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Galleria Tassonomica
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 ATTENZIONE! Per una determinazione sicura ed affidabile, in aggiunta alle foto artistiche, sono necessarie anche un paio di foto scientifiche: una da destra presa longitudinalmente, che mostri lo pneumostoma (apertura per la respirazione) ed una altra che mostri la suola. I Limacidi sono modelli pazienti e con un pizzico di pazienza da parte nostra si possono fare foto su un tronco, sul muschio o su un ramo. Sarete sorpresi nel vedere come possono essere belle le foto dei Limacidi! Una foto all'habitat richiede solo qualche istante in più ma permette di ottenere informazioni preziose per la ricerca scientifica.
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Cmb
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Città: Buers
Prov.: Estero
Regione: Austria
12844 Messaggi
Flora e Fauna |
 Inserito il - 08 luglio 2009 : 14:26:16
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Limax and neuroscience
Clemens M. Brandstetter, Bürs, Austria
Ho trovato questo info:
Link
(purtroppo non funziona ancora...)
Alan Gelperin
Visiting Research Scientist
Adjunct Professor, Dept Neuroscience, U Penn
member, Monell Chemical Senses Center
Molecular Biology
123 Lewis Thomas Laboratory
609-258-7667 (office)
215-898-5885 (office)
215-898-2084 (fax)
gelperin@princeton.edu
Research Interests:
Animals are programmed to solve certain problems by learning predictive relationships among stimuli and storing information about those predictive relationships in a form that is stable for periods ranging from one to 7x105 hours. Remarkably complex associative learning has evolved in animals with neural circuits highly suited to biophysical analysis, such as the terrestrial garden slug Limax maximus. We study odor learning and odor information processing in Limax, as this animal displays robust and reliable one-trial odor conditioning and a variety of higher-order learning modes during olfactory learning. The central circuit which stores odor memories has oscillatory dynamics of its local field potential and propagates activity waves along its apical-basal axis. This dynamics arises from a network of coupled neuronal oscillators that have a gradient of excitability along the apical-basal axis. Oscillatory dynamics is widespread in mammalian cortical networks during sensory processing and motor command generation. Thus we study both synaptic events during learning and the computational function of oscillatory dynamics in the Limax olfactory circuit to shed light on the roles of learning and oscillations during cortical processing.
Our current studies of Limax odor memory formation and odor information processing aim to answer the following four questions: Can odor memory formation be imaged in the isolated nose-brain preparation? Does odor learning-specific uptake of Lucifer yellow reveal neurons that store an odor memory? What is the role of post-hatching neurogenesis in the odor memory storage network and how is it affected by olfactory experience and learning? What are the contributions to synaptic stabilization of genes activated by one-trial odor learning?
Imaging odor memory formation in vitro. Our previous imaging studies of odor responses in the odor memory circuit used naïve brains. We now have a procedure to train a naïve nose-brain preparation in vitro by pairing nerve shock with odor application. We measure action potential generation by identified withdrawal neurons as the output measure. Before conditioning an attractive odor does not activate withdrawal motoneurons while after pairing the odor with nerve shock the odor strongly activates the identified withdrawal motoneurons. We image the odor memory circuit after staining its neurons with a voltage-sensitive dye. We record a series of images with a CCD camera and analyze the patterns of neural activity in response to odor stimulation before and after conditioning. Odor application initially causes a collapse of the apical-basal phase gradient, which in our model of odor memory formation is a necessary precondition for synaptic modification. This can now be tested.
Learning-specific dye uptake. If a slug is given one-trial odor conditioning and then injected with the highly fluorescent dye Lucifer yellow, a band of neurons is found in the odor memory storage circuit containing Lucifer yellow in membrane bound vesicles. Animals given odor exposure alone or unpaired applications of odor and the aversive stimulus do not show neuronal uptake of Lucifer yellow in the odor memory circuit. We are performing imaging experiments to test the hypothesis that the Lucifer yellow containing neurons found after odor conditioning store the odor memory in the strengths of their synaptic connections. We also train the naïve nose-brain preparation in vitro by pairing nerve shock and odor application while applying drugs selectively to the odor learning circuit. This in vitro training technique with drug application restricted to the odor learning circuit allows us to block long-term memory formation and determine if dye uptake is also blocked. We also want to determine if learning-specific Lucifer yellow uptake occurs in mammalian systems.
