Data from: Insect brain plasticity: effects of olfactory input on neuropil size

Insect brains are known to express a high degree of experience-dependent
structural plasticity. One brain structure in particular, the mushroom
body, has been attended to in numerous studies as it is implicated in
complex cognitive processes such as olfactory learning and memory. It is,
however, poorly understood to what extent sensory input per se affects
plasticity of the mushroom bodies. By performing unilateral blocking of
olfactory input on immobilized butterflies, we were able to measure the
effect of passive sensory input on the volumes of antennal lobes and
mushroom body calyces. We showed that the primary and secondary olfactory
neuropils respond in different ways to olfactory input. Antennal lobes
show absolute experience-dependency and increase in volume only if
receiving direct olfactory input from ipsilateral antennae, while mushroom
body calyx volumes were unaffected by the treatment and instead show
absolute age-dependency in this regard. We therefore propose that
cognitive processes related to behavioural expressions are needed in order
for the calyx to show experience-dependent volumetric expansions. Our
results indicate that such experience-dependent volumetric expansions of
calyces observed in other studies may have been caused by cognitive
processes rather than by sensory input, bringing some causative clarity to
a complex neural phenomenon.