الرؤية لدى العلاجيم

عين العلجوم.

The neural basis of prey detection, recognition, and orientation was studied in depth by Jörg-Peter Ewert in a series of experiments that made the toad visual system a model system in neuroethology (neural basis of natural behavior). He began by observing the natural prey catching behavior of the common European toad (Bufo bufo).

Ewert's work with toads yielded several important discoveries (Ewert 1974, 2004). In general, his research revealed the specific neural circuits for recognition of complex visual stimuli. Specifically, he identified two main regions of the brain, the tectum and the thalamic-pretectal region, that were responsible for discriminating prey from non-prey and revealed the neural pathways that connected them. Furthermore, he found that the neural mechanisms are plastic and adaptable to varying environments and conditions (Carew 2000; Zupanc 2004).

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 Natural toad behavior

للمزيد من المعلومات: Amphibian nervous and sensory systems and Frog sight

Bufo bufo

 Feature detectors and the visual system

Tectal prey feature detectors T5.2 project the axons towards bulbar premotor/motor systems. Their response characteristic results from integration in a neuronal network involving retinal ganglion cells R2, R3, R4, pretectal thalamic neurons TH3, and tectal neurons T5.1, T5.3. Arrows: excitatory connections; lines with terminal dots: inhibitory influences. Connections were checked, e.g., by means of intracellular recording postsynaptic potentials, horseradish peroxidase or cobalt-lysine tracing, antidromic electro-stimulation/recording, neurochemical techniques, chemical lesions by kainic acid. Hypothesis after Ewert 1974 and 2004

Visually released prey-catching in common toads: Various brain structures are involved in visual processes, such as feature discrimination (R, Pt, O), learning (P, At, Pt, O), and attention (S, Pt, Lt, O). The underlying neural network is suggested from experiments applying single neuron recording, focal brain stimulation, 14C-2-deoxiglucose labeling, lesioning, and anatomical pathway tracing. - R, retina (contralateral eye); O, optic tectum; Pt, pretectal thalamus; Lt, lateral anterior thalamic nucleus; At, anterior thalamus; P, posterior ventromedial pallium; S, caudal ventral striatum; B/S, bulbar/spinal pre-motor/motor nuclei; arrows: excitatory input; lines with dots: inhibitory influences. After Ewert and Schwippert 2006

 See also

• Feature detection (nervous system)
• Jörg-Peter Ewert
• Neuroethology

 References

• Carew, T.J (2000). Feature analysis in Toads. In Behavioral Neurobiology, Sunderland, MA: Sinauer, 95-119.
• Ewert, J.-P. (1974). The neural basis of visually guided behavior. Scientific American, 230(3), 34-42.
• Ewert, J.-P. (1980). Neuroethology: an introduction to the neurophysiological fundamentals of behavior. Springer-Verlag, Berlin/Heidelberg/New York.
• Ewert J.-P. (2004) Motion perception shapes the visual world of amphibians. In: Prete F.R. (Ed.) Complex Worlds from Simpler Nervous Systems. Cambridge, MA, MIT Press, pp. 117–160
• Ewert J.-P., Schwippert W.W. (2006) Modulation of visual perception and action by forebrain structures and their interactions in amphibians. In: Levin E.D. (ed.) Neurotransmitter Interactions and Cognitive Function. Birkhäuser, Basel, pp. 99–136
• González A., Smeets W.J., Marín O. (1999). Evidences for shared features in the organization of the basal ganglia in tetrapods: studies in amphibians. Eur. J. Morphol., 37(2-3), 151-154.
• Kenigfest N.B., Belekhova M.G., Karamyan O.A., Minakova M.N., Rio J.-P., Reperant J. (2002). Neurochemical organization of the turtle protectum: an immunohistochemical study. Comparative analysis. J. Evol. Biochem. Physiol., 38(6), 673-688.
• Nityananda, V., and J. C. A. Read. 2017. Stereopsis in animals: evolution, function and mechanisms. Journal of Experimental Biology 220:2502–2512.
• Reiner A., Medina L., Veenman C.L. (1998). Structural and functional evolution of the basal ganglia in vertebrates. Brain. Res. Rev., 28, 235-285.
• Zupanc, G. (2004) Behavioral Neurobiology: An Integrative Approach. Oxford University Press. 121-132.

 External links

• Details and references on toad vision—see also: [1].
• Feature detection by artificial neuronal net