Parallel mechanisms of visual memory formation across distinct regions of the honey bee brain

Abstract

Visual learning is vital to the behavioral ecology of the Western honey bee (Apis mellifera). Honey bee workers forage for floral resources, a behavior that requires the learning and long-term memory of visual landmarks, but how these memories are mapped to the brain remains poorly understood. To address this gap in our understanding, we collected bees that successfully learned visual associations in a conditioned aversion paradigm and compared gene expression correlates of memory formation in the mushroom bodies, a higher-order sensory integration center classically thought to contribute to learning, as well as the optic lobes, the primary visual neuropil responsible for sensory transduction of visual information. We quantified expression of CREB and CaMKII, two classical genetic markers of learning, and fen-1, a gene specifically associated with punishment learning in vertebrates. As expected, we found substantial involvement of the mushroom bodies for all three markers but additionally report the involvement of the optic lobes across a similar time course. Our findings imply the molecular involvement of a sensory neuropil during visual associative learning parallel to a higher-order brain region, furthering our understanding of how a tiny brain processes environmental signals.

Keywords: Apis mellifera; Aversive learning; Mushroom bodies.

Fig. 1.

Expression profile of target genes following punishment learning. Each row corresponds to a target gene, each column to a broad brain region. The simplified bar graphs show the mean relative fold-change in expression for each group (C_C, context control; S_C, shock control; L_E, learned) and time point (20 or 80 min) combination. The horizontal dotted line represents the mean relative fold-change in expression of the naïve control (N_C) group, with the solid lines delimiting the range within 1 s.e.m. Significant differences from N_C group expression are indicated by colored circles. Significant expression level differences between time points within a group are indicated by horizontal colored lines.