The short neuropeptide F (sNPF) promotes the formation of appetitive visual memories in honey bees

Abstract

Motivation can critically influence learning and memory. Multiple neural mechanisms regulate motivational states, among which signalling via specific neuropeptides, such as NPY in vertebrates and NPF and its short variant sNPF in invertebrates, plays an essential role. The honey bee (Apis mellifera) is a privileged model for the study of appetitive learning and memory. Bees learn and memorize sensory cues associated with nectar reward while foraging, and their learning is affected by their feeding state. However, the neural underpinnings of their motivational states remain poorly known. Here we focused on the short neuropeptide F (sNPF) and studied if it modulates the acquisition and formation of colour memories. Artificially increasing sNPF levels in partially fed foragers with a reduced motivation to learn colours resulted in significant colour learning and memory above the levels exhibited by starved foragers. Our results thus identify sNPF as a critical component of motivational processes involved in foraging and in the cognitive processes associated with this activity in honey bees.

Keywords: appetitive motivation; honey bees; learning; memory; short neuropeptide F (sNPF).

Figure 1.

Experimental set-up and colour-conditioning procedure. Marked bees were (a) trained in a miniature Y-maze whose end compartments could be closed by a sliding door after each choice, and (b) translocated to the maze entrance for another trial. (c) Each bee was trained, over the course of 10 consecutive trials, to discriminate a yellow from a blue target. One colour was paired with sucrose and the other with water. One hour after conditioning, bees were tested twice for memory retention in the absence of reinforcement, with two refreshment trials interspersed between tests.

Figure 2.

Learning and retention following colour conditioning. Proportion of correct choices in the last trial of colour conditioning (first, filled bar in each panel) and in the two retention tests (second and third, hatched bars in each panel). (a) P-fed, blue-trained: n = 15, yellow-trained: n = 15; (b) starved bees, blue-trained: n = 20, yellow-trained: n = 21; (c) P-fed solvent, blue-trained: n = 15, yellow-trained: n = 15; (d) P-fed sNPF1, blue-trained: n = 15, yellow-trained: n = 15; (e) P-fed sNPF10, blue-trained: n = 15, yellow-trained: n = 15. Error bars represent the 95% boostrapped confidence interval. **p-value < 0.01; *p-value < 0.05.