Activity-Dependent Changes to the Brain and Behavior of the Honey Bee,Apis mellifera(L.)

Abstract

To explore the origins and possible behavioral consequences of structural plasticity in an insect brain, we have taken advantage of the following: (1) the highly compartmentalized nature of the primary antenno-sensory centers (antennal lobes) of the brain, (2) the ease with which individual compartments, or glomeruli, within the antennal-lobe neuropil can be identified, and (3) the predictability of changes to readily identifiable glomeruli in the antennal lobes of the adult worker honey bee. Treatment with the juvenile hormone analog methoprene and hive manipulation techniques are used to induce precocious foraging behavior in young worker honey bees. The impact of these treatments on the ontogeny of olfactory learning performance and on the volumes of readily identifiable glomeruli in the antennal lobes of the bee brain are examined in parallel. The study reveals that (1) significant changes in glomerular volume are activity dependent and (2) associative learning of floral odors improves with experience. Improvements in associative learning performance coincide temporally with increases in glomerular volume. This raises an important question: are changes in glomerular volume that result from shifts in behavior simply a consequence of changes in the use of peripheral sensory pathways, or are they associated with events that underlie learning and the formation of long-term memories?

Importance of social stimuli for the development of learning capability in honeybees

“…Twenty day-old workers and foragers maintained the learning capability. This age-dependent development in workers agrees with previous reports (Ray and Ferneyhough, 1997;Sigg et al, 1997;Morgan et al, 1998). Drones exhibited the same basic pattern, but the timing was earlier than in workers.…”

“…So, when and how is the learning ability acquired-is it developed endogenously or it is developed in response to sensory inputs? Coss et al (1980) noted that the dendritic spines in the calycal interneurons in the mushroom body are different between young and old foragers, and recent works (Gascuel and Masson, 1987;Withers et al, 1993Withers et al, , 1995Durst et al, 1994;Farhbach and Robinson, 1996;Winnington et al, 1996;Fahrbach et al, 1997;Sigg et al, 1997;Morgan et al, 1998) noted the change in the volume of the mushroom body depending on age and foraging experience. However, the relationship between flight experience and such morphological change is still unclear.…”

Synaptic organization in the adult honey bee brain is influenced by brood-temperature control during pupal development

“…In the fruit fly, MB volume was affected by visual experience, and in ants and honey bees, volume increase was associated with age and behavioral maturation. In the bee and Drosophila, volume measurements in the antennal lobes also revealed age-and experience-related changes in distinct olfactory glomeruli (48,49). In the honey bee, volume changes in the MBs were suggested to be caused mainly by dendritic growth of KCs (40).…”

Standard three-dimensional glomeruli of the Manduca sexta antennal lobe: a tool to study both developmental and adult neuronal plasticity

“…Daly et al (2004) have recently shown that olfactory conditioning is combined with a restructuring of electrical odor response patterns in the AL. Work on adult neuronal plasticity in the honeybee has demonstrated that increases in adult glomerular volume are activity-dependent and correlated with better learning performance (Winnington et al 1996;Sigg et al 1997). Quantitative electron-microscopic studies have lead to the suggestion that volume increase and synapse number changes are independent processes that both contribute to structural plasticity in the AL, although synapse reorganization might only play a minor role on neuropilar volume (Brown et al 2002).…”