The Behavior of Animals. Группа авторов

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innate releasing mechanism

       Toward neuronal correlates of releasing systems

      At first glance the giant axon of giant lateral interneuron in crayfish, controlling the escape tail-flip in response to mechanosensory stimulation, serves as a CN (Wiersma & Ikeda 1964). The idea that a neuron triggers a behavior was challenging and sparked intense debate among neuroethologists. Kupfermann and Weiss (1978) pointed out that a CN must fulfill two conditions: its excitation is not only necessary but also sufficient to activate the behavior. This strong definition can be examined: electrically exciting that neuron should be sufficient to elicit the corresponding behavior; removing it should abolish the behavioral response to the peripheral stimulus. For experimental studies, the best candidate of a CN is the reticulospinal Mauthner cell in teleost fish that, in response to vibratory stimulation, triggers the fast-body-bend escape reaction. However, quantitative investigations showed that a Mauthner cell did not fulfill the “double-condition” (Eaton 2001); a command neuron that does it, convincingly, remains to be discovered. If several neurons are involved in a command function, we use the term “command system.”

      In fact, a releasing system—relying on attention and motivation—may take advantage of adequate receptor cells and assemblies of feature-sensitive/selective interneurons. This system translates the information of a sign-stimulus into a command, which is appropriate to activate the corresponding motor system (Figure 2.2).

      Scent-coding by specialized receptor cells in insects

      Figure 2.6 Male silk moth in alerted position, with combed antennae elevated (top). (Courtesy of R.A. Steinbrecht.) Bottom: schematic section through a scent hair with pore tubuli and two scent receptor cells. Arrangement for recording impulses from bombykol receptor. (Modified after R.A. Steinbrecht).

      Figure 2.7 Principles of scent detection in moths by specialist receptor cells and interneurons. (a) In male silk moths a receptor channel is specialized for female’s sex pheromone bombykol. (b) In male nun moths a receptor channel is specialized for the sex pheromone (+)-disparlure. (c) In male gypsy moths two types of receptor channel are specialized for two pheromone compounds: (+)-disparlure stimulates interneurons, whereas (−)-disparlure inhibits their response to (+)-disparlure. (d) In male leaf-roller moths the concurrent excitatory influences of the two receptor channels specialized for the two sex pheromone stereoisomers (Z)-11-tetradecenyl-acetate and (E)-11-tetradecenyl-acetate are essential to activate interneurons. (Compiled from data in Hansen 1984; Kaissling 2014.) Note that a behavioral response requires activation of many specialist receptor cells and corresponding interneurons.

      Other examples of such narrow-band olfactory specialists are the meat receptor in Necrophorus beetles, the rotten-meat receptor in blow-flies Calliphora erythrocephala, and the grass receptor in the locust Locusta migratoria. Grass receptors respond to chemically related components of fresh grass, such as hexenol, hexenal, and hexenic acid (Kafka 1970).

      In leaf-roller moth species, as mentioned above, the males have two types of specialized receptor cells, each one tuned to a different pheromone, both emitted by the conspecific female in a characteristic proportion (e.g., Figure 2.7d), which minimizes the risk of mating with males of inadequate species.

      In addition to specialist receptors there are “generalist receptor cells.” These—showing partly overlapping response spectra—respond differently to various odor compounds. Such cells may be suitable to distinguish odorous substances by individual experience.

      Visual feature detection in amphibians: a multimethodological analysis

       Toward a features-relating-algorithm as a principle in configurational perceptio n

      How

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