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Cellular and Molecular Life Sciences :... Mar 2011Associative learning in goal-directed behaviors, in contrast to reflexive behaviors, can alter processes of decision-making in the selection of appropriate action and... (Review)
Review
Associative learning in goal-directed behaviors, in contrast to reflexive behaviors, can alter processes of decision-making in the selection of appropriate action and its initiation, thereby enabling animals, including humans, to gain a predictive understanding of their external environment. In the mollusc Aplysia, recent studies on appetitive operant conditioning in which the animal learns about the positive consequences of its behavior have provided insights into this form of associative learning which, although ubiquitous, remains mechanistically poorly understood. The findings support increasing evidence that central circuit- and cell-wide sites other than chemical synaptic connections, including electrical coupling and membrane conductances controlling intrinsic neuronal excitability and underlying voltage-dependent plateauing or oscillatory mechanisms, may serve as the neural substrates for behavioral plasticity resulting from operant conditioning. Aplysia therefore continues to provide a model system for understanding learning and memory formation that enables establishing the neurobiological links between behavioral, network, and cellular levels of analysis.
Topics: Animals; Aplysia; Conditioning, Operant; Dopamine; Feeding Behavior; Reward
PubMed: 21042832
DOI: 10.1007/s00018-010-0570-9 -
Zootaxa Dec 2022During the past century eight species of sea hares of the genus Aplysia were recorded from Peru. However, there is disagreement about how many of these species are valid...
During the past century eight species of sea hares of the genus Aplysia were recorded from Peru. However, there is disagreement about how many of these species are valid and their taxonomy needs to be critically evaluated. Based on detailed morphological examinations, this study presents a redescription of Aplysia nigra d'Orbigny, 1837 and Aplysia inca d'Orbigny, 1837, the most common species of Aplysia along the Peruvian coast. They showed consistent morphological differences, mainly in the foot, parapodia development, opaline gland, jaws, radular teeth and penial morphology. Anatomical data for both species are provided for the first time, as well as a comparison with other species of Aplysia reported for the Eastern Pacific. The records of Aplysia keraudreni Rang, 1828, Aplysia dactylomela Rang, 1828 and Aplysia juliana Quoy & Gaimard, 1832 for Peruvian waters are likely erroneous and need to be verified based on collected specimens.
Topics: Animals; Aplysia; Peru; Species Specificity
PubMed: 37044529
DOI: 10.11646/zootaxa.5222.3.1 -
Advances in Second Messenger and... 1994
Review
Topics: Animals; Aplysia; Long-Term Potentiation; Memory; Transcription, Genetic
PubMed: 7848731
DOI: 10.1016/s1040-7952(06)80034-0 -
Progress in Brain Research 2008Synaptic remodeling and synaptic growth accompany various forms of long-term memory. Storage of the long-term memory for sensitization of the gill-withdrawal reflex in... (Review)
Review
Synaptic remodeling and synaptic growth accompany various forms of long-term memory. Storage of the long-term memory for sensitization of the gill-withdrawal reflex in Aplysia has been extensively studied in this respect and is associated with the growth of new synapses by the sensory neurons onto their postsynaptic target neurons. Recent time-lapse imaging studies of living sensory-to-motor neuron synapses in culture have monitored both functional and structural changes simultaneously so as to follow remodeling and growth at the same specific synaptic connections continuously over time and to examine the functional contribution of these learning-related structural changes to the different time-dependent phases of memory storage. Insights provided by these studies suggest the synaptic differentiation and growth induced by learning in the mature nervous system are highly dynamic and often rapid processes that can recruit both molecules and mechanisms used for de novo synapse formation during development.
Topics: Animals; Aplysia; Axonal Transport; Behavior, Animal; Long-Term Potentiation; Memory; Models, Biological; Neuronal Plasticity; Synapses
PubMed: 18394474
DOI: 10.1016/S0079-6123(07)00010-6 -
Journal of Neuroscience Methods Apr 2022A growing body of research demonstrates that focused ultrasound stimulates activity in human and other mammalian nervous systems. However, there is no consensus on which...
BACKGROUND
A growing body of research demonstrates that focused ultrasound stimulates activity in human and other mammalian nervous systems. However, there is no consensus on which sonication parameters are optimal. Furthermore, the mechanism of action behind ultrasound neurostimulation remains poorly understood. An invertebrate model greatly reduces biological complexity, permitting a systematic evaluation of sonication parameters suitable for ultrasound neurostimulation.
