3 The How and Why of Structural Plasticity in the
Adult Honeybee Brain
S uS a n E. Fa h r b a c h & S c o t t D o b r i n3.1. Introduction
What do London taxi drivers and foraging honeybees have in common? Both
must navigate complex environments to reach various destinations and then
return at the end of the workday to a fixed base of operations (garage or
hive). Both improve their navigational skills with practice. Both also exhibit
changes in the volume of specific brain regions that are correlated with navi-
gational experience: the longer the time on the job, the greater the extent of
the changes.
Brain data from London taxi drivers have been collected using noninva-
sive brain imaging (Maguire et al. 2000, 2003, 2006). There is a significant
positive correlation between years on the job as a taxi driver and the volume
of the posterior hippocampus as estimated using noninvasive brain-imaging
techniques. Because many experimental studies have linked the hippocampus
to the ability to solve tasks requiring spatial reasoning, a plausible interpre-
tation of these data is that an enlarged posterior hippocampus is associated
with superior navigational performance within the familiar terrain (Goel et al.
2004). Indirect evidence for this assertion is found in a study that compared
the performance of London taxi drivers with the performance of London bus
drivers. Bus drivers drive as many miles as do taxi drivers but, unlike taxi driv-
ers, navigate predictable, fixed routes rather than the whole of London. On
tests of their ability to recognize London landmarks and to judge proximity
of London landmarks, the taxi drivers, who on average had larger posterior
hippocampi than the bus drivers, scored significantly higher (Maguire et al.
2006).
Studies of the much smaller honeybee brain have been based primarily
on the generation of volume estimates from histological sections (Withers et
al. 1993; Durst et al. 1994; S. Farris et al. 2001). Relative to less experienced
foragers, highly experienced foragers have a larger volume of neuropil associ-
ated with a brain structure called the mushroom bodies (Withers et al. 1993;
Ismail et al. 2006). It is often assumed that the enlarged mushroom bodies of