1. Bumblebees exhibit the memory spacing effect
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James C. Nieh, Jeremy Song, and Nicholas R. T. Toda
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0106 biological sciences ,Trial spacing effect ,Plant Nectar ,Bumblebees ,Olfactory conditioning ,Flowers ,Models, Biological ,010603 evolutionary biology ,01 natural sciences ,Proboscis extension reflex ,Bombus impatiens ,Discrimination Learning ,Memory spacing effect ,Reward ,Memory ,Associative learning ,Animals ,0501 psychology and cognitive sciences ,050102 behavioral science & comparative psychology ,Discrimination learning ,Olfactory memory ,Pollination ,Bumblebee ,Ecology, Evolution, Behavior and Systematics ,Life Sciences, general ,Analysis of Variance ,Original Paper ,biology ,Spacing effect ,05 social sciences ,Environment, general ,Life Sciences ,Association Learning ,General Medicine ,Bees ,biology.organism_classification ,Classical conditioning ,Space Perception ,Memory consolidation ,Cognitive psychology - Abstract
Associative learning is key to how bees recognize and return to rewarding floral resources. It thus plays a major role in pollinator floral constancy and plant gene flow. Honeybees are the primary model for pollinator associative learning, but bumblebees play an important ecological role in a wider range of habitats, and their associative learning abilities are less well understood. We assayed learning with the proboscis extension reflex (PER), using a novel method for restraining bees (capsules) designed to improve bumblebee learning. We present the first results demonstrating that bumblebees exhibit the memory spacing effect. They improve their associative learning of odor and nectar reward by exhibiting increased memory acquisition, a component of long-term memory formation, when the time interval between rewarding trials is increased. Bombus impatiens forager memory acquisition (average discrimination index values) improved by 129% and 65% at inter-trial intervals (ITI) of 5 and 3 min, respectively, as compared to an ITI of 1 min. Memory acquisition rate also increased with increasing ITI. Encapsulation significantly increases olfactory memory acquisition. Ten times more foragers exhibited at least one PER response during training in capsules as compared to traditional PER harnesses. Thus, a novel conditioning assay, encapsulation, enabled us to improve bumblebee-learning acquisition and demonstrate that spaced learning results in better memory consolidation. Such spaced learning likely plays a role in forming long-term memories of rewarding floral resources. © 2009 Springer-Verlag.
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