. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. \ Figure 1. Aplysia in the feeding posture. In this position the animal shows directed turning responses to seaweed applied to the head. prove the efficiency of their behavior is by regulating it according to particular internal states. These internal states are modulated by external and internal stimuli and by an internal endogenous process associated with a circadian activity rhythm. In higher animals, the constellation of state variables that regulate feeding are termed "hunger," and by analogy, a hunger-like st
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. \ Figure 1. Aplysia in the feeding posture. In this position the animal shows directed turning responses to seaweed applied to the head. prove the efficiency of their behavior is by regulating it according to particular internal states. These internal states are modulated by external and internal stimuli and by an internal endogenous process associated with a circadian activity rhythm. In higher animals, the constellation of state variables that regulate feeding are termed "hunger," and by analogy, a hunger-like state also appears to regulate feeding in Aplysia. As in higher animals, feeding in Aplysia is greatly potentiated by pre-exposing the animals to food; the animal exhibits incentive motivation. When a quiescent Aplysia is first stimulated with seaweed, it be- comes activated after a relatively long delay (up to a min-. Figure 2. Vectors indicating the magnitude and direction that the head turns in response to tactile stimuli briefly presented (open loop) to different points on the rhinophores and tentacles. The movements turn the head in the direction of the stimulus. In the open loop condition the animal greatly overshoots the stimulus. If, however, the stimulus is maintained in place (closed loop), when the animal begins the response, the movement is represented by the indicated vectors, but as the animal turns, the response progressively decreases in magnitude so that the mouth comes to be accurately centered over the stimulus. Data from Teyke el al (1990b) too- 80- *\ °\i Y \i \ H ' °\l ,o 60- 40- \T '\I * 20- n . ?^\_, °-° seaweed tactile 01 23456789 10 STIMULUS NUMBER Figure 3. Turning angle evoked by repeated seaweed (open circles) or tactile (filled circles) stimuli. The animals (n = 5) were first induced into the feeding posture by means of seaweed. They were then stimulated at a locus 10° from the mouth, either with a purely tactile stimulus, or with seaweed.
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
