Stimulus-evoked oscillatory synchronization of neural assemblies has b
een described in the olfactory(1-5) and visual(6-8) systems of several
vertebrates and invertebrates. in locusts, information about odour id
entity is contained in the timing of action potentials in an oscillato
ry population response(9-11), suggesting that oscillations may reflect
a common reference far messages encoded in time, Although the stimulu
s-evoked oscillatory phenomenon is reliable, its roles in sensation, p
erception, memory formation and pattern recognition remain to be demon
strated-a task requiring a behavioural paradigm, Using honeybees, we n
ow demonstrate that odour encoding involves, as it does in locusts, th
e oscillatory synchronization of assemblies of projection neurons and
that this synchronization is also selectively abolished by picrotoxin,
an antagonist of the GABA(A) (gamma-aminobutyric acid) receptor. By u
sing a behavioural leaning paradigm, we show that picrotoxin-induced d
esynchronization impairs the discrimination oi molecularly similar odo
rants, but not that of dissimilar odorants, It appears, therefore, tha
t oscillatory synchronization of neuronal assemblies is functionally r
elevant, and essential for fine sensory discrimination This suggests t
hat oscillatory synchronization and the kind of temporal encoding it a
ffords provide an additional dimension by which the brain could segmen
t spatially overlapping stimulus representations.