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J C Sandoz

Publications and source records attributed to J C Sandoz.

8 recordsLinked to original sources
PubMed2005

Associative learning of plant odorants activating the same or different receptor neurones in the moth Heliothis virescens.

The importance of olfactory learning in host plant selection is well demonstrated in insects, including the heliothine moths. In the present study olfactory conditioning of the proboscis extension response was performed to determine the moths' ability to learn and discriminate three plant odorants: beta-ocimene and beta-myrcene (activating the same receptor neurone type), and racemic linalool (activating two different types). The conditioned stimulus (CS) was an air puff with each odorant blown into a constant air stream and over the antennae, and the unconditioned stimulus (US) was sucrose solution applied first to the antennal taste sensilla, then to the proboscis. Conditioning with increasing odorant concentrations induced increased learning performance. The concentration threshold for learning was 100 times lower for racemic linalool than for the two other odorants, a fact that can be correlated with a higher sensitivity of the moths' antennae to racemic linalool as shown in electroantennogram recordings. After correcting for the different odour sensitivities, the moths' ability to discriminate the odorants was studied. Differential conditioning experiments were carried out, in which moths had to distinguish between a rewarded (CS+) odorant and an explicitly unrewarded odorant (CS-), choosing odour concentrations giving the same learning rate in previous experiments. The best discrimination was found with beta-myrcene as the rewarded odorant and racemic linalool as the unrewarded. The opposite combination gave lower discrimination, indicating a higher salience for beta-myrcene than for racemic linalool. The moths could also discriminate between beta-ocimene and beta-myrcene, which was surprising, since they activate the same receptor neurone type. No difference in salience was found between these two odorants.

Acyclic Monoterpenes↗
PubMed2003

Side-specific olfactory conditioning leads to more specific odor representation between sides but not within sides in the honeybee antennal lobes.

Honeybees can be trained to associate odorants to sucrose reward by conditioning the proboscis extension response. Using this paradigm, we have recently shown that bees can solve a side-specific task: they learn simultaneously to discriminate a reinforced odor A from a non-reinforced odor B at one antenna (A+B-) and the reversed problem at the other antenna (A-B+). Side-specific (A+B-/B+A-) conditioning is an interesting tool to measure neurophysiological changes due to olfactory learning because the same odorant is excitatory (CS+) on one brain side and inhibitory (CS-) on the opposite side. In the bee brain, the antennal lobe (AL) is the first olfactory relay where the olfactory memory is established. Using calcium imaging, we compared odor-evoked activity in the functional units, the glomeruli, of the two ALs, both in naive and conditioned individuals. Each odor evoked a different pattern of glomerular activity, which was symmetrical between sides and highly conserved among naive animals. In conditioned bees, response patterns were overall symmetrical but showed more active glomeruli and topical differences between sides. By representing odor vectors in a virtual olfactory space whose dimensions are the responses of 23 identified glomeruli, we found that distances between odor representations on each brain side were significantly higher in conditioned than in naive bees, but only for CS+ and CS-. However, the distance between CS+ and CS- representations was equal to that of naive individuals. Our work suggests that side-specific conditioning decorrelates odor representations between AL sides but not between CS+ and CS- within one AL.

Animals↗
PubMed2001

Asymmetrical generalisation between pheromonal and floral odours in appetitive olfactory conditioning of the honey bee (Apis mellifera L.).

The capacity to generalise between similar but not identical olfactory stimuli is crucial for honey bees, allowing them to find rewarding food sources with varying volatile emissions. We studied bees' generalisation behaviour with odours having different biological values: typical floral odours or alarm compounds. Bees' behavioural and peripheral electrophysiological responses were investigated using a combined proboscis extension response conditioning-electroantennogram assay. Bees were conditioned to pure linalool (floral) or to pure isoamyl acetate (alarm) and were tested with different concentrations of both compounds. Electrophysiological responses were not influenced by conditioning, suggesting that the learning of individual compounds does not rely on modulations of peripheral sensitivity. Behaviourally, generalisation responses of bees conditioned to the alarm compound were much higher than those of bees conditioned to the floral odour. We further demonstrated such asymmetrical generalisation between alarm and floral odours by using differential conditioning procedures. Conditioning to alarm compounds (isoamyl acetate or 2-heptanone) consistently induced more generalisation than conditioning to floral compounds (linalool or phenylacetaldehyde). Interestingly, generalisation between the two alarm compounds, which are otherwise chemically different, was extremely high. These results are discussed in relation to the neural representation of compounds with different biological significance for bees.