Stimulus modulated neurogenesis. Mammals and mollusks add new olfactory receptors throughout life and new olfactory interneurons until adulthood, yet their olfactory systems appear to maintain a constant input-output relation. The odor memory storage circuit in Limax hatches with a zone of active neurogenesis that produces 80% of the neurons found in the adult circuit after hatching. We explore how odor experience and odor learning affect neurogenesis by labeling dividing neurons with bromodeoxyuridine (BrdU) and giving slugs varied odor experiences before developing the BrdU label immunocytochemically. The zone of neurogenesis at hatching is at the most apical position in the odor learning circuit, where activity waves originate. New neurons are added only on the apical side of the band of neurogenesis. Removal of one nose retards neurogenesis until the nose regenerates. We plan to image neurogenesis with 2-photon laser-scanning microscopy using fluorescent nucleotides applied to an in vitro nose-brain preparation which can learn odor-shock associations while the zone of neurogenesis is being imaged.
Odor learning-activated gene expression. Professor Yutaka Kirino and his collaborators at the University of Tokyo have just described (Genes To Cells 6:43, 2001) the activation by one-trial odor conditioning in Limax of a gene coding for an extracellular matrix protein. The gene is expressed in neurons of the odor memory storage circuit and makes a protein that is homologous to proteins found in zebrafish, mice and human. The gene product is secreted into extracellular space and may stabilize connections between neurons in the odor learning circuit. In collaboration with the Kirino laboratory we plan to assess the effect of the new learning-specific extracellular matrix protein on connections between odor memory storage neurons cultured in vitro and on long-term memory formation by the isolated nose-brain preparation trained in vitro.
Publications:
Gelperin, A. (1999) Oscillatory dynamics and information processing in olfactory systems. J. Exp. Biol. 202:1855-1864.
Teyke, T., Wang, J., Gelperin, A. (2000) Lateralized memory storage and crossed inhibition during odor processing by
Limax. J. Comp. Physiol. A, 186:269-278.
Cooke, I. R. C. and Gelperin, A. (2000) In vivo recordings of spontaneous and odor-modulated dynamics in the Limax olfactory lobe. J. Neurobiol. 46:126-141.
Gelperin, A., Flores, J., Raccuia-Behling, F., Cooke, I. (2000) Nitric oxide and carbon monoxide modulate oscillations of olfactory interneurons in a terrestrial mollusk. J. Neurophysiology 83:116-127.
Wang, J., Flores, J., Gelperin, A., and Denk, W., (2001) Initiation and propagation of calcium-dependent action potentials in a coupled network of olfactory interneurons. J. Neurophysiol., 85:977-985.
Ermentrout, B., Wang, J. W., Flores, J. and Gelperin, A. (2001) Model for olfactory discrimination and learning and memory in the Limax procerebral lobe incorporating oscillatory dynamics and wave propagation. J. Neurophysiol. 85:1444-1452.
Gelperin, A. and Hopfield, J. J. (2001) Electronic and computational olfaction. In P. Given (ed.) Chemistry of Taste,. American Chemical Society, Washington, DC. In press
"La distinction des espèces de limaces est extrêmement difficile,
et aucun zoologiste n’est encore parvenu à quelque chose
d’un peu satisfaisant sous ce rapport."
H. M. DUCROTAY DE BLAINVILLE 1823
Riassunto del Forum Natura Mediterraneo degli Limax dell'Italia
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Cmb
Moderatore
Città: Buers
Prov.: Estero
Regione: Austria
12844 Messaggi
Flora e Fauna |
Inserito il - 14 novembre 2010 : 10:22:14
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Trovato un PDF per la tema (Tadashi Nakaya et al. 2001):
Link
Abstract: Odour-taste associative learning in the terrestrial slug offers a useful model for long-term memory formation and retention. The genes which are expressed over 2 h after a learning event are thought to include those related to memory formation and/or consolidation. It is very important to examine what kinds of genes are expressed following associative learning.
We identified a novel slug gene, the expression of which was regulated by associative learning and mostly restricted to the procerebrum (PC), a place that olfactory information is believed to be processed in slug. This gene encodes a 121 amino acid, 18 kDa secretory protein which we term LAPS18. Expression of the LAPS18 gene was induced in somata and the protein spread to neurites in the PC of slugs subjected to paired conditioning. Recombinant LAPS18 promoted the aggregation and movement of PC neurones in culture and they were blocked by the anti-LAPS18 antibody. Beads coupled with LAPS18 protein attached to PC neurones and the beads aggregated through PC cells but not by themselves, suggesting that LAPS18 may require a counterpart molecule for PC neurone aggregation.
An increased expression and translocation of LAPS18 protein after paired conditioning may be needed for long-term memory formation and retention in the slug. Since genes homologous to LAPS18 genes in the land slug Limax are found from vertebrates including human, analysing the expression and function of LAPS18 may be important in understanding the molecular mechanism of memory formation and retention.
"La distinction des espèces de limaces est extrêmement difficile,
et aucun zoologiste n’est encore parvenu à quelque chose
d’un peu satisfaisant sous ce rapport."
H. M. DUCROTAY DE BLAINVILLE 1823
Riassunto del Forum Natura Mediterraneo degli Limax dell'Italia |
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Limax and neuroscience
