiments of Aa t various emb and later tested optokinetic reactions of the operated animals.…”

“…There are two incidental observations, which we have not pursued systemati cally. First, when a piece of neural tube is cut out and discarded, the missing tissues usually are replaced, and a brain which is indistinguishable from that of an unoperated animal is later formed (see Crelin 1952). On the other hand, if the cut piece is rotated or translocated, such an embryological regulation rarely occurs, and a grossly abnormal brain, such as those illustrated in this paper, develops from the surgically disturbed neural tube.…”

The evolution of the retinotectal map during development in Xenopus

“…before the outgrowth of retinal ganglion cell axons. The time of tectal polarization is not known since the only attempted experiments on the tectum comparable to the embryonic eye rotations, did not give clear results (Crelin 1952). Our present findings show that, if the development of an ordered map does indeed require the prior polarization of the retina and tectum, such tectal polarization has occurred by stage 48 in Xenopus.…”

Retention of the original topographic polarity by the 180° rotated tectal reimplant in young adult goldfish

“…On the other hand, the topographic polarization of the optic tectum has not been well explored experimentally as yet. Crelin (1952) reported that when the presumptive optic tectum was rotated 1800 in Ambystoma at an early embryonic stage (Harrison stage 31) before the retinal polarization became fixed, the animal later showed normal vision. When the tectum was reimplanted at a later stage, however, the grafted tectal tissue did not survive.…”