. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 204 J. Z. YOUNG. Figure 7. Transverse section of the inferior frontal system of Octopus vii/garis stained with Cajal's silver method. Abbreviations as Figure 4. cr. cerebral tract (from subvertical lobe): p. tract of probably pain fibers from hind end of bodv. a complex plexus to the vertical lobe. Here there are rel- atively few large cells (65,000), with complex dendrites, exactly like those of the subfrontal, and no less than 25 million amacrine cells. The large cells send their axons down to the subvertical lobe and
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 204 J. Z. YOUNG. Figure 7. Transverse section of the inferior frontal system of Octopus vii/garis stained with Cajal's silver method. Abbreviations as Figure 4. cr. cerebral tract (from subvertical lobe): p. tract of probably pain fibers from hind end of bodv. a complex plexus to the vertical lobe. Here there are rel- atively few large cells (65,000), with complex dendrites, exactly like those of the subfrontal, and no less than 25 million amacrine cells. The large cells send their axons down to the subvertical lobe and so to the posterior buccal, but also back to the lateral superior frontal (Fig. 3). This circuit evidently plays some part in re-enforcing the conjunctions, possibly by maintaining particular patterns by re-excitation. The Distributed Tactile Learning System The system for touch learning thus includes no less than eight distinct lobes with matrix structure (Fig. 3). The relative parts played by the various lobes was studied over a number of years in a large number of animals with divided brains. Lesions were made on one side, and the other was left as a control. In many of the experiments, discrimination was between completely smooth balls (0 rings) and those with 13 incisions. The sequence of train- ing for 129 normal sides is shown in Figure 5. A useful measure of the extent and reliability of dis- crimination is to give a series of 24 extinction tests with balls of differing roughness, shown at short intervals (1- 3 min) without any reward. Such tests are arduous to give, but they show that habituation proceeds more slowly in proportion to similarity of each ball to the one for which reward was previously given (Fig. 8). The capacity for discrimination was also tested by using more nearly similar balls, with 4 and 7 rings. With long training, oc- topuses could probably make some discrimination even between a difference of one ring. By such tests we can compare the discrimin
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
