IMPAIRED ODOR DISCRIMINATION ON DESYNCHRONIZATION OF ODOR-ENCODING NEURAL ASSEMBLIES

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.