NEW METHOD
Here, we describe the use of focused ultrasound stimulation with an ex-vivo abdominal ganglion preparation of the California sea hare, Aplysia californica, a long-standing model system in neurobiology. We developed a system for stimulating an isolated ganglion preparation while obtaining extracellular recordings from nerves. The focused ultrasound stimulation uses one of two single-element transducers, enabling stimulation at four distinct carrier frequencies (0.515 MHz, 1.l MHz, 1.61 MHz, 3.41 MHz).
RESULTS
Using continuous wave ultrasound, we stimulated the ganglion at all four frequencies, and we present quantitative evaluation of elicited activation at four different sonication durations and three peak pressure levels, eliciting up to a 57-fold increase in spiking frequency.
COMPARISON WITH ELECTRICAL STIMULATION
We demonstrated that ultrasound-induced activation is repeatable, and the response consistency is comparable to electrical stimulation.
CONCLUSIONS
Due to the relative ease of long-term recordings for many hours, this ex-vivo ganglion preparation is suitable for investigating sonication parameters and the effects of focused ultrasound stimulation on neurons.
Topics: Animals; Aplysia; Electric Stimulation; Humans; Mammals; Neurons; Transducers
PubMed: 35227740
DOI: 10.1016/j.jneumeth.2022.109536 -
The Journal of Experimental Biology Aug 2019Grasping soft, irregular material is challenging both for animals and robots. The feeding systems of many animals have adapted to this challenge. In particular, the...
Grasping soft, irregular material is challenging both for animals and robots. The feeding systems of many animals have adapted to this challenge. In particular, the feeding system of the marine mollusk , a generalist herbivore, allows it to grasp and ingest seaweeds of varying shape, texture and toughness. On the surface of the grasper of is a structure known as the radula, a thin flexible cartilaginous sheet with fine teeth. Previous studies suggested that intrinsic muscles, I7, are responsible for opening the radula. Lesioning I7 does not prevent animals from grasping and ingesting food. New studies demonstrate that a set of fine muscle fibers on the ventral surface of the radula - the sub-radular fibers (SRFs) - mediate opening movements even if the I7 muscles are absent. Both and lesions demonstrate that removing the SRFs leads to profound deficits in radular opening, and significantly reduces feeding efficiency. A theoretical biomechanical analysis of the actions of the SRFs suggests that they induce the radular surface to open around a central crease in the radular surface and to arch the radular surface, allowing it to softly conform to irregular material. A three-dimensional model of the radular surface, based on observations and magnetic resonance imaging of intact animals, provides support for the biomechanical analysis. These results suggest how a soft grasper can work during feeding, and suggest novel designs for artificial soft graspers.
Topics: Animals; Aplysia; Biomechanical Phenomena; Feeding Behavior; Mouth
PubMed: 31350299
DOI: 10.1242/jeb.191254 -
Progress in Brain Research 2008The marine snail Aplysia has served for more than four decades as an important model system for neurobiological analyses of learning and memory. Until recently, it has... (Review)
Review
The marine snail Aplysia has served for more than four decades as an important model system for neurobiological analyses of learning and memory. Until recently, it has been believed that learning and memory in Aplysia were due predominately, if not exclusively, to presynaptic mechanisms. For example, two nonassociative forms of learning exhibited by Aplysia, sensitization and dishabituation of its defensive withdrawal reflex, have been previously ascribed to presynaptic facilitation of the connections between sensory and motor neurons that mediate the reflex. Recent evidence, however, indicates that postsynaptic mechanisms play a far more important role in learning and memory in Aplysia than formerly appreciated. In particular, dishabituation and sensitization depend on a rise in intracellular Ca(2+) in the postsynaptic motor neuron, postsynaptic exocytosis, and modulation of the functional expression of postsynaptic AMPA-type glutamate receptors. In addition, the expression of the persistent presynaptic changes that occur during intermediate- and long-term dishabituation and sensitization appears to require retrograde signals that are triggered by elevated postsynaptic Ca(2+). The model for learning-related synaptic plasticity proposed here for Aplysia is similar to current mammalian models. This similarity suggests that the cellular mechanisms of learning and memory have been highly conserved during evolution.
