Development of learning and memory in Aplysia. I. Functional assembly of gill and siphon withdrawal.
نویسندگان
چکیده
The marine mollusc Aplysia californica provides an excellent preparation with which to examine the development of the neuronal control of behavior for 2 reasons: first, adult Aplysia exhibit a variety of behaviors that are well understood in cellular terms; and second, the development of Aplysia from embryo to adult has been studied in considerable detail. Among the best understood behaviors in Aplysia are the withdrawal responses of the mantle organs (the gill, siphon, and mantle shelf), which exhibit 2 different kinds of behaviors: "spontaneous" contractions that are part of a fixed action pattern, a respiratory pumping sequence of the mantle organs, and reflex contractions in response to tactile stimuli. We have examined the development of both of these withdrawal behaviors in juvenile stages 9-12 and found that they are functionally assembled according to different ontogenetic timetables. Spontaneous contractions. As soon as the siphon and gill emerge, in stages 9 and 10, respectively, they each show a high rate of spontaneous contraction that gradually diminishes throughout subsequent stages until it reaches the low rate typical of adults (stage 13). Since the siphon emerges first, it already exhibits a significant decline in its spontaneous activity (e.g., in stage 11) when the gill's spontaneous activity is at its highest. In addition to a developmental trend in the rate of contractions, there was also a clear developmental progression in the degree of cocontraction of the siphon and gill during spontaneous contractions. In adults, the siphon and gill show a very high degree of cocontraction during spontaneous pumping. However, in juvenile animals, there was a very low degree. Thus, it appears that the siphon and gill withdrawal components of the fixed action pattern become progressively more functionally coupled during juvenile development. Reflex contractions. As soon as the siphon and gill emerge in their respective developmental stages, they exhibit a brisk withdrawal reflex to tactile stimulation of the siphon. Moreover, at each developmental stage, reflex siphon contractions were graded as a function of stimulus intensity, as they are in the adult. Finally, throughout development tactile stimulation of the siphon invariably evoked coincident contractions of both the siphon and the gill, which is characteristic of the adult reflex. Thus, unlike the fixed action pattern that takes several weeks to mature, the defensive withdrawal reflex closely resembles the adult form as soon as the effector organs emerge during juvenile development.(ABSTRACT TRUNCATED AT 400 WORDS)
منابع مشابه
Development of learning and memory in Aplysia. III. Central neuronal correlates.
The defensive withdrawal reflex of the mantle organs of Aplysia californica has 2 major components, siphon withdrawal and gill withdrawal. In the previous paper of this series (Rankin and Carew, 1987), the development of 2 forms of nonassociative learning, habituation and dishabituation, was examined in the siphon withdrawal component of the reflex. In the present study we examined these same f...
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The development of several forms of nonassociative learning (habituation, dishabituation, and sensitization) has previously been examined in the gill and siphon withdrawal reflex of Aplysia. In the present study we analyzed the development of one of these forms of learning, sensitization, in a different response system in Aplysia, escape locomotion. A broad range of juvenile stages was examined...
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We have found that in the gill- and siphon- withdrawal reflex of Aplysia, the memory for short-term sensitization grades smoothly into long-term memory with increased amounts of sensitization training. One cellular locus for the storage of the memory underlying short-term sensitization is the set of monosynaptic connections between the siphon sensory cells and the gill and siphon motor neurons....
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We have used the gill and siphon withdrawal reflex of Aplysia to study the morphological basis of the persistent synaptic plasticity that underlies long-term sensitization. One critical locus for storage of the memory for sensitization is the set of monosynaptic connections between identified siphon sensory neurons and gill and siphon motor neurons. To complement previous morphological studies ...
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Attempts to explain learning-associated potentiation of synaptic transmission in model systems such as withdrawal reflexes in the mollusk Aplysia or the hippocampus of vertebrates have focused on the mechanisms by which transmitter release is increased in the principal elements of the circuit. Increased transmission in neuronal networks such as the gill and siphon withdrawal reflex (GSWR) of Ap...
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ورودعنوان ژورنال:
- The Journal of neuroscience : the official journal of the Society for Neuroscience
دوره 7 1 شماره
صفحات -
تاریخ انتشار 1987