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A) posterior view of cat brain stem and cerebellum, showing location of the dorsal cochlear nucleus (DCN)
B) side view of cat brain stemC) posterior view illustrating frequency slabs in the “transstrial” axisD) the DCN may be visualized as a loaf of sliced bread, with each slice representing an
isofrequency slab
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Mouse: top row, pyramidal (fusiform) cellssecond row, giant cellsthird row, deep horizontal cellsbottom row, small cells
Cat: as named in figure
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Abbreviations: CW, cartwheel cell; St, stellate cell; Gr, granule cell; Py, pyramidal cell; Gi, giant cell; Ve, vertical cell
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Magenta = 10 kHzGreen = 17.7 kHz
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Figure 6. Responses of DCN neurons to stretch of the pinna muscles. A, Arrows show the direction and location of pressure manually applied to the scutiformcartilage. B, C, Responses of two type IV units (BF of 24.2 and 23.4 kHz) to manual pressure applied as in A. The plots are PSTHs of one repetition of the stimulus made with a bin width of 1 sec. Pressure was applied by the experimenter and maintained for 10 sec (B) and 20 sec (C), marked by the bars; the actual stimulus waveform was not recorded. The neuron in B was responding to continuous broadband noise 20 dB above threshold, and the neuron in C was firing spontaneously. The effect of the pressure was a tonic inhibition, which was maintained as long as the pressure was applied. Horizontal dashed lines show spontaneous rate. The unit in C shows increased firing after release of pressure, possibly attributable to rebound from inhibition or the acoustic effects of the experimenter’s hand above the animal’s head, because this unit was extremely sensitive to sound.
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The circuit shows how excitatory input from the auditory nerve drives both excitatory and inhibitory action in the DCN. We don’t know how the parallel fibers and the ANFs interact, nor do we know what their interactions might mean in terms of physiology or function.
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