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Intracranial EEG recordings of the human olfactory brain at millisecond speed

We have recently implemented intracranial EEG (iEEG) techniques in patients with medically resistant epilepsy to elucidate the spatiotemporal dynamics of odor processing in the human brain, with a focus on piriform cortex, amygdala, hippocampus, and orbitofrontal cortex. These studies provide an important complement to our fMRI experiments, bringing a formal electrophysiological understanding of odor coding and intra-regional and inter-regional coupling in time, space, frequency, and phase. Our recent studies have shown that the slow rhythm of natural breathing entrains electrical activity in human piriform cortex, with a reliance on the nasal vs. oral route of respiration, and that an odor stimulus induces robust theta oscillations (3-7 Hz) in piriform cortex, from which odor information can be decoded within 100-500 ms of a sniff. Ongoing work is investigating the mechanistic underpinnings of odor-induced theta in olfactory perception and decision-making, and the role of targeted stimulation to causally perturb oscillatory rhythms and determine effects on perception and behavior.