Wavelength-dependent waveform characteristics of tectal evoked potentials in rainbow trout

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Abstract:

Wavelength-dependent properties of tectal evoked potentials (TEPs) in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), were examined. It was found that TEP waveforms show distinct variation as a function of wavelength. In addition, the data suggest that the On and Off channels of the tectum each possess different wavelength-dependent characteristics. Middle wavelength stimulation typically evoked a waveform similar to that reported for another anamniote vertebrate, the toad (genus Bufo Laurenti, 1768). For the On and Off responses, this waveform comprised two negative deflections, N1 and N2, which were interrupted by a positive deflection, P2. The N2 deflection was followed by a final positive deflection, P3. Principal component analysis revealed that the N2–P3 complex of the On response was significantly more pronounced at longer wavelengths. In contrast, the N2–P3 complex was most pronounced at middle wavelengths for the Off response. The N1 deflection was relatively invariant with respect to wavelength. Should colour-opponent tectal units provide a significant contribution to the TEP, it is probable that its waveform characteristics provide signs of underlying neural processes which facilitate colour discrimination.

Nous avons étudié les propriétés reliées à la longueur d'onde dans les potentiels générés par le toit optique (TEPs) chez la truite arc-en-ciels, Oncorhynchus mykiss (Walbaum, 1792). Les formes des ondes TEP varient de façon distincte en fonction de la longueur d'onde. De plus, les données indiquent que les voies On et Off du toit optique possèdent chacune des caractéristiques reliées à la longueur d'onde différentes. Une stimulation par des ondes de longueur moyenne génère des formes d'ondes semblables à celles signalées chez le crapaud (genre Bufo Laurenti, 1768), un autre vertébré anamniote. Dans les réactions On et Off, la forme de cette onde comprend deux déflexions négatives, N1 et N2, interrompues par une déflexion positive, P2. La déflexion N2 est suivie d'une déflexion positive finale, P3. Une analyse des composantes principales indique que le complexe N2–P3 de la réaction On est plus prononcée aux longueurs d'onde élevées. En revanche, dans la réaction Off, le complexe N2–P3 est plus marqué aux longueurs d'onde moyennes. La déflexion N1 varie relativement peu en fonction de la longueur d'onde. S'il est vrai que les unités opposantes de perception des couleurs du toit optique contribuent au TEP, les caractéristiques de la forme des ondes devraient probablement fournir des indices sur les processus neurologiques qui facilitent la discrimination des couleurs.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: October 1, 2004

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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