Biomedical Engineering Reference
In-Depth Information
Szyszka et al.
2008
; Hourcade et al.
2010
). For example, plasticity of single
identifi ed neurons in the bee brain, such as the abovementioned VUMmx1 or of the
MB-extrinsic neuron PE1, after olfactory PER conditioning was investigated by
intracellular recordings coupled to PER conditioning (Hammer
1993
; Mauelshagen
1993
) or extracellular recordings (Okada et al.
2007
). Neuroanatomical analyses
have also been employed to assess the effect of olfactory memory formation at the
structural level. It has been shown, for instance, that the density of local microcir-
cuits (called microglomeruli) in the olfactory region of the MB calyces was
increased upon olfactory lLTM formation (Hourcade et al.
2010
).
On a behavioral level, the advent of olfactory classical conditioning of PER has
allowed studying from a psychological perspective several learning-related
phenomena well known in vertebrates, such as overshadowing (Smith
1998
), block-
ing (Smith and Cobey
1994
; Gerber and Ullrich
1999
; Hosler and Smith
2000
;
Guerrieri et al.
2005b
), second-order conditioning (Hussaini et al.
2007
), sensory
preconditioning (Müller et al.
2000
), positive and negative patterning (Deisig et al.
2001
,
2002
,
2003
), spontaneous recovery from extinction (Sandoz and Pham-
Delègue
2004
; Stollhoff et al.
2005
), reversal learning (Komischke et al.
2002
;
Devaud et al.
2007
; Hadar and Menzel
2010
), and reconsolidation (Stollhoff et al.
2008
) in a controlled way.
2.5
Other Forms of PER Conditioning in Honeybees
Researchers manipulated classical conditioning of PER to associate reward with
other sensory stimuli such as monochromatic lights (Hori et al.
2006
), motion cues
(Hori et al.
2007
), polarized light (Sakura et al.
2012
), antennal mechanosensory
stimulations (Giurfa and Malun
2004
), or antennal temperature stimulations
(Hammer et al.
2009
). These are appetitive learning paradigms that use sucrose
solution as positive reinforcer. Besides this, aversive learning paradigms have also
been developed in bees, using mild electric shocks as negative reinforcer (Vergoz
et al.
2007
), yet in this case PER is no longer considered but the sting extension
refl ex (SER). In this aversive learning protocol, an odor CS is associated with an
electric shock US, and the bees learn to respond to the trained odor with an exten-
sion of their sting. Pharmacological approaches using olfactory appetitive condi-
tioning of PER and olfactory aversive conditioning of SER suggested that
octopamine and dopamine subserve appetitive and aversive reinforcement in the
honeybee, respectively (Hammer and Menzel
1998
; Vergoz et al.
2007
).
Recently, Ayestaran et al. (
2010
) showed by means of olfactory conditioning of
PER that aversive substances, such as quinine, salicine, and amygdalin, can induce
a post-ingestional malaise that will later reduce the bees' tendency to respond to the
conditioned odor. Wright et al. (
2010
) also associated odors with toxins, namely,
quinine or amygdalin, mixed in sucrose solution. This work demonstrated that two
distinct monoaminergic pathways, mediated by dopamine and serotonin, respec-
tively, account for conditioned food aversion in honeybees: learned avoidance of
bitter substances is primarily modulated by dopamine, while learning to associate
