CiteULike: brembs's snails

Background illumination effects upon in vitro conditioning in Hermissenda

D Tomsic — 2008-07-30T12:57:51-00:00

Neurobiol Learn Mem, Vol. 74, No. 1. (2000), 56-64.

In the marine snail Hermissenda, associative learning can be accomplished by paired presentations of light and vestibular stimulation. It is generally assumed that associative learning depends upon the intensity or salience of the conditioned or unconditioned stimulus (CS and US, respectively). Accordingly, during Hermissenda conditioning a stronger dark adaptation is expected to render the CS (the light) more salient and hence facilitate association. We studied the influence of background illumination level using an in vitro pairing procedure in Hermissenda. This procedure allows one to assess the effect of conditioning upon a single cell, the B photoreceptor, which is implicated in this learning process. After 15 min of adaptation to a dim background light, B photoreceptors maintained a basal rate of firing, while after adaptation to complete darkness, they stopped firing. Paired and unpaired groups received 10 training trials in either a completely dark or a dim light environment. Although a trial to trial cumulative increase in excitability was found in the paired group trained in darkness, only the paired group trained under dim background light showed a higher input resistance and cell excitability 10 min after training. These results suggest that the background dim illumination was not needed for the induction but played a role in the maintenance of the pairing effect. Possible mechanisms for such a modulatory effect are discussed.

Central localization of plasticity involved in appetitive conditioning in Lymnaea

VA Straub — 2008-07-30T12:57:42-00:00

Learn Mem, Vol. 11, No. 6. (2004), 787-93.

Learning to associate a conditioned (CS) and unconditioned stimulus (US) results in changes in the processing of CS information. Here, we address directly the question whether chemical appetitive conditioning of Lymnaea feeding behavior involves changes in the peripheral and/or central processing of the CS by using extracellular recording techniques to monitor neuronal activity at two stages of the sensory processing pathway. Our data show that appetitive conditioning does not affect significantly the overall CS response of afferent nerves connecting chemosensory structures in the lips and tentacles to the central nervous system (CNS). In contrast, neuronal output from the cerebral ganglia, which represent the first central processing stage for chemosensory information, is enhanced significantly in response to the CS after appetitive conditioning. This demonstrates that chemical appetitive conditioning in Lymnaea affects the central, but not the peripheral processing of chemosensory information. It also identifies the cerebral ganglia of Lymnaea as an important site for neuronal plasticity and forms the basis for detailed cellular studies of neuronal plasticity.

Classical conditioning of Hermissenda: origin of a new response

II Lederhendler — 2008-07-30T12:56:06-00:00

J Neurosci, Vol. 6, No. 5. (1986), 1325-31.

Training of the marine snail Hermissenda crassicornis with paired light and rotation was previously shown to result in acquisition and retention of a behavioral change with many features characteristic of vertebrate associative learning. Here, this behavioral change is demonstrated to be classical, Pavlovian-like conditioning. A new response to light is formed (the CR) that is pairing-specific and resembles the unconditioned response (UCR) to rotation. The conditioned and unconditioned responses are relatively rapid, occurring within seconds of the onset of light or rotation stimuli, and correspond to pairing-specific reductions in speed during the same time period. Since the CR is independent of the presentation of rotation, and it is also expressed by the same effector system (the foot) responsible for the UCR, light stimulation has assumed some of the functional character of rotation.

Operant conditioning in invertebrates.

B Brembs — 2006-09-29T06:48:41-00:00

Curr Opin Neurobiol, Vol. 13, No. 6. (December 2003), pp. 710-717.

Learning to anticipate future events on the basis of past experience with the consequences of one's own behavior (operant conditioning) is a simple form of learning that humans share with most other animals, including invertebrates. Three model organisms have recently made significant contributions towards a mechanistic model of operant conditioning, because of their special technical advantages. Research using the fruit fly Drosophila melanogaster implicated the ignorant gene in operant conditioning in the heat-box, research on the sea slug Aplysia californica contributed a cellular mechanism of behavior selection at a convergence point of operant behavior and reward, and research on the pond snail Lymnaea stagnalis elucidated the role of a behavior-initiating neuron in operant conditioning. These insights demonstrate the usefulness of a variety of invertebrate model systems to complement and stimulate research in vertebrates.