Outcome expectations drive learned behaviour in larval Drosophila

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 273; no. 1604; pp. 2965 - 2968
• Main Authors: Gerber, B, Hendel, T
• Format: Journal Article
• Language: English
• Published: London The Royal Society 07.12.2006
• Subjects: Animals; Association Learning - physiology; Associative learning; Behavior, Animal - physiology; Choice Behavior; Cognition; Cues; Discrimination (Psychology); Drosophila; Drosophila - physiology; Expectation; insect behavior; Insect larvae; Larva - physiology; Larvae; Learning; Memory; Memory trace; Odorants; Odors; Olfaction; Olfactory Pathways - physiology; Outcome; Outcomes of education; Reinforcement (Psychology); smell; Sugars; Taste; Taste - physiology; Training
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.2006.3673

Why does Pavlov's dog salivate? In response to the tone, or in expectation of food? While in vertebrates behaviour can be driven by expected outcomes, it is unknown whether this is true for non-vertebrates as well. We find that, in the Drosophila larva, odour memories are expressed behaviourally only if animals can expect a positive outcome from doing so. The expected outcome of tracking down an odour is determined by comparing the value of the current situation with the value of the memory for that odour. Memory is expressed behaviourally only if the expected outcome is positive. This uncovers a hitherto unrecognized evaluative processing step between an activated memory trace and behaviour control, and argues that learned behaviour reflects the pursuit of its expected outcome. Shown in a system with a simple brain, an apparently cognitive process like representing the expected outcome of behaviour seems to be a basic feature of behaviour control.