Journal of comparative physiology

, Volume 153, Issue 1, pp 99–110

Visual pattern discrimination through interactions of neural networks: a combined electrical brain stimulation, brain lesion, and extracellular recording study inSalamandra salamandra

  • T. Finkenstädt
  • J. -P. Ewert

DOI: 10.1007/BF00610347

Cite this article as:
Finkenstädt, T. & Ewert, J.P. J. Comp. Physiol. (1983) 153: 99. doi:10.1007/BF00610347


In freely movingSalamandra salamandra various brain sites (n = 33) were stimulated monopolarly via chronically implanted electrodes. Stimulation of the optic tectum mainly elicited prey-catching behavior (mean lower current threshold Ilt = 9 μA) and sometimes predator-avoidance behavior (Ilt = 28 μA). Stimulation of the caudal dorsal (Ilt = 27 μA) or rostral dorsal thalamus (Ilt = 26 μA) exclusively released avoidance movements, such as ipsiversive turning, running, or moving backward. Telencephalic stimulation (Ilt = 66 μA) activated backward-creeping, trunk-raising, or jaw-opening/closing.

Brain lesions were produced inn = 64 fire salamanders either by anodal DC current, radiofrequency current, Kainic acid micro-injections, or micro-knife cuts. After ablation of the optic tectum, both visually guided prey-catching and predator-avoidance behaviors failed to occur. Unilateral lesions in the following prosencephalic brain areas caused a strong deficit of configurational prey-selection (‘disinhibition of prey-catching behavior’) and a failure of visual predator-avoidance behavior in response to stimuli moving in certain areas of the visual field: (i) caudal dorsal thalamus (entire contralateral visual field), (ii) rostral dorsal thalamus (frontal visual field of both eyes), and (iii) medial pallium (entire visual field of both eyes). Lesions in the lateral pallium led to a decrease in the threshold of visually guided predator-avoidance behavior.

Action potentials were extracellularly recorded from single tectal T5 neurons in intact animals and following various prosencephalic lesions (i), (ii), or (iii). In all of then = 14 investigated neurons the same alteration of response properties was obtained, corresponding to the change in behavior. Recordings from a single prey-selective class T5(1) neuron pre and post DC coagulation in the ipsilateral caudal dorsal thalamus produced: an increase in the diameter of the excitatory receptive field (ERF) from ≈30 ° to ≈50 ° and a strong deficit in selectivity with regard to moving configurational visual stimuli.



excitatory receptive field


thalamicpretectal region


medial pallium


lateral pallium


direct current


innate releasing mechanism


IRM extended or modified by experience

Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • T. Finkenstädt
    • 1
  • J. -P. Ewert
    • 1
  1. 1.Neuroethology and Biocybernetics Laboratories, FB 19University of Kassel (GhK)KasselFederal Republic of Germany

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