Journal of Comparative Physiology A

, Volume 176, Issue 2, pp 169–180

Pretecto-tectal influences

I. What the toad's pretectum tells its tectum: an antidromic stimulation/recording study
  • H. Buxbaum-Conradi
  • J. -P. Ewert
Original Paper

DOI: 10.1007/BF00239920

Cite this article as:
Buxbaum-Conradi, H. & Ewert, J.P. J Comp Physiol A (1995) 176: 169. doi:10.1007/BF00239920
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Abstract

Optic tectum and pretectum are two main structures for parallel processing of contralateral retinal inputs. Since it is known from anatomic studies that pretectum projects to ipsilateral tectum, the present investigation focuses on the physiological properties of this information transfer. (1) Extracellular single cell recordings from pretectal thalamic nuclei in cane toads Bufo marinus revealed different classes of neurons, TH1 to TH10, comparable to the ones described previously in B. americanus, except TH9. A further class TH11 responded specifically to the temporonasal direction of movement of a large object or textured surface. (2) Most neurons belonged to the classes TH3 and TH4, sensitive particularly to large moving objects and responsive to moving textured surfaces independent of the horizontal direction of movement. Nearly one third could be antidromically activated to electrical stimulation of the ipsilateral optic tectum, by the criterion of the collision test, that is ultimate proof of their pretectotectal projective character. (3) Among the remaining neurons, one tonically discharging TH1 cell fulfilled the collision test. (4) It is suggested that TH3 cells inform topographically corresponding structures of the tectal visual map about large moving objects and their extension perpendicular to the direction of movement, hence contributing to the discrimination between prey and non-prey. Class TH4 pretectotectal projection cells with inputs from the entire monocular or binocular visual field inform the tectum about large objects moving anywhere in the visual field and about a moving textured surrounding that fills the visual field. The latter would allow the tectum to discriminate object motion from self-induced motion.

Key words

Pretectum Neuronal classes Projections to the tectum Antidromic stimulation/recording technique Toad 

Abbreviations

A

stripe in antiworm configuration, oriented perpendicular to the direction of movement

W

stripe in worm configuration, oriented parallel to the direction of movement

S

square

CECT

empirical and theoretical collision interval, respectively

ERF

excitatory receptive field

IRF

inhibitory receptive field

L, R

neuronal response latency and absolute refractory period, respectively

Lpd Lpv P

lateral posterodorsal, lateral posteroventral, and posterior pretectal thalamic nucleus, respectively

NTTN

nasotemporal or temporonasal direction of stimulus movement in the visual field of the eye

OT

optic tectum

TH

classes of pretectal thalamic neurons

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • H. Buxbaum-Conradi
    • 1
  • J. -P. Ewert
    • 1
  1. 1.Abteilung Neurobiologie, Fachbereich Biologie/Chemie, Universität Kassel (GhK)KasselGermany

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