SCIENCE science.orgmation processing ( 6 ). Honey bees are adept
learners of a variety of visual and olfactory
stimuli when associated with a sweet-tasting
sugary reward. Individual bees are then moti-
vated to communicate the value of their per-
ceived experience to hive mates through the
bee waggle dance language ( 7 ). This behav-
ioral paradigm enabled decoding of the bee
dance language that contains information
about direction and distance of profitable
food sources and enables good experimental
access for testing bee sensory perception ( 8 ).
Huang et al. investigated how honey bees
forage, and what might motivate individuals
to leave the hive in search of sweet-tasting re-
wards in the environment. By monitoring the
foraging and subsequent dance language by
bees from different test groups that were cap-
tured at different phases of their activities, it
was possible to understand the potential role
of the dopaminergic system in the anticipa-
tion of wanting a reward. When bees that
had recently visited a profitable food source
started dancing to communicate to other
bees in the hive, the dancing bees showed
a significant increase in dopamine brain
concentrations, which was quantified using
high-performance liquid chromatography on
single brains. However, this increase is tem-
porary and drops by the end of the bee’s wag-
gle dance. When dancing bees subsequently
depart the hive to seek more rewards, dopa-
mine again increases, followed by a decrease
while feeding. These fast transient changes
of dopamine concentrations in the bee brain
show that it is the expectation of wanting a
reward that drives this important compo-
nent of how motivation is modulated in the
reward system—a mechanism similar to that
reported in some mammals ( 1 , 5 ).
The role of dopamine as a biologically
relevant component of foraging motivation
was confirmed in odor-learning experiments
in which bees were topically treated with
increasing dopamine amounts and subse-
quently showed significantly better learning
profiles compared to controls. Bees treated
with exogenous dopamine also demonstrated
improved memory for recalling learned tasks
compared to controls. Thus, modulation of
dopamine concentrations in bee brains is es-
sential in a variety of foraging tasks, includ-
ing expectation, motivating individuals, and
improving their capacity to learn important
flower signaling such as odor to identify prof-
itable foraging options ( 9 ). An improved un-
derstanding of the mechanisms that mediate
expectation, wanting, and motivation in bees
(and likely many other animals) according
to individual experience and resulting dopa-
mine concentrations in the brain could also
explain why behavioral differences between
individuals are frequently reported, even for
individuals from the same hive ( 10 ).
Results from the study of Huang et al. in-
dicate that honey bees share with mammals
common neural mechanisms for encoding
the wanting of stimuli with positive hedonic
value. Thus, as anticipated by Darwin 150
years ago, evolution likely shaped wanting
mechanisms that improve animal fitness,
by experiencing pleasure from nutritious
food, or triggering responses from emo-
tional stimuli linked to survival brain cir-
cuits ( 11 ). Conversely, an imbalance of this
mechanism may have negative effects on fit-
ness by, for example, promoting pathologies
such as addiction ( 1 ).
Honey bees and a variety of native bees
are major pollinators of important crops,
including almonds, citrus fruits, and many
vegetables, with both human nutritional and
economic value in the tens of billions of dol-
lars a year within the US alone ( 12 ). A deeper
understanding of how dopamine modulates
wanting in these important animals can
lead to improved ways of motivating bees
to forage. For example, the queen bee in a
hive is able to deploy chemical pheromones
that will capture the attention of young bees
to entice them to perform certain tasks by
stimulating dopamine pathways in the brain
( 13 ), and equivalent stimulations to drive the
wanting systems of forager bees would likely
benefit pollination services by motivating
them to visit more flowers.
As the honey bee continues to be a key
model for what can be achieved with a
miniaturized brain ( 6 ), understanding the
neural mechanisms of wanting and the
evidence of variability among individuals
( 10 ), depending upon acquired experience,
is informative for explaining different ani-
mal behaviors. jREFERENCES AND NOTES- K. C. Berridge, M. L. Kringelbach, Curr. Opin. Neurobiol.
23 , 294 (2013). - C. Darwin, The Expressions of Emotions in Man and
Animals (Oxford Univ. Press, 1872). - K. C. Berridge, M. L. Kringelbach, Neuron 86 , 646 (2015).
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- K. C. Berridge, T. E. Robinson, Am. Psychol. 71 , 670
(2016). - R. Menzel, Nat. Rev. Neurosci. 13 , 758 (2012).
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Bees (Harvard Univ. Press, 1967). - M. V. Srinivasan, S. Zhang, M. Altwein, J. Tautz, Science
287 , 851 (2000). - A. Kantsa et al., Nat. Ecol. Evol. 1 , 1502 (2017).
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ACKNOWLEDGMENTS
A.G.D. receives funding from the Australian Research Council.10.1126/science.abp8609MATERIALS SCIENCEAn adsorbent
with flexible
nanoscopic
pores
By Tom Willhammar and Xiaodong ZouN
anoporous materials have large sur-
face areas and well-defined pores at
the molecular scale, making them
attractive as selective adsorbents
and catalysts ( 1 ). They can act as
molecular sieves and have garnered
interest because of their potential use as
energy-efficient adsorbents for gas separa-
tion and storage applications, such as car-
bon capture. The adsorption properties of
some of these materials suggest that inter-
actions between the nanoporous material
and the molecules or ions it adsorbs might
induce a degree of structural flexibility in
the pores. On page 491 of this issue, Xiong
et al. ( 2 ) describe changes in the pore ge-
ometry of the industrially important zeo-
lite ZSM-5 during the gas adsorption-de-
sorption process. This direct observation
of structural flexibility in a nanoporous
material reveals ways to manipulate the
dynamic behavior and function of these
materials.
Zeolites have a nanoporous three-dimen-
sional structure built from corner-sharing
silica (SiO 4 ) and alumina (AlO 4 ) tetrahe-
dra. To date, more than 250 different zeo-
lite structures have been discovered ( 3 ),
each with a distinctive pore size and shape.
However, adsorption experiments in these
materials have shown that gas molecules
larger than the expected pore size can en-
ter the material, which indicates structural
flexibility of the material associated with
the so-called “host-guest” interactions. To
understand the size and shape selectivity
properties of a material as an adsorbentDepartment of Materials and Environmental Chemistry,
Stockholm University, SE-106 91 Stockholm, Sweden.
Email: [email protected]; [email protected]Scanning transmission
electron microscopy
shows the adaptive pores
of a zeolite
29 APRIL 2022 • VOL 376 ISSUE 6592 457