Topics: Animals; Aplysia; Avoidance Learning; Behavior, Animal; Memory; Models, Biological; Neuronal Plasticity; Serotonin; Synapses; Synaptic Transmission
PubMed: 18394481
DOI: 10.1016/S0079-6123(07)00017-9 -
Molecular Brain Jun 2008Whereas the induction of short-term memory involves only covalent modifications of constitutively expressed preexisting proteins, the formation of long-term memory... (Review)
Review
Whereas the induction of short-term memory involves only covalent modifications of constitutively expressed preexisting proteins, the formation of long-term memory requires gene expression, new RNA, and new protein synthesis. On the cellular level, transcriptional regulation is thought to be the starting point for a series of molecular steps necessary for both the initiation and maintenance of long-term synaptic facilitation (LTF). The core molecular features of transcriptional regulation involved in the long-term process are evolutionally conserved in Aplysia, Drosophila, and mouse, and indicate that gene regulation by the cyclic AMP response element binding protein (CREB) acting in conjunction with different combinations of transcriptional factors is critical for the expression of many forms of long-term memory. In the marine snail Aplysia, the molecular mechanisms that underlie the storage of long-term memory have been extensively studied in the monosynaptic connections between identified sensory neuron and motor neurons of the gill-withdrawal reflex. One tail shock or one pulse of serotonin (5-HT), a modulatory transmitter released by tail shocks, produces a transient facilitation mediated by the cAMP-dependent protein kinase leading to covalent modifications in the sensory neurons that results in an enhancement of transmitter release and a strengthening of synaptic connections lasting minutes. By contrast, repeated pulses of 5-hydroxytryptamine (5-HT) induce a transcription- and translation-dependent long-term facilitation (LTF) lasting more than 24 h and trigger the activation of a family of transcription factors in the presynaptic sensory neurons including ApCREB1, ApCREB2 and ApC/EBP. In addition, we have recently identified novel transcription factors that modulate the expression of ApC/EBP and also are critically involved in LTF. In this review, we examine the roles of these transcription factors during consolidation of LTF induced by different stimulation paradigms.
Topics: Animals; Aplysia; Aquatic Organisms; Gene Expression Regulation; Memory, Long-Term; Seawater; Snails; Transcription, Genetic
PubMed: 18803855
DOI: 10.1186/1756-6606-1-3 -
Trends in Neurosciences Oct 1989Development can provide a powerful analytic approach for distinguishing and analysing specific behavioral, cellular and molecular processes as they emerge during... (Review)
Review
Development can provide a powerful analytic approach for distinguishing and analysing specific behavioral, cellular and molecular processes as they emerge during ontogeny. Recently, such a developmental strategy has been used to investigate the functional assembly of different forms of non-associative learning (habituation, dishabituation and sensitization) in the marine mollusc Aplysia. This analysis has shown that different forms of learning, as well as their cellular analogs at central synapses, emerge according to very different developmental timetables. Subsequent behavioral studies in adult Aplysia showed that these same forms of learning were also clearly dissociable in the mature animal. These results, taken with earlier studies, suggest that a commonly held 'dual-process' view of non-associative learning, which attempts to account for all forms of non-associative learning as the interaction of only two processes (one decremental and one incremental) requires revision, and that a multi-process view, which includes the possibility of inhibitory as well as facilitatory interactions, is required to account adequately for all of the behavioral features of nonassociative learning.
Topics: Animals; Aplysia; Learning
PubMed: 2479136
DOI: 10.1016/0166-2236(89)90078-7 -
Journal of Neurobiology Jul 1989We have used the gill- and siphon-withdrawal reflex of Aplysia californica to determine the morphological basis of the prolonged changes in synaptic effectiveness that... (Review)
Review
We have used the gill- and siphon-withdrawal reflex of Aplysia californica to determine the morphological basis of the prolonged changes in synaptic effectiveness that underlie long-term habituation and sensitization. We have found that clear structural changes accompany behavioral modification and have demonstrated that these can be detected at the level of identified sensory neuron synapses, a critical site of plasticity for the short-term forms of both types of learning. These alterations occur at two different levels of synaptic organization and include (1) changes in focal regions of synaptic membrane specialization--the number, size and vesicle complement of sensory neuron active zones are larger in sensitized animals and smaller in habituated animals compared with controls--and (2) a parallel but more dramatic and global trend involving modulation of the total number of presynaptic varicosities per sensory neuron. Quantitative analysis of the time course over which these structural alterations occur during sensitization has further demonstrated that changes in the number of varicosities and active zones persist in parallel with the behavioral retention of the memory. This increase in the number of sensory neuron synapses during long-term sensitization in Aplysia is similar to changes in the number of synapses in the mammalian brain following various forms of environmental manipulations and learning (Greenough, 1984). Therefore learning may involve a form of neuronal growth across a broad segment of the animal kingdom, thereby suggesting a role for structural synaptic plasticity during long-term behavioral modifications.
Topics: Animals; Aplysia; Memory; Neuronal Plasticity; Neurons, Afferent; Synapses
PubMed: 2664078
DOI: 10.1002/neu.480200508