Olfactory system oscillations across phyla

- Odor evoked oscillations rely on similar mechanisms across several phyla.
- Slower oscillations help group activity within the olfactory bulb and link brain areas.
- Olfactory bulb or antennal lobe centrifugal input may adjust inhibition modes and frequencies.

Neural oscillations are ubiquitous in olfactory systems of mammals, insects and molluscs. Neurophysiological and computational investigations point to common mechanisms for gamma or odor associated oscillations across phyla (40-100 Hz in mammals, 20-30 Hz in insects, 0.5-1.5 Hz in molluscs), engaging the reciprocal dendrodendritic synapse between excitatory principle neurons and inhibitory interneurons in the olfactory bulb (OB), antennal lobe (AL), or procerebrum (PrC). Recent studies suggest important mechanisms that may modulate gamma oscillations, including neuromodulators and centrifugal input to the OB and AL. Beta (20 Hz) and theta (2-12 Hz) oscillations coordinate activity within and across brain regions. Olfactory beta oscillations are associated with odor learning and depend on centrifugal OB input, while theta oscillations are strongly associated with respiration.