Sensory responsiveness and the effects of equal subjective rewards on tactile learning and memory of honeybees

Abstract

In tactile learning, sucrose is the unconditioned stimulus and reward, which is usually applied to the antenna to elicit proboscis extension and which the bee can drink when it is subsequently applied to the extended proboscis. The conditioned stimulus is a tactile object that the bee can scan with its antennae. In this paper we describe the quantitative relationships between gustatory antennal stimulation, gustatory proboscis stimulation, and tactile learning and memory. Bees are 10-fold more responsive to sucrose solutions when they are applied to the antenna compared to proboscis stimulation. During tactile conditioning, the sucrose solution applied to the proboscis determines the level of acquisition, whereas antennal input is of minor importance. Bees differing in their gustatory responsiveness measured at the antenna differ strongly in their tactile acquisition and memory. We demonstrate how these differences in tactile acquisition and memory can be greatly reduced by calculating equal subjective rewards, based on individual gustatory responsiveness.Learning in animals depends on many factors including the salience of the conditioned stimulus (CS) and the strength of the unconditioned stimulus (US) (Rescorla and Wagner 1972). Even under controlled laboratory conditions, individuals show variance in the rate of acquisition, the asymptote of acquisition, and in retention (Scheiner et al. 2001a(Scheiner et al. ,b, 2003Matzel et al. 2003;Hedden and Gabrieli 2004;Dellu-Hagedorn 2005). Multiple intrinsic factors can contribute to these behavioral differences. Some of these factors may be related to individual differences in evaluating CS and US (Scheiner et al. 1999;Chester et al. 2003). These differences could reflect genetic heterogeneity at the individual level.Studies in honeybees (Apis mellifera L.) can be very useful to identify important factors leading to inter-individual learning differences and their potential sources of control. Associative learning plays an important part in honeybee behavior. Bees learn very fast the location of a foraging site and the numerous characteristics of reward-yielding plants (for review, see Menzel

Cognitive aging is linked to social role in honey bees (Apis mellifera)

“…Interestingly, gustatory response scores correlated positively with acquisition scores in our experiments in all groups except the group that had foraged for >15 days. Normally, acquisition performance in honey bees is accompanied by corresponding differences in gustatory responsiveness (Scheiner et al, 1999(Scheiner et al, , 2001a(Scheiner et al, , b, c, 2003(Scheiner et al, , 2005. Our experiments indicate that this relationship between sensory responsiveness and associative learning performance is different in worker bees with long foraging duration, and it is conceivable that effects of aging on learning performance in honey bees involve impairment in higher cognitive processing.…”

“…Measurements of honey bee gustatory responsiveness are commonly used (for review, see Scheiner et al, 2004), but have not been applied to bees of advanced chronological age or as a function of foraging duration. Associative learning in worker bees correlates strongly with gustatory responsiveness (Scheiner et al, 1999(Scheiner et al, , 2001a(Scheiner et al, , b, c, 2003(Scheiner et al, , 2005. Individuals with high gustatory responsiveness show higher acquisition rates than those with low responsiveness.…”

“…This association is related to the individual evaluation of the sucrose reward. Thus, if workers that differ in gustatory responsiveness receive equal subjective rewards (i.e., a bee with low responsiveness receives a highly concentrated sucrose solution and a bee with high responsiveness is rewarded with a comparatively low-concentrated sucrose solution), they do not differ in their associative learning performance (Scheiner et al, 2005).…”

Standard methods for behavioural studies ofApis mellifera

“…Bees with high responsiveness learn fast, while bees that display a low gustatory responsiveness need more training to form an association (Scheiner et al, 1999;2001a, b, 2003Amdam et al, 2010). If bees differing in their gustatory responsiveness are rewarded with equal subjective rewards, depending on their individual gustatory responsiveness, learning performance does not differ between individuals (Scheiner et al, 2005).…”

“…Several studies on PER-learning in the laboratory showed that the sucrose concentration of the reward and the individual The COLOSS BEEBOOK: behavioural studies 45 responsiveness to sucrose strongly correlate with the learning performance in honey bees (see Scheiner et al, 1999Scheiner et al, , 2003Scheiner et al, , 2004Scheiner et al, , 2005. Bees that received a high-concentrated sucrose solution as reward learned faster than bees receiving a low sucrose concentration.…”