Partial unilateral lesions of the mushroom bodies affect olfactory learning in honeybees Apis mellifera L.

Abstract

The mushroom bodies (MBs) are central structures in the insect brain that have been associated with olfactory learning and memory. Here we used hydroxyurea (HU) to treat honeybee larvae and induce partial MB ablations at the adult stage. We studied olfactory learning in honeybees with unilateral loss of the median calyces of their MBs and compared their ability to solve different forms of olfactory discrimination. When odorants were delivered in a side-specific manner, ablated bees could not solve either discrimination of the unambiguous problem (Paradigm 1: A+, B- on one antenna, C+, D- on the other; A+B-/C+D-) whereas they could solve at least one of both discriminations of the ambiguous problem (Paradigm 2: A+B-/A-B+), namely that proposed to their intact brain side. Non-ablated bees could learn side-specific discriminations on both brain sides. When odorants were delivered simultaneously to both antennae (Paradigm 3: A+B-C+D-), HU-ablated bees learned slower than HU-normal bees. Thus, in all three paradigms, the unilateral loss of a median calyx affected olfactory learning. We propose that the MBs are required for solving elemental olfactory tasks whose complexity is increased by the number of stimuli involved and that MB ablations could have an effect on the inhibition of information exchange between brain hemispheres.

Precocious Locomotor Behavior Begins in the Egg: Development of Leg Muscle Patterns for Stepping in the Chick

“…Results from GO analyses highlight the function of the mushroom bodies in learning and memory, with enrichment in categories such as transcriptional regulation and ion channel activity, among others. These results are consistent with known roles for the mushroom bodies in the regulation of rhythmic behavior, learning and memory [28,29,33,56,57]. In addition, our results nicely correspond with earlier in situ hybridization data and immuno-staining data for genes like Inositol tris-phosphate receptor, CAMKII and PKA that were also shown to be highly expressed in mushroom bodies [48,50,54].…”

“…These include visual information about the landscape and location, direction information, measurement of distance, measurement of gravity to name a few. Based on previous neuroanatomical and behavioral studies in honey bees and other insects, we know that the following CNS regions are likely to be involved in sensory processing and regulation of dance: 1) the optic lobes (OL), which receive sensory input from the compound eyes and the ocelli and are comprised of 3 distinct neuropils, the lamina, medulla and lobula [17][18][19]; 2) the mushroom bodies (MB), which consist of intrinsic neurons called Kenyon cells [20,21] and a complex neuropil arranged into anatomically defined subparts strongly associated with olfactory learning, higher order visual processing, multi-modal sensory integration and general arousal [22][23][24][25][26][27][28][29]; and 3) the central brain (CB), which contains (among other neuropils) the central complex [30], a precisely arranged array of neurons implicated in the control of acoustic communication and coordinated movements during courtship in Drosophila (fruit fly) and gomphocerine grasshoppers [31][32][33], orientation to polarized light [34,35]. We also included the second thoracic ganglion (TG) because it innervates and controls the body parts involved in the dance output namely, the wings, the middle and hind legs, muscles of meso and metathorax and the articulation of the abdomen with the thorax through the propodeum [36].…”

Mushroom Body Extrinsic Neurons in the Honeybee Brain Encode Cues and Contexts Differently

“…1) that consisted of three parts. (1) An odor delivery device (hereafter referred to as olfactometer) blew continuous stream of air over the bee's antennae and delivered odors with precise timing (Galizia et al, 1997;Komischke et al, 2002). (2) A light source with flexible light guides (KL 1500 LCD; Schott) illuminated the reflective paper placed in front of the honeybee.…”

Cognition in Invertebrates

“…When odorants were delivered simultaneously to both antennas (paradigm 3: A þ B À C þ DÀ), ablated bees learned slower than normal bees. Thus, in all three cases, the unilateral loss of a median calyx affected olfactory learning (Komischke et al, 2005). It was proposed that MBs are required for solving elemental olfactory tasks whose complexity is enhanced by virtue of the number of stimuli involved (paradigms 1 and 3: four stimuli) and that MB ablations could have an effect on the inhibition of information exchange between brain hemispheres.…”

“…This and two other paradigms were recently used to test mushroom body (MB)-ablated honeybees and to determine whether intact MBs are necessary to solve nonelemental olfactory discriminations (Komischke et al, 2005). Bees with unilateral lesions of the MBs generated by larval treatment with hydroxyurea (Malun, 1998) were trained under different olfactory conditioning designs.…”