Animals↗
PubMed1999

Pancreatic tuberculosis.

Tuberculosis of the pancreas is a rare gastrointestinal tract entity. This unusual manifestation of tuberculosis should be included in the differential diagnosis of high-risk patients presenting with a pancreatic mass.

Adult↗
PubMed1997

Effect of conditioning on discrimination of oilseed rape volatiles by the honeybee: use of a combined gas chromatography-proboscis extension behavioural assay.

The coupled gas chromatography-proboscis extension assay technique was used on restrained worker bees to study responses to components of an extract of oilseed rape floral volatiles. Bees were stimulated with the effluent from the gas chromatograph after either paired or unpaired conditioning to the extract, or after a control treatment. Proboscis extension activity was elicited in six areas of the chromatogram. However, the number of bees responding in two of these areas were too low to be considered in the present study. One significant area of activity was associated with the major component, (E,E)-alpha-farnesene, whilst the others were associated with several minor components. Although all three groups of bees, irrespective of the treatments applied, showed some responses to the components eluting from the GC column, only bees subjected to paired conditioning consistently responded when re-tested to the mixture. In addition, paired conditioning increased the responsiveness of individuals in terms of the number of bees responding at least once to the effluent from the gas chromatograph. This work confirmed the occurrence of key compounds in floral volatile mixtures. Possible synergistic/inhibitory effects between components, relating to olfactory experience, are discussed.

Animals↗
PubMed1995

Olfactory learning and memory in the honeybee: comparison of different classical conditioning procedures of the proboscis extension response.

Olfactory learning in the honeybee was investigated using the conditioned proboscis extension reflex on restrained individuals. We compared, under the same experimental conditions, the most commonly used conditioning procedures, i.e. 1 trial, 3 massed trials (1 min inter-trial intervals), and 3 spaced trials (10 min inter-trial intervals) procedures, using linalool as the conditioned stimulus. Two experiments were performed in which worker bees were subjected to: (1) a single test at different times (30 s to 14 days) after the conditioning procedure; (2) a first test within 3 h after the conditioning procedure, and were then retested daily (up to 5 tests). The memory trace of a learnt odorant stimulus could last for the lifetime of the bee, even after a single association with sugar. Repeated tests with 1 day inter-test duration induced a strong decrease of the response level, this effect being more pronounced after a 1-trial conditioning.

Animals↗
PubMedDate not supplied

Side-specificity of olfactory learning in the honeybee: generalization between odors and sides.

Honeybees (Apis mellifera) can be trained to associate an odor stimulus with a sucrose reward. The neural structures involved in the detection and integration of olfactory stimuli are represented bilaterally in the brain. Little is known about the respective roles of the two sides of the brain in olfactory learning. Does each side learn independently of the other, or do they communicate, and if so, to what extent and at what level of neural integration? We addressed these questions using the proboscis extension response (PER) conditioning paradigm applied in a preparation that allows the separation of the two input sides during olfactory stimulations. Bees conditioned to two odorants A and B, one being learned on each side (A+/B+ training), showed in extinction tests rather unspecific responses: They responded to both odorants on both sides. This could be attributable to either a transfer of the learned information between sides, or to a generalization between odorants on each side. By subjecting bees to conditioning on one side only (A+/0 training), we found that the learned information is indeed transferred between sides. However, when bees were trained explicitly to give opposite values to the two odorants on the two sides (A+B-/B+A- training), they showed clear side-specific response patterns to these odorants. These results are used in the elaboration of a functional model of laterality of olfactory learning and memory processing in the honeybee brain.

Animals↗