Читать книгу The Behavior of Animals - Группа авторов - Страница 49

Optic tectum and pretectal thalamus are involved in prey catching and predator avoidance. At the neuronal level of analysis, extracellular recordings from toad’s optic tectum reveal monocular T5-type neurons. One type T5.1 is sensitive to extension of feature p. A second type T5.2 is selective in that its activity—according to prey-catching activity (Table 2.5)—increases with extension of p (Figure 2.8 Bp), within limits, but progressively decreases with extension of c (Figure 2.8 Bc) The activity of type T5.2 in response to different configurational objects reflects the probability that an object fits the prey category (Figure 2.8, cf. A, B).

Recordings from pretectal thalamus reveal various types of TH-type neurons, among them monocular neurons TH3 responsive to extension of c or p and c. All these neurons are integrated in a feature-analyzing network.

The “window hypothesis” (Figure 2.10A–C) suggests that feature p is analyzed in a retinotectal processing stream originating in certain classes of retinal ganglion cells (classes R2 and R3) and continuing in tectal prey-selective T5.2-neurons. In parallel, feature c is analyzed in a retinopretectal/thalamic processing stream originating in partly other retinal ganglion cells (classes R3 and R4) and continuing in TH4-neurons that are selective to predatory objects (see also Suggested Reading, Movie A1).

Figure 2.10 “Window hypothesis” of configurational feature analysis in toads. Illustrative schemes of feature-sensitive/selective neurons (symbolized by circles) integrated in a neuronal network (Ewert 1974, 2004). For explanations see text.

In detail, the evaluation of an object as belonging to the prey category results from convergence of both processing streams on tectal T5.2-neurons that weight feature p by excitatory tectal input and feature c by inhibitory pretectal/thalamic input (Figure 2.10A). Predator evaluation results from convergence of both processing streams on pretectal/thalamic TH4-neurons that are weighing p and c by excitatory pretectal/thalamic and excitatory tectal inputs (Figure 2.10C). We speak of parallel distributed interactive processing of information.