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Dietary salt levels affect salt preference and learning in larval Drosophila.

Russell C, Wessnitzer J, Young JM, Armstrong JD, Webb B - PLoS ONE (2011)

Bottom Line: Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased.However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired.Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

View Article: PubMed Central - PubMed

Affiliation: Institute for Perception, Action, and Behaviour, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

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Larvae reared on 0.2 M (light grey) and 0.3 M (dark grey) tested: (left) for untrained preference between Pure (white) and NaCl (shaded) substrate at a concentration 0.025 higher than their food, i.e., 0.225 M and 0.325 M respectively; (right) for odour preference after associative training with the corresponding substrates, tested on Pure.* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/2) does not include 0, see text). In both cases an aversive substrate has a positive reinforcement effect.
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pone-0020100-g003: Larvae reared on 0.2 M (light grey) and 0.3 M (dark grey) tested: (left) for untrained preference between Pure (white) and NaCl (shaded) substrate at a concentration 0.025 higher than their food, i.e., 0.225 M and 0.325 M respectively; (right) for odour preference after associative training with the corresponding substrates, tested on Pure.* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/2) does not include 0, see text). In both cases an aversive substrate has a positive reinforcement effect.

Mentions: As shown in [3], Drosophila larvae respond to low levels of salt with attraction and high levels of salt with aversion. They can also be conditioned to associate odours with salt, showing subsequent attraction to odours paired with low salt and aversion to odours paired with high salt. However, within a specific concentration range, the unconditioned response (UR) exhibited is aversion while the conditioned response (CR) is attraction (compare figure 2 (choice) at the concentration 0.375M NaCl with the same concentration in figure 3B (positive learning) in [3]). In this case, the UR and CR are directly opposite in character; the apparent valence of the US is opposite to its reinforcing effects. While it has long been known in classical conditioning that the CR can differ from the UR [15], it is nevertheless usually expected to be consistent with expectation of the US [16]. But if 0.375M NaCl should be avoided, why should an odour that has been associated with it become more attractive?


Dietary salt levels affect salt preference and learning in larval Drosophila.

Russell C, Wessnitzer J, Young JM, Armstrong JD, Webb B - PLoS ONE (2011)

Larvae reared on 0.2 M (light grey) and 0.3 M (dark grey) tested: (left) for untrained preference between Pure (white) and NaCl (shaded) substrate at a concentration 0.025 higher than their food, i.e., 0.225 M and 0.325 M respectively; (right) for odour preference after associative training with the corresponding substrates, tested on Pure.* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/2) does not include 0, see text). In both cases an aversive substrate has a positive reinforcement effect.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105986&req=5

pone-0020100-g003: Larvae reared on 0.2 M (light grey) and 0.3 M (dark grey) tested: (left) for untrained preference between Pure (white) and NaCl (shaded) substrate at a concentration 0.025 higher than their food, i.e., 0.225 M and 0.325 M respectively; (right) for odour preference after associative training with the corresponding substrates, tested on Pure.* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/2) does not include 0, see text). In both cases an aversive substrate has a positive reinforcement effect.
Mentions: As shown in [3], Drosophila larvae respond to low levels of salt with attraction and high levels of salt with aversion. They can also be conditioned to associate odours with salt, showing subsequent attraction to odours paired with low salt and aversion to odours paired with high salt. However, within a specific concentration range, the unconditioned response (UR) exhibited is aversion while the conditioned response (CR) is attraction (compare figure 2 (choice) at the concentration 0.375M NaCl with the same concentration in figure 3B (positive learning) in [3]). In this case, the UR and CR are directly opposite in character; the apparent valence of the US is opposite to its reinforcing effects. While it has long been known in classical conditioning that the CR can differ from the UR [15], it is nevertheless usually expected to be consistent with expectation of the US [16]. But if 0.375M NaCl should be avoided, why should an odour that has been associated with it become more attractive?

Bottom Line: Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased.However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired.Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

View Article: PubMed Central - PubMed

Affiliation: Institute for Perception, Action, and Behaviour, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

Show MeSH
Related in: MedlinePlus