Present address: Institute of Zoology, University of Bonn, 53115 Bonn, Germany.
The role of the dorsal thalamus in visual processing and object selection: a case of an attentional system in amphibians
Article first published online: 31 AUG 2012
© 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 36, Issue 11, pages 3459–3470, December 2012
How to Cite
Ruhl, T. and Dicke, U. (2012), The role of the dorsal thalamus in visual processing and object selection: a case of an attentional system in amphibians. European Journal of Neuroscience, 36: 3459–3470. doi: 10.1111/j.1460-9568.2012.08271.x
- Issue published online: 4 DEC 2012
- Article first published online: 31 AUG 2012
- Received 8 May 2012, revised 6 July 2012, accepted 30 July 2012
- extracellular recording;
- Plethodon shermani ;
- thalamic lesion;
- visual ascending pathway
In amphibians, the midbrain tectum is regarded as the visual centre for object recognition but the functional role of forebrain centres in visual information processing is less clear. In order to address this question, the dorsal thalamus was lesioned in the salamander Plethodon shermani, and the effects on orienting behaviour or on visual processing in the tectum were investigated. In a two-alternative-choice task, the average number of orienting responses toward one of two competing prey or simple configural stimuli was significantly decreased in lesioned animals compared to that of controls and sham-lesioned animals. When stimuli were presented during recording from tectal neurons, the number of spikes on presentation of a stimulus in the excitatory receptive field and a second salient stimulus in the surround was significantly reduced in controls and sham-lesioned salamanders compared to single presentation of the stimulus in the excitatory receptive field, while this inhibitory effect on the number of spikes of tectal neurons was absent in thalamus-lesioned animals. In amphibians, the dorsal thalamus is part of the second visual pathway which extends from the tectum via the thalamus to the telencephalon. A feedback loop to the tectum is assumed to modulate visual processing in the tectum and to ensure orienting behaviour toward visual objects. It is concluded that the tectum–thalamus–telencephalon pathway contributes to the recognition and evaluation of objects and enables spatial attention in object selection. This attentional system in amphibians resembles that found in mammals and illustrates the essential role of attention for goal-directed visuomotor action.