Spatial and Temporal Organization of the Binocular Input to Frog Optic Tectum

Raybourn, Michael S.

doi:10.1159/000123631

Cited by 11 publications

(1 citation statement)

References 10 publications

(12 reference statements)

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“…contribute to the difference in plasticity? We have determined that the intertectal delay in Xenopus is about 10 ms (Scherer & Udin, 1991), while the delay in Rana has been reported to be substantially longer, 20-45 ms (Gaze & Jacobson, 1963;Raybourn, 1975). In this paper, we have compared the two species using identical stimuli and have confirmed that the delay in Rana is several times longer than that in Xenopus.…”

Section: Introductionsupporting

confidence: 59%

Differential intertectal delay between Rana pipiens and Xenopus laevis: Implications for species-specific visual plasticity

Scherer

Udin

1995

Vis Neurosci

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In the frog Xenopus laevis, the isthmotectal projection, which relays input from the ipsilateral eye, exhibits anatomical reorganization following surgical eye rotation performed during tadpole stages while the isthmotectal projection in the frog Rana pipiens fails to show reorganization. This plasticity has been shown to be dependent upon activation of the N-methyl-D-aspartate (NMDA) receptor located on tectal cell dendrites. The reorganization process in Xenopus is hypothesized to employ a Hebbian mechanism requiring correlated firing of ipsilateral and contralateral inputs to a given tectal cell; when an ipsilateral axon synapses onto a tectal cell that receives input from a contralateral axon with a matching receptive-field location, the correlation in activity triggers stabilization of the ipsilateral synapse. However, in neither Xenopus nor Rana do ipsilateral and contralateral inputs begin to fire simultaneously in response to a given visual stimulus; the ipsilateral input is delayed because it reaches the tectum indirectly, through a polysynaptic relay via the opposite tectum and nucleus isthmi. The objective of this experiment was to test whether there is a significant difference in this intertectal delay between Xenopus laevis and Rana pipiens in order to determine whether intertectal delay could be a contributing factor in this species-specific ability to exhibit visual plasticity. We have found that intertectal delay is 26.16 ms longer in Rana pipiens (36.53 ms) than in Xenopus laevis (10.37 ms).

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Section: Introductionsupporting

confidence: 59%

Differential intertectal delay between Rana pipiens and Xenopus laevis: Implications for species-specific visual plasticity

Scherer

Udin

1995

Vis Neurosci

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The potential binocular field and its tectal representation in rana pipiens

Grobstein

Comer

Kostyk

1980

J of Comparative Neurology

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We have studied binocularity in Rana pipiens using optical, behavioral, and electrophysiological assays. The first two assays yielded a consistent picture of the size and shape of the area of uniocular visual field overlap, the potential binocular field. Potential binocular field has an extent of about 90 degrees on the horizontal in front of the frog, narrows to about 60 degrees above the frog's head, and continues to a point well behind the frog. This differs somewhat from a previous report (Fite, '73). Uniocular visual field extent on the horizontal is in excess of 225 degrees, permitting both a large binocular field and panoramic vision. The electrophysiological assay confirms the large uniocular visual field extent. It further shows that physiological binocularity closely reflects uniocular visual field overlap, in the sense that tectal loci representing positions in the potential binocular field, including those behind the frog's head, display convergent inputs from the two eyes.

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